Refine submit action check (#290)

* feat(actions): replace `nc` check with a `curl` server ping
* feat(actions): display verbose `curl` output when Testflinger ping fails
* chore(actions): move diagnostic step to the very beginning

.github/actions/submit/action.yaml

@@ -21,8 +21,25 @@ inputs:
     default: testflinger.canonical.com
 runs:
   using: composite
-
   steps:
+    - name: Test connection to Testflinger server
+      shell: bash {0}  # allow curl to fail
+      env:
+        SERVER: https://${{ inputs.server }}
+      run: |
+        STATUS=$(curl --stderr error.log -Ivw "%{http_code}\n" -o /dev/null $SERVER/jobs)
+        ERROR=$?
+        if [ ! $ERROR -eq 0 ]; then
+          echo "Unable to ping Testflinger server at $SERVER"
+          cat error.log
+          exit $ERROR
+        elif [ ! $STATUS -eq 200 ]; then
+          echo "Failed server ping at $SERVER, error status: $STATUS"
+          cat error.log
+          exit $STATUS
+        else
+          echo "Successful server ping at $SERVER, status: $STATUS"
+        fi
     - name: Create job file, if required
       id: create-job-file
       shell: bash
@@ -53,26 +70,26 @@ runs:
       shell: bash
       run: sudo snap install testflinger-cli jq
 
-    - name: Test connection to Testflinger server
-      shell: bash
-      run: nc -vz ${{ inputs.server }} 443
-
     - name: Submit job to the Testflinger server
       id: submit
       if: inputs.dry-run != 'true'
       shell: bash
+      env:
+        SERVER: https://${{ inputs.server }}
       run: |
-        JOB_ID=$(testflinger --server https://${{ inputs.server }} submit --quiet "$JOB")
+        JOB_ID=$(testflinger --server $SERVER submit --quiet "$JOB")
         echo "job id: $JOB_ID"
         echo "JOB_ID=$JOB_ID" >> $GITHUB_ENV
 
     - name: Track the status of the job and mirror its exit status
       if: inputs.poll == 'true' && inputs.dry-run != 'true'
       shell: bash
+      env:
+        SERVER: https://${{ inputs.server }}
       run: |
         # poll
-        PYTHONUNBUFFERED=1 testflinger --server https://${{ inputs.server }} poll $JOB_ID
+        PYTHONUNBUFFERED=1 testflinger --server $SERVER poll $JOB_ID
         # retrieve results
-        STATUS=$(testflinger --server https://${{ inputs.server }} results $JOB_ID | jq -er .test_status)
+        STATUS=$(testflinger --server $SERVER results $JOB_ID | jq -er .test_status)
         echo "Test exit status: $STATUS"
         exit $STATUS