gelfie

gelfie is a client for sending GELF data to a server.

Usage

The following example demonstrates how gelfie can be utilized. See the API documentation below for more specific details, including all supported options and methods.

'use strict';
const { GelfClient } = require('gelfie');

(async () => {
  const client = new GelfClient({
    graylogHost: 'your-graylog-host',
    graylogPort: 12201
  });

  client.on('error', console.error);

  await client.connect();
  client.info('informational data to log');
  client.error(new Error('uh oh!'));
  client.debug('debug info', 'gelf full_message', {
    facility: 'gelf facility'
  });

  setTimeout(() => {
    client.close();
  }, 3000);
})();

API

gelfie exports the GelfClient class which is used to send GELF data to a remote server. gelfie also exports a table of log level constants.

GelfClient(options) Constructor

• Arguments
  • options (object) - Configuration data supporting the following options:
    • host (string) - Used as the host field in GELF data. Optional. Defaults to os.hostname() from the Node.js runtime.
    • serializer(field) (function) - A function used to customize the serialization of the GELF short_message and full_message fields. The only parameter passed to the serializer() function is field, which corresponds to the short_message or full_message. Optional. Defaults to GelfClient.defaultSerializer(). An example use of this function is to improve the serialization of objects that do not naturally map to JSON, such as Maps and circular data structures.
    • transport (string) - The type of network transport to use. Valid values are 'udp' and 'tcp'. Optional. Defaults to 'udp'.
    • version (string) - Used as the version field in GELF data. Optional. Defaults to '1.1'.

Constructs a new GelfClient instance. Must be called with new. Internally, the options object is passed to constructor function of the selected transport. Therefore, any transport options must also be included in options. See the documentation of the appropriate transport for a list of supported options.

Transport Specific Options

This section describes options passed to the GelfClient constructor that are specific to individual transports.

UDP

The UDP transport supports the following options:

• bufferSize (integer) - The maximum buffer size that gelfie will attempt to send in a single message. If a message is larger than bufferSize, gelfie will attempt to send it as chunked messages. For this reason, this option impacts chunking behavior. This value cannot be made arbitrarily large due to UDP restrictions related to Maximum Transmission Unit (MTU) sizes. It also should not be made very small, as GELF limits the number of chunks for a single message to 128. Optional. Defaults to 1400.
• compression (string) - Specifies the type of compression to apply to outgoing messages. Compression increases the amount of CPU used to send each message, but can significantly improve network usage. Supported values are 'none' (no compression) and zlib. Optional. Defaults to 'zlib'.
• graylogHost (string) - The Graylog host to send data to.
• graylogPort (integer) - The port on graylogHost to send data to.
• reuseBuffer (boolean) - If true, the transport reuses a single buffer to send all chunks of a single message. This is done to conserve memory. If false, all chunks are sent as quickly as possible using separate buffers. Optional. Defaults to true.

TCP

The TCP transport supports the following options:

• graylogHost (string) - The Graylog host to send data to.
• graylogPort (integer) - The port on graylogHost to send data to.
• maxBacklogSize (integer) - If the underlying TCP socket cannot send data fast enough to keep up with the application, gelfie will respect backpressure, by buffering messages until the socket emits a 'drain' event. At that time, gelfie will attempt to send all buffered messages, while still respecting backpressure. maxBacklogSize defines the maximum number of messages that will be buffered. Attempting to buffer more messages results in an error being emitted. If the transport is closed while there are buffered messages, they will be silently discarded. Optional. Defaults to 1024.
• socketOptions (object) - An object passed to Node's net.Socket. These options will be passed verbatim, with the exception of the host and port options, which take their values from the transport's graylogHost and graylogPort options. Optional. Defaults to { host: graylogHost, port: graylogPort }.

GelfClient.prototype.connect()

• Arguments
  • None
• Returns
  • Nothing

Performs any asynchronous operations required to begin sending GELF data to a remote server. Depending on the transport in use, this function may return a Promise.

GelfClient.prototype.close()

• Arguments
  • None
• Returns
  • Nothing

Shuts down the client. After close() is called, the client is no longer usable.

GelfClient.prototype.emergency(shortMessage[, fullMessage[, additionalFields[, timestamp]]])

GelfClient.prototype.alert(shortMessage[, fullMessage[, additionalFields[, timestamp]]])

GelfClient.prototype.critical(shortMessage[, fullMessage[, additionalFields[, timestamp]]])

GelfClient.prototype.error(shortMessage[, fullMessage[, additionalFields[, timestamp]]])

GelfClient.prototype.warning(shortMessage[, fullMessage[, additionalFields[, timestamp]]])

GelfClient.prototype.notice(shortMessage[, fullMessage[, additionalFields[, timestamp]]])

GelfClient.prototype.info(shortMessage[, fullMessage[, additionalFields[, timestamp]]])

GelfClient.prototype.debug(shortMessage[, fullMessage[, additionalFields[, timestamp]]])

GelfClient.prototype.log(shortMessage[, fullMessage[, additionalFields[, timestamp[, level]]]])

• Arguments
  • shortMessage (any) - Used as the short_message field in GELF data. This value is passed to the client's serializer() function.
  • fullMessage (any) - Used as the full_message field in GELF data. If present, this value is passed to the client's serializer() function. Optional. Defaults to undefined.
  • additionalFields (object) - A collection of fields used as additional_fields in GELF data. The object's own enumerable property names are used as the field names. An underscore is automatically prepended to the property names. Property names that are not valid GELF additional_field names are silently discarded. Optional.
  • timestamp (number) - Used as the timestamp field in GELF data. Optional. If this value is not provided, it is computed from the current time.
  • level (integer) - The logging level. This argument is only supported by the log() function. The other functions (emergency(), error(), etc.) implicitly use their associated log level. This value must be a integer from 0 (inclusive) to 7 (inclusive). Optional. Defaults to 1 if the value is not provided, or is not in the range of valid values.
• Returns
  • Nothing

These functions convert their inputs to GELF and then forward the data to the transport layer to be sent over the network.

GelfClient.defaultSerializer(field)

• Arguments
  • field (any) - Data to be converted to a valid GELF short_message or full_message.
• Returns
  • value (string or undefined) - The representation of field to be sent in an outgoing message.

Converts arbitrary data to a representation suitable for GELF. Strings are returned as is. Error objects are converted to a plain object containing name, message, and stack properties before being passed to JSON.stringify(). All other values are passed directly to JSON.stringify().

Due to the use of JSON.stringify(), circular data structures will cause an exception to be thrown. Similarly, objects such as Maps will not serialize as expected. These limitations can be worked around by passing a custom serializer() function to the GelfClient constructor.

levels

This is an object whose keys are log level names and values are numeric log levels. For example, levels.EMERG is 0, levels.NOTICE is 5, etc.