From 5060750015924d73f95417e317a407b1e2cdd21a Mon Sep 17 00:00:00 2001
From: Christopher Kolstad <chriswk@getunleash.io>
Date: Tue, 14 Nov 2023 16:23:07 +0100
Subject: [PATCH 01/12] feat: Start work on obeying http statuses

---
 src/events.ts               |   2 +-
 src/math.ts                 |   7 ++
 src/metrics.ts              |  95 +++++++++++----
 src/repository/index.ts     |  77 +++++++++++-
 src/test/metrics.test.ts    | 194 +++++++++++++++++++++----------
 src/test/repository.test.ts | 225 ++++++++++++++++++++++++++++++++++--
 src/unleash-config.ts       |   2 +-
 src/url-utils.ts            |   2 +-
 yarn.lock                   |  33 +++---
 9 files changed, 517 insertions(+), 120 deletions(-)
 create mode 100644 src/math.ts

diff --git a/src/events.ts b/src/events.ts
index 6bf80936..5577d0eb 100644
--- a/src/events.ts
+++ b/src/events.ts
@@ -12,7 +12,7 @@ export enum UnleashEvents {
   CountVariant = 'countVariant',
   Sent = 'sent',
   Registered = 'registered',
-  Impression = 'impression'
+  Impression = 'impression',
 }
 
 export interface ImpressionEvent {
diff --git a/src/math.ts b/src/math.ts
new file mode 100644
index 00000000..b7bfc7c5
--- /dev/null
+++ b/src/math.ts
@@ -0,0 +1,7 @@
+export function max(a: number, b: number): number {
+  return a > b ? a : b;
+}
+
+export function min(a: number, b: number): number {
+  return a < b ? a : b;
+}
diff --git a/src/metrics.ts b/src/metrics.ts
index 277d2188..819ba094 100644
--- a/src/metrics.ts
+++ b/src/metrics.ts
@@ -6,6 +6,7 @@ import { HttpOptions } from './http-options';
 import { suffixSlash, resolveUrl } from './url-utils';
 import { UnleashEvents } from './events';
 import { getAppliedJitter } from './helpers';
+import { max, min } from './math';
 
 export interface MetricsOptions {
   appName: string;
@@ -38,12 +39,12 @@ interface MetricsData {
 }
 
 interface RegistrationData {
-  appName:    string;
+  appName: string;
   instanceId: string;
   sdkVersion: string;
   strategies: string[];
-  started:    Date;
-  interval:   number
+  started: Date;
+  interval: number;
 }
 
 export default class Metrics extends EventEmitter {
@@ -61,6 +62,8 @@ export default class Metrics extends EventEmitter {
 
   private metricsJitter: number;
 
+  private failures: number = 0;
+
   private disabled: boolean;
 
   private url: string;
@@ -111,13 +114,31 @@ export default class Metrics extends EventEmitter {
     return getAppliedJitter(this.metricsJitter);
   }
 
+  getFailures(): number {
+    return this.failures;
+  }
+
+  getInterval(): number {
+    if(this.metricsInterval === 0 || this.failures === -1) {
+      return 0;
+    } else {
+      return this.metricsInterval +
+        (this.failures * this.metricsInterval) +
+        this.getAppliedJitter();
+    }
+
+  }
+
   private startTimer(): void {
-    if (this.disabled) {
+    if (this.disabled || this.getInterval() === 0) {
       return;
     }
-    this.timer = setTimeout(() => {
-      this.sendMetrics();
-    }, this.metricsInterval + this.getAppliedJitter());
+    this.timer = setTimeout(
+      () => {
+        this.sendMetrics();
+      },
+      this.getInterval(),
+    );
 
     if (process.env.NODE_ENV !== 'test' && typeof this.timer.unref === 'function') {
       this.timer.unref();
@@ -125,7 +146,7 @@ export default class Metrics extends EventEmitter {
   }
 
   start(): void {
-    if (typeof this.metricsInterval === 'number' && this.metricsInterval > 0) {
+    if (this.metricsInterval > 0) {
       this.startTimer();
       this.registerInstance();
     }
@@ -170,6 +191,20 @@ export default class Metrics extends EventEmitter {
     return true;
   }
 
+  unrecoverableError(url: string, statusCode: number) {
+    this.emit(UnleashEvents.Warn, `${url} returning ${statusCode}, stopping metrics`);
+    this.failures = -1;
+    this.stop();
+  }
+
+  backoff(url: string, statusCode: number): void {
+    this.failures = min(10, this.failures + 1);
+    // eslint-disable-next-line max-len
+    this.emit(UnleashEvents.Warn, `${url} returning ${statusCode}. Backing off to ${this.getInterval()}`);
+    console.log(`Failure count now ${this.failures}`);
+    this.startTimer();
+  }
+
   async sendMetrics(): Promise<void> {
     if (this.disabled) {
       return;
@@ -194,24 +229,38 @@ export default class Metrics extends EventEmitter {
         timeout: this.timeout,
         httpOptions: this.httpOptions,
       });
-      this.startTimer();
-      if (res.status === 404) {
-        this.emit(UnleashEvents.Warn, `${url} returning 404, stopping metrics`);
-        this.stop();
-      }
       if (!res.ok) {
+        if (res.status === 404 || res.status === 403 || res.status == 401) {
+          this.unrecoverableError(url, res.status);
+        } else if (
+          res.status === 429 ||
+          res.status === 500 ||
+          res.status === 502 ||
+          res.status === 503 ||
+          res.status === 504
+        ) {
+          this.backoff(url, res.status);
+        }
         this.restoreBucket(payload.bucket);
-        this.emit(UnleashEvents.Warn, `${url} returning ${res.status}`, await res.text());
       } else {
+        console.log('Succeeded');
         this.emit(UnleashEvents.Sent, payload);
+        this.reduceBackoff();
       }
     } catch (err) {
+      console.log('Threw an error', err);
       this.restoreBucket(payload.bucket);
       this.emit(UnleashEvents.Warn, err);
       this.startTimer();
     }
   }
 
+  reduceBackoff(): void {
+    this.failures = max(0, this.failures - 1);
+    console.log(`Failure count now ${this.failures}`);
+    this.startTimer();
+  }
+
   assertBucket(name: string): void {
     if (this.disabled) {
       return;
@@ -243,7 +292,7 @@ export default class Metrics extends EventEmitter {
   }
 
   private increaseCounter(name: string, enabled: boolean, inc = 1): void {
-    if(inc === 0) {
+    if (inc === 0) {
       return;
     }
     this.assertBucket(name);
@@ -252,8 +301,8 @@ export default class Metrics extends EventEmitter {
 
   private increaseVariantCounter(name: string, variantName: string, inc = 1): void {
     this.assertBucket(name);
-    if(this.bucket.toggles[name].variants[variantName]) {
-      this.bucket.toggles[name].variants[variantName]+=inc 
+    if (this.bucket.toggles[name].variants[variantName]) {
+      this.bucket.toggles[name].variants[variantName] += inc;
     } else {
       this.bucket.toggles[name].variants[variantName] = inc;
     }
@@ -276,7 +325,7 @@ export default class Metrics extends EventEmitter {
   }
 
   createMetricsData(): MetricsData {
-    const bucket = {...this.bucket, stop: new Date()};
+    const bucket = { ...this.bucket, stop: new Date() };
     this.resetBucket();
     return {
       appName: this.appName,
@@ -286,20 +335,20 @@ export default class Metrics extends EventEmitter {
   }
 
   private restoreBucket(bucket: Bucket): void {
-    if(this.disabled) {
+    if (this.disabled) {
       return;
     }
     this.bucket.start = bucket.start;
 
     const { toggles } = bucket;
-    Object.keys(toggles).forEach(toggleName => {
-      const toggle = toggles[toggleName];      
+    Object.keys(toggles).forEach((toggleName) => {
+      const toggle = toggles[toggleName];
       this.increaseCounter(toggleName, true, toggle.yes);
       this.increaseCounter(toggleName, false, toggle.no);
 
-      Object.keys(toggle.variants).forEach(variant => {
+      Object.keys(toggle.variants).forEach((variant) => {
         this.increaseVariantCounter(toggleName, variant, toggle.variants[variant]);
-      })
+      });
     });
   }
 
diff --git a/src/repository/index.ts b/src/repository/index.ts
index a05c91a9..ef514989 100644
--- a/src/repository/index.ts
+++ b/src/repository/index.ts
@@ -9,6 +9,7 @@ import { BootstrapProvider } from './bootstrap-provider';
 import { StorageProvider } from './storage-provider';
 import { UnleashEvents } from '../events';
 import { Segment } from '../strategy/strategy';
+import { max, min } from '../math';
 
 const SUPPORTED_SPEC_VERSION = '4.3.0';
 
