New Relic for Node.js

This package instruments your application for performance monitoring
with New Relic.

Make sure you have a New Relic account before starting. To see all the
features, such as slow transaction traces, you will need a New Relic Pro
subscription (or equivalent).

As with any instrumentation tool, please test before using in production.

Table of contents

• Getting started
• Security
• Configuration
• RUM / browser timings
• Transactions and request naming
• Licensing
• Contributions
• Known issues

Getting started

1. Install node. The agent runs on v4 and
   higher. Development work on this module is done with the latest stable
   release of Node.
2. Install this module via npm install newrelic for the application you want
   to monitor.
3. Copy newrelic.js from node_modules/newrelic into the root directory of
   your application.
4. Edit newrelic.js and replace license_key's value with the license key
   for your account.
5. Add require('newrelic') as the first line of the app's main module.

If you wish to keep the configuration for the module separate from your
application, the module will look for newrelic.js in the directory referenced
by the environment variable NEW_RELIC_HOME if it's set.

When you start your app, New Relic should start up with it and start reporting
data that will appear within the New Relic UI
after a few minutes. Because the agent minimizes the amount of bandwidth it
consumes, it only reports data once a minute, so if you require the module in
tests that take less than a minute to run, it won't have time to report data to
New Relic. The module will write its log to a file named newrelic_agent.log
in the application directory. If New Relic doesn't send data or crashes your
app, the log can help New Relic determine what went wrong, so be sure to send
it along with any bug reports or support requests.

Security

We take security (and the protection of your and your users' privacy) very
seriously. See SECURITY.md for details, but the brief version is
that if you feel you've found a security issue, contact us at security@newrelic.com.

Configuring the module

The module can be tailored to your app's requirements, both from the server and
via the newrelic.js configuration file you created. For complete details on
what can be configured, refer to lib/config/default.js, which documents
the available variables and their default values.

In addition, for those of you running in PaaS environments like Heroku or
Microsoft Azure, all of the configuration variables in newrelic.js have
counterparts that can be set via environment variables. You can mix and match
variables in the configuration file and environment variables freely;
environment variables take precedence.

Here's the list of the most important variables and their values:

• NEW_RELIC_LICENSE_KEY: Your New Relic license key. This is a required
  setting with no default value.
• NEW_RELIC_APP_NAME: The name of this application, for reporting to New
  Relic's servers. This value can be also be a comma-delimited, or
  semicolon-delimited, list of names. This is a required setting with no
  default value. (NOTE: as a convenience to Azure users, the module will use
  APP_POOL_ID as the application name if it's set, so you can use the name
  you chose for your Azure Web Server without setting it twice.)
• NEW_RELIC_NO_CONFIG_FILE: Inhibit loading of the configuration file
  altogether. Use with care. This presumes that all important configuration
  will be available via environment variables, and some log messages assume
  that a config file exists.
• NEW_RELIC_HOME: path to the directory in which you've placed newrelic.js.
• NEW_RELIC_LOG: Complete path to the New Relic agent log, including the
  filename. The agent will shut down the process if it can't create this file,
  and it creates the log file with the same umask of the process. Setting this
  to stdout will write all logging to stdout, and stderr will write all
  logging to stderr.
• NEW_RELIC_LOG_LEVEL: Logging priority for the New Relic agent. Can be one
  of error, warn, info, debug, or trace. debug and trace are
  pretty chatty; unless you're helping New Relic figure out irregularities with
  the module, you're probably best off using info or higher.

For a complete list of environment variables and other configuration options see
Node.js agent configuration on our documentation site.

Browser timings (RUM / Real User Monitoring)

New Relic's instrumentation can extend beyond your application into the client's
browser. The newrelic module can generate <script> headers which, when
inserted into your HTML templates, will capture client-side page load times.

Headers must be manually injected, but no extra configuration is necessary to
enable browser timings.

