[jira] Commented: (ZOOKEEPER-368) Observers: core functionality
[ https://issues.apache.org/jira/browse/ZOOKEEPER-368?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12780516#action_12780516 ] Hudson commented on ZOOKEEPER-368: -- Integrated in ZooKeeper-trunk #545 (See [http://hudson.zones.apache.org/hudson/job/ZooKeeper-trunk/545/]) > Observers: core functionality > -- > > Key: ZOOKEEPER-368 > URL: https://issues.apache.org/jira/browse/ZOOKEEPER-368 > Project: Zookeeper > Issue Type: New Feature > Components: quorum >Reporter: Flavio Paiva Junqueira >Assignee: Henry Robinson > Fix For: 3.3.0 > > Attachments: obs-refactor.patch, observer-refactor.patch, observers > sync benchmark.png, observers.patch, ZOOKEEPER-368.patch, > ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, > ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, > ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, ZOOKEEPER-368.patch > > > Edit (Henry Robinson/henryr) 12/11/09: > This JIRA specifically concerns the implementation of non-voting peers called > Observers, their documentation and their tests. > Explicit goals are 1. not breaking any current ZK functionality, 2. enabling > at least one deployment scenario involving Observers, 3. documentation > describing how to use the feature and 4. tests validating the correct > behaviour of 2. > Non goals of this JIRA are 1. performance optimizations specific to > Observers, 2. compatibility with every feature of ZooKeeper (in particular > all leader election protocols), which are both to be addressed in future > JIRAs. > See http://wiki.apache.org/hadoop/ZooKeeper/Observers for more detail of use > cases, proposed design and usage. > See http://wiki.apache.org/hadoop/ZooKeeper/Observers/ReviewGuide for a brief > commentary on the current patch. > - > Currently, all servers of an ensemble participate actively in reaching > agreement on the order of ZooKeeper transactions. That is, all followers > receive proposals, acknowledge them, and receive commit messages from the > leader. A leader issues commit messages once it receives acknowledgments from > a quorum of followers. For cross-colo operation, it would be useful to have a > third role: observer. Using Paxos terminology, observers are similar to > learners. An observer does not participate actively in the agreement step of > the atomic broadcast protocol. Instead, it only commits proposals that have > been accepted by some quorum of followers. > One simple solution to implement observers is to have the leader forwarding > commit messages not only to followers but also to observers, and have > observers applying transactions according to the order followers agreed upon. > In the current implementation of the protocol, however, commit messages do > not carry their corresponding transaction payload because all servers > different from the leader are followers and followers receive such a payload > first through a proposal message. Just forwarding commit messages as they > currently are to an observer consequently is not sufficient. We have a couple > of options: > 1- Include the transaction payload along in commit messages to observers; > 2- Send proposals to observers as well. > Number 2 is simpler to implement because it doesn't require changing the > protocol implementation, but it increases traffic slightly. The performance > impact due to such an increase might be insignificant, though. > For scalability purposes, we may consider having followers also forwarding > commit messages to observers. With this option, observers can connect to > followers, and receive messages from followers. This choice is important to > avoid increasing the load on the leader with the number of observers. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.
[jira] Commented: (ZOOKEEPER-368) Observers: core functionality
[ https://issues.apache.org/jira/browse/ZOOKEEPER-368?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12779209#action_12779209 ] Mahadev konar commented on ZOOKEEPER-368: - thats great ill commit the patch tonight! > Observers: core functionality > -- > > Key: ZOOKEEPER-368 > URL: https://issues.apache.org/jira/browse/ZOOKEEPER-368 > Project: Zookeeper > Issue Type: New Feature > Components: quorum >Reporter: Flavio Paiva Junqueira >Assignee: Henry Robinson > Fix For: 3.3.0 > > Attachments: obs-refactor.patch, observer-refactor.patch, observers > sync benchmark.png, observers.patch, ZOOKEEPER-368.patch, > ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, > ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, > ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, ZOOKEEPER-368.patch > > > Edit (Henry Robinson/henryr) 12/11/09: > This JIRA specifically concerns the implementation of non-voting peers called > Observers, their documentation and their tests. > Explicit goals are 1. not breaking any current ZK functionality, 2. enabling > at least one deployment scenario involving Observers, 3. documentation > describing how to use the feature and 4. tests validating the correct > behaviour of 2. > Non goals of this JIRA are 1. performance optimizations specific to > Observers, 2. compatibility with every feature of ZooKeeper (in particular > all leader election protocols), which are both to be addressed in future > JIRAs. > See http://wiki.apache.org/hadoop/ZooKeeper/Observers for more detail of use > cases, proposed design and usage. > See http://wiki.apache.org/hadoop/ZooKeeper/Observers/ReviewGuide for a brief > commentary on the current patch. > - > Currently, all servers of an ensemble participate actively in reaching > agreement on the order of ZooKeeper transactions. That is, all followers > receive proposals, acknowledge them, and receive