peterxcli commented on code in PR #8935: URL: https://github.com/apache/ozone/pull/8935#discussion_r2312247216
########## hadoop-hdds/docs/content/design/listener-om.md: ########## @@ -0,0 +1,102 @@ +--- +title: "Listener Ozone Manager" +summary: Read-only Ozone Manager to scale out read performance. +date: 2025-08-27 +jira: HDDS-11523 +status: implementing +author: Janus Chow, Wei-Chiu Chuang +--- +<!-- + Licensed to the Apache Software Foundation (ASF) under one or more + contributor license agreements. See the NOTICE file distributed with + this work for additional information regarding copyright ownership. + The ASF licenses this file to You under the Apache License, Version 2.0 + (the "License"); you may not use this file except in compliance with + the License. You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + + Unless required by applicable law or agreed to in writing, software + distributed under the License is distributed on an "AS IS" BASIS, + WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + See the License for the specific language governing permissions and + limitations under the License. +--> + +## Introduction + +The Listener Ozone Manager (OM) is a read-only, non-voting member of the OM High Availability (HA) group. It receives all log entries from the leader and stays up-to-date, but it does not participate in leader election or consensus votes. This allows Listener OMs to serve read requests from clients, which can significantly improve read performance and reduce the load on the voting OMs. + +## Why use Listener OMs? + +In a standard OM HA setup, all OMs are peers and participate in the Raft consensus protocol. This means that all OMs are involved in the write path, which can become a bottleneck for read-heavy workloads. By introducing Listener OMs, you can scale out your read performance by offloading read requests to these read-only OMs. + +## How it works + +A Listener OM is a regular OM that is configured to be a listener. When an OM is configured as a listener, it is added to the Ratis group as a listener. This means that it will receive all log entries from the leader, but it will not participate in the leader election or consensus votes. Review Comment: Listeners wont participant consensus vote, but not sure if they involve the commit index forwarding condition/criteria. I plan to look into it later, but if you already have knowledge on it, appreciate to hear :) -- 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] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
