Watchdog feature to remove unresponsive cluster nodes.

In some intstances (e.g. while resolving an error) it's possible for a
hung process to hang the entire cluster as they wait for its response.
The cluster can handle terminated processes but hung processes present
a problem.

If the watchdog plugin is loaded and --watchdog-interval is set then
the broker forks a child process that runs a very simple watchdog
program, and starts a timer in the broker process to signal the watchdog
every interval/2 seconds. The watchdog kills its parent if it does not
receive a signal for interval seconds. This allows a stuck broker to be 
removed from the cluster so other cluster members can continue.


git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk/qpid@802927 13f79535-47bb-0310-9956-ffa450edef68

2 files changed, 51 insertions, 33 deletions

diff --git a/cpp/src/tests/cluster.mk b/cpp/src/tests/cluster.mk
index dc592fa4d5..6fc4c64a5e 100644
--- a/cpp/src/tests/cluster.mk
+++ b/cpp/src/tests/cluster.mk
@@ -29,44 +29,46 @@ if HAVE_LIBCPG
 
 
 # ais_check checks pre-requisites for cluster tests and runs them if ok.
-TESTS += \
-    ais_check \
-	run_cluster_tests \
-	federated_cluster_test \
+TESTS +=					\
+	ais_check				\
+	test_watchdog				\
+	run_cluster_tests			\
+	federated_cluster_test			\
 	clustered_replication_test
-	
-EXTRA_DIST += \
-	ais_check \
-	start_cluster \
-	stop_cluster \
-	restart_cluster \
-	cluster_python_tests \
-	cluster_python_tests_failing.txt \
-  	federated_cluster_test \
-  	clustered_replication_test \
-  	run_cluster_tests \
-  	run_long_cluster_tests \
-  	testlib.py \
-  	cluster_tests.py \
-  	long_cluster_tests.py
-  	
 
-LONG_TESTS += \
-	run_long_cluster_tests \
-	start_cluster \
-	cluster_python_tests \
+EXTRA_DIST +=					\
+	ais_check				\
+	start_cluster				\
+	stop_cluster				\
+	restart_cluster				\
+	cluster_python_tests			\
+	cluster_python_tests_failing.txt	\
+	federated_cluster_test			\
+	clustered_replication_test		\
+	run_cluster_tests			\
+	run_long_cluster_tests			\
+	testlib.py				\
+	cluster_tests.py			\
+	long_cluster_tests.py
+
+LONG_TESTS +=					\
+	run_long_cluster_tests			\
+	start_cluster				\
+	cluster_python_tests			\
 	stop_cluster
 
 qpidtest_PROGRAMS += cluster_test
-cluster_test_SOURCES = \
-  	cluster_test.cpp \
-  	unit_test.cpp \
-  	ClusterFixture.cpp \
-  	ClusterFixture.h \
-  	ForkedBroker.h \
-  	ForkedBroker.cpp \
-  	PartialFailure.cpp \
-  	ClusterFailover.cpp
+
+cluster_test_SOURCES =				\
+	cluster_test.cpp			\
+	unit_test.cpp				\
+	ClusterFixture.cpp			\
+	ClusterFixture.h			\
+	ForkedBroker.h				\
+	ForkedBroker.cpp			\
+	PartialFailure.cpp			\
+	ClusterFailover.cpp
+
 cluster_test_LDADD=$(lib_client) $(lib_broker) -lboost_unit_test_framework
 
 qpidtest_SCRIPTS += run_cluster_tests cluster_tests.py run_long_cluster_tests long_cluster_tests.py testlib.py
diff --git a/cpp/src/tests/test_watchdog b/cpp/src/tests/test_watchdog
new file mode 100755
index 0000000000..c2f33501b8
--- /dev/null
+++ b/cpp/src/tests/test_watchdog
@@ -0,0 +1,16 @@
+#!/bin/sh
+# Tests for the watchdog plug-in
+
+# Start a broker with  watchdog, freeze it with kill -STOP, verify that it is killed.
+export QPID_WATCHDOG_EXE=$PWD/../qpidd_watchdog
+PORT=`../qpidd -dp0 --no-data-dir --auth=no --no-module-dir --load-module $PWD/../.libs/watchdog.so --log-to-file=qpidd_watchdog.log --watchdog-interval 1`
+PID=`../qpidd -cp $PORT`
+kill -STOP $PID
+sleep 2
+
+if kill -0 $PID 2>/dev/null; then
+    echo "Hung process did not die."
+    kill $PID
+else
+    true
+fi