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Posted to dev@zookeeper.apache.org by "Vishal K (JIRA)" <ji...@apache.org> on 2010/11/17 17:13:14 UTC
[jira] Created: (ZOOKEEPER-933) Remove wildcard
QuorumPeer.OBSERVER_ID
Remove wildcard QuorumPeer.OBSERVER_ID
---------------------------------------
Key: ZOOKEEPER-933
URL: https://issues.apache.org/jira/browse/ZOOKEEPER-933
Project: Zookeeper
Issue Type: Sub-task
Reporter: Vishal K
Fix For: 3.4.0
1. I have a question about the following piece of code in QCM:
if (remoteSid == QuorumPeer.OBSERVER_ID) {
/* * Choose identifier at random. We need a value to identify * the connection. */
remoteSid = observerCounter--;
LOG.info("Setting arbitrary identifier to observer: " + remoteSid);
}
Should we allow this? The problem with this code is that if a peer
connects twice with QuorumPeer.OBSERVER_ID, we will end up creating
threads for this peer twice. This could result in redundant
SendWorker/RecvWorker threads.
I haven't used observers yet. The documentation
http://hadoop.apache.org/zookeeper/docs/r3.3.0/zookeeperObservers.html
says that just like followers, observers should have server IDs. In
which case, why do we want to provide a wild-card?
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[jira] Commented: (ZOOKEEPER-933) Remove wildcard
QuorumPeer.OBSERVER_ID
Posted by "Vishal K (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/ZOOKEEPER-933?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12933612#action_12933612 ]
Vishal K commented on ZOOKEEPER-933:
------------------------------------
I looks like we need a way to uniquely identify the observer after we receive a connection. One way to do this is to get IP address from the socket. But this is not a good idea.
Instead, we can ask the observer to generate a unique id (uuid or crypto hash) and send <sid, role, uuid> after connecting to a peer (instead of just sid in the current implementation).
>From role, QCM can figure out that the node is observer. It can then ignore the sid and use the uuid passed by the observer.
For followers and leader we will use sid as identifier and for observers we will use uuid.
How does that sound?
> Remove wildcard QuorumPeer.OBSERVER_ID
> ---------------------------------------
>
> Key: ZOOKEEPER-933
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-933
> Project: Zookeeper
> Issue Type: Sub-task
> Reporter: Vishal K
> Fix For: 3.4.0
>
>
> 1. I have a question about the following piece of code in QCM:
> if (remoteSid == QuorumPeer.OBSERVER_ID) {
> /* * Choose identifier at random. We need a value to identify * the connection. */
> remoteSid = observerCounter--;
> LOG.info("Setting arbitrary identifier to observer: " + remoteSid);
> }
> Should we allow this? The problem with this code is that if a peer
> connects twice with QuorumPeer.OBSERVER_ID, we will end up creating
> threads for this peer twice. This could result in redundant
> SendWorker/RecvWorker threads.
> I haven't used observers yet. The documentation
> http://hadoop.apache.org/zookeeper/docs/r3.3.0/zookeeperObservers.html
> says that just like followers, observers should have server IDs. In
> which case, why do we want to provide a wild-card?
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[jira] Commented: (ZOOKEEPER-933) Remove wildcard
QuorumPeer.OBSERVER_ID
Posted by "Flavio Junqueira (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/ZOOKEEPER-933?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12933709#action_12933709 ]
Flavio Junqueira commented on ZOOKEEPER-933:
--------------------------------------------
+1 for the idea, sounds right to me.
> Remove wildcard QuorumPeer.OBSERVER_ID
> ---------------------------------------
>
> Key: ZOOKEEPER-933
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-933
> Project: Zookeeper
> Issue Type: Sub-task
> Reporter: Vishal K
> Fix For: 3.4.0
>
>
> 1. I have a question about the following piece of code in QCM:
> if (remoteSid == QuorumPeer.OBSERVER_ID) {
> /* * Choose identifier at random. We need a value to identify * the connection. */
> remoteSid = observerCounter--;
> LOG.info("Setting arbitrary identifier to observer: " + remoteSid);
> }
> Should we allow this? The problem with this code is that if a peer
> connects twice with QuorumPeer.OBSERVER_ID, we will end up creating
> threads for this peer twice. This could result in redundant
> SendWorker/RecvWorker threads.
> I haven't used observers yet. The documentation
> http://hadoop.apache.org/zookeeper/docs/r3.3.0/zookeeperObservers.html
> says that just like followers, observers should have server IDs. In
> which case, why do we want to provide a wild-card?
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[jira] Commented: (ZOOKEEPER-933) Remove wildcard
QuorumPeer.OBSERVER_ID
Posted by "Flavio Junqueira (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/ZOOKEEPER-933?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12933034#action_12933034 ]
Flavio Junqueira commented on ZOOKEEPER-933:
--------------------------------------------
Hi Vishal, The reason for the wildcard is explained in ZOOKEEPER-599. I'd rather keep this feature for the reasons explained before, but it would be good to prevent the case you mention.
> Remove wildcard QuorumPeer.OBSERVER_ID
> ---------------------------------------
>
> Key: ZOOKEEPER-933
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-933
> Project: Zookeeper
> Issue Type: Sub-task
> Reporter: Vishal K
> Fix For: 3.4.0
>
>
> 1. I have a question about the following piece of code in QCM:
> if (remoteSid == QuorumPeer.OBSERVER_ID) {
> /* * Choose identifier at random. We need a value to identify * the connection. */
> remoteSid = observerCounter--;
> LOG.info("Setting arbitrary identifier to observer: " + remoteSid);
> }
> Should we allow this? The problem with this code is that if a peer
> connects twice with QuorumPeer.OBSERVER_ID, we will end up creating
> threads for this peer twice. This could result in redundant
> SendWorker/RecvWorker threads.
> I haven't used observers yet. The documentation
> http://hadoop.apache.org/zookeeper/docs/r3.3.0/zookeeperObservers.html
> says that just like followers, observers should have server IDs. In
> which case, why do we want to provide a wild-card?
--
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You can reply to this email to add a comment to the issue online.