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https://issues.apache.org/jira/browse/IMPALA-14220?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18008574#comment-18008574
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Quanlong Huang commented on IMPALA-14220:
-----------------------------------------
Agree that the regression is not introduced by the recent is_active_ change. I
think it's there since IMPALA-13850 where we made the reset running
asynchronously. But after the recent is_active_ change, it's more likely to hit
this bug.
> IsActive checks blocked by the getCatalogDelta operation when there are slow
> DDLs
> ---------------------------------------------------------------------------------
>
> Key: IMPALA-14220
> URL: https://issues.apache.org/jira/browse/IMPALA-14220
> Project: IMPALA
> Issue Type: Bug
> Components: Backend, Catalog
> Reporter: Quanlong Huang
> Assignee: Riza Suminto
> Priority: Blocker
> Fix For: Impala 5.0.0
>
>
> When catalogd HA is enabled, catalogd will check whther it's the active one
> before serving each request, i.e. in
> [AcceptRequest()|https://github.com/apache/impala/blob/8d56eea72518aa11a36aa086dc8961bc8cdbd1fd/be/src/catalog/catalog-server.cc#L593]:
> {code:cpp}
> Status AcceptRequest(CatalogServiceVersion::type client_version) {
> ...
> } else if (FLAGS_enable_catalogd_ha && !catalog_server_->IsActive()) {
> status = Status(Substitute("Request for Catalog service is rejected
> since "
> "catalogd $0 is in standby mode", server_address_));
> }
> {code}
> This check requires holding the catalog_lock_:
> {code:cpp}
> bool CatalogServer::IsActive() {
> lock_guard<mutex> l(catalog_lock_);
> return is_active_;
> }{code}
> [https://github.com/apache/impala/blob/8d56eea72518aa11a36aa086dc8961bc8cdbd1fd/be/src/catalog/catalog-server.cc#L896]
> This lock is also held by
> [GatherCatalogUpdatesThread|https://github.com/apache/impala/blob/8d56eea72518aa11a36aa086dc8961bc8cdbd1fd/be/src/catalog/catalog-server.cc#L905]
> (a.k.a. topic update thread) which invokes JNI method GetCatalogDelta to
> collect catalog updates.
> It's known that collecting catalog updates could be blocked by slow DDLs that
> holding the table lock for a long time (IMPALA-6671). The topic update thread
> usually waits for 1 minute (configured by topic_update_tbl_max_wait_time_ms /
> 2) on the table lock and then skips it with a warning like this:
> {noformat}
> Table tpch.lineitem (version=2373, lastSeen=2373) is skipping topic update
> (2387, 2388] due to lock contention{noformat}
> If the table hasn't been collected 3 consecutive times (configured by
> catalog_max_lock_skipped_topic_updates), topic update thread will wait
> infinitely on it in the next time.
> So when the topic update thread is slow in collecting one round of updates,
> it holds the catalog_lock_ for a long time and blocks all new requests on
> this catalogd. This impacts performance on all queries that requires loading
> metadata from catalogd.
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