dosubot[bot] commented on issue #2576:
URL:
https://github.com/apache/incubator-hugegraph/issues/2576#issuecomment-2225037702
<!-- Answer -->
To resolve the cache invalidation issue of the partition->leader shard in
`ClientCache`, you need to ensure that the cache is properly reset and
reinitialized when the leader changes in the PD cluster. Here are the key steps
to address this:
1. **Set Initialization Flag to False**: After resetting the cache, set the
initialization flag to false to allow reinitialization.
2. **Update Cache on Miss**: If the cache misses, update the cache with the
results of the query from the PD.
The provided code already includes mechanisms to handle leader change events
and invalidate the cache:
```java
storeWatcher = pdWatch.watchNode(new PDWatch.Listener<>() {
@Override
public void onNext(NodeEvent response) {
log.info("PDClient receive store event {} {}",
response.getEventType(),
Long.toHexString(response.getNodeId()));
if (response.getEventType() == NODE_PD_LEADER_CHANGE) {
// pd raft change
var leaderIp = response.getGraph();
log.info("watchNode: pd leader changed to {}, current watch:{}",
leaderIp, pdWatch.getCurrentHost());
closeStub(!Objects.equals(pdWatch.getCurrentHost(), leaderIp));
connectPdWatch(leaderIp);
}
invalidStoreCache(response.getNodeId());
eventListeners.forEach(listener -> {
listener.onStoreChanged(response);
});
}
@Override
public void onError(Throwable throwable) {
log.error("watchNode exception {}", throwable.getMessage());
closeStub(false);
}
});
```
Additionally, the `updatePartitionLeader` method is used to update the cache
when the leader changes:
```java
public void updatePartitionLeader(String graphName, int partId, long
leaderStoreId) {
KVPair<Metapb.Partition, Metapb.Shard> partShard = null;
try {
partShard = this.getPartitionById(graphName, partId);
if (partShard != null && partShard.getValue().getStoreId() !=
leaderStoreId) {
var shardGroup = this.getShardGroup(partId);
Metapb.Shard shard = null;
List<Metapb.Shard> shards = new ArrayList<>();
for (Metapb.Shard s : shardGroup.getShardsList()) {
if (s.getStoreId() == leaderStoreId) {
shard = s;
shards.add(Metapb.Shard.newBuilder(s)
.setStoreId(s.getStoreId())
.setRole(Metapb.ShardRole.Leader).build());
} else {
shards.add(Metapb.Shard.newBuilder(s)
.setStoreId(s.getStoreId())
.setRole(Metapb.ShardRole.Follower).build());
}
}
if (config.isEnableCache()) {
if (shard == null) {
cache.removePartition(graphName, partId);
}
}
}
} catch (PDException e) {
log.error("getPartitionException: {}", e.getMessage());
}
}
```
Ensure these methods are correctly invoked and the cache is properly
configured to handle these updates. This will help manage the cache
invalidation issue effectively
<sup>[[1]](https://github.com/apache/incubator-hugegraph/blob/master/hugegraph-pd/hg-pd-client/src/main/java/org/apache/hugegraph/pd/client/PDClient.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/PartitionCache.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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