Note: This repository is archived since Epsagon is no longer supported

Epsagon Tracing for Node.js

This package provides tracing to Node.js applications for the collection of distributed tracing and performance metrics in Epsagon.

Contents

• Installation
• Usage
  • Auto-tracing
  • Calling the SDK
  • Tagging Traces
  • Custom Errors
  • Filter Sensitive Data
  • Ignore Endpoints
  • Trace URL
• Frameworks
• Integrations
• Configuration
• Getting Help
• Opening Issues
• License

Installation

To install Epsagon, simply run:

npm install epsagon

Usage

Important: Epsagon is activated and instruments the supported libraries once the module is imported.

Auto-tracing

The simplest way to get started in some frameworks is to install epsagon-frameworks:

npm install epsagon-frameworks

epsagon-frameworks extends the base epsagon support to more frameworks.

And run your node command:

export EPSAGON_TOKEN=<epsagon-token>
export EPSAGON_APP_NAME=<app-name-stage>
export EPSAGON_METADATA=FALSE
export NODE_OPTIONS='-r epsagon-frameworks'
<node command>

For example:

export EPSAGON_TOKEN=<your-token>
export EPSAGON_APP_NAME=express-prod
export EPSAGON_METADATA=FALSE
export NODE_OPTIONS='-r epsagon-frameworks'
node app.js

When using inside a Dockerfile, you can use ENV instead of export.

You can see the list of auto-tracing supported frameworks

Calling the SDK

Another simple alternative is to copy the snippet into your code:

const epsagon = require('epsagon-frameworks');

epsagon.init({
  token: 'epsagon-token',
  appName: 'app-name-stage',
  metadataOnly: false,
  sendBatch: false,
});

To run on your framework please refer to supported frameworks

Tagging Traces

You can add custom tags to your traces, for easier filtering and aggregations.

Add the following call inside your code:

epsagon.label('key', 'value');
epsagon.label('userId', userId);

You can also use it to ship custom metrics:

epsagon.label('key', 'metric')
epsagon.label('itemsInCart', itemsInCart)

You can also set global labels as part of the Epsagon initialisation:

epsagon.init({
  token: 'epsagon-token',
  appName: 'app-name-stage',
  labels: [['key', 'value'], ['userId', userId]],
});

Valid types are string, boolean and number.

In some frameworks tagging can be done in different ways.

Custom Errors

You can set a trace as an error (although handled correctly) to get an alert or just follow it on the dashboard.

Add the following call inside your code:

try {
  // something bad happens
} catch (err) {
  epsagon.setError(err);
}

// or manually specify Error object
epsagon.setError(Error('My custom error'));

Custom Warnings

This API allows you to flag the trace with a warning and also enables more flexible alerting

Add the following call inside your code:

try {
  // something bad happens
} catch (err) {
  epsagon.setWarning(err);
}

// Or manually specify Error object
epsagon.setWarning(Error('My custom error'));

In some frameworks custom errors can be declared in different ways.

Filter Sensitive Data

You can pass a list of sensitive properties and hostnames and they will be filtered out from the traces:

epsagon.init({
  token: 'epsagon-token',
  appName: 'app-name-stage',
  metadataOnly: false,
  ignoredKeys: ['password', /.*_token$/],
  ignoredDBTables: ['users', /.*password$/],
  urlPatternsToIgnore: ['example.com', 'auth.com'],
});

The ignoredKeys property can contain strings (will perform a loose match, so that First Name also matches first_name), regular expressions, and predicate functions. ignoredDBTables works similary, except will ignore response rows from DB queries.

Also, you can set urlPatternsToIgnore to ignore HTTP calls to specific domains.

Ignore Endpoints

You can ignore certain incoming requests by specifying endpoints:

epsagon.ignoreEndpoints(['/healthcheck'])

Trace URL

You can get the Epsagon dashboard URL for the current trace, using the following:

# Inside some endpoint or function
console.log('Epsagon trace URL:', epsagon.getTraceUrl())

This can be useful to have an easy access the trace from different platforms.

