dosubot[bot] commented on issue #2634:
URL:
https://github.com/apache/incubator-hugegraph/issues/2634#issuecomment-2287765404
<!-- Answer -->
Yes, it is possible for another thread to make modifications in the
`getPartitionById` method after the `waitGraphLock` method is called, because
`waitGraphLock` only waits until the lock is released and does not hold the
lock itself.
To ensure thread safety in this scenario, you should use the `lockGraph`
method to acquire the lock before performing the get query and then release the
lock using the `unlockGraph` method after the query is done. Here is how you
can modify the `getPartitionById` method to ensure thread safety:
```java
public KVPair<Metapb.Partition, Metapb.Shard> getPartitionById(String
graphName, int partId) {
try {
lockGraph(graphName); // Acquire the lock
GraphCache graph = initGraph(graphName);
Partition partition = graph.getPartition(partId);
if (partition == null) {
return null;
}
KVPair<ShardGroup, Shard> group = groups.get(partId);
if (group == null) {
return null;
}
Shard shard = group.getValue();
if (shard == null) {
return null;
}
return new KVPair<>(partition, shard);
} finally {
unlockGraph(graphName); // Release the lock
}
}
```
By acquiring the lock before accessing the `partitionCache` and releasing it
afterward, you ensure that no other thread can modify the cache while the
current thread is performing the get query. This approach leverages the
`ReentrantReadWriteLock` from the `GraphCache` class to manage concurrent
access to the partitions, ensuring thread safety
<sup>[[1]](https://github.com/apache/incubator-hugegraph/blob/master/hugegraph-pd/hg-pd-common/src/main/java/org/apache/hugegraph/pd/common/PartitionCache.java)</sup><sup>[[2]](https://github.com/apache/incubator-hugegraph/blob/master/hugegraph-pd/hg-pd-common/src/main/java/org/apache/hugegraph/pd/common/GraphCache.java)</sup><sup>[[3]](https://github.com/apache/incubator-hugegraph/blob/master/hugegraph-pd/hg-pd-client/src/main/java/org/apache/hugegraph/pd/client/ClientCache.java)</sup>.
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