massakam opened a new pull request, #4244: URL: https://github.com/apache/bookkeeper/pull/4244
### Motivation If the system property `readonlymode.enabled` is set to true on a ZooKeeper server, read-only mode is enabled. Data can be read from the server in read-only mode even if that server is split from the quorum. https://zookeeper.apache.org/doc/current/zookeeperAdmin.html#Experimental+Options%2FFeatures To connect to the server in read-only mode, the client must also allow read-only mode. The `ZooKeeperClient` class in the bookkeeper repository also has an option called `allowReadOnlyMode`. https://github.com/apache/bookkeeper/blob/15171e1904f7196d8e9f4116ab2aecdf582e0032/bookkeeper-server/src/main/java/org/apache/bookkeeper/zookeeper/ZooKeeperClient.java#L219-L222 However, even if this option is set to true, the connection to the server in read-only mode will actually fail. The cause is in the `ZooKeeperWatcherBase` class. When the `ZooKeeperWatcherBase` class receives the `SyncConnected` event, it releases `clientConnectLatch` and assumes that the connection is complete. https://github.com/apache/bookkeeper/blob/15171e1904f7196d8e9f4116ab2aecdf582e0032/bookkeeper-server/src/main/java/org/apache/bookkeeper/zookeeper/ZooKeeperWatcherBase.java#L128-L144 However, if the server is in read-only mode, it will receive `ConnectedReadOnly` instead of `SyncConnected`. This causes the connection to time out without being completed. ### Changes Modified the switch statement in the `ZooKeeperWatcherBase` class to release `clientConnectLatch` when `ConnectedReadOnly` is received if the `allowReadOnlyMode` option is true. By the way, `allowReadOnlyMode` is never set to true in BookKeeper. So this change would be useless for BookKeeper. However, it is useful for Pulsar. Because Pulsar also uses `ZooKeeperWatcherBase` and needs to be able to connect to ZooKeeper in read-only mode. https://github.com/apache/pulsar/blob/cba1600d0f6a82f1ea194f3214a80f283fe8dc27/pulsar-metadata/src/main/java/org/apache/pulsar/metadata/impl/PulsarZooKeeperClient.java#L242-L244 -- 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]
