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Date: Tue, 29 Apr 2014 17:30:33 +0900
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Subject: Regarding large number of watch count
From: Jung Young Seok <jung.youngseok@gmail.com>
To: "user@zookeeper.apache.org" <user@zookeeper.apache.org>
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Dear Zookeeper-user,

We have 3 zookeeper node clustered.
The zookeeper is used as application lock coordinator.
Client creates node(key) when it needs lock then release and delete the
node(key) when the usage is done.

Strangely, zk_watch_count has been increased.
In case of leader, zk_watch_count reached 6804.

==================================================================
Detailed information is below. (mntr)

1. Zoo-1 (Follower)
Status Information: OK Zookeeper State : follower zk_avg_latency 2
zk_max_latency 215 zk_min_latency 0 zk_packets_received 9001127
zk_packets_sent 9027569 zk_num_alive_connections 3 zk_outstanding_requests
0 zk_server_state follower zk_znode_count 12 zk_watch_count 1786
zk_ephemerals_count 2 zk_approximate_data_size 525
zk_open_file_descriptor_count 29 zk_max_file_descriptor_count 4096
Performance Data: zk_version 3.4.6-1569965, built on 02/20/2014 09:09 GMT
2. Zoo-2 (Follower)
Status Information: OK Zookeeper State : follower zk_avg_latency 0
zk_max_latency 6 zk_min_latency 0 zk_packets_received 3539 zk_packets_sent
3538 zk_num_alive_connections 2 zk_outstanding_requests 0 zk_server_state
follower zk_znode_count 12 zk_watch_count 0 zk_ephemerals_count 2
zk_approximate_data_size 525 zk_open_file_descriptor_count 28
zk_max_file_descriptor_count 4096 Performance Data: zk_version
3.4.6-1569965, built on 02/20/2014 09:09 GMT
3. Zoo-3 (Leader) Status Information: OK Zookeeper State : leader
zk_avg_latency 1 zk_max_latency 214 zk_min_latency 0 zk_packets_received
21575604 zk_packets_sent 21638420 zk_num_alive_connections 4
zk_outstanding_requests 0 zk_server_state leader zk_znode_count 18
zk_watch_count 6804 zk_ephemerals_count 5 zk_approximate_data_size 954
zk_open_file_descriptor_count 32 zk_max_file_descriptor_count 4096
zk_followers 2 zk_synced_followers 2 zk_pending_syncs 0 Performance Data:
zk_version 3.4.6-1569965, built on 02/20/2014 09:09 GMT

==================================================================

My questions are,
1. Is it normal case that zk_watch_count reached 6804?

2. Why has zk_watch_count been increased?
- We use tomcat + Apache Curator + Zookeeper 3.4.6

3. Would it make trouble if zk_watch_count reach too large number?

4. Is there any way that I can reduce the zk_watch_count?

I'd be glad on any opinion.
Thank you in advance

Regards,
Youngseok Jung

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