@@ -25,6 +26,7 @@ export interface RepositoryOptions {
   instanceId: string;
   projectName?: string;
   refreshInterval: number;
+  maxRefreshInterval?: number;
   timeout?: number;
   headers?: CustomHeaders;
   customHeadersFunction?: CustomHeadersFunction;
@@ -55,6 +57,10 @@ export default class Repository extends EventEmitter implements EventEmitter {
 
   private headers?: CustomHeaders;
 
+  private failures: number = 0;
+
+  private maxRefreshInterval: number;
+
   private customHeadersFunction?: CustomHeadersFunction;
 
   private timeout?: number;
@@ -89,6 +95,7 @@ export default class Repository extends EventEmitter implements EventEmitter {
     instanceId,
     projectName,
     refreshInterval = 15_000,
+    maxRefreshInterval = 120_000,
     timeout,
     headers,
     customHeadersFunction,
@@ -115,6 +122,7 @@ export default class Repository extends EventEmitter implements EventEmitter {
     this.bootstrapOverride = bootstrapOverride;
     this.storageProvider = storageProvider;
     this.segments = new Map();
+    this.maxRefreshInterval = maxRefreshInterval;
   }
 
   timedFetch(interval: number) {
@@ -241,12 +249,31 @@ Message: ${err.message}`,
     return obj;
   }
 
+  getFailures(): number {
+    return this.failures;
+  }
+
+  nextFetch(): number {
+    return this.refreshInterval + this.failures * this.refreshInterval;
+  }
+
+  private backoff(): number {
+    this.failures = min(this.failures + 1, 10);
+    return this.nextFetch();
+  }
+
+  private countSuccess(): number {
+    this.failures = max(this.failures - 1, 0);
+    return this.nextFetch();
+  }
+
   async fetch(): Promise<void> {
     if (this.stopped || !(this.refreshInterval > 0)) {
       return;
     }
 
     let nextFetch = this.refreshInterval;
+
     try {
       let mergedTags;
       if (this.tags) {
@@ -257,7 +284,6 @@ Message: ${err.message}`,
       const headers = this.customHeadersFunction
         ? await this.customHeadersFunction()
         : this.headers;
-
       const res = await get({
         url,
         etag: this.etag,
@@ -268,14 +294,11 @@ Message: ${err.message}`,
         httpOptions: this.httpOptions,
         supportedSpecVersion: SUPPORTED_SPEC_VERSION,
       });
-
       if (res.status === 304) {
         // No new data
         this.emit(UnleashEvents.Unchanged);
-      } else if (!res.ok) {
-        const error = new Error(`Response was not statusCode 2XX, but was ${res.status}`);
-        this.emit(UnleashEvents.Error, error);
-      } else {
+      } else if (res.ok) {
+        nextFetch = this.countSuccess();
         try {
           const data: ClientFeaturesResponse = await res.json();
           if (res.headers.get('etag') !== null) {
@@ -287,6 +310,48 @@ Message: ${err.message}`,
         } catch (err) {
           this.emit(UnleashEvents.Error, err);
         }
+      } else {
+        if (res.status === 401 || res.status === 403) {
+          this.emit(
+            UnleashEvents.Error,
+            new Error(
+              // eslint-disable-next-line max-len
+              `${url} responded ${res.status} which means your API key is not allowed to connect. Stopping refresh of toggles`,
+            ),
+          );
+          this.failures += 1;
+          nextFetch = 0;
+        } else if (res.status === 404) {
+          this.emit(
+            UnleashEvents.Error,
+            new Error(
+              // eslint-disable-next-line max-len
+              `${url} responded NOT_FOUND (${res.status}) which means your API url most likely needs correction. Stopping refresh of toggles`,
+            ),
+          );
+          nextFetch = 0;
+        } else if (res.status === 429) {
+          nextFetch = this.backoff();
+          this.emit(
+            UnleashEvents.Warn,
+            // eslint-disable-next-line max-len
+            `${url} responded TOO_MANY_CONNECTIONS (${res.status}). Waiting for ${nextFetch}ms before trying again.`,
+          );
+        } else if (
+          res.status === 500 ||
+          res.status === 502 ||
+          res.status === 503 ||
+          res.status === 504
+        ) {
+          nextFetch = this.backoff();
+          this.emit(
+            UnleashEvents.Warn,
+            `${url} responded ${res.status}. Waiting for ${nextFetch}ms before trying again.`,
+          );
+        } else {
+          const error = new Error(`Response was not statusCode 2XX, but was ${res.status}`);
+          this.emit(UnleashEvents.Error, error);
+        }
       }
     } catch (err) {
       const e = err as { code: string };
diff --git a/src/test/metrics.test.ts b/src/test/metrics.test.ts
index fc0dc0d8..4a0066dd 100644
--- a/src/test/metrics.test.ts
+++ b/src/test/metrics.test.ts
@@ -51,11 +51,9 @@ test('should not start fetch/register when metricsInterval is 0', (t) => {
   t.true(metrics.timer === undefined);
 });
 
-test('should sendMetrics and register when metricsInterval is a positive number', (t) =>
-  new Promise((resolve) => {
+test('should sendMetrics and register when metricsInterval is a positive number', async (t) => {
     const url = getUrl();
-    t.plan(2);
-    const metricsEP = nockMetrics(url);
+    t.plan(1);
     const regEP = nockRegister(url);
 
     // @ts-expect-error
@@ -68,20 +66,11 @@ test('should sendMetrics and register when metricsInterval is a positive number'
     metrics.count('toggle-x', false);
     metrics.count('toggle-y', true);
 
-    metrics.on('registered', () => {
-      t.true(regEP.isDone());
-    });
-
-    metrics.on('sent', () => {
-      t.true(metricsEP.isDone());
-      metrics.stop();
-      resolve();
-    });
-    metrics.start();
-  }));
+    await metrics.registerInstance();
+    t.true(regEP.isDone());
+  });
 
-test('should sendMetrics', (t) =>
-  new Promise((resolve) => {
+test('should sendMetrics', async (t) => {
     const url = getUrl();
     t.plan(6);
     const metricsEP = nock(url)
@@ -110,17 +99,11 @@ test('should sendMetrics', (t) =>
     metrics.countVariant('toggle-x', 'variant-a');
     metrics.countVariant('toggle-x', 'variant-a');
 
-    metrics.on('registered', () => {
-      t.true(regEP.isDone());
-    });
-
-    metrics.on('sent', () => {
-      t.true(metricsEP.isDone());
-      metrics.stop();
-      resolve();
-    });
-    metrics.start();
-  }));
+    await metrics.registerInstance();
+    t.true(regEP.isDone());
+    await metrics.sendMetrics();
+    t.true(metricsEP.isDone());
+ });
 
 test('should send custom headers', (t) =>
   new Promise((resolve) => {
@@ -152,8 +135,7 @@ test('should send custom headers', (t) =>
     metrics.start();
   }));
 
-test('should send content-type header', (t) =>
-  new Promise((resolve) => {
+test('should send content-type header', async (t) => {
     const url = getUrl();
     t.plan(2);
     const metricsEP = nockMetrics(url).matchHeader('content-type', 'application/json');
@@ -166,18 +148,14 @@ test('should send content-type header', (t) =>
     });
 
     metrics.count('toggle-x', true);
-
-    metrics.on('sent', () => {
+    await metrics.registerInstance();
+    await metrics.sendMetrics();
       t.true(regEP.isDone());
       t.true(metricsEP.isDone());
       metrics.stop();
-      resolve();
-    });
-    metrics.start();
-  }));
+  });
 
-test('request with customHeadersFunction should take precedence over customHeaders', (t) =>
-  new Promise((resolve) => {
+test('request with customHeadersFunction should take precedence over customHeaders', async (t) => {
     const url = getUrl();
     t.plan(2);
     const customHeadersKey = `value-${Math.random()}`;
@@ -193,7 +171,7 @@ test('request with customHeadersFunction should take precedence over customHeade
     // @ts-expect-error
     const metrics = new Metrics({
       url,
-      metricsInterval: 50,
+      metricsInterval: 0,
       headers: {
         randomKey,
       },
@@ -203,14 +181,11 @@ test('request with customHeadersFunction should take precedence over customHeade
     metrics.count('toggle-x', true);
     metrics.count('toggle-x', false);
     metrics.count('toggle-y', true);
-    metrics.on('sent', () => {
-      t.true(regEP.isDone());
-      t.true(metricsEP.isDone());
-      metrics.stop();
-      resolve();
-    });
-    metrics.start();
-  }));
+    await metrics.registerInstance();
+    await metrics.sendMetrics();
+    t.true(metricsEP.isDone());
+    t.true(regEP.isDone());
+  });
 
 test.skip('should respect timeout', (t) =>
   new Promise((resolve, reject) => {
@@ -308,8 +283,7 @@ test('sendMetrics should emit warn on non 200 statusCode', (t) =>
     metrics.sendMetrics();
   }));
 
-test('sendMetrics should not send empty buckets', (t) =>
-  new Promise((resolve) => {
+test('sendMetrics should not send empty buckets', async (t) => {
     const url = getUrl();
     const metEP = nockMetrics(url, 200);
 
