docs: adding file for load testing data generation

[asthamohta]

No description provided.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 42.86%. Comparing base (483fbfd) to head (8c562c9).
Report is 2 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1733      +/-   ##
============================================
+ Coverage     42.66%   42.86%   +0.20%     
- Complexity     3382     3702     +320     
============================================
  Files           815      815              
  Lines         47693    47703      +10     
  Branches       5109     5110       +1     
============================================
+ Hits          20350    20450     +100     
+ Misses        25687    25592      -95     
- Partials       1656     1661       +5     

Components	Coverage Δ
spanner-templates	63.33% <100.00%> (+0.65%)	⬆️
spanner-import-export	64.36% <ø> (-0.09%)	⬇️
spanner-live-forward-migration	75.06% <ø> (+0.29%)	⬆️
spanner-live-reverse-replication	69.73% <100.00%> (+2.60%)	⬆️
spanner-bulk-migration	83.68% <100.00%> (+0.21%)	⬆️

see 9 files with indirect coverage changes

[Polber]

LGTM, but just want to point out that there is already a Load Testing framework within this repo that can be leveraged, if desired.

For example,
https://github.com/GoogleCloudPlatform/DataflowTemplates/blob/main/v2/jdbc-to-googlecloud/src/test/java/com/google/cloud/teleport/v2/templates/JdbcToBigQueryLT.java
which runs the StreamingDataGenerator template to stream data to Pub/Sub, and then (in this case) runs the PubSubToBigQuery template to stream data from Pub/Sub to BigQuery either after accumulating a backlog (testBacklog10gb) or simply running for an hour (testSteadyState1hr) in parallel with the StreamingDataGenerator template.

This framework also automatically generates a job metrics table and writes to BigQuery.

A separate load testing workflow already exists for Spanner: https://github.com/GoogleCloudPlatform/DataflowTemplates/blob/main/.github/workflows/spanner-load-tests.yml (runs daily at 2am)
and could be modified (or another created) for your specific needs.

[asthamohta]

Thankyou @Polber, we will be leveraging the load testing framework but we want to generate the data for the load tests ahead of time. Also we have sometimes need to test new use cases for customers and if Spanner Migration Tool works for them. We are documenting this method here so that others can leverage the technique as well.

[darshan-sj]

LGTM