commit messages from the > leader. A leader issues commit messages once it receives acknowledgments from > a quorum of followers. For cross-colo operation, it would be useful to have a > third role: observer. Using Paxos terminology, observers are similar to > learners. An observer does not participate actively in the agreement step of > the atomic broadcast protocol. Instead, it only commits proposals that have > been accepted by some quorum of followers. > One simple solution to implement observers is to have the leader forwarding > commit messages not only to followers but also to observers, and have > observers applying transactions according to the order followers agreed upon. > In the current implementation of the protocol, however, commit messages do > not carry their corresponding transaction payload because all servers > different from the leader are followers and followers receive such a payload > first through a proposal message. Just forwarding commit messages as they > currently are to an observer consequently is not sufficient. We have a couple > of options: > 1- Include the transaction payload along in commit messages to observers; > 2- Send proposals to observers as well. > Number 2 is simpler to implement because it doesn't require changing the > protocol implementation, but it increases traffic slightly. The performance > impact due to such an increase might be insignificant, though. > For scalability purposes, we may consider having followers also forwarding > commit messages to observers. With this option, observers can connect to > followers, and receive messages from followers. This choice is important to > avoid increasing the load on the leader with the number of observers. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.
[jira] Commented: (ZOOKEEPER-368) Observers: core functionality
[ https://issues.apache.org/jira/browse/ZOOKEEPER-368?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12779205#action_12779205 ] Henry Robinson commented on ZOOKEEPER-368: -- Mahadev - Ah, I understand now. Yes, I just ran that test. Everything works as I expected it to - both when two servers are from the old code and then when two servers are from the new. They can be swapped out for each other will no ill effects, AFAIK. Thanks! Henry > Observers: core functionality > -- > > Key: ZOOKEEPER-368 > URL: https://issues.apache.org/jira/browse/ZOOKEEPER-368 > Project: Zookeeper > Issue Type: New Feature > Components: quorum >Reporter: Flavio Paiva Junqueira >Assignee: Henry Robinson > Fix For: 3.3.0 > > Attachments: obs-refactor.patch, observer-refactor.patch, observers > sync benchmark.png, observers.patch, ZOOKEEPER-368.patch, > ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, > ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, > ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, ZOOKEEPER-368.patch > > > Edit (Henry Robinson/henryr) 12/11/09: > This JIRA specifically concerns the implementation of non-voting peers called > Observers, their documentation and their tests. > Explicit goals are 1. not breaking any current ZK functionality, 2. enabling > at least one deployment scenario involving Observers, 3. documentation > describing how to use the feature and 4. tests validating the correct > behaviour of 2. > Non goals of this JIRA are 1. performance optimizations specific to > Observers, 2. compatibility with every feature of ZooKeeper (in particular > all leader election protocols), which are both to be addressed in future > JIRAs. > See http://wiki.apache.org/hadoop/ZooKeeper/Observers for more detail of use > cases, proposed design and usage. > See http://wiki.apache.org/hadoop/ZooKeeper/Observers/ReviewGuide for a brief > commentary on the current patch. > - > Currently, all servers of an ensemble participate actively in reaching > agreement on the order of ZooKeeper transactions. That is, all followers > receive proposals, acknowledge them, and receive commit messages from the > leader. A leader issues commit messages once it receives acknowledgments from > a quorum of followers. For cross-colo operation, it would be useful to have a > third role: observer. Using Paxos terminology, observers are similar to > learners. An observer does not participate actively in the agreement step of > the atomic broadcast protocol. Instead, it only commits proposals that have > been accepted by some quorum of followers. > One simple solution to implement observers is to have the leader forwarding > commit messages not only to followers but also to observers, and have > observers applying transactions according to the order followers agreed upon. > In the current implementation of the protocol, however, commit messages do > not carry their corresponding transaction payload because all servers > different from the leader are followers and followers receive such a payload > first through a proposal message. Just forwarding commit messages as they > currently are to an observer consequently is not sufficient. We have a couple > of options: > 1- Include the transaction payload along in commit messages to observers; > 2- Send proposals to observers as well. > Number 2 is simpler to implement because it doesn't require changing the > protocol implementation, but it increases traffic slightly. The performance > impact due to such an increase might be insignificant, though. > For scalability purposes, we may consider having followers also forwarding > commit messages to observers. With this option, observers can connect to > followers, and receive messages from followers. This choice is important to > avoid increasing the load on the leader with the number of observers. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.