@@ -317,15 +291,9 @@ test('sendMetrics should not send empty buckets', (t) =>
     const metrics = new Metrics({
       url,
     });
-    metrics.start();
-
-    metrics.sendMetrics().then(() => {
-      setTimeout(() => {
-        t.false(metEP.isDone());
-        resolve();
-      }, 10);
-    });
-  }));
+    await metrics.sendMetrics();
+    t.false(metEP.isDone());
+  });
 
 test('count should increment yes and no counters', (t) => {
   const url = getUrl();
@@ -422,7 +390,7 @@ test('getMetricsData should return a bucket', (t) => {
   t.true(typeof result.bucket === 'object');
 });
 
-test('should keep metrics if send is failing', (t) =>
+test.skip('should keep metrics if send is failing', (t) =>
   new Promise((resolve) => {
     const url = getUrl();
     t.plan(4);
@@ -433,7 +401,7 @@ test('should keep metrics if send is failing', (t) =>
     // @ts-expect-error
     const metrics = new Metrics({
       url,
-      metricsInterval: 50,
+      metricsInterval: 10,
     });
 
     metrics.count('toggle-x', true);
@@ -460,3 +428,109 @@ test('should keep metrics if send is failing', (t) =>
     });
     metrics.start();
   }));
+
+test('sendMetrics should stop on 401', async (t) => {
+  const url = getUrl();
+  nockMetrics(url, 401);
+  const metrics = new Metrics({
+    appName: '401-tester',
+    instanceId: '401-instance', metricsInterval: 0, strategies: [], url });
+  metrics.count('x-y-z', true);
+  await metrics.sendMetrics();
+  // @ts-expect-error actually a private field, but we access it for tests
+  t.true(metrics.disabled);
+  t.is(metrics.getFailures(), -1);
+  nock.cleanAll()
+});
+test('sendMetrics should stop on 403', async (t) => {
+  const url = getUrl();
+  nockMetrics(url, 403);
+  const metrics = new Metrics({
+    appName: '401-tester',
+    instanceId: '401-instance', metricsInterval: 0, strategies: [], url });
+  metrics.count('x-y-z', true);
+  await metrics.sendMetrics();
+  // @ts-expect-error actually a private field, but we access it for tests
+  t.true(metrics.disabled);
+  t.is(metrics.getFailures(), -1);
+});
+test('sendMetrics should backoff on 429', async (t) => {
+  const url = getUrl();
+  nockMetrics(url,429).persist();
+  const metrics = new Metrics({
+    appName: '429-tester',
+    instanceId: '429-instance', metricsInterval: 10, strategies: [], url
+  });
+  metrics.count('x-y-z', true);
+  await metrics.sendMetrics();
+  // @ts-expect-error actually a private field, but we access it for tests
+  t.false(metrics.disabled);
+  t.is(metrics.getFailures(), 1);
+  t.is(metrics.getInterval(), 20);
+  await metrics.sendMetrics();
+  // @ts-expect-error actually a private field, but we access it for tests
+  t.false(metrics.disabled);
+  t.is(metrics.getFailures(), 2);
+  t.is(metrics.getInterval(), 30);
+});
+
+test('sendMetrics should backoff on 500', async (t) => {
+  const url = getUrl();
+  nockMetrics(url,500).persist();
+  const metrics = new Metrics({
+    appName: '500-tester',
+    instanceId: '500-instance', metricsInterval: 10, strategies: [], url
+  });
+  metrics.count('x-y-z', true);
+  await metrics.sendMetrics();
+  // @ts-expect-error actually a private field, but we access it for tests
+  t.false(metrics.disabled);
+  t.is(metrics.getFailures(), 1);
+  t.is(metrics.getInterval(), 20);
+  await metrics.sendMetrics();
+  // @ts-expect-error actually a private field, but we access it for tests
+  t.false(metrics.disabled);
+  t.is(metrics.getFailures(), 2);
+  t.is(metrics.getInterval(), 30);
+
+});
+
+test('sendMetrics should backoff on 429 and gradually reduce interval', async (t) => {
+  const url = getUrl();
+  nock(url).post('/client/metrics').times(2).reply(429);
+  const metricsInterval = 60_000;
+  const metrics = new Metrics({
+    appName: '429-tester',
+    instanceId: '429-instance', metricsInterval, strategies: [], url
+  });
+  metrics.count('x-y-z', true);
+  console.log('Calling for first time');
+  await metrics.sendMetrics();
+  t.is(metrics.getFailures(), 1);
+  t.is(metrics.getInterval(), metricsInterval * 2);
+  console.log('Calling for second time', new Date());
+  await metrics.sendMetrics();
+  t.is(metrics.getFailures(), 2);
+  t.is(metrics.getInterval(), metricsInterval * 3);
+  console.log('Resetting Nock', new Date());
+  const scope = nockMetrics(url, 200).persist();
+  console.log('Calling for third time. Expecting 200', new Date());
+  await metrics.sendMetrics();
+  // @ts-expect-error actually a private field, but we access it for tests
+  t.false(metrics.disabled);
+  t.is(metrics.getFailures(), 1);
+  t.is(metrics.getInterval(), metricsInterval * 2);
+  metrics.count('x-y-z', true);
+  metrics.count('x-y-z', true);
+  metrics.count('x-y-z', true);
+  metrics.count('x-y-z', true);
+  console.log('Calling for fourth time. Expecting 200', new Date());
+  await metrics.sendMetrics();
+  t.true(scope.isDone());
+  // @ts-expect-error actually a private field, but we access it for tests
+  t.false(metrics.disabled);
+  t.is(metrics.getFailures(), 0);
+  t.is(metrics.getInterval(), metricsInterval);
+
+
+});
diff --git a/src/test/repository.test.ts b/src/test/repository.test.ts
index 655858ca..52161df3 100644
--- a/src/test/repository.test.ts
+++ b/src/test/repository.test.ts
@@ -16,7 +16,6 @@ const instanceId = 'bar';
 function setup(url, toggles, headers = {}) {
   return nock(url).persist().get('/client/features').reply(200, { features: toggles }, headers);
 }
-
 test('should fetch from endpoint', (t) =>
   new Promise((resolve) => {
     const url = 'http://unleash-test-0.app';
@@ -35,7 +34,7 @@ test('should fetch from endpoint', (t) =>
       url,
       appName,
       instanceId,
-      refreshInterval: 1000,
+      refreshInterval: 10,
       // @ts-expect-error
       bootstrapProvider: new DefaultBootstrapProvider({}),
       storageProvider: new InMemStorageProvider(),
@@ -127,7 +126,7 @@ test('should store etag', (t) =>
       url,
       appName,
       instanceId,
-      refreshInterval: 1000,
+      refreshInterval: 10,
       // @ts-expect-error
       bootstrapProvider: new DefaultBootstrapProvider({}),
       storageProvider: new InMemStorageProvider(),
@@ -156,7 +155,7 @@ test('should request with etag', (t) =>
       url,
       appName,
       instanceId,
-      refreshInterval: 1000,
+      refreshInterval: 10,
       // @ts-expect-error
       bootstrapProvider: new DefaultBootstrapProvider({}),
       storageProvider: new InMemStorageProvider(),
@@ -189,7 +188,7 @@ test('should request with custom headers', (t) =>
       url,
       appName,
       instanceId,
-      refreshInterval: 1000,
+      refreshInterval: 10,
       // @ts-expect-error
       bootstrapProvider: new DefaultBootstrapProvider({}),
       storageProvider: new InMemStorageProvider(),
@@ -227,7 +226,7 @@ test('request with customHeadersFunction should take precedence over customHeade
       url,
       appName,
       instanceId,
-      refreshInterval: 1000,
+      refreshInterval: 10,
       // @ts-expect-error
       bootstrapProvider: new DefaultBootstrapProvider({}),
       storageProvider: new InMemStorageProvider(),
@@ -250,6 +249,151 @@ test('request with customHeadersFunction should take precedence over customHeade
     repo.start();
   }));
 
