(maven-mvnd) branch master updated: Fix daemon connection race condition (#1078)

[gnodet]

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gnodet pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/maven-mvnd.git


The following commit(s) were added to refs/heads/master by this push:
     new 6189475f Fix daemon connection race condition (#1078)
6189475f is described below

commit 6189475f1b7cd42850b11900d4a5fec03b64048e
Author: Guillaume Nodet <gno...@gmail.com>
AuthorDate: Fri Jul 19 13:42:11 2024 +0200

    Fix daemon connection race condition (#1078)
    
    The Server was using a SynchrnousQueue to coordinate the main thread
    and the background thread that receives the request from the client.
    A SynchronousQueue only allows insertions when a corresponding call
    to `get` is in progress. However, since the receiver thread is started
    before the call to `get`, there was a short time window, where the call
    to `queue.offer` could fail and simply return `false`. This return code
    was ignored.
    
    A possible solution would have been to call `put` instead of `offer`,
    but I decided to replace the queue with a Future, since we only wait
    for a single element.
    
    Co-authored-by: Stefan Oehme <st.oe...@gmail.com>
---
 daemon/src/main/java/org/mvndaemon/mvnd/daemon/Server.java | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/daemon/src/main/java/org/mvndaemon/mvnd/daemon/Server.java 
b/daemon/src/main/java/org/mvndaemon/mvnd/daemon/Server.java
index 6d9586cf..9d95876b 100644
--- a/daemon/src/main/java/org/mvndaemon/mvnd/daemon/Server.java
+++ b/daemon/src/main/java/org/mvndaemon/mvnd/daemon/Server.java
@@ -37,11 +37,11 @@ import java.util.Locale;
 import java.util.Map;
 import java.util.Objects;
 import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.Executors;
 import java.util.concurrent.LinkedBlockingDeque;
 import java.util.concurrent.PriorityBlockingQueue;
 import java.util.concurrent.ScheduledExecutorService;
-import java.util.concurrent.SynchronousQueue;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.locks.Condition;
 import java.util.concurrent.locks.Lock;
@@ -271,13 +271,13 @@ public class Server implements AutoCloseable, Runnable {
 
         try (DaemonConnection connection = new DaemonConnection(socket)) {
             LOGGER.info("Waiting for request");
-            SynchronousQueue<Message> request = new SynchronousQueue<>();
+            CompletableFuture<Message> request = new CompletableFuture<>();
             new DaemonThread(() -> {
                         Message message = connection.receive();
-                        request.offer(message);
+                        request.complete(message);
                     })
                     .start();
-            Message message = request.poll(1, TimeUnit.MINUTES);
+            Message message = request.get(1, TimeUnit.MINUTES);
             if (message == null) {
                 LOGGER.info("Could not receive request after one minute, 
dropping connection");
                 updateState(DaemonState.Idle);