c++ and zk session management

hi,

I have a service (long living) that establish connection to ZK and holds it:

zookeeper_init(zkConnectionString.c_str(), zkWatcherCallback, 10000,
NULL, callbackContext, 0);

and after I simply subscribe to notification. I did check when I
interrupt connection and it successfully reconnect by itself. I also
print debug message when connection lost and restored. But when I
deployed service to many servers I see that few services lost
connection and sit disconnected. So I definitely doing something
wrong. What is correct algorithm to keep service always connected (i
do not do anything special to reconnect as I saw during my test that
library did this for me, why not always?).

my zk callback function is the following:

void ConfigManagerImpl::zkWatcher(zhandle_t*, int type, int state,
const char *path, void* context)

ConfigManagerImpl* me = (ConfigManagerImpl*)context;
LOG(INFO) << "CM:zkWatcher event:" << type << ":" << state <<
" (" << ZookeeperInterface::watcherEvent2String(type) <<
":" << ZookeeperInterface::state2String(state) + ")";

if (ZOO_SESSION_EVENT == type) {
me->updateZKConnected(state == ZOO_CONNECTED_STATE);
} else if (ZOO_CHANGED_EVENT == type) {
LOG(INFO) << "CM:zkWatcher changed event, path=" << path;

if (me->_zkFullPathToActiveVersion == path) {
me->_threadBlocker.signal(); // wake thread to read config

} else if (ZOO_DELETED_EVENT == type) {
if (me->_zkFullPathToActiveVersion == path) {
LOG(ERROR) << "CM:zkWatcher deleted active-external node
event, path=" << path;
me->_threadBlocker.signal(); // wake thread to read config
in a loop because we just lost notifications

Thank you for any insights!