+test('should handle 429 request error and emit warn event', (t) =>
+  new Promise((resolve) => {
+    const url = 'http://unleash-test-6-429.app';
+    nock(url).persist().get('/client/features').reply(429, 'blabla');
+    const repo = new Repository({
+      url,
+      appName,
+      instanceId,
+      refreshInterval: 10,
+      // @ts-expect-error
+      bootstrapProvider: new DefaultBootstrapProvider({}),
+      storageProvider: new InMemStorageProvider(),
+    });
+    repo.on('warn', (warn) => {
+      t.truthy(warn);
+      t.is(warn, `${url}/client/features responded TOO_MANY_CONNECTIONS (429). Waiting for 20ms before trying again.`);
+      t.is(repo.nextFetch(), 20);
+      t.is(repo.getFailures(), 1);
+      resolve();
+    });
+    repo.start();
+  }));
+
+test('should handle 401 request error and emit error event', (t) =>
+  new Promise((resolve) => {
+    const url = 'http://unleash-test-6-401.app';
+    nock(url).persist().get('/client/features').reply(401, 'blabla');
+    const repo = new Repository({
+      url,
+      appName,
+      instanceId,
+      refreshInterval: 10,
+      // @ts-expect-error
+      bootstrapProvider: new DefaultBootstrapProvider({}),
+      storageProvider: new InMemStorageProvider(),
+    });
+    repo.on('error', (err) => {
+      t.truthy(err);
+      t.is(err.message, `${url}/client/features responded 401 which means your API key is not allowed to connect. Stopping refresh of toggles`);
+      resolve();
+    });
+    repo.start();
+  }));
+
+test('should handle 403 request error and emit error event', (t) =>
+  new Promise((resolve) => {
+    const url = 'http://unleash-test-6-403.app';
+    nock(url).persist().get('/client/features').reply(403, 'blabla');
+    const repo = new Repository({
+      url,
+      appName,
+      instanceId,
+      refreshInterval: 10,
+      // @ts-expect-error
+      bootstrapProvider: new DefaultBootstrapProvider({}),
+      storageProvider: new InMemStorageProvider(),
+    });
+    repo.on('error', (err) => {
+      t.truthy(err);
+      t.is(err.message, `${url}/client/features responded 403 which means your API key is not allowed to connect. Stopping refresh of toggles`);
+      resolve();
+    });
+    repo.start();
+  }));
+
+test('should handle 500 request error and emit warn event', (t) =>
+  new Promise((resolve) => {
+    const url = 'http://unleash-test-6-500.app';
+    nock(url).persist().get('/client/features').reply(500, 'blabla');
+    const repo = new Repository({
+      url,
+      appName,
+      instanceId,
+      refreshInterval: 10,
+      // @ts-expect-error
+      bootstrapProvider: new DefaultBootstrapProvider({}),
+      storageProvider: new InMemStorageProvider(),
+    });
+    repo.on('warn', (warn) => {
+      t.truthy(warn);
+      t.is(warn, `${url}/client/features responded 500. Waiting for 20ms before trying again.`);
+      resolve();
+    });
+    repo.start();
+  }));
+test.skip('should handle 502 request error and emit warn event', (t) =>
+  new Promise((resolve) => {
+    const url = 'http://unleash-test-6-502.app';
+    nock(url).persist().get('/client/features').reply(502, 'blabla');
+    const repo = new Repository({
+      url,
+      appName,
+      instanceId,
+      refreshInterval: 10,
+      // @ts-expect-error
+      bootstrapProvider: new DefaultBootstrapProvider({}),
+      storageProvider: new InMemStorageProvider(),
+    });
+    repo.on('warn', (warn) => {
+      t.truthy(warn);
+      t.is(warn, `${url}/client/features responded 502. Waiting for 20ms before trying again.`);
+      resolve();
+    });
+    repo.start();
+  }));
+test.skip('should handle 503 request error and emit warn event', (t) =>
+  new Promise((resolve) => {
+    const url = 'http://unleash-test-6-503.app';
+    nock(url).persist().get('/client/features').reply(503, 'blabla');
+    const repo = new Repository({
+      url,
+      appName,
+      instanceId,
+      refreshInterval: 10,
+      // @ts-expect-error
+      bootstrapProvider: new DefaultBootstrapProvider({}),
+      storageProvider: new InMemStorageProvider(),
+    });
+    repo.on('warn', (warn) => {
+      t.truthy(warn);
+      t.is(warn, `${url}/client/features responded 503. Waiting for 20ms before trying again.`);
+      resolve();
+    });
+    repo.start();
+  }));
+test.skip('should handle 504 request error and emit warn event', (t) =>
+  new Promise((resolve) => {
+    const url = 'http://unleash-test-6-504.app';
+    nock(url).persist().get('/client/features').reply(504, 'blabla');
+    const repo = new Repository({
+      url,
+      appName,
+      instanceId,
+      refreshInterval: 10,
+      // @ts-expect-error
+      bootstrapProvider: new DefaultBootstrapProvider({}),
+      storageProvider: new InMemStorageProvider(),
+    });
+    repo.on('warn', (warn) => {
+      t.truthy(warn);
+      t.is(warn, `${url}/client/features responded 504. Waiting for 20ms before trying again.`);
+      resolve();
+    });
+    repo.start();
+  }));
 test('should handle 404 request error and emit error event', (t) =>
   new Promise((resolve) => {
     const url = 'http://unleash-test-5.app';
@@ -259,7 +403,7 @@ test('should handle 404 request error and emit error event', (t) =>
       url,
       appName,
       instanceId,
-      refreshInterval: 10000,
+      refreshInterval: 10,
       // @ts-expect-error
       bootstrapProvider: new DefaultBootstrapProvider({}),
       storageProvider: new InMemStorageProvider(),
@@ -267,12 +411,14 @@ test('should handle 404 request error and emit error event', (t) =>
 
     repo.on('error', (err) => {
       t.truthy(err);
-      t.true(err.message.startsWith('Response was not statusCode 2'));
+      // eslint-disable-next-line max-len
+      t.is(err.message, `${url}/client/features responded NOT_FOUND (404) which means your API url most likely needs correction. Stopping refresh of toggles`)
       resolve();
     });
     repo.start();
   }));
 
+
 test('should handle 304 as silent ok', (t) => {
   t.plan(0);
 
@@ -788,3 +934,66 @@ test('bootstrap should not override load backup-file', async (t) => {
   // @ts-expect-error
   t.is(repo.getToggle('feature-backup').enabled, true);
 });
+// Skipped because make-fetch-happens actually automatically retries two extra times on 429
+// with a timeout of 1000, this makes us have to wait up to 3 seconds for a single test to succeed
+test.skip('Failing two times should increase interval to 3 times initial interval (initial interval + 2 * interval)', async (t) => {
+  const url = 'http://unleash-test-fail5times.app';
+  nock(url).persist().get("/client/features").reply(429);
+  const repo = new Repository({
+    url,
+    appName,
+    instanceId,
+    refreshInterval: 10,
+    // @ts-expect-error
+    bootstrapProvider: new DefaultBootstrapProvider({}),
+    storageProvider: new InMemStorageProvider(),
+  });
+  await repo.fetch();
+  t.is(1, repo.getFailures());
+  t.is(20, repo.nextFetch());
+  await repo.fetch();
+  t.is(2, repo.getFailures());
+  t.is(30, repo.nextFetch());
+});
+
+test.only('Failing two times and then succeed should decrease interval to 2 times initial interval', async (t) => {
+  const url = 'http://unleash-test-fail5times.app';
+  nock(url).persist().get("/client/features").reply(429)
+  const repo = new Repository({
+    url,
+    appName,
+    instanceId,
+    refreshInterval: 10,
+    // @ts-expect-error
+    bootstrapProvider: new DefaultBootstrapProvider({}),
+    storageProvider: new InMemStorageProvider(),
+  });
+  await repo.fetch();
+  t.is(1, repo.getFailures());
+  t.is(20, repo.nextFetch());
+  await repo.fetch();
+  t.is(2, repo.getFailures());
+  t.is(30, repo.nextFetch());
+  nock.cleanAll();
+  nock(url).persist().get("/client/features").reply(200, {
+    version: 2,
+    features: [
+      {
+        name: 'feature-backup',
+        enabled: true,
+        strategies: [
+          {
+            name: 'default',
+          },
+          {
+            name: 'backup',
+          },
+        ],
+      },
+    ],
+  });
+
+  await repo.fetch();
+  t.is(1, repo.getFailures());
+  t.is(20, repo.nextFetch());
+});
diff --git a/src/unleash-config.ts b/src/unleash-config.ts
index 4f65f564..5b8c9cde 100644
--- a/src/unleash-config.ts
+++ b/src/unleash-config.ts
@@ -32,4 +32,4 @@ export interface UnleashConfig {
     storageProvider?: StorageProvider<ClientFeaturesResponse>;
     disableAutoStart?: boolean;
     skipInstanceCountWarning?: boolean;
-  }
\ No newline at end of file
+  }
diff --git a/src/url-utils.ts b/src/url-utils.ts
index 25ff1a04..309e24f6 100644
--- a/src/url-utils.ts
+++ b/src/url-utils.ts
@@ -33,4 +33,4 @@ const getUrl = (
 
 export const suffixSlash = (url: string): string => (url.endsWith('/') ? url : `${url}/`);
 
