codelipenghui commented on code in PR #21011: URL: https://github.com/apache/pulsar/pull/21011#discussion_r1300028168
########## pip/pip-294.md: ########## @@ -0,0 +1,66 @@ +# Background knowledge + +There are mainly two `LoadManager` implementation in Pulsar broker: `ExtensibleLoadManager` and `ModularLoadManagerImpl`. `ModularLoadManagerImpl` is the default load manager, and `ExtensibleLoadManager` is a new load manager which is proposed after 3.0.0 version. + +## ModularLoadManagerImpl +`ModularLoadManagerImpl` rely on zk to store and synchronize metadata about load, which pose greate pressure on zk, threatening the stability of system. Every broker will upload its `LocalBrokerData` to zk, and leader broker will retrieve all `LocalBrokerData` from zk, generate all `BundleData` from each `LocalBrokerData`, and update all `BundleData` to zk. + +## ExtensibleLoadManager +`ExtensibleLoadManager` depends on system topics and table views for load balance metadata store and replication. Though not using zk to store and synchronize metadata about load, it is still necessary to control the number of bundles that need to be updated, for which there is a `loadBalancerMaxNumberOfBundlesInBundleLoadReport` configuration in `ExtensibleLoadManager` that select the top k bundles. Review Comment: Is the `loadBalancerMaxNumberOfBundlesInBundleLoadReport` also work for `ModularLoadManagerImpl`? If yes, it's better to have a separated section. ########## pip/pip-294.md: ########## @@ -0,0 +1,56 @@ +# Background knowledge + +Load balance module in Pulsar broker rely on zk to store and synchronize metadata about load. Every broker will upload its `LocalBrokerData` to zk, and leader broker will retrieve all `LocalBrokerData` from zk ,generate all `BundleData` from each `LocalBrokerData`, and update all `BundleData` to zk. + + +# Motivation + +As every bundle in the cluster corresponds to a zk node, it is common that there are thousands of zk nodes in a cluster, which results into thousands of read/update operations to zk. This will cause a lot of pressure on zk. + +**As All Load Shedding Algorithm pick bundles from top to bottom based on throughput/msgRate, bundles with low throughput/msgRate are rarely be selected for shedding. So there is no need to update these bundleData to zk frequently.** Review Comment: Ok, we'd better change to "So that we don't need to contain these bundles in the bundle load report" -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
