bharath v created IMPALA-7961:
---------------------------------
Summary: Concurrent catalog heavy workloads can cause queries with
SYNC_DDL to fail fast
Key: IMPALA-7961
URL: https://issues.apache.org/jira/browse/IMPALA-7961
Project: IMPALA
Issue Type: Bug
Components: Catalog
Reporter: bharath v
When catalog server is under heavy load with concurrent updates to objects,
queries with SYNC_DDL can fail with the following message.
*User facing error message:*
{noformat}
ERROR: CatalogException: Couldn't retrieve the catalog topic version for the
SYNC_DDL operation after 3 attempts.The operation has been successfully
executed but its effects may have not been broadcast to all the coordinators.
{noformat}
*Exception from the catalog server log:*
{noformat}
I1031 00:00:49.168761 1127039 CatalogServiceCatalog.java:1903] Operation using
SYNC_DDL is waiting for catalog topic version: 236535. Time to identify topic
version (msec): 1088
I1031 00:00:49.168824 1125528 CatalogServiceCatalog.java:1903] Operation using
SYNC_DDL is waiting for catalog topic version: 236535. Time to identify topic
version (msec): 12625
I1031 00:00:49.168851 1131986 jni-util.cc:230]
org.apache.impala.catalog.CatalogException: Couldn't retrieve the catalog topic
version for the SYNC_DDL operation after 3 attempts.The operation has been
successfully executed but its effects may have not been broadcast to all the
coordinators.
at
org.apache.impala.catalog.CatalogServiceCatalog.waitForSyncDdlVersion(CatalogServiceCatalog.java:1891)
at
org.apache.impala.service.CatalogOpExecutor.execDdlRequest(CatalogOpExecutor.java:336)
at org.apache.impala.service.JniCatalog.execDdl(JniCatalog.java:146)
::::
{noformat}
*What this means*
This means that the Catalog operation is actually successful (the change has
been committed to HMS and Catalog server cache) but the Catalog server noticed
that it is taking longer than expected time for it to broadcast the changes
(for whatever reason) and instead of hanging in there, it fails fast. The
coordinators are expected to eventually sync up in the background.
*Problem*
- This violates the contract of the SYNC_DDL query option since the query
returns early.
- This is a behavioral regression from pre IMPALA-5058 state where the queries
would wait forever for SYNC_DDL based changes to propagate.
*Notes*
- Usual suspect here is heavily concurrent catalog operations with long running
DDLs.
- Introduced by IMPALA-5058
Please refer to the jira comment for technical explanation as to why this is
happening.
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