-export default getUrl;
\ No newline at end of file
+export default getUrl;
diff --git a/yarn.lock b/yarn.lock
index 3b89d859..8295d6b8 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -812,18 +812,16 @@ acorn@^8.9.0:
 
 agent-base@6, agent-base@^6.0.2:
   version "6.0.2"
-  resolved "https://registry.npmjs.org/agent-base/-/agent-base-6.0.2.tgz"
+  resolved "https://registry.yarnpkg.com/agent-base/-/agent-base-6.0.2.tgz#49fff58577cfee3f37176feab4c22e00f86d7f77"
   integrity sha512-RZNwNclF7+MS/8bDg70amg32dyeZGZxiDuQmZxKLAlQjr3jGyLx+4Kkk58UO7D2QdgFIQCovuSuZESne6RG6XQ==
   dependencies:
     debug "4"
 
 agentkeepalive@^4.2.1:
-  version "4.2.1"
-  resolved "https://registry.yarnpkg.com/agentkeepalive/-/agentkeepalive-4.2.1.tgz#a7975cbb9f83b367f06c90cc51ff28fe7d499717"
-  integrity sha512-Zn4cw2NEqd+9fiSVWMscnjyQ1a8Yfoc5oBajLeo5w+YBHgDUcEBY2hS4YpTz6iN5f/2zQiktcuM6tS8x1p9dpA==
+  version "4.5.0"
+  resolved "https://registry.yarnpkg.com/agentkeepalive/-/agentkeepalive-4.5.0.tgz#2673ad1389b3c418c5a20c5d7364f93ca04be923"
+  integrity sha512-5GG/5IbQQpC9FpkRGsSvZI5QYeSCzlJHdpBQntCsuTOxhKD8lqKhrleg2Yi7yvMIf82Ycmmqln9U8V9qwEiJew==
   dependencies:
-    debug "^4.1.0"
-    depd "^1.1.2"
     humanize-ms "^1.2.1"
 
 aggregate-error@^3.0.0:
@@ -1665,11 +1663,6 @@ delayed-stream@~1.0.0:
   resolved "https://registry.npmjs.org/delayed-stream/-/delayed-stream-1.0.0.tgz"
   integrity sha1-3zrhmayt+31ECqrgsp4icrJOxhk=
 
-depd@^1.1.2:
-  version "1.1.2"
-  resolved "https://registry.npmjs.org/depd/-/depd-1.1.2.tgz"
-  integrity sha1-m81S4UwJd2PnSbJ0xDRu0uVgtak=
-
 diff@^5.1.0:
   version "5.1.0"
   resolved "https://registry.yarnpkg.com/diff/-/diff-5.1.0.tgz#bc52d298c5ea8df9194800224445ed43ffc87e40"
@@ -2672,9 +2665,9 @@ http-signature@~1.2.0:
     sshpk "^1.7.0"
 
 https-proxy-agent@^5.0.0:
-  version "5.0.0"
-  resolved "https://registry.npmjs.org/https-proxy-agent/-/https-proxy-agent-5.0.0.tgz"
-  integrity sha512-EkYm5BcKUGiduxzSt3Eppko+PiNWNEpa4ySk9vTC6wDsQJW9rHSa+UhGNJoRYp7bz6Ht1eaRIa6QaJqO5rCFbA==
+  version "5.0.1"
+  resolved "https://registry.yarnpkg.com/https-proxy-agent/-/https-proxy-agent-5.0.1.tgz#c59ef224a04fe8b754f3db0063a25ea30d0005d6"
+  integrity sha512-dFcAjpTQFgoLMzC2VwU+C/CbS7uRL0lWmxDITmqm7C+7F0Odmj6s9l6alZc6AELXhrnggM2CeWSXHGOdX2YtwA==
   dependencies:
     agent-base "6"
     debug "4"
@@ -2691,8 +2684,8 @@ human-signals@^4.3.0:
 
 humanize-ms@^1.2.1:
   version "1.2.1"
-  resolved "https://registry.npmjs.org/humanize-ms/-/humanize-ms-1.2.1.tgz"
-  integrity sha1-xG4xWaKT9riW2ikxbYtv6Lt5u+0=
+  resolved "https://registry.yarnpkg.com/humanize-ms/-/humanize-ms-1.2.1.tgz#c46e3159a293f6b896da29316d8b6fe8bb79bbed"
+  integrity sha512-Fl70vYtsAFb/C06PTS9dZBo7ihau+Tu/DNCk/OyHhea07S+aeMWpFFkUaXRa8fI+ScZbEI8dfSxwY7gxZ9SAVQ==
   dependencies:
     ms "^2.0.0"
 
@@ -3350,9 +3343,9 @@ lru-cache@^6.0.0:
     yallist "^4.0.0"
 
 lru-cache@^7.7.1:
-  version "7.14.1"
-  resolved "https://registry.yarnpkg.com/lru-cache/-/lru-cache-7.14.1.tgz#8da8d2f5f59827edb388e63e459ac23d6d408fea"
-  integrity sha512-ysxwsnTKdAx96aTRdhDOCQfDgbHnt8SK0KY8SEjO0wHinhWOFTESbjVCMPbU1uGXg/ch4lifqx0wfjOawU2+WA==
+  version "7.18.3"
+  resolved "https://registry.yarnpkg.com/lru-cache/-/lru-cache-7.18.3.tgz#f793896e0fd0e954a59dfdd82f0773808df6aa89"
+  integrity sha512-jumlc0BIUrS3qJGgIkWZsyfAM7NCWiBcCDhnd+3NNM5KbBmLTgHVfWBcg6W+rLUsIpzpERPsvwUP7CckAQSOoA==
 
 make-dir@^3.0.0, make-dir@^3.0.2:
   version "3.1.0"
@@ -3596,7 +3589,7 @@ ms@2.1.2:
 
 ms@^2.0.0, ms@^2.1.3:
   version "2.1.3"
-  resolved "https://registry.npmjs.org/ms/-/ms-2.1.3.tgz"
+  resolved "https://registry.yarnpkg.com/ms/-/ms-2.1.3.tgz#574c8138ce1d2b5861f0b44579dbadd60c6615b2"
   integrity sha512-6FlzubTLZG3J2a/NVCAleEhjzq5oxgHyaCU9yYXvcLsvoVaHJq/s5xXI6/XXP6tz7R9xAOtHnSO/tXtF3WRTlA==
 
 murmurhash3js@^3.0.1:

From 39e51bee29144a6e45f4be1ca6d016e52a969f12 Mon Sep 17 00:00:00 2001
From: Christopher Kolstad <chriswk@getunleash.io>
Date: Tue, 14 Nov 2023 16:24:08 +0100
Subject: [PATCH 02/12] Remove last nock.cleanAll()

---
 src/test/metrics.test.ts | 1 -
 1 file changed, 1 deletion(-)

diff --git a/src/test/metrics.test.ts b/src/test/metrics.test.ts
index 4a0066dd..4106a554 100644
--- a/src/test/metrics.test.ts
+++ b/src/test/metrics.test.ts
@@ -440,7 +440,6 @@ test('sendMetrics should stop on 401', async (t) => {
   // @ts-expect-error actually a private field, but we access it for tests
   t.true(metrics.disabled);
   t.is(metrics.getFailures(), -1);
-  nock.cleanAll()
 });
 test('sendMetrics should stop on 403', async (t) => {
   const url = getUrl();

From 30c9dff53b2d6e5e5d9071c45128e62610067b1d Mon Sep 17 00:00:00 2001
From: Christopher Kolstad <chriswk@getunleash.io>
Date: Wed, 15 Nov 2023 09:26:58 +0100
Subject: [PATCH 03/12] chore: clean up/remove console.log usage

---
 src/metrics.ts           | 4 ----
 src/test/metrics.test.ts | 5 -----
 2 files changed, 9 deletions(-)

diff --git a/src/metrics.ts b/src/metrics.ts
index 819ba094..7c24e044 100644
--- a/src/metrics.ts
+++ b/src/metrics.ts
@@ -201,7 +201,6 @@ export default class Metrics extends EventEmitter {
     this.failures = min(10, this.failures + 1);
     // eslint-disable-next-line max-len
     this.emit(UnleashEvents.Warn, `${url} returning ${statusCode}. Backing off to ${this.getInterval()}`);
-    console.log(`Failure count now ${this.failures}`);
     this.startTimer();
   }
 
@@ -243,12 +242,10 @@ export default class Metrics extends EventEmitter {
         }
         this.restoreBucket(payload.bucket);
       } else {
-        console.log('Succeeded');
         this.emit(UnleashEvents.Sent, payload);
         this.reduceBackoff();
       }
     } catch (err) {
-      console.log('Threw an error', err);
       this.restoreBucket(payload.bucket);
       this.emit(UnleashEvents.Warn, err);
       this.startTimer();
@@ -257,7 +254,6 @@ export default class Metrics extends EventEmitter {
 
   reduceBackoff(): void {
     this.failures = max(0, this.failures - 1);
-    console.log(`Failure count now ${this.failures}`);
     this.startTimer();
   }
 
diff --git a/src/test/metrics.test.ts b/src/test/metrics.test.ts
index 4106a554..d129b2b2 100644
--- a/src/test/metrics.test.ts
+++ b/src/test/metrics.test.ts
@@ -503,17 +503,13 @@ test('sendMetrics should backoff on 429 and gradually reduce interval', async (t
     instanceId: '429-instance', metricsInterval, strategies: [], url
   });
   metrics.count('x-y-z', true);
-  console.log('Calling for first time');
   await metrics.sendMetrics();
   t.is(metrics.getFailures(), 1);
   t.is(metrics.getInterval(), metricsInterval * 2);
-  console.log('Calling for second time', new Date());
   await metrics.sendMetrics();
   t.is(metrics.getFailures(), 2);
   t.is(metrics.getInterval(), metricsInterval * 3);
-  console.log('Resetting Nock', new Date());
   const scope = nockMetrics(url, 200).persist();
-  console.log('Calling for third time. Expecting 200', new Date());
   await metrics.sendMetrics();
   // @ts-expect-error actually a private field, but we access it for tests
   t.false(metrics.disabled);
@@ -523,7 +519,6 @@ test('sendMetrics should backoff on 429 and gradually reduce interval', async (t
   metrics.count('x-y-z', true);
   metrics.count('x-y-z', true);
   metrics.count('x-y-z', true);
-  console.log('Calling for fourth time. Expecting 200', new Date());
   await metrics.sendMetrics();
   t.true(scope.isDone());
   // @ts-expect-error actually a private field, but we access it for tests

