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https://issues.apache.org/jira/browse/CASSANDRA-18739?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17752667#comment-17752667
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Stefan Miklosovic commented on CASSANDRA-18739:
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Hi [~claude], thanks for this!
I looked into it and this might be a solution. I restarted a node and it just
worked ...
The approach I took is that we do not need KeyspaceMetadata (which is null)
upon function's creation. That is not necessary. We just need that stuff in
runtime when you do queries etc and by that time it is already initialized.
(1) https://github.com/apache/cassandra/pull/2566/files
> UDF functions fail to load on rolling restart
> ---------------------------------------------
>
> Key: CASSANDRA-18739
> URL: https://issues.apache.org/jira/browse/CASSANDRA-18739
> Project: Cassandra
> Issue Type: Bug
> Components: Feature/UDF
> Reporter: Claude Warren
> Assignee: Claude Warren
> Priority: Normal
> Attachments: udf_error.cql, udf_error_data.cql
>
> Time Spent: 10m
> Remaining Estimate: 0h
>
> UDFs fail to reload properly after a rolling restart.
> h3. *Symptom:*
> NPE thrown when used after restart.
> h3. *Steps to recreate:*
> # Create a cluster as per cql file
> # Populate the cluster with data.cql.
> # Execute SELECT city_measurements(city, measurement, 16.5) AS m FROM current
> # expect min and max values for cities.
> # Performing a rolling restart on one server.
> # When the server is back up
> # Execute SELECT city_measurements(city, measurement, 16.5) AS m FROM current
> # expect: error result with NPE message.
> {*}Analysis{*}:
> During system restart the SchemaKeyspace.fetchNonSystemKeyspaces() is called,
> when a keyspace with a UDF is loaded the SchemaKeyspace method
> createUDFFromRow() is called, this in turn calls UDFunction.create() which
> eventually calls back to UDFunction constructor where the
> Schema.instance.getKeyspaceMetadata() is called with the keyspace for the UDF
> name as the argument. However, the keyspace for the UDF name is being
> constructed and is not yet in the instance so the method returns null for the
> KeyspaceMetadata. That null KeyspaceMetadata is then used in the udfContext.
> Later when the UDF method is called, if there is a need to call a method on
> the keyspaceMetadata, such as udfContext.newUDTValue() where the
> implementation uses keyspaceMetadata.types, a null pointer is thrown.
> I have verified this affects version 4.0, 4.1 and trunk. I have not verified
> 3.x but I suspect it is the same there.
> I modified UDFunction constructor to assert that the metadata was not null
> and received the following stack trace
> ERROR [main] 2023-08-09 11:44:46,408 CassandraDaemon.java:911 - Exception
> encountered during startup
> java.lang.AssertionError: No metadata for temperatures.city_measurements_sfunc
> at
> org.apache.cassandra.cql3.functions.UDFunction.<init>(UDFunction.java:240)
> at
> org.apache.cassandra.cql3.functions.JavaBasedUDFunction.<init>(JavaBasedUDFunction.java:195)
> at
> org.apache.cassandra.cql3.functions.UDFunction.create(UDFunction.java:276)
> at
> org.apache.cassandra.schema.SchemaKeyspace.createUDFFromRow(SchemaKeyspace.java:1182)
> at
> org.apache.cassandra.schema.SchemaKeyspace.fetchUDFs(SchemaKeyspace.java:1131)
> at
> org.apache.cassandra.schema.SchemaKeyspace.fetchFunctions(SchemaKeyspace.java:1119)
> at
> org.apache.cassandra.schema.SchemaKeyspace.fetchKeyspace(SchemaKeyspace.java:859)
> at
> org.apache.cassandra.schema.SchemaKeyspace.fetchKeyspacesWithout(SchemaKeyspace.java:848)
> at
> org.apache.cassandra.schema.SchemaKeyspace.fetchNonSystemKeyspaces(SchemaKeyspace.java:836)
> at org.apache.cassandra.schema.Schema.loadFromDisk(Schema.java:132)
> at org.apache.cassandra.schema.Schema.loadFromDisk(Schema.java:121)
> at
> org.apache.cassandra.service.CassandraDaemon.setup(CassandraDaemon.java:287)
> at
> org.apache.cassandra.service.CassandraDaemon.activate(CassandraDaemon.java:765)
> at
> org.apache.cassandra.service.CassandraDaemon.main(CassandraDaemon.java:889)
>
> {{*Possible solution:*}}
> *Version 4.x*
> Create a KeyspaceMetadata.Builder class that uses accepts the types, tables
> and views but uses a builder for the functions.
> Add a KeyspaceMetadata constructor to accept the KeyspaceMetadata.Builder so
> that the function builder keyspaceMetadata value can be set correctly during
> construction of the KeyspaceMetadata.
> Modify SchemaKeyspace.fetchKeyspace(string) so that it uses the
> KeyspaceMetadata.Builder.
>
> *Version 5.x*
> Similar to 4.x except that the KeyspaceMetadata.Builder will have to have
> builders for Views and Tables because the functions necessary to construct
> those objects will not be available until the KeyspaceMetadata.Builder
> constructs it.
>
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