Basics

• Insert the result of newrelic.getBrowserTimingHeader() into your html page.
• The browser timing headers should be placed in the beginning of your <head> tag.
  • As an exception to the above, for maximum IE compatibility, the results of
    getBrowserTimingHeader() should be placed after any
    X-UA-COMPATIBLE HTTP-EQUIV meta tags.
• Do not cache the header, call it once for every request.

Example

Below is an example using express and pug; Express is a popular web
application framework, and pug is a popular template module. Although the
specifics are different for other frameworks, the general approach described
below should work in most cases.

The simplest way to insert browser timing headers is to pass the newrelic
module into your template, and call newrelic.getBrowserTimingHeader() from
within the template.

app.js:

var newrelic = require('newrelic');
var app = require('express')();

// In Express, this lets you call newrelic from within a template.
app.locals.newrelic = newrelic;

app.get('/user/:id', function (req, res) {
  res.render('user');
});
app.listen(process.env.PORT);

layout.pug:

doctype html
html
  head
    != newrelic.getBrowserTimingHeader()
    title= title
    link(rel='stylesheet', href='/stylesheets/style.css')
  body
    block content

By defaults calls to newrelic.getBrowserTimingHeader() should return valid
headers. You can disable header generation without removing your template
code. In your newrelic.js file, add the following to disable header generation.

exports.config = {
  // ... other config
  browser_monitoring : {
    enable : false
  }
};

You can also set the environment variable NEW_RELIC_BROWSER_MONITOR_ENABLE=false.

It is safe to leave the header generation code in place even when you're not
using it. If browser timings are disabled, or there is an error such that
working headers cannot be generated, the newrelic module will generate an
innocuous HTML comment. If the newrelic module is disabled entirely no content
will be generated.

Transactions and request naming

In order to get the most value out of New Relic for Node.js, you may have to do
a little work to help us figure out how your application is structured. New
Relic works on the assumption that it can group requests to your application
into transactions, which are defined by giving one or more request paths a
name. These names are used to visualize where your app is spending its time (in
transaction breakdowns), to identify slow requests, and to group scoped
metrics. For example, this can identify slow database queries by showing which
requests are spending a long time waiting on the database.

If you're using Express, Restify or Hapi with their default routers and are
satisfied with your application being represented by those frameworks' route
matchers, you may not need to do anything. However, if you want more specific
names than are provided by your framework, you may want to use one or more of
the tools described further on.

The simplest way to tell that you need to read further in this document is if
you feel too many of your requests are being lumped together under the
catch-all name /*. All requests that aren't otherwise named by the module
will end up grouped under /*.

Background

If you've been working with Node for a while, you're probably accustomed to
thinking of your application's requests in terms of raw URLs. One of the great
things about Node is that it makes it so easy and simple to work with HTTP, and
that extends to things like parsing URLs and creating your own strategies for
naming and routing requests for services like RESTful APIs. This presents a
challenge for New Relic, because we need to keep the number of names we're
tracking small enough that we can keep the New Relic user experience snappy,
and also so we don't overwhelm you with so much data that it's difficult for
you to see the problem spots in your applications. URLs are not a good fit for
how New Relic sees performance.

Another of Node's great strengths is that it provides a lot of tools that build
on top of the http module to simplify writing web services. Unfortunately,
that variety greatly complicates things for us, with our limited resources, and
so we offer a few different tools to help you give us the information we need
to provide you useful metrics about your application:

• we can read the route names from the Express, Restify, and Hapi routers, if
  you're using them (and as said above, for many of you, this may be all you
  need)
• we offer an API for naming the current request, either with simple names or,
  if you prefer, grouped into controllers with actions
• and we support rules stored in your module's configuration that can mark
  requests to be renamed or ignored based on regular expressions matched
  against the request's raw URLs (also available as API calls)

Requests are mapped to transaction names using a deterministic process:

1. On an incoming request, the module creates a New Relic transaction that
   includes the HTTP request method and other metadata. As a fallback (for use
   in the error tracer), each transaction is named after its raw request URL.
2. When a framework using a supported router is in use, the agent copies the
   framework name, route path and request method onto the transaction as its
   transaction name.
3. Within handlers, you can make calls to the module's API to explicitly set
   the name of the route to whatever you want, or mark the route to be ignored
   (or explicitly not ignored, see the below discussion of rules). As noted
   below, the last API call wins when there is more than one.
4. When the transaction is finished (i.e. the response has been completely
   streamed out to the client), any naming or ignoring rules you have specified
   in your configuration are applied. NOTE: Older versions of the module
   only applied these rules if nothing else had named the transaction, which
   made using rules with router-based automatic naming impossible. You must be
   using the latest version of New Relic to combine naming and ignoring rules
   with naming set by the router instrumentation.
5. Finally, New Relic may have its own rules that it applies to the transaction
   name, either because the request is for something New Relic rolls up by
   default (i.e. static assets like images or CSS files), or because New Relic
   is applying rules to remedy metric grouping issues.
6. If nothing has named the transaction after steps 1-5, the transaction is
   named /*, which puts that request in the undifferentiated, default bucket
   for requests. This will typically only happen in situations where your
   application uses either no framework, or a framework with a router that
   isn't currently supported by New Relic.

Let's go through the naming tools one at a time.

Router introspection

Express is the most popular web framework in use within the Node community, and
a number of important services are also using Restify. Both frameworks map
routes to handlers, and both use a similar pattern to do so: they match one or
more HTTP methods (e.g. GET or the ever-popular OPTIONS – let's hear it for
CORS) along with a potentially parameterized path (e.g. /user/:id) or a
regular expression (e.g. /^/user/([-0-9a-f]+)$/). New Relic will capture both
those pieces of information in the request name. If you have support for slow
transaction traces and have included request.parameters.* attributes, the
transaction trace will also have the request's parameters and their values
attached to it. Likewise, request parameters and their values will be attached
to any errors recorded by the agent.

The only important thing to know about New Relic's support for Express, Restify,
or Hapi is that if you're dissatisfied with the names it comes up with, you can
use the API calls described below to come up with more descriptive names. Also,
if you use a different web framework or router and would like to see support
for it added, please check out
custom intrumentation.

Request naming with the module API

The API is what's handed back from require('newrelic'), so

var newrelic = require('newrelic');

is all you need. Please note that you still need to ensure that loading the New
Relic module is the first thing your application does, as it needs to bootstrap
itself before the rest of your application loads, but you can safely require
the module from multiple modules in your application – it will only initialize
itself once.

newrelic.setTransactionName(name)

Name the current request. You can call this function anywhere within the
context of an HTTP request handler, at any time after handling of the request
has started, but before the request has finished. A good rule of thumb is that
if the request and response objects are in scope, you can set the name.

Explicitly calling newrelic.setTransactionName() will override any names set
by Express, Restify or Hapi routes. Calls to newrelic.setTransactionName() and
newrelic.setControllerName() will overwrite each other. The last call made
before the request ends wins.

VERY IMPORTANT NOTE: Do not include highly variable information like GUIDs,
numerical IDs, or timestamps in the request names you create. If your request
is slow enough to generate a transaction trace, that trace will contain the
original URL. If you enable parameter capture, the parameters will also be
attached to the trace. The request names are used to group requests for New
Relic's many charts and tables, and those visualizations' value drops as the
number of different request names increases. If you have 50 or so different
transaction names, you're probably pushing it. If you have more than a couple
hundred, you need to rethink your naming strategy.

newrelic.setControllerName(name, [action])

Name the current request using a controller-style pattern, optionally including
the current controller action. If the action is omitted, New Relic will include
the HTTP method (e.g. GET, POST) as the action. The rules for when you can
call newrelic.setControllerName() are the same as they are for
newrelic.setTransactionName().

Explicitly calling newrelic.setControllerName() will override any names set by
Express, Restify, or Hapi routes. Calls to newrelic.setTransactionName() and
newrelic.setControllerName() will overwrite each other. The last one to run
before the request ends wins.

See the above note on newrelic.setTransactionName(), which also applies to
this function.