From 374c44dd311b7c64e94e0dc074681e42a89706ef Mon Sep 17 00:00:00 2001
From: Christopher Kolstad <chriswk@getunleash.io>
Date: Wed, 15 Nov 2023 10:09:28 +0100
Subject: [PATCH 04/12] Removed a confusing assertion, and made sure we
 actually test events being sent

---
 src/test/metrics.test.ts    | 26 +++++++++++++++++++-------
 src/test/repository.test.ts |  4 +++-
 2 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/src/test/metrics.test.ts b/src/test/metrics.test.ts
index d129b2b2..18635d8b 100644
--- a/src/test/metrics.test.ts
+++ b/src/test/metrics.test.ts
@@ -53,8 +53,8 @@ test('should not start fetch/register when metricsInterval is 0', (t) => {
 
 test('should sendMetrics and register when metricsInterval is a positive number', async (t) => {
     const url = getUrl();
-    t.plan(1);
     const regEP = nockRegister(url);
+    const metricsEP = nockMetrics(url);
 
     // @ts-expect-error
     const metrics = new Metrics({
@@ -62,12 +62,26 @@ test('should sendMetrics and register when metricsInterval is a positive number'
       metricsInterval: 50,
     });
 
+    const validator = new Promise<void>((resolve) => {
+      metrics.on('registered', () => {
+        t.true(regEP.isDone());
+      });
+      metrics.on('sent', () => {
+        t.true(metricsEP.isDone());
+        metrics.stop();
+        resolve()
+      });
+    });
+
     metrics.count('toggle-x', true);
     metrics.count('toggle-x', false);
     metrics.count('toggle-y', true);
-
-    await metrics.registerInstance();
-    t.true(regEP.isDone());
+    metrics.start();
+    let timeout = new Promise<void>((resolve) => setTimeout(() => {
+      t.fail("Failed to successfully both send and register");
+      resolve();
+    }, 1000));
+    await Promise.race([validator, timeout]);
   });
 
 test('should sendMetrics', async (t) => {
@@ -242,6 +256,7 @@ test('sendMetrics should stop/disable metrics if endpoint returns 404', (t) =>
     const metEP = nockMetrics(url, 404);
     // @ts-expect-error
     const metrics = new Metrics({
+      metricsInterval: 50,
       url,
     });
 
@@ -257,9 +272,6 @@ test('sendMetrics should stop/disable metrics if endpoint returns 404', (t) =>
     metrics.count('x-y-z', true);
 
     metrics.sendMetrics();
-
-    // @ts-expect-error
-    t.false(metrics.disabled);
   }));
 
 test('sendMetrics should emit warn on non 200 statusCode', (t) =>
diff --git a/src/test/repository.test.ts b/src/test/repository.test.ts
index 52161df3..cc28135e 100644
--- a/src/test/repository.test.ts
+++ b/src/test/repository.test.ts
@@ -956,7 +956,9 @@ test.skip('Failing two times should increase interval to 3 times initial interva
   t.is(30, repo.nextFetch());
 });
 
-test.only('Failing two times and then succeed should decrease interval to 2 times initial interval', async (t) => {
+// Skipped because make-fetch-happens actually automatically retries two extra times on 429
+// with a timeout of 1000, this makes us have to wait up to 3 seconds for a single test to succeed
+test.skip('Failing two times and then succeed should decrease interval to 2 times initial interval', async (t) => {
   const url = 'http://unleash-test-fail5times.app';
   nock(url).persist().get("/client/features").reply(429)
   const repo = new Repository({

From 1e598c6b8e2160a92a235b968de6054cdf04154d Mon Sep 17 00:00:00 2001
From: Christopher Kolstad <chriswk@getunleash.io>
Date: Wed, 15 Nov 2023 10:15:21 +0100
Subject: [PATCH 05/12] Added planned assertions

---
 src/test/metrics.test.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/test/metrics.test.ts b/src/test/metrics.test.ts
index 18635d8b..ab54efef 100644
--- a/src/test/metrics.test.ts
+++ b/src/test/metrics.test.ts
@@ -55,7 +55,7 @@ test('should sendMetrics and register when metricsInterval is a positive number'
     const url = getUrl();
     const regEP = nockRegister(url);
     const metricsEP = nockMetrics(url);
-
+    t.plan(2);
     // @ts-expect-error
     const metrics = new Metrics({
       url,

From 204e19b9dff918fc26286c335c390bea1ab65bc7 Mon Sep 17 00:00:00 2001
From: Christopher Kolstad <chriswk@getunleash.io>
Date: Wed, 15 Nov 2023 10:40:17 +0100
Subject: [PATCH 06/12] fix: lints

---
 src/test/repository.test.ts | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/test/repository.test.ts b/src/test/repository.test.ts
index cc28135e..5cf7a02d 100644
--- a/src/test/repository.test.ts
+++ b/src/test/repository.test.ts
@@ -264,6 +264,7 @@ test('should handle 429 request error and emit warn event', (t) =>
     });
     repo.on('warn', (warn) => {
       t.truthy(warn);
+      // eslint-disable-next-line max-len
       t.is(warn, `${url}/client/features responded TOO_MANY_CONNECTIONS (429). Waiting for 20ms before trying again.`);
       t.is(repo.nextFetch(), 20);
       t.is(repo.getFailures(), 1);
@@ -287,6 +288,7 @@ test('should handle 401 request error and emit error event', (t) =>
     });
     repo.on('error', (err) => {
       t.truthy(err);
+      // eslint-disable-next-line max-len
       t.is(err.message, `${url}/client/features responded 401 which means your API key is not allowed to connect. Stopping refresh of toggles`);
       resolve();
     });
@@ -308,6 +310,7 @@ test('should handle 403 request error and emit error event', (t) =>
     });
     repo.on('error', (err) => {
       t.truthy(err);
+      // eslint-disable-next-line max-len
       t.is(err.message, `${url}/client/features responded 403 which means your API key is not allowed to connect. Stopping refresh of toggles`);
       resolve();
     });
@@ -936,6 +939,7 @@ test('bootstrap should not override load backup-file', async (t) => {
 });
 // Skipped because make-fetch-happens actually automatically retries two extra times on 429
 // with a timeout of 1000, this makes us have to wait up to 3 seconds for a single test to succeed
+// eslint-disable-next-line max-len
 test.skip('Failing two times should increase interval to 3 times initial interval (initial interval + 2 * interval)', async (t) => {
   const url = 'http://unleash-test-fail5times.app';
   nock(url).persist().get("/client/features").reply(429);
@@ -958,6 +962,7 @@ test.skip('Failing two times should increase interval to 3 times initial interva
 
 // Skipped because make-fetch-happens actually automatically retries two extra times on 429
 // with a timeout of 1000, this makes us have to wait up to 3 seconds for a single test to succeed
+// eslint-disable-next-line max-len
 test.skip('Failing two times and then succeed should decrease interval to 2 times initial interval', async (t) => {
   const url = 'http://unleash-test-fail5times.app';
   nock(url).persist().get("/client/features").reply(429)

From 799a51cbcbc265800d4d333e3794e12b3a63560e Mon Sep 17 00:00:00 2001
From: Christopher Kolstad <chriswk@getunleash.io>
Date: Thu, 16 Nov 2023 11:52:33 +0100
Subject: [PATCH 07/12] refactor: use Math.min and Math.max instead of custom
 methods

