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https://issues.apache.org/jira/browse/IMPALA-9532?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17063658#comment-17063658
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Vihang Karajgaonkar commented on IMPALA-9532:
---------------------------------------------
IMPALA-9483 might be a different issue since it is related to {{BuiltinsDb and
it doesn't get affected during the global invalidate.}}
> Functions can disappear when a concurrent invalidate metadata is running
> ------------------------------------------------------------------------
>
> Key: IMPALA-9532
> URL: https://issues.apache.org/jira/browse/IMPALA-9532
> Project: IMPALA
> Issue Type: Bug
> Components: Catalog
> Reporter: Vihang Karajgaonkar
> Priority: Major
> Labels: concurrency
>
> The global invalidate metadata takes a write lock on the {{versionLock_}}.
> However, the locking protocol for ddls release the {{versionLock_}} as soon
> as the table level lock is acquired. This allows for a concurrent
> {{invalidate metadata}} to run while the DDL operation is in progress. This
> can lead to weird race conditions. One such example is below can lead to
> functions disappearing from the catalog until a invalidate metadata is issued
> again.
> Following sequence of events can reproduce this race condition:
> {noformat}
> [localhost:21000] default> create function default.f() returns int location
> '/test-warehouse/libTestUdfs.so' symbol='NoArgs';
> Query: create function default.f() returns int location
> '/test-warehouse/libTestUdfs.so' symbol='NoArgs'
> +----------------------------+
> | summary |
> +----------------------------+
> | Function has been created. |
> +----------------------------+
> Fetched 1 row(s) in 10.26s
> --> Session 2 invokes invalidate metadata concurrently
> [localhost:21001] default> invalidate metadata; Query: invalidate metadata
> Query submitted at: 2020-03-18 15:04:25 (Coordinator:
> http://vihang-Precision-21575:25001) Query progress can be monitored at:
> http://<redacted>/query_plan?query_id=d3463484ff635684:620fbfef00000000
> Fetched 0 row(s) in 4.30s
> --> drop function from session1 says function does not exist but show
> functions shows it.
> [localhost:21000] default> drop function f();
> Query: drop function f()
> ERROR: CatalogException: Function: f() does not exist.
> [localhost:21000] default> show functions;
> Query: show functions
> +-------------+-----------+-------------+---------------+
> | return type | signature | binary type | is persistent |
> +-------------+-----------+-------------+---------------+
> | INT | f() | NATIVE | true |
> +-------------+-----------+-------------+---------------+
> Fetched 1 row(s) in 0.01s
> [localhost:21000] default>
> -- Session 2 never sees the function f:
> [localhost:21001] default> show functions;
> Query: show functions
> Fetched 0 row(s) in 0.00s
> {noformat}
> When the create function statement is executing in {{CatalogOpExecutor}} we
> apply the alterDatabase in HMS to persist the new db parameters here:
> [https://github.com/apache/impala/blob/master/fe/src/main/java/org/apache/impala/service/CatalogOpExecutor.java#L1409]
> Note the we have released the {{versionLock_}} by line 1409. Meanwhile a
> concurrent {{invalidate metadata}} fetches the db params from HMS here
> [https://github.com/apache/impala/blob/master/fe/src/main/java/org/apache/impala/catalog/CatalogServiceCatalog.java#L1326]
> which will override the parameters of the newly created Db object. Hence
> effectively we are removing the function from the parameters since the
> operation 1 to alterDatabase is not yet committed in HMS.
> All subsequent commands of {{show functions}}, {{drop function}} will show
> inconsistent results. I was able to reproduce this race condition by added a
> sleep statement just before the alterDatabase call in the createFunction
> method.
> Note: Above code links are based of commit hash
> {{7dd13f72784514a59f82c9a7a5e2250503dbfaf0}}
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