[jira] Commented: (ZOOKEEPER-368) Observers: core functionality
[ https://issues.apache.org/jira/browse/ZOOKEEPER-368?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12779194#action_12779194 ] Mahadev konar commented on ZOOKEEPER-368: - thanks henry for the comments and testing! Thanks for all the hard work and responses. I have one more question. Sorry I couldnt find the answer to that, so wanted to ask again. I know looking at the code that this shouldnt be a problem but I think it is worth running a small test for it. - the test is to have 2 servers (s1, S2) from the old code and 1 server (s3) with the new code and verify that s1/s2 or s3 are all capable of becoming the leader and everything works fine with neone of them becoming a leader. This could be done by bringing up s1, s2 and s3 at the same time and killing them one at a time and bringing the other up. SOmething like testing a rolling upgrade wherein one server is the new code and the other servers are old code. This is not testing observers but just testing (though I think it should work fine looking at the code) that the older versions will work with the new version irrespective of which of them is the leader. > Observers: core functionality > -- > > Key: ZOOKEEPER-368 > URL: https://issues.apache.org/jira/browse/ZOOKEEPER-368 > Project: Zookeeper > Issue Type: New Feature > Components: quorum >Reporter: Flavio Paiva Junqueira >Assignee: Henry Robinson > Fix For: 3.3.0 > > Attachments: obs-refactor.patch, observer-refactor.patch, observers > sync benchmark.png, observers.patch, ZOOKEEPER-368.patch, > ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, > ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, > ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, ZOOKEEPER-368.patch > > > Edit (Henry Robinson/henryr) 12/11/09: > This JIRA specifically concerns the implementation of non-voting peers called > Observers, their documentation and their tests. > Explicit goals are 1. not breaking any current ZK functionality, 2. enabling > at least one deployment scenario involving Observers, 3. documentation > describing how to use the feature and 4. tests validating the correct > behaviour of 2. > Non goals of this JIRA are 1. performance optimizations specific to > Observers, 2. compatibility with every feature of ZooKeeper (in particular > all leader election protocols), which are both to be addressed in future > JIRAs. > See http://wiki.apache.org/hadoop/ZooKeeper/Observers for more detail of use > cases, proposed design and usage. > See http://wiki.apache.org/hadoop/ZooKeeper/Observers/ReviewGuide for a brief > commentary on the current patch. > - > Currently, all servers of an ensemble participate actively in reaching > agreement on the order of ZooKeeper transactions. That is, all followers > receive proposals, acknowledge them, and receive commit messages from the > leader. A leader issues commit messages once it receives acknowledgments from > a quorum of followers. For cross-colo operation, it would be useful to have a > third role: observer. Using Paxos terminology, observers are similar to > learners. An observer does not participate actively in the agreement step of > the atomic broadcast protocol. Instead, it only commits proposals that have > been accepted by some quorum of followers. > One simple solution to implement observers is to have the leader forwarding > commit messages not only to followers but also to observers, and have > observers applying transactions according to the order followers agreed upon. > In the current implementation of the protocol, however, commit messages do > not carry their corresponding transaction payload because all servers > different from the leader are followers and followers receive such a payload > first through a proposal message. Just forwarding commit messages as they > currently are to an observer consequently is not sufficient. We have a couple > of options: > 1- Include the transaction payload along in commit messages to observers; > 2- Send proposals to observers as well. > Number 2 is simpler to implement because it doesn't require changing the > protocol implementation, but it increases traffic slightly. The performance > impact due to such an increase might be insignificant, though. > For scalability purposes, we may consider having followers also forwarding > commit messages to observers. With this option, observers can connect to > followers, and receive messages from followers. This choice is important to > avoid increasing the load on the leader with the number of observers. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.
