dpol1 opened a new issue, #3036:
URL: https://github.com/apache/hugegraph/issues/3036
- Follow-up to #3011.
That PR made `CachedSchemaTransactionV2` listen for `schema-cache-clear` meta
events and drop the matching local V2 caches, so a schema change on one
server
no longer leaves other nodes serving stale schema in HStore / multi-server
mode.
The catch is the listener registers exactly once per JVM. The gRPC watch
behind
it is process-wide and there is no `unlisten`. If the Meta transport
reconnects
and the old watch gets dropped, the listener goes deaf and nothing brings it
back. There is already a manual recovery hook,
`resetMetaListenerForReconnect()`, but nothing calls it, because Meta
exposes no
reconnect signal to hang it on.
The two halves of the gap, both in `CachedSchemaTransactionV2`:
- The listener-lifetime comment explaining why recovery is not automatic
today:
https://github.com/apache/hugegraph/blob/master/hugegraph-server/hugegraph-core/src/main/java/org/apache/hugegraph/backend/cache/CachedSchemaTransactionV2.java#L52-L58
- The `resetMetaListenerForReconnect()` hook that has no caller and the
javadoc
saying it must be wired to a Meta reconnect callback:
https://github.com/apache/hugegraph/blob/master/hugegraph-server/hugegraph-core/src/main/java/org/apache/hugegraph/backend/cache/CachedSchemaTransactionV2.java#L254-L270
### What should happen
After the Meta transport reconnects, the JVM-wide `schema-cache-clear`
listener
comes back on its own and keeps delivering events for every graph. No
operator
action.
### What happens now
`MetaManager` / `MetaDriver` expose `listen` and `keepAlive` but no reconnect
callback. A dropped watch goes unnoticed, events stop arriving, and the node
can
keep serving stale schema until someone calls
`resetMetaListenerForReconnect()`
by hand. Nothing does.
### Proposed fix
Two parts, same theme, easiest to do in one go:
1. Give `MetaManager` / `MetaDriver` a reconnect callback (something like
`listenReconnect` / `onTransportReconnect`) that fires when the transport
reconnects and the previous watch is gone.
2. Point `CachedSchemaTransactionV2` at that callback so it re-registers the
listener. `resetMetaListenerForReconnect()` stops being a manual entry
point
and becomes the callback target.
### How to verify
Two servers against HStore/Meta. Force a Meta reconnect (restart Meta or kill
the connection), then change a schema on server A and assert server B clears
its
V2 caches and stops returning stale schema.
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