How to Troubleshoot n8n Errors

1// Execution history shows:
2// - Timestamp of the execution
3// - Status: Success, Error, or Running
4// - Workflow name
5// - Execution duration
6// - Mode: Manual, Trigger, Webhook, or Retry
7//
8// Click a failed execution to see:
9// - Which node failed (highlighted in red)
10// - The exact error message
11// - Input data that caused the failure
12// - Output data from preceding nodes

1// Common data issues to check:
2//
3// 1. Missing field:
4//    Expected: {{ $json.email }}
5//    Actual input: { "name": "John" }  ← no email field
6//
7// 2. Wrong data type:
8//    Expected: number for price calculation
9//    Actual input: { "price": "29.99" }  ← string, not number
10//
11// 3. Empty input:
12//    Expected: at least one item
13//    Actual input: []  ← no items, node has nothing to process
14//
15// 4. Nested data:
16//    Expected: {{ $json.name }}
17//    Actual input: { "data": { "user": { "name": "John" } } }
18//    Fix: {{ $json.data.user.name }}

1# Enable debug logging
2export N8N_LOG_LEVEL=debug
3export N8N_LOG_OUTPUT=console
4
5# Restart n8n to apply
6n8n start
7
8# In Docker:
9docker stop n8n
10docker run -d --name n8n \
11  -e N8N_LOG_LEVEL=debug \
12  -p 5678:5678 \
13  -v n8n_data:/home/node/.n8n \
14  docker.n8n.io/n8nio/n8n
15
16# View logs in Docker:
17docker logs n8n --tail 100 -f
18
19# After debugging, switch back:
20export N8N_LOG_LEVEL=info

1// Category 1: Credential errors
2// Messages: "401 Unauthorized", "Invalid API key", "Authentication failed"
3// Fix: Verify credentials in Settings → Credentials. Test by creating a new credential.
4
5// Category 2: Data format errors
6// Messages: "Cannot read property X of undefined", "Expected string, got object"
7// Fix: Inspect the input data on the failing node. Add a Set or Code node to transform data.
8
9// Category 3: Rate limit errors
10// Messages: "429 Too Many Requests", "Rate limit exceeded"
11// Fix: Add a Wait node between API calls, use SplitInBatches, or reduce trigger frequency.
12
13// Category 4: Timeout errors
14// Messages: "ETIMEDOUT", "Timeout exceeded", "socket hang up"
15// Fix: Increase node timeout in Settings, check API server status, reduce request payload.
16
17// Category 5: Expression errors
18// Messages: "Expression evaluation error", "Cannot read property of null"
19// Fix: Check expression syntax. Use optional chaining: {{ $json.field?.subfield }}.

1// Error monitoring workflow
2// Node 1: Error Trigger
3// Node 2: Code node to format the error
4const execution = $json.execution;
5const workflow = $json.workflow;
6
7return [{
8  json: {
9    alert: `Workflow "${workflow.name}" failed`,
10    error: execution.error?.message || 'Unknown error',
11    executionId: execution.id,
12    timestamp: new Date().toISOString(),
13    mode: execution.mode,
14    url: `https://n8n.example.com/execution/${execution.id}`
15  }
16}];
17
18// Node 3: Send to Slack, Email, or save to database