[jira] Commented: (ZOOKEEPER-368) Observers: core functionality
[ https://issues.apache.org/jira/browse/ZOOKEEPER-368?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12779186#action_12779186 ] Flavio Paiva Junqueira commented on ZOOKEEPER-368: -- I have just made sure that the docs compile, and after Henry's response, I don't have further comments. + 1, good job, Henry! > Observers: core functionality > -- > > Key: ZOOKEEPER-368 > URL: https://issues.apache.org/jira/browse/ZOOKEEPER-368 > Project: Zookeeper > Issue Type: New Feature > Components: quorum >Reporter: Flavio Paiva Junqueira >Assignee: Henry Robinson > Fix For: 3.3.0 > > Attachments: obs-refactor.patch, observer-refactor.patch, observers > sync benchmark.png, observers.patch, ZOOKEEPER-368.patch, > ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, > ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, > ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, ZOOKEEPER-368.patch > > > Edit (Henry Robinson/henryr) 12/11/09: > This JIRA specifically concerns the implementation of non-voting peers called > Observers, their documentation and their tests. > Explicit goals are 1. not breaking any current ZK functionality, 2. enabling > at least one deployment scenario involving Observers, 3. documentation > describing how to use the feature and 4. tests validating the correct > behaviour of 2. > Non goals of this JIRA are 1. performance optimizations specific to > Observers, 2. compatibility with every feature of ZooKeeper (in particular > all leader election protocols), which are both to be addressed in future > JIRAs. > See http://wiki.apache.org/hadoop/ZooKeeper/Observers for more detail of use > cases, proposed design and usage. > See http://wiki.apache.org/hadoop/ZooKeeper/Observers/ReviewGuide for a brief > commentary on the current patch. > - > Currently, all servers of an ensemble participate actively in reaching > agreement on the order of ZooKeeper transactions. That is, all followers > receive proposals, acknowledge them, and receive commit messages from the > leader. A leader issues commit messages once it receives acknowledgments from > a quorum of followers. For cross-colo operation, it would be useful to have a > third role: observer. Using Paxos terminology, observers are similar to > learners. An observer does not participate actively in the agreement step of > the atomic broadcast protocol. Instead, it only commits proposals that have > been accepted by some quorum of followers. > One simple solution to implement observers is to have the leader forwarding > commit messages not only to followers but also to observers, and have > observers applying transactions according to the order followers agreed upon. > In the current implementation of the protocol, however, commit messages do > not carry their corresponding transaction payload because all servers > different from the leader are followers and followers receive such a payload > first through a proposal message. Just forwarding commit messages as they > currently are to an observer consequently is not sufficient. We have a couple > of options: > 1- Include the transaction payload along in commit messages to observers; > 2- Send proposals to observers as well. > Number 2 is simpler to implement because it doesn't require changing the > protocol implementation, but it increases traffic slightly. The performance > impact due to such an increase might be insignificant, though. > For scalability purposes, we may consider having followers also forwarding > commit messages to observers. With this option, observers can connect to > followers, and receive messages from followers. This choice is important to > avoid increasing the load on the leader with the number of observers. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.
[jira] Commented: (ZOOKEEPER-368) Observers: core functionality
[ https://issues.apache.org/jira/browse/ZOOKEEPER-368?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12779184#action_12779184 ] Henry Robinson commented on ZOOKEEPER-368: -- Flavio - Thanks for your comments! 1. Will do. 2. QuorumPeerTestBase is extended by QuorumPeerMainTest and ObserverTest; it seemed to make sense to introduce a base class rather than have ObserverTest extend QuorumPeerMainTest and then have to manually disable the tests that I didn't want to run. Also, it makes the test classes themselves shorter and easier to reason about, 3. See above. Henry > Observers: core functionality > -- > > Key: ZOOKEEPER-368 > URL: https://issues.apache.org/jira/browse/ZOOKEEPER-368 > Project: Zookeeper > Issue Type: New Feature > Components: quorum >Reporter: Flavio Paiva Junqueira >Assignee: Henry Robinson > Fix For: 3.3.0 > > Attachments: obs-refactor.patch, observer-refactor.patch, observers > sync benchmark.png, observers.patch, ZOOKEEPER-368.patch, > ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, > ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, > ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, ZOOKEEPER-368.patch > > > Edit (Henry Robinson/henryr) 12/11/09: > This JIRA specifically concerns the implementation of non-voting peers called > Observers, their documentation and their tests. > Explicit goals are 1. not breaking any current ZK functionality, 2. enabling > at least one deployment scenario involving Observers, 3. documentation > describing how to use the feature and 4. tests validating the correct > behaviour of 2. > Non goals of this JIRA are 1. performance optimizations specific to > Observers, 2. compatibility with every feature of ZooKeeper (in particular > all leader election protocols), which are both to be addressed in future > JIRAs. > See http://wiki.apache.org/hadoop/ZooKeeper/Observers for more detail of use > cases, proposed design and usage. > See http://wiki.apache.org/hadoop/ZooKeeper/Observers/ReviewGuide for a brief > commentary on the current patch. > - > Currently, all servers of an ensemble participate actively in reaching > agreement on the order of ZooKeeper transactions. That is, all followers > receive proposals, acknowledge them, and receive commit messages from the > leader. A leader issues commit messages once it receives acknowledgments from > a quorum of followers. For cross-colo operation, it would be useful to have a > third role: observer. Using Paxos terminology, observers are similar to > learners. An observer does not participate actively in the agreement step of > the atomic broadcast protocol. Instead, it only commits proposals that have > been accepted by some quorum of followers. > One simple solution to implement observers is to have the leader forwarding > commit messages not only to followers but also to observers, and have > observers applying transactions according to the order followers agreed upon. > In the current implementation of the protocol, however, commit messages do > not carry their corresponding transaction payload because all servers > different from the leader are followers and followers receive such a payload > first through a proposal message. Just forwarding commit messages as they > currently are to an observer consequently is not sufficient. We have a couple > of options: > 1- Include the transaction payload along in commit messages to observers; > 2- Send proposals to observers as well. > Number 2 is simpler to implement because it doesn't require changing the > protocol implementation, but it increases traffic slightly. The performance > impact due to such an increase might be insignificant, though. > For scalability purposes, we may consider having followers also forwarding > commit messages to observers. With this option, observers can connect to > followers, and receive messages from followers. This choice is important to > avoid increasing the load on the leader with the number of observers. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.