Frameworks

The following frameworks are supported by Epsagon. Some require installing also epsagon-frameworks

Framework	Supported Version	Epsagon Library	Auto-tracing Supported
AWS Lambda	All	epsagon	(Through the dashboard only)
Step Functions	All	epsagon
OpenWhisk Action	All	epsagon
Google Cloud Function	All	epsagon
AWS Batch	All	epsagon
Generic	All	epsagon
Express	>=3.0.0	epsagon-frameworks
Hapi	>=17.0.0	epsagon-frameworks
Koa	>=1.1.0	epsagon-frameworks
WS (Websocket)	>=7.3.1	epsagon-frameworks
restify	>=7.0.0	epsagon-frameworks
fastify	>=3.0.0	epsagon-frameworks
KafkaJS	>=1.2.0	epsagon-frameworks
kafka-node	>=3.0.0	epsagon-frameworks
PubSub	>=1.1.0	epsagon-frameworks
SQS Consumer	>=4.0.0	epsagon-frameworks
amqplib	>=0.5.0	epsagon-frameworks
bunnybus	>=7.0.0	epsagon-frameworks
NATS	>=1.4.0	epsagon-frameworks

AWS Lambda

Tracing Lambda functions can be done in three methods:

1. Auto-tracing through the Epsagon dashboard.
2. Using the serverless-plugin-epsagon if you're using The Serverless Framework.
3. Calling the SDK.

Make sure to choose just one of the methods

Calling the SDK is simple:

const epsagon = require('epsagon');
epsagon.init({
  token: 'epsagon-token',
  appName: 'app-name-stage',
  metadataOnly: false,
});

// Wrap your entry point
module.exports.handler = epsagon.lambdaWrapper((event, context, callback) => {
  // Your code is here
});

// Async functions example
module.exports.handler = epsagon.lambdaWrapper(async (event) => {
  // Your code is here
});

Step Functions

Tracing Step Functions is similar to regular Lambda functions, but the wrapper changes from lambdaWrapper to stepLambdaWrapper:

const epsagon = require('epsagon');
epsagon.init({
  token: 'epsagon-token',
  appName: 'app-name-stage',
  metadataOnly: false,
});

// Wrap your entry point
module.exports.handler = epsagon.stepLambdaWrapper((event, context, callback) => {
  // Your code is here
});

// Async functions example
module.exports.handler = epsagon.stepLambdaWrapper(async (event) => {
  // Your code is here
});

ECS Step - You should pass Epsagon step_dict id from ECS state input into EPSAGON_STEPS_ID environment variables of the container, EPSAGON_STEPS_NUM is the step number of the ECS (default: 0). check the configuration section.

OpenWhisk Action

You should pass the Epsagon token to your action as a default parameter, so that you don't have to expose important credentials in your code. The name of the parameter can be configured using token_param, in this example we use epsagon-token:

const epsagon = require('epsagon');

function main(params) {
  // Your code is here
}

module.exports.main = epsagon.openWhiskWrapper(
  main,
  {
    token_param: 'epsagon-token', // name of the action parameter to take the token from
    appName: 'app-name-stage',
    metadataOnly: false
  }
);

Google Cloud Function

Tracing Google Cloud Functions by wrapping your entry point with the epsagon.googleCloudFunctionWrapper:

const epsagon = require('epsagon');
epsagon.init({
  token: 'epsagon-token',
  appName: 'app-name-stage',
  metadataOnly: false,
  sendBatch: false,
});

// Wrap your entry point
exports.helloWorld = epsagon.googleCloudFunctionWrapper((req, res) => {
  res.status(200).send('hello world');
});

AWS Batch

Tracing batch jobs running in AWS Batch can be done by calling epsagon.wrapBatchJob() at the main handler/entrypoint of the code:

const epsagon = require('epsagon');
epsagon.init({
  token: 'epsagon-token',
  appName: 'app-name-stage',
  metadataOnly: false,
  labels: [["key", "value"]],
  traceCollectorURL: "https://eu-central-1.tc.epsagon.com" // default region is us-east-1
});

epsagon.wrapBatchJob();

function process(params) {
  try {
    // your code here
  } catch (error) {
    // some other code here
    process.exitCode = 1; //exits gracefully
  }
}

Express

Tracing Express application can be done in two methods:

1. Auto-tracing using the environment variable.
2. Calling the SDK.

Calling the SDK is simple, and should be done in your main js file where the application is being initialized:

const epsagon = require('epsagon-frameworks');

epsagon.init({
  token: 'epsagon-token',
  appName: 'app-name-stage',
  metadataOnly: false,
});

Tagging traces or setting custom errors can be by:

app.get('/', (req, res) => {
  req.epsagon.label('key', 'value');
  req.epsagon.setError(Error('My custom error'));
}

Hapi

Tracing Hapi application can be done in two methods:

