[Bugfix] Alter_column on metrics table only called for mysql database engine

[marijncv]

What changes are proposed in this pull request?

The migration needed to (re)set the default value for is_nan in the metrics table is now only run for the mysql database engine. Closes #4343

How is this patch tested?

Running the database initialization tests in the github workflow. I've added a test for the mssql engine.

Release Notes

Is this a user-facing change?

• No. You can skip the rest of this section.
• Yes. Give a description of this change to be included in the release notes for MLflow users.

Fix for bug that occurred in initialization/migration of the Tracking Server backend using a mssql engine.

What component(s), interfaces, languages, and integrations does this PR affect?

Components

• area/artifacts: Artifact stores and artifact logging
• area/build: Build and test infrastructure for MLflow
• area/docs: MLflow documentation pages
• area/examples: Example code
• area/model-registry: Model Registry service, APIs, and the fluent client calls for Model Registry
• area/models: MLmodel format, model serialization/deserialization, flavors
• area/projects: MLproject format, project running backends
• area/scoring: MLflow Model server, model deployment tools, Spark UDFs
• area/server-infra: MLflow Tracking server backend
• area/tracking: Tracking Service, tracking client APIs, autologging

Interface

• area/uiux: Front-end, user experience, plotting, JavaScript, JavaScript dev server
• area/docker: Docker use across MLflow's components, such as MLflow Projects and MLflow Models
• area/sqlalchemy: Use of SQLAlchemy in the Tracking Service or Model Registry
• area/windows: Windows support

Language

• language/r: R APIs and clients
• language/java: Java APIs and clients
• language/new: Proposals for new client languages

Integrations

• integrations/azure: Azure and Azure ML integrations
• integrations/sagemaker: SageMaker integrations
• integrations/databricks: Databricks integrations

How should the PR be classified in the release notes? Choose one:

• rn/breaking-change - The PR will be mentioned in the "Breaking Changes" section
• rn/none - No description will be included. The PR will be mentioned only by the PR number in the "Small Bugfixes and Documentation Updates" section
• rn/feature - A new user-facing feature worth mentioning in the release notes
• rn/bug-fix - A user-facing bug fix worth mentioning in the release notes
• rn/documentation - A user-facing documentation change worth mentioning in the release notes

[harupy]

@marijncv Thanks for the PR! I'll review soon!

[harupy]

Is there any command that can check the SQL server is ready? I'm wondering if we can do something like below to avoid always sleeping for 60 seconds:

for BACKOFF in 0 1 2 4 8 16 32 64; do
    sleep $BACKOFF
    if <check_sql_server_is_ready>; then
        exit 0
    fi
done
exit 1

[marijncv]

Thanks @harupy for this great suggestion! I've updated the script to use this retry mechanism

[GlamTam]

tested it in our env and works great!

[harupy]

@marijncv Thanks for the PR and creating tests for mssql! Left some comments.

[marijncv]

Thanks for the comments! I've tried to address them in the latest commit

[harupy]

LGTM!