[jira] Commented: (ZOOKEEPER-368) Observers: core functionality
[ https://issues.apache.org/jira/browse/ZOOKEEPER-368?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12779178#action_12779178 ] Henry Robinson commented on ZOOKEEPER-368: -- Thanks Ben! I agree that 581 is a genuine issue, I'll take it up over on its JIRA. Mahadev - An Observer won't be able to connect to a pre-Observer ensemble because it doesn't send FOLLOWERINFO (rather, it sends OBSERVERINFO). The effect is that it retries, and is rejected. I have just verified this. If a server is brought down and reconnects as an Observer, it will be able to connect to the ensemble without problem. The Leader does not validate the type of the Learner that connects so it happily accepts the OBSERVERINFO handshake and carries on. It is possible that, if the process was restarted very quickly and the server was originally the Leader, that there might be some confusion when the Observer refuses to issue proposals. My belief is that the old Leader would be identified as failed. This should probably be considered user error? Users must not try and start the cluster with different configurations at each node. I can think of similar 'bugs' in the current code where different servers have different configurations and therefore acknowledge different quorum groups, meaning that there wouldn't be consensus on who is the Leader, for example. > Observers: core functionality > -- > > Key: ZOOKEEPER-368 > URL: https://issues.apache.org/jira/browse/ZOOKEEPER-368 > Project: Zookeeper > Issue Type: New Feature > Components: quorum >Reporter: Flavio Paiva Junqueira >Assignee: Henry Robinson > Fix For: 3.3.0 > > Attachments: obs-refactor.patch, observer-refactor.patch, observers > sync benchmark.png, observers.patch, ZOOKEEPER-368.patch, > ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, > ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, > ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, ZOOKEEPER-368.patch > > > Edit (Henry Robinson/henryr) 12/11/09: > This JIRA specifically concerns the implementation of non-voting peers called > Observers, their documentation and their tests. > Explicit goals are 1. not breaking any current ZK functionality, 2. enabling > at least one deployment scenario involving Observers, 3. documentation > describing how to use the feature and 4. tests validating the correct > behaviour of 2. > Non goals of this JIRA are 1. performance optimizations specific to > Observers, 2. compatibility with every feature of ZooKeeper (in particular > all leader election protocols), which are both to be addressed in future > JIRAs. > See http://wiki.apache.org/hadoop/ZooKeeper/Observers for more detail of use > cases, proposed design and usage. > See http://wiki.apache.org/hadoop/ZooKeeper/Observers/ReviewGuide for a brief > commentary on the current patch. > - > Currently, all servers of an ensemble participate actively in reaching > agreement on the order of ZooKeeper transactions. That is, all followers > receive proposals, acknowledge them, and receive commit messages from the > leader. A leader issues commit messages once it receives acknowledgments from > a quorum of followers. For cross-colo operation, it would be useful to have a > third role: observer. Using Paxos terminology, observers are similar to > learners. An observer does not participate actively in the agreement step of > the atomic broadcast protocol. Instead, it only commits proposals that have > been accepted by some quorum of followers. > One simple solution to implement observers is to have the leader forwarding > commit messages not only to followers but also to observers, and have > observers applying transactions according to the order followers agreed upon. > In the current implementation of the protocol, however, commit messages do > not carry their corresponding transaction payload because all servers > different from the leader are followers and followers receive such a payload > first through a proposal message. Just forwarding commit messages as they > currently are to an observer consequently is not sufficient. We have a couple > of options: > 1- Include the transaction payload along in commit messages to observers; > 2- Send proposals to observers as well. > Number 2 is simpler to implement because it doesn't require changing the > protocol implementation, but it increases traffic slightly. The performance > impact due to such an increase might be insignificant, though. > For scalability purposes, we may consider having followers also forwarding > commit messages to observers. With this option, observers can connect to > followers, and receive messages from followers. This choice is important to > avoid increasing the load on the
