Output Plugins

Output plugins define where and how log records are emitted. The library supports multiple active plugins simultaneously and ships with two built-in implementations.

Plugin Management

Output plugins can be managed at runtime using the following methods:

Method	Description
log.addOutputPlugin(plugin)	Adds a plugin alongside any existing ones.
log.setOutputPlugins(...plugins)	Replaces all existing plugins with the given one(s).
log.getOutputPlugins()	Returns the list of currently registered plugins.

StdoutOutputPlugin

The default plugin, registered automatically on startup. It writes log records to stdout or a configured sink function. It remains active unless explicitly replaced via setOutputPlugins().

OpenTelemetryLogsOutputPlugin Experimental

Note: This plugin relies on @opentelemetry/api-logs, which is marked as experimental by the OpenTelemetry project. Therefore consider this plugin experimental as well and be prepared for potential breaking changes in future releases.

Available since version 8.1.0. Emits log records via the OpenTelemetry Logs API. Only message logs are forwarded, whereas request logs are not emitted. It requires a configured OTel SDK with a LoggerProvider and appropriate exporters, either via the global OTel SDK (e.g. @opentelemetry/sdk-node) or passed explicitly to the constructor. The plugin itself does not initialize any OTel SDK components.

Registering the Plugin

import log, { OpenTelemetryLogsOutputPlugin } from 'cf-nodejs-logging-support';

// Keep stdout output and also emit via OTel:
log.addOutputPlugin(new OpenTelemetryLogsOutputPlugin());

// Emit via OTel only:
log.setOutputPlugins(new OpenTelemetryLogsOutputPlugin());

The constructor accepts the following optional parameters:

Parameter	Type	Description
loggerProvider	LoggerProvider	OTel LoggerProvider to use. Defaults to the global provider.
context	Context or (record) => Context | undefined	OTel context to attach to emitted log records. Can be a static Context or a resolver function that receives the log record and returns a context.

Including Fields as Attributes

By default, only custom fields are forwarded as OTel log attributes. This can be changed with setIncludeFieldsAsAttributes():

import log, { OpenTelemetryLogsOutputPlugin, FieldInclusionMode } from 'cf-nodejs-logging-support';

const plugin = new OpenTelemetryLogsOutputPlugin();
plugin.setIncludeFieldsAsAttributes(FieldInclusionMode.AllFields);

log.addOutputPlugin(plugin);

Mode	Description
FieldInclusionMode.CustomFieldsOnly	Only custom fields are added as attributes (default)
FieldInclusionMode.AllFields	All log record fields are added as attributes
FieldInclusionMode.None	No fields are added as attributes

Exception Attributes

When logging an error, the plugin automatically maps error information to the standard OTel exception attributes:

OTel Attribute	Source
exception.type	Error name
exception.message	Error message
exception.stacktrace	Stack trace

Logging Level Mapping

The plugin maps the library’s log levels to OTel severity levels as follows:

Logging Level	OTel Severity Text	OTel Severity Number
error	ERROR	17
warn	WARN	13
info	INFO	9
verbose	DEBUG2	6
debug	DEBUG	5
silly	TRACE	1