Resolving Sync and Replication Issues in Plastic SCM

Details: Category: Version Control; By Mindful Chase; 20.Jul; Hits: 15

Plastic SCM is a powerful, enterprise-grade version control system widely used in large-scale game development and asset-heavy pipelines. While its distributed model and branching capabilities are strong, teams often encounter complex synchronization issues, particularly when repositories become out of sync or exhibit corrupted merge histories. One persistent issue is the failure of replication or pull operations with vague errors such as "cannot connect to replication server" or "object not found." These problems can interrupt continuous integration flows, break automated pipelines, and cause confusion across teams working in distributed environments. This article provides in-depth troubleshooting guidance to resolve sync and replication failures in Plastic SCM.

Mindful Chase

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Understanding Plastic SCM Synchronization

Centralized vs Distributed Sync

Plastic SCM supports both centralized and DVCS workflows. Sync operations rely on replication servers or direct peer-to-peer operations. Failures can arise from misconfigured replication endpoints, missing changesets, or network issues.

Common Symptoms

Push or pull commands hang indefinitely
Error: "The object does not exist on source repository"
Replications succeed but branches appear empty or incomplete
Failed merges with inconsistent changelists

Root Causes

1. Incomplete Object Transfers

When pulling changes, Plastic may fail silently if blobs (binary objects) are missing. These can result from interrupted transfers or misconfigured object storage paths.

2. GUID Mismatches Between Repositories

Plastic uses GUIDs to identify repositories. Sync will fail if repositories were cloned improperly or had GUIDs manually altered.

3. Unlinked or Detached Changesets

In rare cases, database-level issues cause orphaned changesets that appear in one repo but not another, blocking branch merges or replications.

4. Permissions and Access Control

Role-based permissions may silently block syncs, especially when changes originate from users without replication rights on target servers.

Diagnostic Strategy

Step 1: Validate Repo Connectivity

cm lrep --server=rep:myserver:8087

Check if the server and target repository respond. Confirm that both sides see consistent repository names and GUIDs.

Step 2: Check Sync Status

cm sync list --repository=YourRepo

Displays tracked repositories and current state of replication. Use this to detect missing branches or failed changesets.

Step 3: Inspect Logs

Review client and server logs under PlasticSCM5/client/logs or server/logs. Look for timeouts, missing object errors, or authentication failures.

Step 4: Force Object Verification

cm verifyrep --repository=YourRepo --objects

Validates the integrity of objects and metadata across repositories. Use this before force pushing or reinitializing replication.

Step-by-Step Fixes

1. Reinitialize Replication Link

cm sync reset --repository=YourRepo --server=rep:myserver:8087

This clears old state and allows a clean replication handshake.

2. Repair Broken Changesets

Use cm find changeset where not branch to locate orphaned changesets. Integrate them into a valid branch using the GUI or CLI merge commands.

3. Manually Sync Metadata

cm pull --repository=YourRepo --objects

This ensures all associated metadata, branches, and labels are pulled explicitly, bypassing smart sync heuristics.

4. Correct Repository GUIDs

If GUID mismatches are confirmed, use cm mkrep --name=RepoName --guid=CorrectGUID to realign repositories. Requires admin access.

Architectural Implications

Impact on CI/CD Pipelines

Sync failures in Plastic SCM can cause stale branches, broken automation workflows, and merge delays. Ensure agents authenticate properly and validate repo health during CI init steps.

Geo-Distributed Teams

When teams work across continents, replication latency and partial object fetches are more likely. Always configure replication servers with compression, bandwidth caps, and retry logic enabled.

Best Practices

Use consistent GUID-based cloning for repositories
Enable automatic sync health checks in build agents
Use cm diff --format=xml to script consistency audits between repos
Isolate long-lived branches in isolated sync channels
Rotate logs and monitor for sync bottlenecks on server-side regularly

Conclusion

Sync issues in Plastic SCM are rarely surface-level problems. They often stem from metadata corruption, GUID mismatches, or partial object transmission. By combining log analysis, metadata verification, and replication controls, DevOps teams and project managers can prevent disruptions and ensure that distributed repositories remain consistent and conflict-free across environments.

FAQs

1. Why does my sync complete but branches are missing?

Only metadata may have been replicated. Use cm pull --objects to ensure complete branch and object transfer.

2. What causes orphaned changesets?

Database corruption, interrupted syncs, or direct repo edits can result in changesets not attached to any branch. Always audit syncs after force-pushes.

3. How do I verify repository GUIDs?

Run cm lrep --format=xml and compare GUIDs across replicas. GUID mismatches can silently block replication and syncs.

4. Can I sync only a specific branch?

Yes. Use cm sync branch br:/main/task123 to sync only that branch and its dependencies.

5. Is it safe to reset a replication link?

Yes, but ensure no partial sync is in progress. Back up server metadata before using cm sync reset in production environments.

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