[jira] Commented: (ZOOKEEPER-368) Observers: core functionality
[ https://issues.apache.org/jira/browse/ZOOKEEPER-368?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12779176#action_12779176 ] Flavio Paiva Junqueira commented on ZOOKEEPER-368: -- Henry, thanks for all the changes, a few quick comments: # You've added a TODO to leader.java, which was a good catch. I don't want to make you generate another patch just to fix the majority check on that message, so if prefer not to do it, could you make sure there is a jira to fix it? # I didn't quite understand why you moved all that code between QuorumPeerMainTest and QuorumPeerTestBase. Would you mind just commenting quickly? # Mahadev gave some good suggestions for tests we should perform before committing. Would you mind running those tests? > Observers: core functionality > -- > > Key: ZOOKEEPER-368 > URL: https://issues.apache.org/jira/browse/ZOOKEEPER-368 > Project: Zookeeper > Issue Type: New Feature > Components: quorum >Reporter: Flavio Paiva Junqueira >Assignee: Henry Robinson > Fix For: 3.3.0 > > Attachments: obs-refactor.patch, observer-refactor.patch, observers > sync benchmark.png, observers.patch, ZOOKEEPER-368.patch, > ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, > ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, > ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, ZOOKEEPER-368.patch > > > Edit (Henry Robinson/henryr) 12/11/09: > This JIRA specifically concerns the implementation of non-voting peers called > Observers, their documentation and their tests. > Explicit goals are 1. not breaking any current ZK functionality, 2. enabling > at least one deployment scenario involving Observers, 3. documentation > describing how to use the feature and 4. tests validating the correct > behaviour of 2. > Non goals of this JIRA are 1. performance optimizations specific to > Observers, 2. compatibility with every feature of ZooKeeper (in particular > all leader election protocols), which are both to be addressed in future > JIRAs. > See http://wiki.apache.org/hadoop/ZooKeeper/Observers for more detail of use > cases, proposed design and usage. > See http://wiki.apache.org/hadoop/ZooKeeper/Observers/ReviewGuide for a brief > commentary on the current patch. > - > Currently, all servers of an ensemble participate actively in reaching > agreement on the order of ZooKeeper transactions. That is, all followers > receive proposals, acknowledge them, and receive commit messages from the > leader. A leader issues commit messages once it receives acknowledgments from > a quorum of followers. For cross-colo operation, it would be useful to have a > third role: observer. Using Paxos terminology, observers are similar to > learners. An observer does not participate actively in the agreement step of > the atomic broadcast protocol. Instead, it only commits proposals that have > been accepted by some quorum of followers. > One simple solution to implement observers is to have the leader forwarding > commit messages not only to followers but also to observers, and have > observers applying transactions according to the order followers agreed upon. > In the current implementation of the protocol, however, commit messages do > not carry their corresponding transaction payload because all servers > different from the leader are followers and followers receive such a payload > first through a proposal message. Just forwarding commit messages as they > currently are to an observer consequently is not sufficient. We have a couple > of options: > 1- Include the transaction payload along in commit messages to observers; > 2- Send proposals to observers as well. > Number 2 is simpler to implement because it doesn't require changing the > protocol implementation, but it increases traffic slightly. The performance > impact due to such an increase might be insignificant, though. > For scalability purposes, we may consider having followers also forwarding > commit messages to observers. With this option, observers can connect to > followers, and receive messages from followers. This choice is important to > avoid increasing the load on the leader with the number of observers. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.
