From 1295fb19329025e242da556223b1cf935feef2b6 Mon Sep 17 00:00:00 2001
From: Kohsuke Kawaguchi <kk@kohsuke.org>
Date: Tue, 18 Oct 2016 20:12:54 +0200
Subject: [PATCH] Improve the caller/callee correlation diagnostics

I was trying to diagnose a remoting call that bridges two VMs that is
hanging. This can be made easier if thread dump allows us to correlate
the caller/callee.

This change adds the request ID to thread name so that thread dump will
show this clearly

Also fixes one incorrect use of toString() in diagnosis, which should
be getName() --- see all the other uses of thread names.
---
 src/main/java/hudson/remoting/Request.java | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/main/java/hudson/remoting/Request.java b/src/main/java/hudson/remoting/Request.java
index 2839b546a..ab6f62958 100644
--- a/src/main/java/hudson/remoting/Request.java
+++ b/src/main/java/hudson/remoting/Request.java
@@ -139,7 +139,7 @@ public final RSP call(Channel channel) throws EXC, InterruptedException, IOExcep
                 final String name = t.getName();
                 try {
                     // wait until the response arrives
-                    t.setName(name+" / waiting for "+channel);
+                    t.setName(name+" / waiting for "+channel.getName()+" id="+id);
                     while(response==null && !channel.isInClosed())
                         // I don't know exactly when this can happen, as pendingCalls are cleaned up by Channel,
                         // but in production I've observed that in rare occasion it can block forever, even after a channel
@@ -233,6 +233,8 @@ public boolean isDone() {
 
             public RSP get() throws InterruptedException, ExecutionException {
                 synchronized(Request.this) {
+                    String oldThreadName = Thread.currentThread().getName();
+                    Thread.currentThread().setName(oldThreadName+" for "+channel.getName()+" id="+id);
                     try {
                         while(response==null) {
                             if (isCancelled()) {
@@ -250,6 +252,8 @@ public RSP get() throws InterruptedException, ExecutionException {
                             // couldn't cancel. ignore.
                         }
                         throw e;
+                    } finally {
+                        Thread.currentThread().setName(oldThreadName);
                     }
 
                     if(response.exception!=null)
@@ -320,7 +324,7 @@ private int calcLastIoId() {
 
             public void run() {
                 String oldThreadName = Thread.currentThread().getName();
-                Thread.currentThread().setName(oldThreadName+" for "+channel.getName());
+                Thread.currentThread().setName(oldThreadName+" for "+channel.getName()+" id="+id);
                 try {
                     Command rsp;
                     CURRENT.set(Request.this);