php zookeeper watcher doesn't work - php

Question

I'm trying to use zookeeper in a php app, and I've done most of the get($path)/set($path, $value)/getChildren($path) functions following https://github.com/andreiz/php-zookeeper, except the watch_callback function that just doesn't work.
My php version is 5.6.14 and thread safety disabled, and I'm using apache2.4.
Here is some code snippet
class Zookeeper_Module {
private $zookeeper;
public function __construct(){
$this->ci = & get_instance();
$zookeeper_server = $this->ci->config->item('zookeeper_server');
$this->zookeeper = new Zookeeper($zookeeper_server);
}
public function set($path, $value){
$this->zookeeper->set($path, $value);
}
public function get($path, $watch_cb = null){
return $this->zookeeper->get($path, $watch_cb);
}
public function get_watch_cb($event_type = '', $stat = '', $path = ''){
error_log('hello from get_watcher_cb');
$value = $this->get($path, array($this, 'get_watch_cb'));
// update redis cache
$this->ci->cache->redis->save('some cache key', $value);
}
}
class MyTest{
public function get(){
$zookeeper = new Zookeeper_Module ();
$value = $zookeeper->get( '/foo/bar', array (
$zookeeper,
'get_watch_cb'
) );
}
public function set(){
$zookeeper = new Zookeeper_Module ();
$zookeeper->set( '/foo/bar', 'some value');
}
}
I can successfully get or set a node value, but I can neither catch watch callback log nor have redis cache updated.

Answer 1

I write a more simple demo, very similar with this https://github.com/andreiz/php-zookeeper/wiki, and the watcher works fine in this demo.
The most significant difference is
while( true ) {
echo '.';
sleep(2);
}
While java has a jvm container hosting watchers, php doesn't has a container to do it, so we have to use a while(true) to keep watchers alive.
So I add a while(true) in my code and now the watcher works fine.
But I don't want to add a terrible while(true) in a web app, so the final solution is adding a java app to communicate with zookeeper and save results in redis, and php app just reads info from redis.