[jira] Commented: (ZOOKEEPER-368) Observers: core functionality
[ https://issues.apache.org/jira/browse/ZOOKEEPER-368?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12778704#action_12778704 ] Mahadev konar commented on ZOOKEEPER-368: - henry, did you get a chance to test observers with old (meaning without hte patch) zookeeper servers? repeating my comments here: - looking at the patch it seems like it would work with servers prior to including this patch. Did you try some testing with current servers (killing one at a time and brining them up in a round robin fashion) just to make sure it works all fine with the current servers (not including the patch)? - what happens if a server configured as follower is suddenly brought down and is made an observer and the other way around as well? Just checking to see if we have these scenarios covered because such mistakes are easy to make when setting up servers > Observers: core functionality > -- > > Key: ZOOKEEPER-368 > URL: https://issues.apache.org/jira/browse/ZOOKEEPER-368 > Project: Zookeeper > Issue Type: New Feature > Components: quorum >Reporter: Flavio Paiva Junqueira >Assignee: Henry Robinson > Fix For: 3.3.0 > > Attachments: obs-refactor.patch, observer-refactor.patch, observers > sync benchmark.png, observers.patch, ZOOKEEPER-368.patch, > ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, > ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, > ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, ZOOKEEPER-368.patch > > > Edit (Henry Robinson/henryr) 12/11/09: > This JIRA specifically concerns the implementation of non-voting peers called > Observers, their documentation and their tests. > Explicit goals are 1. not breaking any current ZK functionality, 2. enabling > at least one deployment scenario involving Observers, 3. documentation > describing how to use the feature and 4. tests validating the correct > behaviour of 2. > Non goals of this JIRA are 1. performance optimizations specific to > Observers, 2. compatibility with every feature of ZooKeeper (in particular > all leader election protocols), which are both to be addressed in future > JIRAs. > See http://wiki.apache.org/hadoop/ZooKeeper/Observers for more detail of use > cases, proposed design and usage. > See http://wiki.apache.org/hadoop/ZooKeeper/Observers/ReviewGuide for a brief > commentary on the current patch. > - > Currently, all servers of an ensemble participate actively in reaching > agreement on the order of ZooKeeper transactions. That is, all followers > receive proposals, acknowledge them, and receive commit messages from the > leader. A leader issues commit messages once it receives acknowledgments from > a quorum of followers. For cross-colo operation, it would be useful to have a > third role: observer. Using Paxos terminology, observers are similar to > learners. An observer does not participate actively in the agreement step of > the atomic broadcast protocol. Instead, it only commits proposals that have > been accepted by some quorum of followers. > One simple solution to implement observers is to have the leader forwarding > commit messages not only to followers but also to observers, and have > observers applying transactions according to the order followers agreed upon. > In the current implementation of the protocol, however, commit messages do > not carry their corresponding transaction payload because all servers > different from the leader are followers and followers receive such a payload > first through a proposal message. Just forwarding commit messages as they > currently are to an observer consequently is not sufficient. We have a couple > of options: > 1- Include the transaction payload along in commit messages to observers; > 2- Send proposals to observers as well. > Number 2 is simpler to implement because it doesn't require changing the > protocol implementation, but it increases traffic slightly. The performance > impact due to such an increase might be insignificant, though. > For scalability purposes, we may consider having followers also forwarding > commit messages to observers. With this option, observers can connect to > followers, and receive messages from followers. This choice is important to > avoid increasing the load on the leader with the number of observers. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.
[jira] Commented: (ZOOKEEPER-368) Observers: core functionality
[ https://issues.apache.org/jira/browse/ZOOKEEPER-368?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12778612#action_12778612 ] Hadoop QA commented on ZOOKEEPER-368: - +1 overall. Here are the results of testing the latest attachment http://issues.apache.org/jira/secure/attachment/12425104/ZOOKEEPER-368.patch against trunk revision 835618. +1 @author. The patch does not contain any @author tags. +1 tests included. The patch appears to include 25 new or modified tests. +1 javadoc. The javadoc tool did not generate any warning messages. +1 javac. The applied patch does not increase the total number of javac compiler warnings. +1 findbugs. The patch does not introduce any new Findbugs warnings. +1 release audit. The applied patch does not increase the total number of release audit warnings. +1 core tests. The patch passed core unit tests. +1 contrib tests. The patch passed contrib unit tests. Test results: http://hudson.zones.apache.org/hudson/job/Zookeeper-Patch-h8.grid.sp2.yahoo.net/64/testReport/ Findbugs warnings: http://hudson.zones.apache.org/hudson/job/Zookeeper-Patch-h8.grid.sp2.yahoo.net/64/artifact/trunk/build/test/findbugs/newPatchFindbugsWarnings.html Console output: http://hudson.zones.apache.org/hudson/job/Zookeeper-Patch-h8.grid.sp2.yahoo.net/64/console This message is automatically generated. > Observers: core functionality > -- > > Key: ZOOKEEPER-368 > URL: https://issues.apache.org/jira/browse/ZOOKEEPER-368 > Project: Zookeeper > Issue Type: New Feature > Components: quorum >Reporter: Flavio Paiva Junqueira >Assignee: Henry Robinson > Fix For: 3.3.0 > > Attachments: obs-refactor.patch, observer-refactor.patch, observers > sync benchmark.png, observers.patch, ZOOKEEPER-368.patch, > ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, > ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, > ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, ZOOKEEPER-368.patch > > > Edit (Henry Robinson/henryr) 12/11/09: > This JIRA specifically concerns the implementation of