Architecture Overview

Key Components

Rundeck consists of core services including the Web UI, Scheduler, Execution Engine, and Node Executor plugins. These components interact via an event-driven engine, often backed by a relational database and optionally integrated with LDAP, key storage, and external logging systems.

Scalability Considerations

As Rundeck scales, job concurrency, plugin execution, and database write load can create hidden bottlenecks. High-availability (HA) setups using clustered services and remote nodes further complicate observability and troubleshooting.

Common Symptoms and Their Hidden Causes

  • Jobs remain in a "running" state indefinitely
  • Scheduled jobs fail silently with no execution logs
  • Remote SSH executions randomly time out
  • Rundeck UI becomes unresponsive under load
  • Audit logs missing for completed jobs

Root Cause Analysis

1. Orphaned Execution Threads

Jobs that exceed their allocated timeout but do not clean up properly result in orphaned threads occupying scheduler slots. These threads may persist until a service restart.

2. Misconfigured Node Executor Plugins

When using custom or community node executors (e.g., WinRM, SaltStack), misconfiguration or lack of retries can cause silent command failures or incorrect exit code handling.

3. Database Lock Contention

On PostgreSQL or MySQL backends, concurrent job logs and state transitions can cause transaction locks, especially when log storage is set to `db` instead of `filesystem`.

4. Event Bus Saturation

Rundeck's internal event bus handles job lifecycle hooks, plugin events, and log updates. Under high job concurrency, this queue may saturate, causing delayed or lost state changes.

Diagnostics and Observability

1. Thread Dump Analysis

jstack  | grep -A 20 "JobThread"

Useful to identify hanging executions or blocked threads in the execution pool.

2. Database Lock Inspection (PostgreSQL)

SELECT * FROM pg_locks l JOIN pg_stat_activity a ON l.pid = a.pid WHERE NOT granted;

Reveal which queries or processes are holding locks that block job progress.

3. Job Execution Debug Mode

rundeckd --debug
tail -f /var/log/rundeck/service.log

Enable verbose logging to inspect plugin loading, node resolution, and job execution paths.

Step-by-Step Fixes

1. Clean Orphaned Jobs and Threads

Manually clear hung executions via the API or CLI:

rd executions list -s running
rd executions delete

Restart the Rundeck service if threads persist in memory.

2. Optimize Database Backend

  • Switch execution logs from DB to file-based storage
  • Tune PostgreSQL with higher `max_connections` and `work_mem`
  • Enable asynchronous logging where supported

3. Harden Node Executor Settings

ssh-authentication: privateKey
ssh-connection-timeout: 10s
retry-attempts: 3

Standardize and test plugins in staging before pushing into HA environments.

Architectural Best Practices

  • Use filesystem log storage to reduce DB pressure
  • Isolate job types into projects to limit plugin interference
  • Enable cluster mode with quorum configuration for HA
  • Schedule batch-heavy jobs during off-peak hours
  • Externalize audit logs to Splunk or ELK for compliance and debugging

Conclusion

Rundeck is a critical piece of the DevOps stack, but its flexibility and plugin-based architecture can introduce hidden complexities as environments scale. By leveraging low-level diagnostics, tuning core configurations, and hardening integrations, teams can prevent common pitfalls and maintain resilient orchestration across diverse infrastructure landscapes.

FAQs

1. Why do jobs randomly hang in Rundeck?

This is often due to orphaned threads from incomplete executions or plugin failures. Use thread dumps and API-based job status to identify stuck processes.

2. How can I reduce database load in high-throughput environments?

Switch to file-based log storage and move audit logs to external systems. Also, tune your DB engine for higher concurrency thresholds.

3. Can Rundeck run in active-active HA mode?

Yes, with proper clustering setup and shared storage. Ensure node identity and database configurations are consistent across instances.

4. How do I debug remote command failures?

Check node executor plugin settings and inspect `/var/log/rundeck/service.log` for SSH-related timeouts or misconfigurations.

5. What's the best way to monitor Rundeck health?

Use built-in metrics endpoints with Prometheus/Grafana integration, and external log aggregation for deeper observability.