Root cause: With -max=0 (unlimited volumes), volumes are created on-demand,
but no volumes existed when tests started, causing first write to fail.
Solution:
- Explicitly trigger volume growth via /vol/grow API
- Create 3 volumes with replication=000 before running tests
- Verify volumes exist before proceeding
- Fail early with clear message if volumes can't be created
Changes:
- POST to http://localhost:9333/vol/grow?replication=000&count=3
- Wait up to 10 seconds for volumes to appear
- Show volume count and layout status
- Exit with error if no volumes after 10 attempts
- Applied to both spark-tests and spark-example jobs
This ensures writable volumes exist before Spark tries to write data.