non-voting peers called > Observers, their documentation and their tests. > Explicit goals are 1. not breaking any current ZK functionality, 2. enabling > at least one deployment scenario involving Observers, 3. documentation > describing how to use the feature and 4. tests validating the correct > behaviour of 2. > Non goals of this JIRA are 1. performance optimizations specific to > Observers, 2. compatibility with every feature of ZooKeeper (in particular > all leader election protocols), which are both to be addressed in future > JIRAs. > See http://wiki.apache.org/hadoop/ZooKeeper/Observers for more detail of use > cases, proposed design and usage. > See http://wiki.apache.org/hadoop/ZooKeeper/Observers/ReviewGuide for a brief > commentary on the current patch. > - > Currently, all servers of an ensemble participate actively in reaching > agreement on the order of ZooKeeper transactions. That is, all followers > receive proposals, acknowledge them, and receive commit messages from the > leader. A leader issues commit messages once it receives acknowledgments from > a quorum of followers. For cross-colo operation, it would be useful to have a > third role: observer. Using Paxos terminology, observers are similar to > learners. An observer does not participate actively in the agreement step of > the atomic broadcast protocol. Instead, it only commits proposals that have > been accepted by some quorum of followers. > One simple solution to implement observers is to have the leader forwarding > commit messages not only to followers but also to observers, and have > observers applying transactions according to the order followers agreed upon. > In the current implementation of the protocol, however, commit messages do > not carry their corresponding transaction payload because all servers > different from the leader are followers and followers receive such a payload > first through a proposal message. Just forwarding commit messages as they > currently are to an observer consequently is not sufficient. We have a couple > of options: > 1- Include the transaction payload along in commit messages to observers; > 2- Send proposals to observers as well. > Number 2 is simpler to implement because it doesn't require changing the > protocol implementation, but it increases traffic slightly. The performance > impact due to such an increase might be insignificant, though. > For scalability purposes, we may consider having followers also forwarding > commit messages to observers. With this option, observers can connect to > followers, and receive messages from followers. This choice is important to > avoid incre
[jira] Commented: (ZOOKEEPER-368) Observers: core functionality
[ https://issues.apache.org/jira/browse/ZOOKEEPER-368?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12778447#action_12778447 ] Mahadev konar commented on ZOOKEEPER-368: - henry, you dont have to upload the diff the built docs (pdf/html). THe person committing the patch will run ant docs and commit the updated docs in src/docs. > Observers: core functionality > -- > > Key: ZOOKEEPER-368 > URL: https://issues.apache.org/jira/browse/ZOOKEEPER-368 > Project: Zookeeper > Issue Type: New Feature > Components: quorum >Reporter: Flavio Paiva Junqueira >Assignee: Henry Robinson > Attachments: obs-refactor.patch, observer-refactor.patch, observers > sync benchmark.png, observers.patch, ZOOKEEPER-368.patch, > ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, > ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, > ZOOKEEPER-368.patch, ZOOKEEPER-368.patch, ZOOKEEPER-368.patch > > > Edit (Henry Robinson/henryr) 12/11/09: > This JIRA specifically concerns the implementation of non-voting peers called > Observers, their documentation and their tests. > Explicit goals are 1. not breaking any current ZK functionality, 2. enabling > at least one deployment scenario involving Observers, 3. documentation > describing how to use the feature and 4. tests validating the correct > behaviour of 2. > Non goals of this JIRA are 1. performance optimizations specific to > Observers, 2. compatibility with every feature of ZooKeeper (in particular > all leader election protocols), which are both to be addressed in future > JIRAs. > See http://wiki.apache.org/hadoop/ZooKeeper/Observers for more detail of use > cases, proposed design and usage. > See http://wiki.apache.org/hadoop/ZooKeeper/Observers/ReviewGuide for a brief > commentary on the current patch. > - > Currently, all servers of an ensemble participate actively in reaching > agreement on the order of ZooKeeper transactions. That is, all followers > receive proposals, acknowledge them, and receive commit messages from the > leader. A leader issues commit messages once it receives acknowledgments from > a quorum of followers. For cross-colo operation, it would be useful to have a > third role: observer. Using Paxos terminology, observers are similar to > learners. An observer does not participate actively in the agreement step of > the atomic broadcast protocol. Instead, it only commits proposals that have > been accepted by some quorum of followers. > One simple solution to implement observers is to have the leader forwarding > commit messages not only to followers but also to observers, and have > observers applying transactions according to the order followers agreed upon. > In the current implementation of the protocol, however, commit messages do > not carry their corresponding transaction payload because all servers > different from the leader are followers and followers receive such a payload > first through a proposal message. Just forwarding commit messages as they > currently are to an observer consequently is not sufficient. We have a couple > of options: > 1- Include the transaction payload along in commit messages to observers; > 2- Send proposals to observers as well. > Number 2 is simpler to implement because it doesn't require changing the > protocol implementation, but it increases traffic slightly. The performance > impact due to such an increase might be insignificant, though. > For scalability purposes, we may consider having followers also forwarding > commit messages to observers. With this option, observers can connect to > followers, and receive messages from followers. This choice is important to > avoid increasing the load on the leader with the number of observers. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.
