Introduce PreTlsHandshakeException to indicate the exception raised b…

…efore TLS handshake starts (line#5344)

Motivation:
Got a report from @mauhiz that the current exception that is raised before TLS handshake starts, is not sufficiently clear and can cause confusion.

Modifications:
- Change the exception type from `IllegalStateException` to `PreTlsHandshakeException`.
- Refine the exception message to be more explicit.

Result:
- `PreTlsHandshakeException` is now used when an exception is raised before a TLS handshake starts.

core/src/main/java/com/linecorp/armeria/client/HttpClientPipelineConfigurator.java

@@ -295,12 +295,13 @@ public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws E
                     // A legacy HTTPS server such as Microsoft-IIS/8.5 may reset the connection
                     // if no cipher suites in common.
                     final String tlsVersion = sslHandler.engine().getSession().getProtocol();
-                    final IllegalStateException maybeHandshakeException = new IllegalStateException(
-                            "An unexpected exception during TLS handshake. " +
-                            "Possible reasons: no cipher suites in common, unsupported TLS version, etc. " +
+                    final PreTlsHandshakeException preTlsHandshakeException = new PreTlsHandshakeException(
+                            "An unexpected exception before a TLS handshake starts. The possible reason could" +
+                            " be one of: [connection forcefully closed by peer, unsupported TLS version, " +
+                            "no cipher suites in common, etc.] " +
                             "(TLS version: " + tlsVersion + ", cipher suites: " + sslCtx.cipherSuites() + ')',
                             cause);
-                    setPendingException(ctx, maybeHandshakeException);
+                    setPendingException(ctx, preTlsHandshakeException);
                     return;
                 }
                 if (handshakeFailed &&

core/src/main/java/com/linecorp/armeria/client/PreTlsHandshakeException.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2023 LINE Corporation
+ *
+ * LINE Corporation licenses this file to you under the Apache License,
+ * version 2.0 (the "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at:
+ *
+ *   https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+
+package com.linecorp.armeria.client;
+
+import javax.net.ssl.SSLException;
+
+import com.linecorp.armeria.common.Flags;
+
+/**
+ * An {@link SSLException} raised before starting a TLS handshake.
+ */
+public final class PreTlsHandshakeException extends SSLException {
+
+    private static final long serialVersionUID = -4425286273254997423L;
+
+    /**
+     * Creates a new instance.
+     */
+    public PreTlsHandshakeException(String message, Throwable cause) {
+        super(message, cause);
+    }
+
+    @Override
+    public Throwable fillInStackTrace() {
+        if (Flags.verboseExceptionSampler().isSampled(getClass())) {
+            super.fillInStackTrace();
+        }
+        return this;
+    }
+}