Rules for naming and ignoring requests

If you don't feel like putting calls to the New Relic module directly into your
application code, you can use pattern-based rules to name requests. There are
two sets of rules: one for renaming requests, and one to mark requests to be
ignored by New Relic.

If you're using socket.io, you will have a use case for ignoring rules right
out of the box. You'll probably want to add a rule like the following:

// newrelic.js
exports.config = {
  // other configuration
  rules : {
    ignore : [
      '^/socket.io/.*/xhr-polling'
    ]
  }
};

This will keep socket.io long-polling from dominating your response-time
metrics and blowing out the apdex metrics for your application.

rules.name

A list of rules used to set the name of the transaction to name when the URL
matches pattern.

Can also be set via the environment variable NEW_RELIC_NAMING_RULES, with
multiple rules passed in as a list of comma-delimited JSON object literals:
NEW_RELIC_NAMING_RULES='{"pattern":"^t","name":"u"},{"pattern":"^u","name":"t"}'

Each rule is defined using the following format:

{
  // required
  pattern : "pattern",
  name : "name",

  // optional
  precedence: 1,
  terminate_chain: true,
  replace_all: false
}

Additional attributes are ignored.

Note: these rules take precedence over automatic naming from router
instrumentations and are applied to the URL path, not the name returned by the
router instrumentation.

pattern (required)

The pattern used to match the URL. It can be set as either a string or a
JavaScript regular expression literal. For example, "^/abc/123$" is equivalent
to /^\/abc\/123$/.

The pattern can be written to match the complete URL, or just a part of it.

name (required)

The value that is used to replace the URL (or part of it) that matches the pattern.
It is also possible to use regular expression group references. See examples below.

rules.precedence (optional)

By default the rules are evaluated in reverse order (from last to first). If you
find this behavior counterintuitive, the execution order can be reversed by
setting the feature flag reverse_naming_rules to false. Furthermore, if you
prefer to have complete control over the order, each rule can be given a
precedence attribute. The precedence is an integer number, and rules are
evaluated in ascending order. If precedence is not explicitly defined, it will
be set to 500 by default.

rules.terminate_chain (optional)

When set to true, no further rules will be evaluated if this rule is a match.
The default is true.

Setting this to false is useful when multiple rules should be used together. For
example, one rule could be replacing a common pattern in many different URLs,
while subsequent rule(s) would be more specific.

rules.replace_all (optional)

When set to true, all matches of the pattern will be replaced. Otherwise, only
the first match will be replaced. The default is false. Using the g flag with
regular expression literal will have the same effect. For example:

  pattern: '[0-9]+',
  replace_all: true

will have the same effect as

  pattern: /[0-9]+/g

Testing

The agent comes with a command-line tool for testing naming rules. For more
information run the following command in terminal window in a directory where
your app is installed.

node node_modules/.bin/newrelic-naming-rules

Examples

Match full URL:

  pattern: "^/items/[0-9]+$",
  name: "/items/:id"

Replace the first match in any URL:

  pattern: "[0-9]+",
  name: ":id"

will result in:

/orders/123 => /orders/:id

/items/123 => /items/:id

/orders/123/items/123 => /orders/:id/items/123

Replace all matches in any URL:

  pattern: "[0-9]+",
  name: ":id",
  replace_all: true

will result in:

/orders/123/items/123 => /orders/:id/items/:id

Using regular expression match group references:

  pattern: '^/(items, orders)/[0-9]+$',
  name: '/\\1/:id'

will result in:

/orders/123 => /orders/:id

/items/123 => /items/:id

rules.ignore

A list of patterns for matching incoming request URLs to be ignored. When using
ignoring rules with instrumented routers, the matches are still made against
the URL paths, not the name returned by the router instrumentation. Patterns may
be strings or regular expressions.

Can also be set via the environment variable NEW_RELIC_IGNORING_RULES, with
multiple rules passed in as a list of comma-delimited patterns:
NEW_RELIC_IGNORING_RULES='^/socket\.io/\*/xhr-polling,ignore_me' Note that
currently there is no way to escape commas in patterns.

