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Common Patterns

Frequently encountered issues and their solutions. These patterns appear across different EventSource types and Sensor configurations.

"Nothing Happens" Checklist

When events don't trigger workflows, check in order:

Step Check Command
1 EventSource running kubectl get eventsources -n argo-events
2 EventSource receiving kubectl logs -l eventsource-name=<name>
3 EventBus healthy kubectl get eventbus -n argo-events
4 Sensor running kubectl get sensors -n argo-events
5 Sensor receiving kubectl logs -l sensor-name=<name>
6 Workflows created kubectl get workflows -n argo-workflows

Stop at the first failure. That's where your problem is.

Pattern: JSON Body Not Parsed

Symptom: Events arrive, filters don't match, no errors.

Cause: Pub/Sub, Kafka, and other messaging systems wrap messages. Without explicit parsing, the body is a string.

Fix:

# Pub/Sub
spec:
  pubsub:
    event:
      jsonBody: true  # Required for JSON parsing

# Kafka
spec:
  kafka:
    event:
      jsonBody: true

# Webhook (usually automatic, but can set explicitly)
spec:
  webhook:
    event:
      jsonBody: true

Pattern: Wrong Dependency Name

Symptom: Sensor logs show event received, but trigger parameter injection fails.

Cause: dependencyName in trigger doesn't match dependency definition.

# Wrong - names don't match
dependencies:
  - name: image-push            # Defined as "image-push"

triggers:
  - template:
      parameters:
        - src:
            dependencyName: push  # References "push" - doesn't exist!

# Correct - names match
dependencies:
  - name: image-push

triggers:
  - template:
      parameters:
        - src:
            dependencyName: image-push  # Matches dependency name

Pattern: EventSource/Sensor Name Mismatch

Symptom: Sensor never receives events.

Cause: Sensor dependency references wrong EventSource or event name.

# EventSource defines
metadata:
  name: github-events  # EventSource name
spec:
  github:
    push:              # Event name is "push"

# Sensor must match exactly
dependencies:
  - name: my-dep
    eventSourceName: github-events  # Must match EventSource name
    eventName: push                  # Must match event name in spec

Pattern: Namespace Mismatch

Symptom: Components running but not connected.

Cause: EventSource, EventBus, and Sensor must be in the same namespace.

# Check namespaces match
kubectl get eventsources,eventbus,sensors -A | grep -E "NAME|argo"

If they're in different namespaces, events won't flow between them.

Pattern: Default EventBus Not Found

Symptom: EventSource or Sensor fails with "eventbus not found".

Cause: Components look for EventBus named default unless specified.

Fix: Either create default EventBus:

apiVersion: argoproj.io/v1alpha1
kind: EventBus
metadata:
  name: default  # Must be named "default"
  namespace: argo-events
spec:
  jetstream:
    version: "2.9.11"

Or specify EventBus name in components:

spec:
  eventBusName: my-custom-eventbus

Pattern: Trigger Fires Multiple Times

Symptom: Same event triggers multiple workflow executions.

Causes:

  1. Multiple Sensor replicas with bug: Older versions had deduplication issues
  2. Event republished: Source system sending duplicates
  3. Retry after partial success: Trigger succeeded but ack failed

Fix: Make workflows idempotent (see Idempotency Patterns).

Pattern: Old Events Replaying

Symptom: Events from hours/days ago suddenly trigger.

Cause: EventBus persistence replaying unacknowledged messages after restart.

Fix: Configure message retention:

spec:
  jetstream:
    settings: |
      max_age: "1h"  # Messages expire after 1 hour

Or investigate why messages weren't acknowledged (Sensor failure, slow processing).

Pattern: Sensor Restart Loop

Symptom: Sensor pod repeatedly restarts.

Common causes:

  1. Invalid trigger spec: Malformed YAML crashes sensor

    kubectl describe pod -l sensor-name=<name> | grep -A10 "Events:"

  2. Memory exhaustion: Event volume too high

    kubectl top pod -l sensor-name=<name>

  3. Dependency error: Can't connect to EventBus

    kubectl logs -l sensor-name=<name> --previous

Pattern: GitHub Webhooks Not Arriving

Symptom: GitHub configured, EventSource running, no events.

Checklist:

  1. Webhook delivery status: GitHub repo → Settings → Webhooks → Recent Deliveries
  2. Secret mismatch: GitHub secret must match EventSource secret
  3. SSL issues: GitHub requires valid SSL for webhook URLs
  4. Firewall: External traffic must reach your cluster
# Test external accessibility
curl -I https://your-webhook-url.example.com/github

# Check GitHub's view
# In GitHub webhook settings, look for red X marks on recent deliveries

Pattern: Rate Limiting Upstream

Symptom: EventSource works initially, then stops receiving.

Cause: External system rate limiting your requests.

Fix: Add delays or reduce polling frequency:

# For polling EventSources
spec:
  calendar:
    example:
      interval: 60s  # Don't poll too frequently

For webhook-based sources, this isn't usually an issue.

Log Everything First

When debugging, enable debug logging on all components temporarily. The performance hit is worth the visibility. Disable after resolving the issue.

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