Configuration Properties

Flowman supports some configuration properties, which influence the behavior. These properties either can be set on the command line via --conf (See flowexec documentation), or in the config section of the flow specification (see module documentation) or in the namespace configuration (see namespace documentation)

List of Configuration Properties

General Properties

• flowman.spark.enableHive (type: boolean) (default:true) If set to false, then Hive support will be disabled in Flowman.

• flowman.home (type: string) Contains the home location of the Flowman installation. This will be set implicitly by the system environment variable FLOWMAN_HOME.

• flowman.conf.directory (type: string) Contains the location of the Flowman configuration directory. This will be set implicitly by the system environment variable FLOWMAN_CONF_DIR or FLOWMAN_HOME.

• flowman.plugin.directory (type: string) Contains the location of the Flowman plugin directory. This will be set implicitly by the system environment variable FLOWMAN_PLUGIN_DIR or FLOWMAN_HOME.

• flowman.hive.analyzeTable (type: boolean) (default:true) If enabled (i.e. set to true), then Flowman will perform a ANALYZE TABLE for all Hive table updates.

• flowman.impala.computeStats (type: boolean) (default:true) If enabled (i.e. set to true), then Flowman will perform a COMPUTE STATS within the Impala Catalog plugin whenever a Hive table is updated. The REFRESH statements will always be executed by the plugin.

• flowman.externalCatalog.ignoreErrors (type: boolean) (default:false) If enabled (i.e. set to true), then Flowman will ignore all errors from external catalogs like Impala. This is desired in many cases, such that these will not block processing.

Execution related Properties

• flowman.execution.target.forceDirty (type: boolean) (default:false) (since Flowman 0.14.0) When enabled (i.e. set to true), then Flowman will treat all targets as being dirty. Otherwise, Flowman will check the existence of targets and/or the history to decide if a rebuild is required.

• flowman.execution.target.useStateStore (type: boolean) (default:false) (since Flowman 0.20.0) When enabled (i.e. set to false), then Flowman will ignore the history information to check if a target needs a rebuild. Otherwise, the history store will be trusted for deciding if a target needs a rebuild.

• flowman.execution.executor.class (type: class) (default: com.dimajix.flowman.execution.SimpleExecutor) (since Flowman 0.16.0) Configure the executor to use. The default SimpleExecutor will process all targets in the correct order sequentially. The alternative implementation com.dimajix.flowman.execution.ParallelExecutor will run multiple targets in parallel (if they do not depend on each other)

• flowman.execution.executor.parallelism (type: int) (default: 4) (since Flowman 0.16.0) The number of targets to be executed in parallel, when the ParallelExecutor is used.

• flowman.execution.check.parallelism (type: int) (default: 1) (since Flowman 0.29.1) The number of data quality checks to be executed in parallel.

• flowman.execution.mapping.parallelism (type: int) (default: 1) (since Flowman 0.19.0) The number of mappings to be processed in parallel. Increasing this number may help in scenarios where many relations are read from, and their initial setup is slow (for example due to slow directory listings). With the default value of 1, the parallelism is completely disabled and a non-threaded code path is used instead.

• flowman.execution.relation.schemaCache (type: boolean) (default: true) (since Flowman 0.22.0) Turn on/off caching of schema information of relations. Caching this information (which is enabled per default) can speed up schema inference, which is used for relation schemas and when creating the documentation of relations and mappings. Turning off the cache is mainly for debugging purposes.

• flowman.execution.wait.timeout (type: int) (default: 180) (since Flowman 1.1.0) The number of seconds Flowman waits for schema inference, mapping instantiation etc. before a warning is displayed.

• flowman.execution.scheduler.class (type: class) (default: com.dimajix.flowman.execution.DependencyScheduler) (since Flowman 0.16.0) Configure the scheduler to use, which essentially decides which target to build next.

  • The default DependencyScheduler will sort all targets according to their dependency.

  • The simpler ManualScheduler will simply respect the order of targets as specified in a job. This may not work well with parallel execution if targets have dependencies.

• flowman.spark.eagerCache (type: boolean) (default: false) Turns on automatic eager caching of Spark jobs that reference a single cached DataFrame multiple times. This is to avoid parallel computation of the same partitions, which can be seen in some scenarios.

Relation related Properties

• flowman.default.relation.migrationPolicy (type: string) (default:RELAXED) (since Flowman 0.18.0) Sets the default policy when to migrate tables. Possible values are:

  • STRICT: A migration will be initiated, whenever the physical table definition does not match the required one, even if the types would be compatible.

  • RELAXED: A migration will only be initiated, whenever the physical table definition is not sufficient for storing information with the required schema. If all types are compatible, not migration will be initiated.

• flowman.default.relation.migrationStrategy (type: string) (default:ALTER) (since Flowman 0.18.0) Sets the strategy to use how tables should be migrated. Possible values are:

  • NEVER even if a migration would be required, it will not be performed. No error will be generated.

  • FAIL even if a migration would be required, it will not be performed, instead an error will be generated.

  • ALTER Flowman will try to modify an existing table with ALTER TABLE statements. This will preserve all current contents of the record. On the other hand, this strategy might not be well supported with all table types and/or changes.

  • ALTER_REPLACE Flowman will try to modify an existing table with ALTER TABLE statements. If that is not possible, the table will be dropped and recreated. Note that all contents will be lost if a table replacement is required.

  • REPLACE If a migration is required, Flowman will always replace the existing table with a new one. Note that all contents will be lost.