API for adding naming and ignoring rules

newrelic.addNamingRule(pattern, name)

Programmatic version of rules.name above. Naming rules can not be removed
until the Node process is restarted. They can also be added via the module's
configuration. Both parameters are mandatory.

newrelic.addIgnoringRule(pattern)

Programmatic version of rules.ignore above. Ignoring rules can not be removed
until the Node process is restarted. They can also be added via the module's
configuration. The pattern is mandatory.

Other API calls

newrelic.addCustomAttribute(name, value)

Set a custom attribute value to be attached to a transaction trace and/or error
in the New Relic UI. This must be called within the context of a transaction,
so it has a place to set the custom attributes.

newrelic.addCustomAttributes(params)

Set multiple custom attribute values to be attached to a transaction trace and/or
error in the New Relic UI. This must be called within the context of a transaction,
so it has a place to set the custom attribute.

Example of setting multiple custom attribute at once:

newrelic.addCustomAttributes({test: 'value', test2: 'value2'});

newrelic.setIgnoreTransaction(ignored)

Tell the module explicitly whether or not a given request should be ignored.
Allows you to explicitly filter out long-polling routes or requests you know
are going to be time-consuming in an uninteresting way, and also allows you
to gather metrics for requests that would otherwise be ignored. Note that
to prevent a transaction from being ignored with this function, you must
pass false as the parameter – in this case null or undefined will be
ignored.

newrelic.noticeError(error, customParameters)

If your app is doing its own error handling with domains or try/catch clauses,
but you want all of the information about how many errors are coming out of the
app to be centrally managed, use this call. Unlike most of the calls here, this
function can be used outside of route handlers, but will have additional
context if called from within transaction scope. If custom parameters are
passed in on an object literal, they will be passed back to New Relic for
display.

newrelic.shutdown([options], callback)

Use this method to gracefully shut down the agent. When called with
options.collectPendingData set to true, the agent will send any pending data
to the New Relic servers before shutting down. This is useful when you want to
shut down the Node process and make sure that all transactions and/or errors are
captured by New Relic.

Example of collecting pending data before shutting down the process:

newrelic.shutdown({ collectPendingData: true }, function(error) {
  process.exit()
})

Custom Instrumentation

Custom transaction should be used for instrumenting socket.io or other
varieties of socket servers, and background jobs. These are things that the
agent can't automatically instrument because without your knowledge of your
application, the agent can't tell when they should begin and end.

Read more at:
https://docs.newrelic.com/docs/agents/nodejs-agent/supported-features/nodejs-custom-instrumentation

newrelic.startWebTransaction(url, handle)

url is the name of the web transaction. It should be pretty static, not
including anything like user ids or any other data that is very specific to the
request. handle is the function you'd like to wrap in the web transaction.
Both custom and auto instrumentation will be captured as part of the
transaction.

If called within an active web transaction, it will act as a nested tracer. If
called within an active background transaction, it will create a new,
independent transaction and any calls within the handle will be bound to the
new web transaction.

Custom transactions can be ended within the handle in one of three ways:

1. Call transaction.end(). The transaction can be received by calling
   newrelic.getTransaction() first thing in the handler function. Then,
   when you call transaction.end() timing will stop.
2. Return a promise. The transaction will end when the promise resolves or
   rejects.
3. Do neither. If no promise is returned, and getTransaction() isn't
   called, the transaction will end immediately after the handle returns.

newrelic.startBackgroundTransaction(name [, group], handle)

name is the name of the job. It should be pretty static, and not include job
ids or anything very specific to that run of the job. group is optional, and
allows you to group types of jobs together. This should follow similar rules as
the name. handle is a function that encompasses your background job. Both
custom and auto instrumentation will be captured as part of the transaction.

If called within an active background transaction, it will act as a nested
tracer. If called within an active web transaction, it will create a new
transaction and any calls within the handle will be bound to the new,
independent background transaction.

