4.0.0: WebClient HTTP keep-alive support appears to be broken

[barchetta]

Environment Details

• Helidon Version: 4.0.0 and 4.0.1
• Helidon SE
• JDK version: java 21.0.1 2023-10-17 LTS
• OS: MacOS

---

Problem Description

The Helidon 4 WebClient HTTP keep-alive support appears to be broken. Even with keepAlive(true) the client does not reuse connections.

Steps to reproduce

See the attached test case: client.zip

This is based on the stand-alone webclient example that has been modified to set keepAlive(true) and to perform 10 GET requests sequentially. After the test is run (see README) netstat shows 10 connections in TIME_WAIT instead of one:

tcp4       0      0  127.0.0.1.56044        127.0.0.1.8080         TIME_WAIT
tcp4       0      0  127.0.0.1.56045        127.0.0.1.8080         TIME_WAIT
tcp4       0      0  127.0.0.1.56046        127.0.0.1.8080         TIME_WAIT
tcp4       0      0  127.0.0.1.56047        127.0.0.1.8080         TIME_WAIT
tcp4       0      0  127.0.0.1.56048        127.0.0.1.8080         TIME_WAIT
tcp4       0      0  127.0.0.1.56049        127.0.0.1.8080         TIME_WAIT
tcp4       0      0  127.0.0.1.56050        127.0.0.1.8080         TIME_WAIT
tcp4       0      0  127.0.0.1.56051        127.0.0.1.8080         TIME_WAIT
tcp4       0      0  127.0.0.1.56052        127.0.0.1.8080         TIME_WAIT
tcp4       0      0  127.0.0.1.56053        127.0.0.1.8080         TIME_WAIT

[barchetta]

@romain-grecourt came up with this patch and appears to fix the issue. But it needs further review for correctness:

diff --git a/webclient/http1/src/main/java/io/helidon/webclient/http1/Http1ClientResponseImpl.java b/webclient/http1/src/main/java/io/helidon/webclient/http1/Http1ClientResponseImpl.java
index 16d4edc47b..3af52f6187 100644
--- a/webclient/http1/src/main/java/io/helidon/webclient/http1/Http1ClientResponseImpl.java
+++ b/webclient/http1/src/main/java/io/helidon/webclient/http1/Http1ClientResponseImpl.java
@@ -160,6 +160,8 @@ class Http1ClientResponseImpl implements Http1ClientResponse {
             try {
                 if (headers().contains(HeaderValues.CONNECTION_CLOSE)) {
                     connection.closeResource();
+                } else if (headers().contains(HeaderValues.CONNECTION_KEEP_ALIVE)) {
+                    connection.releaseResource();
                 } else {
                     if (entityLength == 0) {
                         connection.releaseResource();

[AshwinPrabhuB]

I had seen this in H3 but failed to report it since I found the Ning HTTP client to meet all our requirements out of the box. Consider backporting this to H3 as well