Configure remote logging in GenericUdfCallHandler

[kaklakariada]

Remote logging allows reading log messages from the virtual schema. This however only works for the adapter, not the loader class GenericUdfCallHandler (called byUdfEntryPoint in IMPORT_FROM_S3_DOCUMENT_FILES for the S3 VS).

Root cause is that GenericUdfCallHandler does not configure logging similar to RequestDispatcher in virtual-schema-common-java.

To make this work we need to pass the logging configuration (i.e. host, port and log level) to the importer via UDF parameters.

Note: UDF parameters are hard coded in the SCRIPT definitions of the virtual schemas, e.g.

CREATE OR REPLACE JAVA SET SCRIPT ADAPTER.IMPORT_FROM_S3_DOCUMENT_FILES(
  DATA_LOADER VARCHAR(2000000),
  SCHEMA_MAPPING_REQUEST VARCHAR(2000000),
  CONNECTION_NAME VARCHAR(500))
  EMITS(...) AS
    %scriptclass com.exasol.adapter.document.UdfEntryPoint;
    %jar /buckets/bfsdefault/default/document-files-virtual-schema-dist-7.3.7-s3-2.8.4.jar;
/

While we could add an additional parameter for the logging config, this is not a future proof solution. It would be better to use a single generic parameter that contains all necessary values serialized as JSON or Java objects. This is a breaking change because users need to update their SCRIPT definitions.

Proposal for new SCRIPT definitions:

CREATE OR REPLACE JAVA SET SCRIPT ADAPTER.IMPORT_FROM_S3_DOCUMENT_FILES(
  SERIALIZED_PARAMETERS VARCHAR(2000000))
  EMITS(...) AS
    %scriptclass com.exasol.adapter.document.UdfEntryPoint;
    %jar /buckets/bfsdefault/default/document-files-virtual-schema-dist-7.3.7-s3-2.8.4.jar;
/

Advantage: we can add additional parameter values at any time without breaking the interface.

Disadvantage: breaking change for VS users, because the parameters in the SET SCRIPT adapter definition change.

Required changes:

• Update GenericUdfCallHandler to expect a single parameter and extract values from it
• Update UdfCallBuilder to serialize all parameters into a single string and add it to the pushdown query
• Update SCRIPT definitions in all user guides of all document based virtual schemas to use the new parameter
• Increment major version of all affected projects as this is a breaking change.