Lost connection causes memory usage to grow indefinitely

# on a debian(linux) host with docker 

docker run -it --privileged --name=test-container -v /var/run/docker.sock:/var/run/docker.sock -v `pwd`:/sources debian:bullseye bash

# install required packages

apt update && apt -y install vim g++ valgrind wget gnupg git docker.io

# download sources and switch to 3.3.10 tag

cd /tmp && git clone https://github.com/couchbase/libcouchbase.git && cd libcouchbase && git checkout 3.3.10

# create patch

cat > instancepool.patch << EOF

diff --git a/example/instancepool/main.cc b/example/instancepool/main.cc

index 52244526..e725f10a 100644

--- a/example/instancepool/main.cc

+++ b/example/instancepool/main.cc

@@ -20,15 +20,18 @@

 #include <vector>

 #include <cstring>

 #include <cstdlib>

+#include <signal.h>

 using namespace lcb;

 extern "C" {

 static void get_callback(lcb_INSTANCE *instance, int, const lcb_RESPBASE *rb)

 {

+    lcb_STATUS rc;

     const lcb_RESPGET *rg = reinterpret_cast< const lcb_RESPGET * >(rb);

-    if (lcb_respget_status(rg) != LCB_SUCCESS) {

-        fprintf(stderr, "%p: Couldn't get key", instance);

+    rc = lcb_respget_status(rg);

+    if (rc != LCB_SUCCESS) {

+        fprintf(stderr, "%p: Couldn't get key: %s\n", instance, lcb_strerror_short(rc));

     } else {

         const char *key, *value;

         size_t nkey, nvalue;

@@ -51,26 +54,36 @@ class MyPool : public Pool

         // care about

         fprintf(stderr, "Initializing %p\n", instance);

         lcb_install_callback(instance, LCB_CALLBACK_GET, get_callback);

+        lcb_U32 tmo = 50 * 1000;

+        lcb_cntl(instance, LCB_CNTL_SET, LCB_CNTL_OP_TIMEOUT, &tmo);

     }

 };

+static int running = 1;

+static void sigint_handler(int unused)

+{

+    running = 0;

+}

+

 extern "C" {

 static void *pthr_func(void *arg)

 {

     Pool *pool = reinterpret_cast< Pool * >(arg);

-    lcb_CMDGET *gcmd;

-    lcb_cmdget_create(&gcmd);

-    lcb_cmdget_key(gcmd, "foo", 3);

     // Get an instance to use

     lcb_INSTANCE *instance = pool->pop();

-    // Issue the command

-    lcb_get(instance, NULL, gcmd);

-    lcb_cmdget_destroy(gcmd);

+    while (running) {

+        lcb_CMDGET *gcmd;

+        lcb_cmdget_create(&gcmd);

+        lcb_cmdget_key(gcmd, "foo", 3);

+        // Issue the command

+        lcb_get(instance, NULL, gcmd);

+        lcb_cmdget_destroy(gcmd);

-    // Wait for the command to complete

-    lcb_wait(instance, LCB_WAIT_DEFAULT);

+        // Wait for the command to complete

+        lcb_wait(instance, LCB_WAIT_DEFAULT);

+    }

     // Release back to pool

     pool->push(instance);

@@ -95,7 +108,7 @@ int main(int argc, char *argv[])

         lcb_createopts_credentials(options, argv[3], strlen(argv[3]), argv[2], strlen(argv[2]));

     }

-    pool = new MyPool(options, 5);

+    pool = new MyPool(options, NUM_WORKERS);

     err = pool->connect();

     if (err != LCB_SUCCESS) {

@@ -103,6 +116,13 @@ int main(int argc, char *argv[])

         exit(EXIT_FAILURE);

     }

+    /* setup CTRL-C handler */

+    struct sigaction action;

+    sigemptyset(&action.sa_mask);

+    action.sa_handler = sigint_handler;

+    action.sa_flags = 0;

+    sigaction(SIGINT, &action, NULL);

+

     for (size_t ii = 0; ii < NUM_WORKERS; ii++) {

         pthread_create(&workers[ii], NULL, pthr_func, pool);

     }

@@ -117,3 +137,4 @@ int main(int argc, char *argv[])

     lcb_createopts_destroy(options);

     return 0;

 }

+

EOF

# apply patch

patch example/instancepool/main.cc instancepool.patch

# add couchbase repo

wget -q https://packages.couchbase.com/clients/c/repos/deb/couchbase.key  -O- | apt-key add -

echo "deb https://packages.couchbase.com/clients/c/repos/deb/debian11 bullseye bullseye/main" >> /etc/apt/sources.list

apt update && apt install -y libcouchbase3 libcouchbase-dev libcouchbase-dbg

# compile modified test

g++ -std=c++17 -o /tmp/couchbase-instancepool example/instancepool/main.cc example/instancepool/pool.cc -lcouchbase -lpthread

# start and setup couchbase server

docker run -d --name db -p 8091-8096:8091-8096 -p 11210-11211:11210-11211 couchbase:community-7.2.2

sleep 10 # make sure server is initialized

docker exec db couchbase-cli cluster-init --cluster-name test-cluster --cluster-username Administrator --cluster-password 123456

sleep 10 # make sure cluster is initialized

docker exec db couchbase-cli bucket-create --cluster localhost --username Administrator --password 123456 --bucket test-bucket --bucket-type couchbase --bucket-ramsize 512

db_ip=$(docker inspect -f '\{{range.NetworkSettings.Networks}}\{{.IPAddress}}\{{end}}' db)

# start test

/tmp/couchbase-instancepool couchbase://${db_ip}/test-bucket 123456 Administrator

$ ps -p 6381 -o %mem,rss,cmd

%MEM   RSS CMD

 1.8 609152 /tmp/couchbase-instancepool couchbase://172.17.0.3/test-bucket 123456 Administrator