b3b2dbaca3
The insert DMLs executed by workload management to add rows to the
completed queries Iceberg table time out after 10 seconds because
that is the default FETCH_ROWS_TIMEOUT_MS value. If the DML queues up
in admission control, this timeout will quickly cause the DML to be
cancelled. The fix is to set the FETCH_ROWS_TIMEOUT_MS query option
to 0 for the workload management insert DMLs.
Even though the workload management DMLs do not retrieve any rows,
the FETCH_ROWS_TIMEOUT_MS value still applies because the internal
server functions call into the client request state's
ExecQueryOrDmlRequest() function which starts query execution and
immediately returns. Then, the BlockOnWait function in
impala-server.cc is called. This function times out based on the
FETCH_ROWS_TIMEOUT_MS value.
A new coordinator startup flag 'query_log_dml_exec_timeout_s' is
added to specify the EXEC_TIME_LIMIT_S query option on the workload
management insert DML statements. This flag ensures the DMLs will
time out if they do not complete in a reasonable timeframe.
While adding the new coordinator startup flag, a bug in the
internal-server code was discovered. This bug caused a return status
of 'ok' even when the query exec time limit was reached and the query
cancelled. This bug has also been fixed.
Testing:
1. Added new custom cluster test that simulates a busy cluster where
the workload management DML queues for longer than 10 seconds.
2. Existing tests in test_query_log and test_admission_controller
passed.
3. One internal-server-test ctest was modified to assert for a
returned status of error when a query is cancelled.
4. Added a new cusom cluster test that asserts the workload
management DML is cancelled based on the value of the new
coordinator startup flag.
Change-Id: I0cc7fbce40eadfb253d8cff5cbb83e2ad63a979f
Reviewed-on: http://gerrit.cloudera.org:8080/22511
Reviewed-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>
Tested-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>
Welcome to Impala
Lightning-fast, distributed SQL queries for petabytes of data stored in open data and table formats.
Impala is a modern, massively-distributed, massively-parallel, C++ query engine that lets you analyze, transform and combine data from a variety of data sources:
- Best of breed performance and scalability.
- Support for data stored in Apache Iceberg, HDFS, Apache HBase, Apache Kudu, Amazon S3, Azure Data Lake Storage, Apache Hadoop Ozone and more!
- Wide analytic SQL support, including window functions and subqueries.
- On-the-fly code generation using LLVM to generate lightning-fast code tailored specifically to each individual query.
- Support for the most commonly-used Hadoop file formats, including Apache Parquet and Apache ORC.
- Support for industry-standard security protocols, including Kerberos, LDAP and TLS.
- Apache-licensed, 100% open source.
More about Impala
The fastest way to try out Impala is a quickstart Docker container. You can try out running queries and processing data sets in Impala on a single machine without installing dependencies. It can automatically load test data sets into Apache Kudu and Apache Parquet formats and you can start playing around with Apache Impala SQL within minutes.
To learn more about Impala as a user or administrator, or to try Impala, please visit the Impala homepage. Detailed documentation for administrators and users is available at Apache Impala documentation.
If you are interested in contributing to Impala as a developer, or learning more about Impala's internals and architecture, visit the Impala wiki.
Supported Platforms
Impala only supports Linux at the moment. Impala supports x86_64 and has experimental support for arm64 (as of Impala 4.0). Impala Requirements contains more detailed information on the minimum CPU requirements.
Supported OS Distributions
Impala runs on Linux systems only. The supported distros are
- Ubuntu 16.04/18.04
- CentOS/RHEL 7/8
Other systems, e.g. SLES12, may also be supported but are not tested by the community.
Export Control Notice
This distribution uses cryptographic software and may be subject to export controls. Please refer to EXPORT_CONTROL.md for more information.
Build Instructions
See Impala's developer documentation to get started.
Detailed build notes has some detailed information on the project layout and build.