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Logs

DoubleDino can expose log files through the /logs endpoint.

Logs can contain plain text, JSON, or mixed content. DoubleDino transforms the returned content while preserving its structure where possible.

Query logs​

Use the lines parameter to retrieve recent log lines:

curl -G "http://localhost:8080/logs" \
  --data-urlencode "lines=10" \
  -H "x-api-key: your-api-key"

DoubleDino reads the requested log content, transforms it, and returns the result. The original log file is not modified.

Plain text​

Plain text log entries are transformed while remaining readable.

For example:

2026-07-21 08:15:40 [ERROR] User login failure for [email protected]

can become:

2026-07-21 08:15:40 [ERROR] User login failure for [email protected]

JSON logs​

JSON log entries are transformed recursively, including nested objects and arrays.

For example:

{
  "event": "checkout_completed",
  "payload": {
    "customer": "Alice",
    "email": "[email protected]",
    "amount": 4250.45
  }
}

can become:

{
  "event": "checkout_completed",
  "payload": {
    "customer": "Dkyr",
    "email": "[email protected]",
    "amount": 4250.45
  }
}

The JSON structure remains intact.

Mixed logs​

A log file can contain different formats. DoubleDino processes the content and transforms values in both plain text and structured JSON entries.

Preserved expressions​

Administrators can configure expressions that remain unchanged using DD_PRESERVED_EXPRESSIONS.

If dynamic expressions are enabled, developers can also provide additional expressions for a request using the x-preserve-expressions header:

curl -G "http://localhost:8080/logs" \
  --data-urlencode "lines=100" \
  -H "x-api-key: your-api-key" \
  -H "x-preserve-expressions: payment_gateway_rejected"

Dynamic expressions are available only when the administrator has enabled:

DD_ALLOW_DYNAMIC_EXPRESSIONS=true

Only use this when you need additional expressions to remain visible. Developers cannot change expressions configured by the administrator.

Excluding JSON keys​

Administrators can configure JSON keys that should not be transformed using DD_EXCLUDE_KEYS.

For example:

DD_EXCLUDE_KEYS=status,code,request_id

Given:

{
  "status": 500,
  "request_id": "abc123",
  "email": "[email protected]"
}

the excluded keys remain unchanged while other values are transformed:

{
  "status": 500,
  "request_id": "abc123",
  "email": "[email protected]"
}

Read-only​

DoubleDino does not modify log files.

The requested content is read, transformed inside DoubleDino, and returned to the client. The original logs remain unchanged.