HBASE-30220: A replica cluster can have read-only mode disabled even when another active cluster already exists#8377
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…when another active cluster already exists Code generated with Claude Opus 4.6 and modified by hand after Change-Id: Ifb6992d1c9d6982cdcec0522d7b75ed9f985c0e3
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These unit test failures are not relevant. |
anmolnar
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Only a few nitpicks from me.
| * already exists on the same storage location. | ||
| */ | ||
| @InterfaceAudience.Public | ||
| public class ReadOnlyTransitionException extends DoNotRetryIOException { |
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nit: Could encapsulate a String field identifying the current active cluster's ID and emitted to log when the exception is converted to string.
| * Returns a copied version of the provided Configuration object that has | ||
| * {@link HConstants#HBASE_GLOBAL_READONLY_ENABLED_KEY} set to true. | ||
| */ | ||
| public static Configuration getReadOnlyEnabledConfigurationCopy(Configuration conf) { |
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I think setReadOnlyEnabledConfigurationCopy would be a better name for this method.
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IMO the name should use get instead of set since the method returns a modified copy of the configuration. The original configuration is left untouched.
…an in HBaseServerBase Change-Id: I2794ed6ce5e6ea3665d55185c0938fa430525f85
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https://issues.apache.org/jira/browse/HBASE-30220
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These changes were generated using Claude Opus 4.6 and then modified by hand.
Summary
In a Read-Replica cluster setup, the active cluster allows both reads and writes, while the replica clusters only allow reads. In this type of setup, only one cluster should be an active cluster at a time. Although the current code prevents starting an active cluster while another one exists, it is still possible to simple turn a running replica into an active cluster despite another active cluster already existing. The changes in this pull request prevent this behavior.
A cluster is promoted from replica to active by changing the
hbase.global.readonly.enabledvariable fromtruetofalseinhbase-site.xmland then runningupdate_all_configin the HBase shell. The current active cluster is tracked by having the cluster's ID in a file calledactive.cluster.suffix.id. This file does not exist when all clusters are replicas.Key Changes
volatile booleanflag calledreadOnlyTransitionBlockedto HBaseServerBase. This is used to track whether a cluster was prevented from becoming an active cluster due to another active cluster already existing.falsetotrue, thenreadOnlyTransitionBlockedis set totrue, and a new exception calledReadOnlyTransitionExceptionis thrown in the HBase shell.staticmethod toAbstractReadOnlyControllercalledisAnotherClusterActive(). This returns true when the cluster ID inactive.cluster.suffix.iddoes not match the current cluster.onConfigurationChange()inHMaster,HRegionServer, andHRegionto prevent the replica cluster from being promoted to an active cluster when another active cluster exists.