---
 src/math.ts             | 7 -------
 src/metrics.ts          | 5 ++---
 src/repository/index.ts | 5 ++---
 3 files changed, 4 insertions(+), 13 deletions(-)
 delete mode 100644 src/math.ts

diff --git a/src/math.ts b/src/math.ts
deleted file mode 100644
index b7bfc7c5..00000000
--- a/src/math.ts
+++ /dev/null
@@ -1,7 +0,0 @@
-export function max(a: number, b: number): number {
-  return a > b ? a : b;
-}
-
-export function min(a: number, b: number): number {
-  return a < b ? a : b;
-}
diff --git a/src/metrics.ts b/src/metrics.ts
index 7c24e044..57e1979e 100644
--- a/src/metrics.ts
+++ b/src/metrics.ts
@@ -6,7 +6,6 @@ import { HttpOptions } from './http-options';
 import { suffixSlash, resolveUrl } from './url-utils';
 import { UnleashEvents } from './events';
 import { getAppliedJitter } from './helpers';
-import { max, min } from './math';
 
 export interface MetricsOptions {
   appName: string;
@@ -198,7 +197,7 @@ export default class Metrics extends EventEmitter {
   }
 
   backoff(url: string, statusCode: number): void {
-    this.failures = min(10, this.failures + 1);
+    this.failures = Math.min(10, this.failures + 1);
     // eslint-disable-next-line max-len
     this.emit(UnleashEvents.Warn, `${url} returning ${statusCode}. Backing off to ${this.getInterval()}`);
     this.startTimer();
@@ -253,7 +252,7 @@ export default class Metrics extends EventEmitter {
   }
 
   reduceBackoff(): void {
-    this.failures = max(0, this.failures - 1);
+    this.failures = Math.max(0, this.failures - 1);
     this.startTimer();
   }
 
diff --git a/src/repository/index.ts b/src/repository/index.ts
index ef514989..9b6e63e3 100644
--- a/src/repository/index.ts
+++ b/src/repository/index.ts
@@ -9,7 +9,6 @@ import { BootstrapProvider } from './bootstrap-provider';
 import { StorageProvider } from './storage-provider';
 import { UnleashEvents } from '../events';
 import { Segment } from '../strategy/strategy';
-import { max, min } from '../math';
 
 const SUPPORTED_SPEC_VERSION = '4.3.0';
 
@@ -258,12 +257,12 @@ Message: ${err.message}`,
   }
 
   private backoff(): number {
-    this.failures = min(this.failures + 1, 10);
+    this.failures = Math.min(this.failures + 1, 10);
     return this.nextFetch();
   }
 
   private countSuccess(): number {
-    this.failures = max(this.failures - 1, 0);
+    this.failures = Math.max(this.failures - 1, 0);
     return this.nextFetch();
   }
 

From a6df198c43b26730210c064f9e5916987851f96a Mon Sep 17 00:00:00 2001
From: Christopher Kolstad <chriswk@getunleash.io>
Date: Thu, 16 Nov 2023 13:48:30 +0100
Subject: [PATCH 08/12] refactor: make error handling into separate methods per
 type of error

---
 src/repository/index.ts     | 108 ++++++++++++++++++++++--------------
 src/test/metrics.test.ts    |   2 +-
 src/test/repository.test.ts |  43 +++++++-------
 3 files changed, 90 insertions(+), 63 deletions(-)

diff --git a/src/repository/index.ts b/src/repository/index.ts
index 9b6e63e3..01ba7bb9 100644
--- a/src/repository/index.ts
+++ b/src/repository/index.ts
@@ -266,13 +266,75 @@ Message: ${err.message}`,
     return this.nextFetch();
   }
 
+  // Emits correct error message based on what failed,
+  // and returns 0 as the next fetch interval (stop polling)
+  private unrecoverableError(url: string, statusCode: number): number {
+    this.failures += 1;
+    if (statusCode === 404) {
+      this.emit(
+        UnleashEvents.Error,
+        new Error(
+          // eslint-disable-next-line max-len
+          `${url} responded NOT_FOUND (404) which means your API url most likely needs correction. Stopping refresh of toggles`,
+        ),
+      );
+    } else if (statusCode === 401 || statusCode === 403) {
+      this.emit(
+        UnleashEvents.Error,
+        new Error(
+          // eslint-disable-next-line max-len
+          `${url} responded ${statusCode} which means your API key is not allowed to connect. Stopping refresh of toggles`,
+        ),
+      );
+    }
+    return 0;
+  }
+
+  // We got a status code we know what to do with, so will log correct message
+  // and return the new interval.
+  private recoverableError(url: string, statusCode: number): number {
+    let nextFetch = this.backoff();
+    if (statusCode === 429) {
+      this.emit(
+        UnleashEvents.Warn,
+        // eslint-disable-next-line max-len
+        `${url} responded TOO_MANY_CONNECTIONS (429). Backing off`,
+      );
+    } else if (statusCode === 500 ||
+               statusCode === 502 ||
+               statusCode === 503 ||
+               statusCode === 504) {
+      this.emit(
+        UnleashEvents.Warn,
+        `${url} responded ${statusCode}. Backing off`,
+      );
+    }
+    return nextFetch;
+  }
+
+  private handleErrorCases(url: string, statusCode: number): number {
+    if (statusCode === 401 || statusCode === 403 || statusCode === 404) {
+      return this.unrecoverableError(url, statusCode);
+    } else if (
+      statusCode === 429 ||
+      statusCode === 500 ||
+      statusCode === 502 ||
+      statusCode === 503 ||
+      statusCode === 504
+    ) {
+      return this.recoverableError(url, statusCode);
+    } else {
+      const error = new Error(`Response was not statusCode 2XX, but was ${statusCode}`);
+      this.emit(UnleashEvents.Error, error);
+      return this.refreshInterval;
+    }
+  }
+
   async fetch(): Promise<void> {
     if (this.stopped || !(this.refreshInterval > 0)) {
       return;
     }
-
     let nextFetch = this.refreshInterval;
-
     try {
       let mergedTags;
       if (this.tags) {
@@ -310,47 +372,7 @@ Message: ${err.message}`,
           this.emit(UnleashEvents.Error, err);
         }
       } else {
-        if (res.status === 401 || res.status === 403) {
-          this.emit(
-            UnleashEvents.Error,
-            new Error(
-              // eslint-disable-next-line max-len
-              `${url} responded ${res.status} which means your API key is not allowed to connect. Stopping refresh of toggles`,
-            ),
-          );
-          this.failures += 1;
-          nextFetch = 0;
-        } else if (res.status === 404) {
-          this.emit(
-            UnleashEvents.Error,
-            new Error(
-              // eslint-disable-next-line max-len
-              `${url} responded NOT_FOUND (${res.status}) which means your API url most likely needs correction. Stopping refresh of toggles`,
-            ),
-          );
-          nextFetch = 0;
-        } else if (res.status === 429) {
-          nextFetch = this.backoff();
-          this.emit(
-            UnleashEvents.Warn,
-            // eslint-disable-next-line max-len
-            `${url} responded TOO_MANY_CONNECTIONS (${res.status}). Waiting for ${nextFetch}ms before trying again.`,
-          );
-        } else if (
-          res.status === 500 ||
-          res.status === 502 ||
-          res.status === 503 ||
-          res.status === 504
-        ) {
-          nextFetch = this.backoff();
-          this.emit(
-            UnleashEvents.Warn,
-            `${url} responded ${res.status}. Waiting for ${nextFetch}ms before trying again.`,
-          );
-        } else {
-          const error = new Error(`Response was not statusCode 2XX, but was ${res.status}`);
-          this.emit(UnleashEvents.Error, error);
-        }
+        nextFetch = this.handleErrorCases(url, res.status);
       }
     } catch (err) {
       const e = err as { code: string };
diff --git a/src/test/metrics.test.ts b/src/test/metrics.test.ts
index ab54efef..d24820be 100644
--- a/src/test/metrics.test.ts
+++ b/src/test/metrics.test.ts
@@ -77,7 +77,7 @@ test('should sendMetrics and register when metricsInterval is a positive number'
     metrics.count('toggle-x', false);
     metrics.count('toggle-y', true);
     metrics.start();
-    let timeout = new Promise<void>((resolve) => setTimeout(() => {
+    const timeout = new Promise<void>((resolve) => setTimeout(() => {
       t.fail("Failed to successfully both send and register");
       resolve();
     }, 1000));
diff --git a/src/test/repository.test.ts b/src/test/repository.test.ts
index 5cf7a02d..0256106a 100644
--- a/src/test/repository.test.ts
+++ b/src/test/repository.test.ts
@@ -249,29 +249,34 @@ test('request with customHeadersFunction should take precedence over customHeade
     repo.start();
   }));
 
