@fluent-org/logger

Fluent Forward Protocol implementation for Node.js. Built upon fluent-logger-node.

Install

$ npm install @fluent-org/logger

Client

@fluent-org/logger provides a fully functional client that implements the Forward protocol. It supports reconnection, acknowledgements, timeouts, event retries, and more, and exposes its functionality via a simple typed Promise interface.

For a full list of the client options and methods, see the FluentClient docs

Prerequisites

The fluent daemon should be listening in forward mode.

A simple starting configuration for Fluentd is the following:

<source>
  @type forward
  port 24224
</source>

<match **.*>
  @type stdout
</match>

See the FluentD docs for more info.

A similar starting configuration for Fluent Bit is the following:

[INPUT]
    Name              forward
    Listen            0.0.0.0
    Port              24224
    Buffer_Chunk_Size 1M
    Buffer_Max_Size   6M

[OUTPUT]
    Name   stdout
    Match  *

See the Fluent Bit docs for more info.

Sending an event record to an upstream Fluent server

const FluentClient = require("@fluent-org/logger").FluentClient;
const logger = new FluentClient("tag_prefix", {
  socket: {
    host: "localhost",
    port: 24224,
    timeout: 3000, // 3 seconds
  }
});

The emit method has following signature

emit(data: Record<string, any>): Promise<void>;
emit(data: Record<string, any>, timestamp: number | Date | EventTime): Promise<void>;
emit(label: string, data: Record<string, any>): Promise<void>;
emit(label: string, data: Record<string, any>, timestamp: number | Date | EventTime): Promise<void>;

The returned Promise is resolved once the event is written to the socket, or rejected if an error occurs.

Acknowledgements

The Fluent forward protocol provides explicit support for acknowledgements, which allow the client to be sure that the event reached its destination.

Enabling acknowledgements means that the promise returned by emit will be resolved once the client receives an explicit acknowledgement from the server.

const FluentClient = require("@fluent-org/logger").FluentClient;
const logger = new FluentClient("tag_prefix", {
  ack: {}
});

Event modes

The Fluent forward protocol provides multiple message modes, Message, Forward, PackedForward(default), CompressedPackedForward. The Fluent client supports all of them.

const FluentClient = require("@fluent-org/logger").FluentClient;
const logger = new FluentClient("tag_prefix", {
  eventMode: "Message" | "Forward" | "PackedForward" | "CompressedPackedForward"
});

Disable automatic reconnect

const logger = new FluentClient("tag_prefix", {
  socket: {
    host: "localhost",
    port: 24224,
    timeout: 3000, // 3 seconds
    disableReconnect: true
  }
});
// If you disable reconnections, the socket has to be manually connected, 
// connect() returns a promise, which rejects on connection errors.
logger.connect();

Shared key authentication

Logger configuration:

const logger = new FluentClient("tag_prefix", {
  socket: {
    host: "localhost",
    port: 24224,
    timeout: 3000, // 3 seconds
  },
  security: {
    clientHostname: "client.localdomain",
    sharedKey: "secure_communication_is_awesome"
  }
});

Fluentd configuration:

<source>
  @type forward
  port 24224
  <security>
    self_hostname input.testing.local
    shared_key secure_communication_is_awesome
  </security>
</source>

<match dummy.*>
  @type stdout
</match>

TLS/SSL encryption

Logger configuration:

const logger = new FluentClient("tag_prefix", {
  socket: {
    host: "localhost",
    port: 24224,
    timeout: 3000, // 3 seconds
    tls: {
      ca: fs.readFileSync("/path/to/ca_cert.pem")
    },
  },
  security: {
    clientHostname: "client.localdomain",
    sharedKey: "secure_communication_is_awesome"
  },
});

Fluentd configuration:

<source>
  @type forward
  port 24224
  <transport tls>
    ca_cert_path /path/to/ca_cert.pem
    ca_private_key_path /path/to/ca_key.pem
    ca_private_key_passphrase very_secret_passphrase
  </transport>
  <security>
    self_hostname input.testing.local
    shared_key secure_communication_is_awesome
  </security>
</source>

<match dummy.*>
  @type stdout
</match>

FYI: You can generate certificates using the fluent-ca-generate command since Fluentd 1.1.0.

Mutual TLS Authentication

Logger configuration:

const logger = new FluentClient("tag_prefix", {
  socket: {
    host: "localhost",
    port: 24224,
    timeout: 3000, // 3 seconds
    tls: {
      ca: fs.readFileSync("/path/to/ca_cert.pem"),
      cert: fs.readFileSync("/path/to/client-cert.pem"),
      key: fs.readFileSync("/path/to/client-key.pem"),
      passphrase: "very-secret"
    },
  },
  security: {
    clientHostname: "client.localdomain",
    sharedKey: "secure_communication_is_awesome"
  }
});

Fluentd configuration:

<source>
  @type forward
  port 24224
  <transport tls>
    ca_path /path/to/ca-cert.pem
    cert_path /path/to/server-cert.pem
    private_key_path /path/to/server-key.pem
    private_key_passphrase very_secret_passphrase
    client_cert_auth true
  </transport>
  <security>
    self_hostname input.testing.local
    shared_key secure_communication_is_awesome
  </security>
</source>

<match dummy.*>
  @type stdout
</match>

EventTime support

We can also specify an EventTime as a timestamp. See the EventTime docs

const FluentClient = require("@fluent-org/logger").FluentClient;
const EventTime = require("@fluent-org/logger").EventTime;
const eventTime = new EventTime(1489547207, 745003500); // 2017-03-15 12:06:47 +0900
const logger = new FluentClient("tag_prefix", {
  socket: {
    host: "localhost",
    port: 24224,
    timeout: 3000, // 3 seconds
  }
});
logger.emit("tag", { message: "This is a message" }, eventTime);

Handling errors

The Fluent client will manage errors internally, and reject promises on errors. If you”d like to access the non-user facing internal errors, you can do so by passing errorHandler

const FluentClient = require("@fluent-org/logger").FluentClient;
const logger = new FluentClient("tag_prefix", {
  onSocketError: (err: Error) => {
    console.error("error!", err)
  }
});

Retrying events

Sometimes it makes sense to resubmit events if their initial submission failed. You can do this by specifying eventRetry.

const FluentClient = require("@fluent-org/logger").FluentClient;
const logger = new FluentClient("tag_prefix", {
  eventRetry: {}
});

Server

@fluent-org/logger includes a fully functional forward server which can be used as a downstream Fluent sink.

const FluentServer = require("@fluent-org/logger").FluentServer;

const server = new FluentServer({ listenOptions: { port: 24224 }});

await server.listen();

Fluentd config:

<match pattern>
  @type forward
  send_timeout 60s
  recover_wait 10s
  hard_timeout 60s

  <server>
    name fluent_node 
    host 127.0.0.1
    port 24224
    weight 60
  </server>

  <secondary>
    @type file
    path /var/log/fluent/forward-failed
  </secondary>
</match>

See the FluentD docs for more info.

Alternatively, see the Fluent Bit docs for info on setting up Fluent Bit.

For a full list of the server options and methods, see the FluentServer docs

License

Apache License, Version 2.0.

About NodeJS versions

This package is compatible with NodeJS versions >= 12.