Claude Warren created CASSANDRA-18739:
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Summary: USF 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
Attachments: udf_error.cql, udf_error_data.cql
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 ShcemaKeyspace method
createUDFFromRow() is called, this in tern 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
{{{}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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