1. Auto-tracing using the environment variable.
2. Calling the SDK.

Calling the SDK is simple, and should be done in your main js file where the application is being initialized:

const epsagon = require('epsagon-frameworks');

epsagon.init({
  token: 'epsagon-token',
  appName: 'app-name-stage',
  metadataOnly: false,
});

Tagging traces or setting custom errors can be by:

server.route({
  method: 'GET',
  path:'/',
  handler: (request, h) => {
      request.epsagon.label('key', 'value');
      request.epsagon.setError(Error('My custom error'));
  }
});

Koa

Tracing Koa application can be done in two methods:

1. Auto-tracing using the environment variable.
2. Calling the SDK.

Calling the SDK is simple, and should be done in your main js file where the application is being initialized:

const epsagon = require('epsagon-frameworks');

epsagon.init({
  token: 'epsagon-token',
  appName: 'app-name-stage',
  metadataOnly: false,
});

Tagging traces or setting custom errors can be by:

app.use(async ctx => {
  ctx.epsagon.label('key', 'value');
  ctx.epsagon.setError(Error('My custom error'));
});

WS (Websocket)

Tracing ws consumers can be done in two methods:

1. Auto-tracing using the environment variable.
2. Calling the SDK.

Calling the SDK is simple, and should be done in your main js file where the consumer is being initialized:

const epsagon = require('epsagon-frameworks');

epsagon.init({
  token: 'epsagon-token',
  appName: 'app-name-stage',
  metadataOnly: false,
});

Tagging traces or setting custom errors can be by:

socket.on('message', (message) => {
    message.epsagon.label('key', 'value');
    message.epsagon.setError(Error('My custom error'));
}) 

restify

Tracing restify application can be done in two methods:

1. Auto-tracing using the environment variable.
2. Calling the SDK.

Calling the SDK is simple, and should be done in your main js file where the application is being initialized:

const epsagon = require('epsagon-frameworks');

epsagon.init({
  token: 'epsagon-token',
  appName: 'app-name-stage',
  metadataOnly: false,
});

Tagging traces or setting custom errors can be by:

function respond(req, res, next) {
  req.epsagon.label('key', 'value');
  req.epsagon.setError(Error('My custom error'));
}

fastify

Tracing fastify application can be done in two methods:

1. Auto-tracing using the environment variable.
2. Calling the SDK.

Calling the SDK is simple, and should be done in your main js file where the application is being initialized:

const epsagon = require('epsagon-frameworks');

epsagon.init({
  token: 'epsagon-token',
  appName: 'app-name-stage',
  metadataOnly: false,
});

Tagging traces or setting custom errors can be by:

fastify.get('/', (request, reply) => {
  request.epsagon.label('key', 'value');
  request.epsagon.setError(Error('My custom error'));
  reply.send({ hello: 'world' })
})

KafkaJS

Tracing kafkajs consumers can be done in two methods:

1. Auto-tracing using the environment variable.
2. Calling the SDK.

Calling the SDK is simple, and should be done in your main js file where the consumer is being initialized:

const epsagon = require('epsagon-frameworks');

epsagon.init({
  token: 'epsagon-token',
  appName: 'app-name-stage',
  metadataOnly: false,
});

Tagging traces or setting custom errors can be by:

await consumer.run({
  eachMessage: async ({ topic, partition, message }) => {
    message.epsagon.label('key', 'value');
    message.epsagon.setError(Error('My custom error'));
  },
})

kafka-node

Tracing kafka0node consumers can be done in two methods:

1. Auto-tracing using the environment variable.
2. Calling the SDK.

Calling the SDK is simple, and should be done in your main js file where the consumer is being initialized:

const epsagon = require('epsagon-frameworks');

epsagon.init({
  token: 'epsagon-token',
  appName: 'app-name-stage',
  metadataOnly: false,
});

Tagging traces or setting custom errors can be by:

consumer.on('message', function (message) {
  message.epsagon.label('key', 'value');
  message.epsagon.setError(Error('My custom error'));
})

PubSub

Tracing @google-cloud/pubsub consumers can be done in two methods:

1. Auto-tracing using the environment variable.
2. Calling the SDK.

Calling the SDK is simple, and should be done in your main js file where the consumer is being initialized:

const epsagon = require('epsagon-frameworks');

epsagon.init({
  token: 'epsagon-token',
  appName: 'app-name-stage',
  metadataOnly: false,
});

