Troubleshooting PXF

PXF Errors

The following table describes some errors you may encounter while using PXF:

Error Message Discussion
Protocol “pxf” does not exist Cause: The pxf extension was not registered.
Solution: Create (enable) the PXF extension for the database as described in the PXF Enable Procedure.
Invalid URI pxf://<path-to-data>: missing options section Cause: The LOCATION URI does not include the profile or other required options.
Solution: Provide the profile and required options in the URI when you submit the CREATE EXTERNAL TABLE command.
PXF server error : Input path does not exist: hdfs://<namenode>:8020/<path-to-file> Cause: The HDFS file that you specified in <path-to-file> does not exist.
Solution: Provide the path to an existing HDFS file.
PXF server error : NoSuchObjectException(message:<schema>.<hivetable> table not found) Cause: The Hive table that you specified with <schema>.<hivetable> does not exist.
Solution: Provide the name of an existing Hive table.
PXF server error : Failed connect to localhost:5888; Connection refused (<segment-id> slice<N> <segment-host>:<port> pid=<process-id>)
Cause: The PXF Service is not running on <segment-host>.
Solution: Restart PXF on <segment-host>.
PXF server error: Permission denied: user=<user>, access=READ, inode=“<filepath>”:-rw——- Cause: The Greenplum Database user that executed the PXF operation does not have permission to access the underlying Hadoop service (HDFS or Hive). See Configuring the Hadoop User, User Impersonation, and Proxying.
PXF server error: PXF service could not be reached. PXF is not running in the tomcat container Cause: The pxf extension was updated to a new version but the PXF server has not been updated to a compatible version.
Solution: Ensure that the PXF server has been updated and restarted on all hosts.
ERROR: could not load library “/usr/local/greenplum-db-x.x.x/lib/postgresql/” Cause: Some steps have not been completed after a Greenplum Database upgrade or migration, such as pxf cluster register.
Solution: Make sure you follow the steps outlined for PXF Upgrade and Migration.

Most PXF error messages include a HINT that you can use to resolve the error, or to collect more information to identify the error.

PXF Logging

Refer to the Logging topic for more information about logging levels, configuration, and the pxf-app.out and pxf-service.log log files.

Addressing PXF JDBC Connector Time Zone Errors

You use the PXF JDBC connector to access data stored in an external SQL database. Depending upon the JDBC driver, the driver may return an error if there is a mismatch between the default time zone set for the PXF Service and the time zone set for the external SQL database.

For example, if you use the PXF JDBC connector to access an Oracle database with a conflicting time zone, PXF logs an error similar to the following: ORA-00604: error occurred at recursive SQL level 1
ORA-01882: timezone region not found

Should you encounter this error, you can set default time zone option(s) for the PXF Service in the $PXF_BASE/conf/ configuration file, PXF_JVM_OPTS property setting. For example, to set the time zone:

export PXF_JVM_OPTS="<current_settings> -Duser.timezone=America/Chicago"

You can use the PXF_JVM_OPTS property to set other Java options as well.

As described in previous sections, you must synchronize the updated PXF configuration to the Greenplum Database cluster and restart the PXF Service on each host.

About PXF External Table Child Partitions

Greenplum Database supports partitioned tables, and permits exchanging a leaf child partition with a PXF external table.

When you read from a partitioned Greenplum table where one or more partitions is a PXF external table and there is no data backing the external table path, PXF returns an error and the query fails. This default PXF behavior is not optimal in the partitioned table case; an empty child partition is valid and should not cause a query on the parent table to fail.

The IGNORE_MISSING_PATH PXF custom option is a boolean that specifies the action to take when the external table path is missing or invalid. The default value is false, PXF returns an error when it encounters a missing path. If the external table is a child partition of a Greenplum table, you want PXF to ignore a missing path error, so set this option to true.

For example, PXF ignores missing path errors generated from the following external table:

CREATE EXTERNAL TABLE ext_part_87 (id int, some_date date)
  LOCATION ('pxf://bucket/path/?PROFILE=s3:parquet&SERVER=s3&IGNORE_MISSING_PATH=true')
FORMAT 'CUSTOM' (formatter = 'pxfwritable_import');

The IGNORE_MISSING_PATH custom option applies only to file-based profiles, including *:text, *:parquet, *:avro, *:json, *:AvroSequenceFile, and *:SequenceFile. This option is not available when the external table specifies the hbase, hive[:*], or jdbc profiles, or when reading from S3 using S3-Select.

Addressing Hive MetaStore Connection Errors

The PXF Hive connector uses the Hive MetaStore to determine the HDFS locations of Hive tables. Starting in PXF version 6.2.1, PXF retries a failed connection to the Hive MetaStore a single time. If you encounter one of the following error messages or exceptions when accessing Hive via a PXF external table, consider increasing the retry count:

  • Failed to connect to the MetaStore Server.
  • Could not connect to meta store ...
  • org.apache.thrift.transport.TTransportException: null

PXF uses the hive-site.xml hive.metastore.failure.retries property setting to identify the maximum number of times it will retry a failed connection to the Hive MetaStore. The hive-site.xml file resides in the configuration directory of the PXF server that you use to access Hive.

Perform the following procedure to configure the number of Hive MetaStore connection retries that PXF will attempt; you may be required to add the hive.metastore.failure.retries property to the hive-site.xml file:

  1. Log in to the Greenplum Database master node.

  2. Identify the name of your Hive PXF server.

  3. Open the $PXF_BASE/servers/<hive-server-name>/hive-site.xml file in the editor of your choice, add the hive.metastore.failure.retries property if it does not already exist in the file, and set the value. For example, to configure 5 retries:

  4. Save the file and exit the editor.

  5. Synchronize the PXF configuration to all hosts in your Greenplum Database cluster:

    gpadmin@gpmaster$ pxf cluster sync
  6. Re-run the failing SQL external table command.