1. Call transaction.end(). The transaction can be received by calling
   newrelic.getTransaction() first thing in the handler function. Then,
   when you call transaction.end() timing will stop.
2. Return a promise. The transaction will end when the promise resolves or
   rejects.
3. Do neither. If no promise is returned, and getTransaction() isn't
   called, the transaction will end immediately after the handle returns.

newrelic.getTransaction()

This takes no arguments and returns the currently active transaction. If the
returned transaction is a custom one, started with either startWebTransaction
or startBackgroundTransaction, then transaction.end() must be called to
end the transaction.

newrelic.startSegment(name, record, handler, callback)

name is the name of the segment. record is a boolean value signalling
whether or not to record the segment as a metric. handler is the function
being recorded. callback is an optional function that is passed to the
handler and fired after all other work is complete.

Timing is from when startSegment is called until the handler is done
executing, or when the callback is fired, if it's supplied. This method
should be called inside of a transaction to get data. If it is called outside
of a transaction it will just pass through.

newrelic.recordMetric(name, value)

name is the metric name to record. it must be a string and may be prepended
with segments for category and label. (eg. /my_category/my_label/my_name).
Custom metrics are automatically prepended with Custom, resulting in metrics of
the form: Custom/${name}.

value is either a numerical value to associate with the metric sample,
or an object representing multiple samples for the metric. If value is
an object, it must include keys for count, total, min, max, and
sumOfSquares.

newrelic.incrementMetric(name[, amount])

name is the metric name to record, it must be a string that beings with
Custom/ typically followed by segments for category and label.
(eg. Custom/my_category/my_label).

amount is optional, but must be an integer if provided. amount is
the number of times to increment the metrics count, it defaults to 1.

The fine print

This is the Node-specific version of New Relic's transaction naming API
documentation. The naming API exists to help us deal with the very real problem
that trying to handle too many metrics will make New Relic slow for everybody,
not just the account with too many metrics. If, in conversation with New Relic
Support, you see discussion of "metric explosion", this is what they're talking
about.

While we have a variety of strategies for dealing with these issues, the most
severe is simply to block offending applications. The main reason for you
to be careful in using our request-naming tools is to prevent that from
happening to your applications. We will do everything in our power to ensure
that you have a good experience with New Relic even if your application is
causing us trouble, but sometimes this will require manual intervention on the
part of our team, and this can take a little while.

Contributions

We owe a debt to all of the beta testers and users who have provided us with
feedback, and in some cases significant pieces of code. (If you wish to
contribute, please see CONTRIBUTING.md in this directory.) In particular, we're
indebted to these people:

• Hernan Silberman, for his work on the memcached instrumentation.
• Jeff Howell <jhowell@kabam.com>, for coming up with a much simpler way
  to instrument node-mongodb-native, as well as pointing out a problem with the
  Connect instrumentation.

Recent changes

Information about changes to the module are in NEWS.md.

Known issues:

• New Relic for Node is only supported on Node.js 6 and newer. Some features
  may behave differently between the supported versions of Node. The agent is
  optimized for newer versions of Node.
• There are irregularities around transaction trace capture and display. If you
  notice missing or incorrect information from transaction traces, let us know.
• There are over 20,000 30,000 40,000 A
  LOT of modules on npm. We can only instrument a tiny number of them.
  Even for the modules we support, there are a very large number of ways to use
  them. If you see data you don't expect on New Relic and have the time to
  produce a reduced version of the code that is producing the strange data, it
  will be used to improve the module and you will have the Node team's
  gratitude.
• The CPU and memory overhead incurred by New Relic for Node is relatively
  minor (~1-10%, depending on how much of the instrumentation your apps end up
  using). GC activity is significantly increased while the agent is active, due
  to the large number of ephemeral objects created by metrics gathering.
• When using Node's included clustering support, each worker process will open
  its own connection to New Relic's servers, and will incur its own overhead
  costs.

New Relic features available for other platforms not yet in Node.js

• explain plans
• thread profiling
• X-ray transactions (depends on thread profiling)
• capacity planning

LICENSE

New Relic for Node is free-to-use, proprietary software. Please see the full
license (found in LICENSE in this distribution) for details on its
license and the licenses of its dependencies.