This plugin allows vdk-core to interface with and execute queries against an Impala database.
Features
- It provides a powerful recovery mechanism handling a lot of challenges - like eventual consistency issues in Impala and more. In one production deployment of VDK it was able to improve SLA of Impala from 95% (queries directly to Impala) to 99% (queries using VDK to Impala).
- It automatically classifies error based on who is best responsible to handle them - user (job owner) vs platform (infra owner).
- It provides a default implementation of Kimball templates for generating SCD1, SCD2 dimension tables, Periodic Snapshot Fact Table
- It can collect lineage data, assuming a lineage logger has been provided through the vdk-core configuration (see
vdk config-helpfor more info)
Usage
Run
pip install vdk-impala
After this, data jobs will have access to a Impala database connection, managed by Versatile Data Kit SDK.
If it is the only database plugin installed , vdk would automatically use it.
Otherwise, users need to set VDK_DB_DEFAULT_TYPE=IMPALA as an environment variable or set 'db_default_type' option in the data job config file (config.ini).
For example
def run(job_input: IJobInput):
job_input.execute_query("select 'Hi Impala!'")
Lineage
The package can gather lineage data for all successful Impala SQL queries that have actually read or written data. Other plugins can read and optionally send the lineage data to separate system. They need to provide ILineageLogger implementation and hook this way:
@hookimpl
def vdk_initialize(context: CoreContext) -> None:
context.state.set(StoreKey[ILineageLogger]("impala-lineage-logger"), MyLogger())
Lineage is calculated based on the executed query profile. It is retrieved via the cursor by executing additional RPC request against the same Impala node that has coordinated the query right after the original query has successfully finished. See https://impala.apache.org/docs/build/html/topics/impala_logging.html for more information how profiles are stored and here https://impala.apache.org/docs/build/impala-3.1.pdf for more information about the profiles themselves.
If enabled, query plan is retrieved for every successfully executed query against Impala excluding keepalive queries like "Select 1".
Kimbal dimensional modeling templates
- SCD1
- SCD2 dimension tables
- Periodic Snapshot Fact Table
See the following tutorial for more details. It is based on Trino but the process is equivalent for Impala (only the database configuration requires change).
Configuration
Run vdk config-help - search for those prefixed with "IMPALA_" to see what configuration options are available.
Disclaimer
This plugin is tested against a specific impala version. The version comes from the docker-compose.yaml container's impala version. For more information on the imapala version tested against please google the docker image.
Testing
Testing this plugin locally requires installing the dependencies listed in vdk-plugins/vdk-impala/requirements.txt
Run
pip install -r requirements.txt
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Release files for vdk-impala 0.4.663931565
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Release files / vdk-impala-0.4.663931565.tar.gz
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