Add script for migrating environment from Composer 2 to Composer 3

[FilipStefaniuk]

Description

Add script for migrating Composer 2 to Composer 3.

Checklist

• I have followed Sample Guidelines from AUTHORING_GUIDE.MD
• README is updated to include all relevant information
• Tests pass: nox -s py-3.9 (see Test Environment Setup)
• Lint pass: nox -s lint (see Test Environment Setup)
• These samples need a new API enabled in testing projects to pass (let us know which ones)
• These samples need a new/updated env vars in testing projects set to pass (let us know which ones)
• This sample adds a new sample directory, and I updated the CODEOWNERS file with the codeowners for this sample
• This sample adds a new Product API, and I updated the Blunderbuss issue/PR auto-assigner with the codeowners for this sample
• Please merge this PR for me once it is approved

[gemini-code-assist]

Hello @FilipStefaniuk, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

Summary of Changes

This pull request introduces a new script, composer_migrate.py, designed to facilitate the migration of Google Cloud Composer environments from version 2 to version 3. The script automates the process of creating a new Composer 3 environment with a configuration mirroring the source Composer 2 environment, pausing DAGs, saving a snapshot of the Composer 2 environment, loading it into the new Composer 3 environment, and then unpausing the DAGs that were active in the source environment. The PR also includes a markdown document composer_migrate.md that describes how to use the new script.

Highlights

• Migration Script: Adds composer_migrate.py, a standalone script to migrate Composer 2 environments to Composer 3 using snapshots.
• Configuration Conversion: Includes logic to convert Composer 2 environment configurations to compatible Composer 3 configurations, adjusting CPU, memory, and storage settings.
• DAG Management: Automates pausing DAGs in the source environment before migration and unpausing them in the target environment after the snapshot is loaded.
• Documentation: Provides a composer_migrate.md document detailing the script's usage, prerequisites, limitations, and troubleshooting steps.

Changelog

• composer/tools/composer_migrate.md
  • Introduces a new markdown document explaining the usage of the composer_migrate.py script.
  • Details the prerequisites, limitations, and troubleshooting steps for migrating Composer 2 environments to Composer 3.
  • Provides examples for dry run and migration execution.
• composer/tools/composer_migrate.py
  • Adds a new Python script for migrating Composer 2 environments to Composer 3.
  • Implements functions to interact with the Composer API using gcloud and curl.
  • Includes logic to fetch environment configurations, create new environments, pause/unpause DAGs, and save/load snapshots.
  • Adds functions to adjust workload configurations (CPU, memory, storage) for compatibility with Composer 3.
  • Implements a main function to orchestrate the migration process and command-line argument parsing.

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---

From two to three it goes,
Composer's versioning flows,
Snapshots pave the way,
To a brighter, newer day,
DAGs rise where old code shows.

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[gemini-code-assist]

Code Review

The pull request introduces a script to migrate Composer 2 environments to Composer 3, which is a valuable tool. The script automates the process of obtaining configurations, creating new environments, pausing/unpausing DAGs, and saving/loading snapshots. The documentation is also well-written and provides clear instructions on how to use the script. However, there are some areas that could be improved, particularly in error handling and validation.

Summary of Findings

• Missing Error Handling: The script lacks comprehensive error handling, especially for gcloud commands. This could lead to unexpected failures and difficulties in troubleshooting. Adding more robust error handling would improve the script's reliability.
• Missing Input Validation: The script does not perform sufficient validation of input parameters or environment configurations. This could cause the script to fail if the source environment has unsupported configurations or if the target Airflow version is incompatible. Input validation is crucial for preventing unexpected errors.
• Potential Race Condition in DAG Pausing: Pausing DAGs one by one can be time-consuming and may lead to inconsistencies if DAGs are modified during the process. Consider pausing DAGs in batches or providing an option to pause them manually before running the script.

Merge Readiness

The pull request introduces a useful script with clear documentation. However, the identified issues related to error handling, input validation, and DAG pausing should be addressed before merging. Addressing these points will significantly improve the script's reliability and usability. I am unable to approve this pull request, and recommend that other reviewers also look at this code before merging.

[rbiegacz]

Reviewed.

[leahecole]

LGTM, talked to @FilipStefaniuk offline and I know this script has tests in g3, which is totally appropriate for this tool. @rbiegacz if you approve on Github we'll be able to merge!