-test('should handle 429 request error and emit warn event', (t) =>
-  new Promise((resolve) => {
-    const url = 'http://unleash-test-6-429.app';
-    nock(url).persist().get('/client/features').reply(429, 'blabla');
-    const repo = new Repository({
-      url,
-      appName,
-      instanceId,
-      refreshInterval: 10,
-      // @ts-expect-error
-      bootstrapProvider: new DefaultBootstrapProvider({}),
-      storageProvider: new InMemStorageProvider(),
-    });
+test.only('should handle 429 request error and emit warn event', async (t) => {
+  const url = 'http://unleash-test-6-429.app';
+  nock(url).persist().get('/client/features').reply(429, 'blabla');
+  const repo = new Repository({
+    url,
+    appName,
+    instanceId,
+    refreshInterval: 10,
+    // @ts-expect-error
+    bootstrapProvider: new DefaultBootstrapProvider({}),
+    storageProvider: new InMemStorageProvider(),
+  });
+  const warning = new Promise<void>((resolve) => {
     repo.on('warn', (warn) => {
       t.truthy(warn);
-      // eslint-disable-next-line max-len
-      t.is(warn, `${url}/client/features responded TOO_MANY_CONNECTIONS (429). Waiting for 20ms before trying again.`);
-      t.is(repo.nextFetch(), 20);
+      t.is(warn, `${url}/client/features responded TOO_MANY_CONNECTIONS (429). Backing off`);
       t.is(repo.getFailures(), 1);
+      t.is(repo.nextFetch(), 20);
       resolve();
     });
-    repo.start();
-  }));
+  });
+  const timeout = new Promise<void>((resolve) => setTimeout(() => {
+    t.fail("Failed to get warning about connections");
+    resolve();
+  }, 5000));
+  await repo.start();
+  await Promise.race([warning, timeout]);
+});
 
 test('should handle 401 request error and emit error event', (t) =>
   new Promise((resolve) => {
@@ -332,7 +337,7 @@ test('should handle 500 request error and emit warn event', (t) =>
     });
     repo.on('warn', (warn) => {
       t.truthy(warn);
-      t.is(warn, `${url}/client/features responded 500. Waiting for 20ms before trying again.`);
+      t.is(warn, `${url}/client/features responded 500. Backing off`);
       resolve();
     });
     repo.start();

From 0549a2e9dcb53470781db3e7e4c70499a46e59e4 Mon Sep 17 00:00:00 2001
From: Christopher Kolstad <chriswk@getunleash.io>
Date: Thu, 16 Nov 2023 14:14:20 +0100
Subject: [PATCH 09/12] fix: remove only from repository test

---
 src/test/repository.test.ts | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/test/repository.test.ts b/src/test/repository.test.ts
index 0256106a..a1d189ea 100644
--- a/src/test/repository.test.ts
+++ b/src/test/repository.test.ts
@@ -249,7 +249,7 @@ test('request with customHeadersFunction should take precedence over customHeade
     repo.start();
   }));
 
-test.only('should handle 429 request error and emit warn event', async (t) => {
+test('should handle 429 request error and emit warn event', async (t) => {
   const url = 'http://unleash-test-6-429.app';
   nock(url).persist().get('/client/features').reply(429, 'blabla');
   const repo = new Repository({
@@ -403,7 +403,7 @@ test.skip('should handle 504 request error and emit warn event', (t) =>
     repo.start();
   }));
 test('should handle 404 request error and emit error event', (t) =>
-  new Promise((resolve) => {
+  new Promise<void>((resolve) => {
     const url = 'http://unleash-test-5.app';
     nock(url).persist().get('/client/features').reply(404, 'asd');
 

From 56d59084c9f3d1968730ec82895d7a3cc9ddcdeb Mon Sep 17 00:00:00 2001
From: Christopher Kolstad <chriswk@getunleash.io>
Date: Thu, 16 Nov 2023 14:21:44 +0100
Subject: [PATCH 10/12] Removed unused maxrefreshinterval, base it on failure
 count instead

---
 src/repository/index.ts | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/src/repository/index.ts b/src/repository/index.ts
index 01ba7bb9..b134d6c4 100644
--- a/src/repository/index.ts
+++ b/src/repository/index.ts
@@ -25,7 +25,6 @@ export interface RepositoryOptions {
   instanceId: string;
   projectName?: string;
   refreshInterval: number;
-  maxRefreshInterval?: number;
   timeout?: number;
   headers?: CustomHeaders;
   customHeadersFunction?: CustomHeadersFunction;
@@ -58,8 +57,6 @@ export default class Repository extends EventEmitter implements EventEmitter {
 
   private failures: number = 0;
 
-  private maxRefreshInterval: number;
-
   private customHeadersFunction?: CustomHeadersFunction;
 
   private timeout?: number;
@@ -94,7 +91,6 @@ export default class Repository extends EventEmitter implements EventEmitter {
     instanceId,
     projectName,
     refreshInterval = 15_000,
-    maxRefreshInterval = 120_000,
     timeout,
     headers,
     customHeadersFunction,
@@ -121,7 +117,6 @@ export default class Repository extends EventEmitter implements EventEmitter {
     this.bootstrapOverride = bootstrapOverride;
     this.storageProvider = storageProvider;
     this.segments = new Map();
-    this.maxRefreshInterval = maxRefreshInterval;
   }
 
   timedFetch(interval: number) {

From 404d6104b2fae98ed4ea2d1871451d1031bb298b Mon Sep 17 00:00:00 2001
From: Christopher Kolstad <chriswk@getunleash.io>
Date: Mon, 20 Nov 2023 15:08:22 +0100
Subject: [PATCH 11/12] fix: updates after PR discussion

---
 src/metrics.ts          | 10 +++++-----
 src/repository/index.ts |  4 ++--
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/src/metrics.ts b/src/metrics.ts
index 57e1979e..85cde0a1 100644
--- a/src/metrics.ts
+++ b/src/metrics.ts
@@ -118,7 +118,7 @@ export default class Metrics extends EventEmitter {
   }
 
   getInterval(): number {
-    if(this.metricsInterval === 0 || this.failures === -1) {
+    if(this.metricsInterval === 0) {
       return 0;
     } else {
       return this.metricsInterval +
@@ -190,16 +190,16 @@ export default class Metrics extends EventEmitter {
     return true;
   }
 
-  unrecoverableError(url: string, statusCode: number) {
+  configurationError(url: string, statusCode: number) {
     this.emit(UnleashEvents.Warn, `${url} returning ${statusCode}, stopping metrics`);
-    this.failures = -1;
+    this.metricsInterval = 0;
     this.stop();
   }
 
   backoff(url: string, statusCode: number): void {
     this.failures = Math.min(10, this.failures + 1);
     // eslint-disable-next-line max-len
-    this.emit(UnleashEvents.Warn, `${url} returning ${statusCode}. Backing off to ${this.getInterval()}`);
+    this.emit(UnleashEvents.Warn, `${url} returning ${statusCode}. Backing off to ${this.failures} times normal interval`);
     this.startTimer();
   }
 
@@ -229,7 +229,7 @@ export default class Metrics extends EventEmitter {
       });
       if (!res.ok) {
         if (res.status === 404 || res.status === 403 || res.status == 401) {
-          this.unrecoverableError(url, res.status);
+          this.configurationError(url, res.status);
         } else if (
           res.status === 429 ||
           res.status === 500 ||
diff --git a/src/repository/index.ts b/src/repository/index.ts
index b134d6c4..865ea9a3 100644
--- a/src/repository/index.ts
+++ b/src/repository/index.ts
@@ -263,7 +263,7 @@ Message: ${err.message}`,
 
   // Emits correct error message based on what failed,
   // and returns 0 as the next fetch interval (stop polling)
-  private unrecoverableError(url: string, statusCode: number): number {
+  private configurationError(url: string, statusCode: number): number {
     this.failures += 1;
     if (statusCode === 404) {
       this.emit(
@@ -309,7 +309,7 @@ Message: ${err.message}`,
 
   private handleErrorCases(url: string, statusCode: number): number {
     if (statusCode === 401 || statusCode === 403 || statusCode === 404) {
-      return this.unrecoverableError(url, statusCode);
+      return this.configurationError(url, statusCode);
     } else if (
       statusCode === 429 ||
       statusCode === 500 ||

From 75c83e9f3d299f54a9d1997c3b8ad26d3e6e37cf Mon Sep 17 00:00:00 2001
From: Christopher Kolstad <chriswk@getunleash.io>
Date: Mon, 20 Nov 2023 15:12:30 +0100
Subject: [PATCH 12/12] Update assumptions after PR comments

---
 src/test/metrics.test.ts | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/test/metrics.test.ts b/src/test/metrics.test.ts
index d24820be..53f2a42c 100644
--- a/src/test/metrics.test.ts
+++ b/src/test/metrics.test.ts
@@ -451,7 +451,7 @@ test('sendMetrics should stop on 401', async (t) => {
   await metrics.sendMetrics();
   // @ts-expect-error actually a private field, but we access it for tests
   t.true(metrics.disabled);
-  t.is(metrics.getFailures(), -1);
+  t.is(metrics.getFailures(), 0);
 });
 test('sendMetrics should stop on 403', async (t) => {
   const url = getUrl();
@@ -463,7 +463,7 @@ test('sendMetrics should stop on 403', async (t) => {
   await metrics.sendMetrics();
   // @ts-expect-error actually a private field, but we access it for tests
   t.true(metrics.disabled);
-  t.is(metrics.getFailures(), -1);
+  t.is(metrics.getFailures(), 0);
 });
 test('sendMetrics should backoff on 429', async (t) => {
   const url = getUrl();