Tagging traces or setting custom errors can be by:

await consumer.run({
  eachMessage: async ({ topic, partition, message }) => {
    message.epsagon.label('key', 'value');
    message.epsagon.setError(Error('My custom error'));
  },
})

SQS Consumer

Tracing sqs-consumer consumers can be done in two methods:

1. Auto-tracing using the environment variable.
2. Calling the SDK.

Calling the SDK is simple, and should be done in your main js file where the consumer is being initialized:

const epsagon = require('epsagon-frameworks');

epsagon.init({
  token: 'epsagon-token',
  appName: 'app-name-stage',
  metadataOnly: false,
});

Tagging traces or setting custom errors can be by:

const messageHandler = message => {
  message.epsagon.label('key', 'value');
  message.epsagon.setError(Error('My custom error'));
};

Or in batch message handler:

const batchMessageHandler = messages => {
  messages[0].epsagon.label('key', 'value');
  messages[0].epsagon.setError(Error('My custom error'));
};

amqplib

Tracing amqplib consumers can be done in two methods:

1. Auto-tracing using the environment variable.
2. Calling the SDK.

Calling the SDK is simple, and should be done in your main js file where the consumer is being initialized:

const epsagon = require('epsagon-frameworks');

epsagon.init({
  token: 'epsagon-token',
  appName: 'app-name-stage',
  metadataOnly: false,
});

Tagging traces or setting custom errors can be by:

ch.consume(q, function cons(msg) {
  if (msg !== null) {
    msg.epsagon.label('key', 'value');
    msg.epsagon.setError(Error('My custom error'));
    ch.ack(msg);
  }
});

bunnybus

Tracing bunnybus consumers can be done in two methods:

1. Auto-tracing using the environment variable.
2. Calling the SDK.

Calling the SDK is simple, and should be done in your main js file where the consumer is being initialized:

const epsagon = require('epsagon-frameworks');

epsagon.init({
  token: 'epsagon-token',
  appName: 'app-name-stage',
  metadataOnly: false,
});

Tagging traces or setting custom errors can be by:

// epsagon is added as an argument to the handler
handler: async ({message, metaData, ack, rej, requeue, epsagon}) => {
    epsagon.label('key', 'value');
    epsagon.setError(Error('My custom error'));
    await ack();
}

NATS

Tracing nats consumers can be done in two methods:

1. Auto-tracing using the environment variable.
2. Calling the SDK.

Calling the SDK is simple, and should be done in your main js file where the consumer is being initialized:

const epsagon = require('epsagon-frameworks');

epsagon.init({
  token: 'epsagon-token',
  appName: 'app-name-stage',
  metadataOnly: false,
});

Generic

For any tracing, you can simply use the generic Epsagon wrapper using the following example:

const epsagon = require('epsagon');
epsagon.init({
  token: 'epsagon-token',
  appName: 'app-name-stage',
  metadataOnly: false,
});


function main(params) {
  // Your code is here
}

const wrappedMain = epsagon.nodeWrapper(main);

Integrations

Epsagon provides out-of-the-box instrumentation (tracing) for many popular frameworks and libraries.

Library	Supported Version
http	Fully supported
https	Fully supported
http2	Fully supported
dns	Fully supported
fs	Fully supported
aws-sdk	>=2.2.0
amazon-dax-client	>=1.0.2
@google-cloud	>=2.0.0
@google-cloud/pubsub	>=1.1.0
mysql	>=2
mysql2	>=1
pg	>=4
mongodb	>=2.2.12
kafkajs	>=1.2.0
kafka-node	>=3.0.0
amqplib	>=0.5.0
amqp	>=0.2.0
redis	>=0.12.1
ioredis	>=4.0.0
cassandra-driver	>=3.3.0
mqtt	>=2.13.1
nats	>=1.4.0
openwhisk	>=3.0.0
@azure/cosmos	>=3.7.5
@azure/storage-blob	>=12.2.0
ldapjs	>=2.1.0
ws	>=7.3.1
pino	>=6.0.0
bunyan	>=1.8.0
winston	>=2.4.5

Configuration

Advanced options can be configured as a parameter to the init() method or as environment variables.

