Googlecloudplatform Dataflowtemplates Dataflowtemplates

Skill: Dataflow Template Logical Error Debugging

Trigger

/smt-e2e-dataflow-debugging <FILE_NAME>.tfvars

Scope

This skill is STRICTLY restricted to testing the following templates:

• gcs-spanner-dv
• sourcedb-to-spanner
• datastream-to-spanner
• spanner-to-sourcedb

Goal

To debug logical errors and data discrepancies by comparing source data (e.g., Cloud SQL) with destination data (e.g., Spanner).

Prerequisites

• The Dataflow job must be able to launch and run to a terminal state (Succeeded, Failed) using the provided .tfvars file. This skill is NOT for debugging startup/runtime crashes.
• terraform CLI installed and configured.
• gcloud CLI installed and authenticated (gcloud auth login).
• mvn (Maven) and a compatible JDK installed.
• git installed.
• Access to the source database (e.g., Cloud SQL) instance, database, and credentials.
• Access to the destination Spanner instance and database.
• Appropriate IAM permissions for Dataflow, Cloud SQL, Spanner, GCS, and Cloud Logging.
• Database client tools installed (e.g., psql, mysql client, or willingness to use gcloud sql connect).

Variables

• <FILE_NAME>.tfvars: The Terraform variables file.
• <YOUR_PROJECT_ID>: The target Google Cloud Project ID.
• <YOUR_REGION>: The Google Cloud region for the Dataflow job.
• <JOB_ID>: The Dataflow Job ID.
• <JOB_NAME>: The name of the Dataflow job.
• Cloud SQL Connection Info (Extracted from .tfvars):
  • <CSQL_INSTANCE>: Cloud SQL instance name.
  • <CSQL_DATABASE>: Cloud SQL database name.
  • <CSQL_USER>: Cloud SQL username.
  • <CSQL_PASSWORD>: Cloud SQL password (if applicable).
  • <CSQL_PROJECT>: Project of the Cloud SQL instance.
• Spanner Connection Info (Extracted from .tfvars):
  • <SPANNER_INSTANCE>: Spanner instance name.
  • <SPANNER_DATABASE>: Spanner database name.
  • <SPANNER_PROJECT>: Project of the Spanner instance.
• <MAVEN_MODULE_PATH>: The relative path to the template's maven module (e.g. v2/sourcedb-to-spanner).
• <TEMPLATE_NAME>: The name of the template.
• <YOUR_STAGING_BUCKET>: Cloud Storage bucket for staging.

Global Agent Rules

• Fail-Fast Protocol: If any executed terminal command returns an error or non-zero exit code, STOP IMMEDIATELY. Output the error to the user and ask for intervention. Do not attempt autonomous retries.
• Data Privacy: Ensure no real PII, credentials, or production connection details are exposed in logs or command outputs.

Workflow Phases

Phase 1: Deployment & Job Monitoring

1. Deploy the Dataflow Job:
   • Navigate to the directory containing <FILE_NAME>.tfvars.
   • Initialize Terraform:

     terraform init
     

   • Launch the job:

     terraform apply --var-file=<FILE_NAME>.tfvars -auto-approve
     

2. Monitor Status: Wait for the job to reach a terminal state (Succeeded or Failed). Monitor status via Google Cloud Console or gcloud.

Phase 2: Log Collection & Initial Analysis

1. Retrieve Job IDs: Infer <JOB_ID> and <JOB_NAME> from the Terraform output or by listing active jobs:

   gcloud dataflow jobs list --project=<YOUR_PROJECT_ID> --region=<YOUR_REGION>
   

2. Inspect Job Logs: Retrieve job message logs to identify warnings or non-obvious issues:

   gcloud logging read 'resource.type="dataflow_step" AND resource.labels.job_id="<JOB_ID>" AND logName=~"projects/.*/logs/dataflow.googleapis.com%2Fjob-message"' \
     --project=<YOUR_PROJECT_ID> \
     --limit=200 \
     --format="table(timestamp, textPayload, severity)" --order=asc
   

3. Inspect Worker Logs: Check worker execution logs for specific exceptions or stack traces:

   gcloud logging read 'resource.type="dataflow_step" AND logName=~"projects/.*/logs/dataflow.googleapis.com%2Fworker" AND resource.labels.job_id="<JOB_ID>"' \
     --project=<YOUR_PROJECT_ID> \
     --limit=500 \
     --format="table(timestamp, jsonPayload.message, severity)" --order=asc
   

Phase 3: Data Inspection & Validation

1. Inspect Source Data (Cloud SQL): Connect to the Cloud SQL instance and query source tables:

   # For PostgreSQL
   gcloud sql connect <CSQL_INSTANCE> --user=<CSQL_USER> --project=<CSQL_PROJECT>
   # For MySQL
   gcloud sql connect <CSQL_INSTANCE> --user=<CSQL_USER> --project=<CSQL_PROJECT>
   

   Execute validation queries:

   SELECT COUNT(*) FROM your_source_table;
   SELECT * FROM your_source_table LIMIT 10;
   

2. Inspect Destination Data (Spanner): Execute SQL queries on the destination Spanner database:

   gcloud spanner databases execute-sql <SPANNER_DATABASE> \
     --instance=<SPANNER_INSTANCE> \
     --project=<SPANNER_PROJECT> \
     --sql="SELECT COUNT(*) FROM your_destination_table"
   
   gcloud spanner databases execute-sql <SPANNER_DATABASE> \
     --instance=<SPANNER_INSTANCE> \
     --project=<SPANNER_PROJECT> \
     --sql="SELECT * FROM your_destination_table LIMIT 10"
   

Phase 4: Discrepancy Verification & Resolution

1. Analyze Differences:
   • Row Counts: Do source and destination row counts match?
   • Schema Mapping: Are column types and names mapped correctly?
   • Value Assertions: Check NULL values, string encoding, timestamps, and precision.
2. Code Correction: Locate the transformation logic in the .java files under the GoogleCloudPlatform/DataflowTemplates repository and fix the bug.
3. Re-stage Template: Rebuild and upload the updated Flex Template:

   mvn clean package -PtemplatesStage -DskipTests \
     -DprojectId="<YOUR_PROJECT_ID>" \
     -DbucketName="<YOUR_STAGING_BUCKET>" \
     -DstagePrefix="templates" \
     -DtemplateName="<TEMPLATE_NAME>" \
     -pl <MAVEN_MODULE_PATH> -am
   

Phase 5: Re-testing & Iteration

1. Clean Destination Table: Delete destination records to prepare for a clean run:

   gcloud spanner databases execute-sql <SPANNER_DATABASE> \
     --instance=<SPANNER_INSTANCE> \
     --project=<SPANNER_PROJECT> \
     --sql="DELETE FROM your_destination_table WHERE true"
   

2. Re-run Job: Deploy the job again with the newly built template (Phase 1) and verify the fix.

Important Considerations

• Idempotency: Ensure clean test tables before re-running to avoid duplicate count errors.
• Data Volume: Limit queries to subsets when working with large volumes.
• Terraform State: Avoid modifying resources manually outside of Terraform to prevent state drift.

Source: GoogleCloudPlatform/DataflowTemplates — distributed by TomeVault.