error-log-logger

error-log-logger

An error-only access logger: it builds the shared access-log entry and ships it to a remote TCP sink only when the request accumulated errors (context.errors is non-empty). Requests that did not fail produce nothing.

Denials and throttles are not errors

context.errors holds one record per node that could not do its job — upstream unreachable, an IdP callout that failed, a counter store that is down, input the node cannot parse. Deliberate responses are not in it. A request that exits on an outcome port — an auth denial (denied), a throttle (limited), an open circuit breaker (broken), an injected abort (abort), a redirect (redirect) — carries no error record, so this node emits nothing for it. That is by design: those are the gateway working as configured.

To ship a record of denials or throttles, place a regular access logger (logging, http-logger, ...) on the path those outcome ports take.

Delivery is fire-and-forget. Place this node in the response pipeline after the upstream node (and after any node whose errors you want captured).

Configuration

Key	Type	Default	Description
host	string	— (required)	TCP sink hostname or IP.
port	integer	— (required)	TCP sink port (0–65535).
timeout	integer (s)	3	Connect/send timeout.
level	string	"WARN"	Accepted for config compatibility. featherbit logs on the presence of context.errors, not on a syslog severity threshold. Must be one of STDERR, EMERG, ALERT, CRIT, ERR, ERROR, WARN, NOTICE, INFO, DEBUG.
tls	bool	false	Not yet supported — true is rejected at config load.
log_format	object	—	Custom name -> "$var" entry; replaces the default structured entry.
batch_max_size	integer	1000	Entries per batch; 1 flushes every entry immediately.
inactive_timeout	integer (s)	5	Flush when idle this long.
buffer_duration	integer (s)	60	Flush when the oldest buffered entry is this old.
max_retry_count	integer	0	Retries after a failed flush.
retry_delay	integer (s)	1	Delay between retries.
max_pending_entries	integer	10000	Queue capacity; entries are dropped (with a warning) when full.

- id: error-log
  type: error-log-logger
  config:
    host: 127.0.0.1
    port: 5044

Behavior

When context.errors is non-empty, builds the shared access-log entry (which includes the errors array) and pushes it to the batch sink as one newline-delimited JSON object. When there are no errors, nothing is emitted — including for the deliberate outcome exits listed above. The node is a pure passthrough: only its success port is ever taken.

Behavior notes

• Source of logs: featherbit logs request-level errors (context.errors) rather than the gateway's own internal error-log lines — featherbit has no internal error-log file to tail. Note that this is narrower than APISIX's error log, which also records rejections written by plugins: here a deliberate rejection is an outcome, not an error, and is not captured.
• Only the tcp sink (host/port) is implemented; the skywalking, clickhouse, and kafka sinks are out of scope for this socket-focused node.
• level is accepted but not enforced as a severity threshold.
• tls is not yet supported; tls: true is rejected at config load.

Errors

This node never fails at execution time: it always returns through success, so its error port is never taken.