Wire Debug Log

Wire-level HTTP request/response log for troubleshooting OAP communication. Off by default. Very verbose — only use when actively debugging.

debugLog:
  enabled: false
  file: ./horizon-wire.jsonl
  maxBodyChars: 8192
  redactAuthHeaders: true

Fields

Field	Type	Default	Required	Notes
`enabled`	boolean	`false`	no	Master switch. When `true`, every outbound OAP request and inbound response is logged to `file`. Off otherwise.
`file`	string	`./horizon-wire.jsonl`	no	Filesystem path to the wire log. JSON Lines, one entry per request. Append-only, no rotation.
`maxBodyChars`	number	`8192`	no	Maximum body size (in characters) to log per request/response. Larger bodies are truncated with a marker. Prevents unbounded log growth from large MQE responses. Non-negative integer; `0` means do not log bodies.
`redactAuthHeaders`	boolean	`true`	no	When `true`, `Authorization` and `Proxy-Authorization` headers (basic-auth credentials sent to OAP) are replaced with `<redacted>` in the log. Set to `true` in production.

One JSON line per outbound request/response pair, with these fields:

Field	Meaning
`ts`	Request start time (ISO 8601).
`method`	HTTP method.
`url`	Full request URL.
`status`	Response HTTP status. Absent when the request failed before a response arrived.
`elapsedMs`	Wall-clock milliseconds from request start to response (or failure).
`requestHeaders` / `responseHeaders`	Header maps, with auth redaction per `redactAuthHeaders`.
`requestBody` / `responseBody`	Bodies as text, truncated at `maxBodyChars` with a `…[truncated, N chars total]` marker. Omitted entirely when `maxBodyChars: 0`.
`error`	Present instead of `status` / response fields when the request failed at the network level (timeout, refused connection); carries the error message.

GraphQL queries are logged as POST bodies; admin REST endpoints (runtime-rule, inspect, etc.) appear as their underlying method.

“Why does OAP return X?” Tail the log while you reproduce the issue:
```
tail -f horizon-wire.jsonl | jq -c 'select(.status >= 400)'
```
MQE expression debugging. Read the literal execExpression mutation Horizon sends, then run it directly against OAP with curl to compare.
Capability probing. The introspection probes that determine which OAP features Horizon thinks are available appear as ordinary entries the first time each feature is used.

High volume. A busy dashboard fires dozens of requests per page load; expect hundreds of MB/day with enabled: true.
Timeout covers the body while enabled. To log the response, Horizon buffers each OAP reply before handing it on, so oap.timeoutMs then bounds the full body download — a very large, slow response that normally finishes after the header timeout window can abort while the log is on. Binary payloads pass through byte-identical and are logged as a size marker.
No rotation. Pair with a log shipper or a logrotate sidecar.
Off in production by default unless you are actively troubleshooting a specific issue.
Enabling it is announced. Starting the BFF with enabled: true emits a warning line in the app log as a reminder that every outbound OAP request/response is being appended (very verbose — disable after troubleshooting).
Auth-header redaction is on by default. Disabling it (redactAuthHeaders: false) leaks basic-auth credentials into the log — running that way emits its own startup warning. Only flip off for a single-session troubleshooting run, and clear the file afterward.
An unwritable path drops entries, not the process. If the target directory can’t be created or written, the entry is dropped and an error is logged; OAP traffic itself is unaffected.

enabled, file, maxBodyChars, redactAuthHeaders all hot-reload. Flipping enabled: false → true starts logging on the next outbound call.