Parameter	Environment Variable	Type	Default	Description
token	EPSAGON_TOKEN	String	-	Epsagon account token
appName	EPSAGON_APP_NAME	String	Application	Application name that will be set for traces
metadataOnly	EPSAGON_METADATA	Boolean	true	Whether to send only the metadata (true) or also the payloads (false)
useSSL	EPSAGON_SSL	Boolean	true	Whether to send the traces over HTTPS SSL or not
traceCollectorURL	EPSAGON_COLLECTOR_URL	String	-	The address of the trace collector to send trace to
isEpsagonDisabled	DISABLE_EPSAGON	Boolean	false	A flag to completely disable Epsagon (can be used for tests or locally)
keysToAllow	EPSAGON_ALLOWED_KEYS	Boolean	-	Array of keys to automatically label in the trace
ignoredKeys	EPSAGON_IGNORED_KEYS	Array	-	Array of keys names (can be string or regex) to be removed from the trace
ignoredDBTables	EPSAGON_IGNORED_DB_TABLES	Array	-	Array of DB Table names (can be string or regex) to ignore response from trace.
removeIgnoredKeys	EPSAGON_REMOVE_IGNORED_KEYS	Boolean	false	Whether to remove ignored keys instead of masking them
urlPatternsToIgnore	EPSAGON_URLS_TO_IGNORE	Array	[]	Array of URL patterns to ignore the calls
sendTimeout	EPSAGON_SEND_TIMEOUT_SEC	Float	1.0	The timeout duration in seconds to send the traces to the trace collector
sendBatch	EPSAGON_SEND_BATCH	Boolean	true	Whether to set the traces in batch mode, effective under high scale (set false for development)
batchSize	EPSAGON_BATCH_SIZE	Integer	5	The traces' batch size, when batch mode is activated
decodeHTTP	EPSAGON_DECODE_HTTP	Boolean	true	Whether to decode and decompress HTTP responses into the payload
httpErrorStatusCode	EPSAGON_HTTP_ERR_CODE	Integer	400	The minimum number of an HTTP response status code to treat as an error
-	EPSAGON_ALLOW_ERR_MESSAGE_STATUS	Boolean	true	Whether to override http.status_code with a Status Code found in a raised Error's Message
-	EPSAGON_PROPAGATE_LAMBDA_ID	Boolean	false	Insert Lambda request ID into the response payload
-	DISABLE_EPSAGON_PATCH	Boolean	false	Disable the library patching (instrumentation)
isConsolePatched	EPSAGON_PATCH_CONSOLE	Boolean	false	Enable console module patching (instrumentation) for labelling
-	EPSAGON_DEBUG	Boolean	false	Enable debug prints for troubleshooting
-	EPSAGON_PROPAGATE_NATS_ID	Boolean	false	Whether to propagate a correlation ID in NATS.io calls for distributed tracing
-	EPSAGON_ADD_NODE_PATH	String	-	List of folders to looks for node_modules when patching libraries. Separated by :
-	EPSAGON_AUTO_ADD_NODE_PATHS	Boolean	false	Auto add node_modules sub folders to look when patching libraries.
-	EPSAGON_DNS_INSTRUMENTATION	Boolean	false	Whether to capture dns calls into the trace
-	EPSAGON_FS_INSTRUMENTATION	Boolean	false	Whether to capture node file system calls into the trace
-	EPSAGON_LOGGING_TRACING_ENABLED	Boolean	true	whether to add an Epsagon ID to the logs in order to correlate traces to logs in the dashboard
-	EPSAGON_STEPS_ID	String	-	The Epsagon step id from the ECS step functions state input
-	EPSAGON_STEPS_NUM	String	0	The step number of the ECS step functions state
-	EPSAGON_ALLOW_NO_ROUTE	Boolean	false	Whether to capture non-matched route requests in Express.js
-	EPSAGON_LAMBDA_TIMEOUT_THRESHOLD_MS	Integer	200	The threshold in milliseconds to send the trace before a Lambda timeout occurs
-	EPSAGON_PAYLOADS_TO_IGNORE	Array	-	Array of dictionaries to not instrument. Example: '[{"source": "serverless-plugin-warmup"}]'

Getting Help

If you have any issue around using the library or the product, please don't hesitate to:

• Use the documentation.
• Use the help widget inside the product.
• Open an issue in GitHub.

Opening Issues

If you encounter a bug with the Epsagon library for Node.js, we want to hear about it.

When opening a new issue, please provide as much information about the environment:

• Library version, Node.js runtime version, dependencies, etc.
• Snippet of the usage.
• A reproducible example can really help.

The GitHub issues are intended for bug reports and feature requests. For help and questions about Epsagon, use the help widget inside the product.

License

Provided under the MIT license. See LICENSE for details.

Copyright 2021, Epsagon