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Updating master
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can you give a little more context here? if a number of nodes register with the same service, you want to pick the one with the lowest sequential id to write to? how/where do you use these sequential nodes? |
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yes but there's an issue that i found in deleting the node, because @key doesn't contain the sequence and the node doesn't know which sequence did it get, i'll work on that and update the code. as for usage, yes it's for leader election, to use the node with the lowest sequence as the master node, suitable for services that must have a leader/master such as DB's, the consumer that will have synapse installed, will read the lowest sequence node from haproxy and consider it the master node |
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@igor47 the pull request is ready now |
lib/nerve/service_watcher.rb
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i think you meant || here instead of | ?
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i am not sure how this code would be used right now; i would like to see a matching PR for nerve that takes advantage of this feature before merging. i am concerned that if the sequential id is being appended to the node name ( additionally, i've heard concerns about the general node naming strategy for nerve. i might be open to the idea of making all node names sequential ids, and including more information (like hostname) in the node information instead. this would solve the problem we fix here. |
lib/nerve/reporter.rb
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the '-' is inserted to help visualize the sequence and separate from the port in the node path/key
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I'm currently working on consuming this feature and will be opening a PR for the usage of it. as for using the sequence as an id, a key must be provided before the sequence can be appended to it, that is not a problem however and it's still a valid approach because each time a new sequential node is created with the same key, a new sequence will be appended and thus can fix the issue. |
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I opened a PR for synapse to consume this feature, and use haproxy to set the slave nodes as backup servers airbnb/synapse#29 |
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+1 for this. Would be a very useful feature when dealing with master/slave db pairs and similar setups. |
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@igor47 what's the status of merging this PR? |
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added the ability to use ZK leader election capability