It has been observed that in the presence of a network failure/outage, some HTTP requests appear to block (in the ForkJoin common pool) indefinitely.

The requests are: 1) GET, 2) secure HTTPS, 3) HTTP/1.1, 4) using a proxy, 5) have an explicit request timeout set, and 6) the client has a connect timeout set.

The HTTP Client in question is: 1) long running, for several hours (may have entries in its keep-alive cache, and 2) is shared across multiple (two or three) threads.

Environment: running with system properties that set the proxy: http.proxyHost, http.proxyPort.

Client created like:
  private final HttpClient client = HttpClient.newBuilder().connectTimeout(Duration.ofSeconds(10)).build();

Example request:
  var requestBuilder = HttpRequest.newBuilder()
            .uri(uri)
            .timeout(Duration.ofSeconds(30))
            .header("Content-type", "application/json");


Example partial stack trace:
"pool-1-thread-16" #52 prio=5 os_prio=0 cpu=8534.52ms elapsed=55491.00s tid=0x00007f30bc0f0000 nid=0x70 waiting on condition [0x000
07f30eca08000]
   java.lang.Thread.State: WAITING (parking)
        at jdk.internal.misc.Unsafe.park(java.base@14.0.1/Native Method)
        - parking to wait for <0x00000000acfee3a8> (a java.util.concurrent.CompletableFuture$Signaller)
        at java.util.concurrent.locks.LockSupport.park(java.base@14.0.1/LockSupport.java:211)
        at java.util.concurrent.CompletableFuture$Signaller.block(java.base@14.0.1/CompletableFuture.java:1860)
        at java.util.concurrent.ForkJoinPool.managedBlock(java.base@14.0.1/ForkJoinPool.java:3137)
        at java.util.concurrent.CompletableFuture.waitingGet(java.base@14.0.1/CompletableFuture.java:1887)
        at java.util.concurrent.CompletableFuture.get(java.base@14.0.1/CompletableFuture.java:2062)
        at jdk.internal.net.http.HttpClientImpl.send(java.net.http@14.0.1/HttpClientImpl.java:543)
        at jdk.internal.net.http.HttpClientFacade.send(java.net.http@14.0.1/HttpClientFacade.java:119)
        at org.openjdk.skara.network.RestRequestCache.send(org.openjdk.skara.network/RestRequestCache.java:113)
  ...