• flowman.default.relation.input.columnMismatchPolicy (type: string) (default:IGNORE) (since Flowman 0.20.0) Defines how Flowman should handle a mismatch between the actual columns of a relation when reading from it and the columns as defined in the relation. Per default, Flowman ignores any mismatch and simply passes through the schema of the actual relation. See relations for possible options and more details.

• flowman.default.relation.input.typeMismatchPolicy (type: string) (default:IGNORE) (since Flowman 0.20.0) Defines how Flowman should handle a mismatch between the types of the actual schema of a relation when reading from it and the types of the schema as defined in the relation. Per default, Flowman ignores any mismatch and simply passes through the types of the actual relation. See relations for possible options and more details.

• flowman.default.relation.input.charVarcharPolicy (type: string) (default:IGNORE) (since Flowman 0.26.1) Defines how Flowman will handle CHAR(n)/VARCHAR(n) data on reading. Per default Flowman will truncate/pad CHAR(n) columns and truncate VARCHAR(n) columns. See relations for possible options and more details.

• flowman.default.relation.output.columnMismatchPolicy (type: string) (default:ADD_REMOVE_COLUMNS) (since Flowman 0.20.0) Defines how Flowman should handle a mismatch of columns of records being written to a relation and the relations actual defined columns. Per default Flowman will add/remove columns to/from records such that they match the current physical layout. See relations for possible options and more details.

• flowman.default.relation.output.typeMismatchPolicy (type: string) (default:CAST_ALWAYS) (since Flowman 0.20.0) Defines how Flowman should handle a mismatch of columns of records being written to a relation and the relations actual defined columns. Per default Flowman will add/remove columns to/from records such that they match the current physical layout. See relations for possible options and more details.

• flowman.default.relation.output.charVarcharPolicy (type: string) (default:PAD_AND_TRUUNCATE) (since Flowman 0.26.1) Defines how Flowman will handle CHAR(n)/VARCHAR(n) data when writing. Per default Flowman will truncate/pad CHAR(n) columns and truncate VARCHAR(n) columns. See relations for possible options and more details.

Target related Properties

• flowman.default.target.verifyPolicy (type: string) (default:EMPTY_AS_FAILURE) (since Flowman 0.22.0) Defines the default target policy that is used during the VERIFY execution phase. The setting controls how Flowman interprets an empty table. Normally you’d expect that all target tables contain records, but this might not always be the case, for example when the source tables are already empty. Possible values are

  • EMPTY_AS_FAILURE: Flowman will report an empty target table as an error in the VERIFY phase.

  • EMPTY_AS_SUCCESS: Flowman will ignore empty tables, but still check for existence in the VERIFY phase.

  • EMPTY_AS_SUCCESS_WITH_ERRORS: An empty output table is handled as partially successful.

• flowman.default.target.outputMode (type: string) (default:OVERWRITE) Sets the default target output mode. Possible values are

  • OVERWRITE: Will overwrite existing data. Only supported in batch output.

  • APPEND: Will append new records to existing data

  • UPDATE: Will update existing data. Only supported in streaming output.

  • IGNORE_IF_EXISTS: Silently skips the output if it already exists.

  • ERROR_IF_EXISTS: Throws an error if the output already exists Note that you can still explicitly specify a different output mode in each target.

• flowman.default.target.buildPolicy (type: string) (default:SMART) Sets the default target build policy, which takes effect in the BUILD phase. Possible values are

  • ALWAYS: A target is always considered to be dirty.

  • IF_EMPTY: A target is considered to be dirty, if the specified target partition does not exist (or is empty).

  • IF_TAINTED: A target is considered to be dirty, only if it is tainted by a dirty dependency.

  • SMART: A target is considered to be dirty, if the target partition is empty, or when the output mode is set to APPEND or when no partition is specified (full overwrite)

  • COMPAT: A target is considered to be dirty, if the target is empty, or when the output mode is set to APPEND. This setting provides the same behaviour as Flowman before version 0.30.0.

• flowman.default.target.rebalance (type: boolean) (default:false) (since Flowman 0.15.0) If set to true, Flowman will try to write similar records per each output file. Rebalancing might be an expensive operation since it will invoke a Spark network shuffle. Note that you can still explicitly use different settings per target.

• flowman.default.target.parallelism (type: int) (default:16) (since Flowman 0.15.0) Sets the default number of output files per target. If set to zero or a negative value, the number of output files is implicitly determined by the number of internal Spark partitions, i.e. no explicit change will be performed. Note that you can still explicitly use different settings per target.

Workarounds

Sometimes some workarounds are required, especially for non-quite-open-source Big Data platforms.

• flowman.workaround.analyze_partition (type: boolean) (since Flowman 0.18.0) Enables a workaround for CDP 7.1, where ANALYZE TABLES wouldn’t always work correctly (especially in unit tests). The workaround is enabled per default if the Spark version matches ?.?.?.7.?.?.?.+ (i.e. 2.4.0.7.1.6.0-297) AND if the Spark repository URL contains “cloudera”.

Example

You can set the properties either at namespace level or at project level in the config section as follows:

# default-namespace.yml

config:
  # Generic Spark configs  
  - spark.sql.suffle.partitions=20
  - spark.sql.session.timeZone=UTC
  # Flowman specific config  
  - flowman.workaround.analyze_partition=true
  - flowman.default.relation.migrationStrategy=FAIL

The default namespace is configured with the conf/default-namespace.yml file in your Flowman installation directory.