@google-cloud/trace-agent
Advanced tools
Node.js Support for StackDriver Trace
A comprehensive list of changes in each version may be found in the CHANGELOG.
Read more about the client libraries for Cloud APIs, including the older Google APIs Client Libraries, in Client Libraries Explained.
Table of contents:
npm install @google-cloud/trace-agent
Warning
cloud-trace-nodejsis in maintenance mode. This means that we'll continue to fix bugs add add security patches. We'll consider merging new feature contributions (depending on the anticipated maintenance cost). But we won't develop new features ourselves.In particular, we will not add support for new major versions of libraries.
We encourage users to migrate to OpenTelemetry JS Instrumentation instead.
This module provides automatic tracing for Node.js applications with Cloud Trace. Cloud Trace is a feature of Google Cloud Platform that collects latency data (traces) from your applications and displays it in near real-time in the Google Cloud Console.
The Trace Agent supports Node 8+.
Note: Using the Trace Agent requires a Google Cloud Project with the Cloud Trace API enabled and associated credentials. These values are auto-detected if the application is running on Google Cloud Platform. If your application is not running on GCP, you will need to specify the project ID and credentials either through the configuration object, or with environment variables. See Setting Up Cloud Trace for Node.js for more details.
Note: The Trace Agent does not currently work out-of-the-box with Google Cloud Functions (or Firebase Cloud Functions). See #725 for a tracking issue and details on how to work around this.
Simply require and start the Trace Agent as the first module in your application:
require('@google-cloud/trace-agent').start();
// ...
If you want to use import, you will need to do the following to import all required types:
import * as TraceAgent from '@google-cloud/trace-agent';
Optionally, you can pass a configuration object to the start() function as follows:
require('@google-cloud/trace-agent').start({
samplingRate: 5, // sample 5 traces per second, or at most 1 every 200 milliseconds.
ignoreUrls: [ /^\/ignore-me/ ] // ignore the "/ignore-me" endpoint.
ignoreMethods: [ 'options' ] // ignore requests with OPTIONS method (case-insensitive).
});
// ...
The object returned by start() may be used to create custom trace spans:
const tracer = require('@google-cloud/trace-agent').start();
// ...
app.get('/', async () => {
const customSpan = tracer.createChildSpan({name: 'my-custom-span'});
await doSomething();
customSpan.endSpan();
// ...
});
The trace agent can do automatic tracing of the following web frameworks:
The agent will also automatically trace RPCs from the following modules:
http, https, and http2 core modulesYou can use the Custom Tracing API to trace other modules in your application.
To request automatic tracing support for a module not on this list, please file an issue. Alternatively, you can write a plugin yourself.
To load an additional plugin, specify it in the agent's configuration:
require('@google-cloud/trace-agent').start({
plugins: {
// You may use a package name or absolute path to the file.
'my-module': '@google-cloud/trace-agent-plugin-my-module',
'another-module': path.join(__dirname, 'path/to/my-custom-plugins/plugin-another-module.js')
}
});
This list of plugins will be merged with the list of built-in plugins, which will be loaded by the plugin loader. Each plugin is only loaded when the module that it patches is loaded; in other words, there is no computational overhead for listing plugins for unused modules.
The custom tracing API can be used to create custom trace spans. A span is a particular unit of work within a trace, such as an RPC request. Spans may be nested; the outermost span is called a root span, even if there are no nested child spans. Root spans typically correspond to incoming requests, while child spans typically correspond to outgoing requests, or other work that is triggered in response to incoming requests. This means that root spans shouldn't be created in a context where a root span already exists; a child span is more suitable here. Instead, root spans should be created to track work that happens outside of the request lifecycle entirely, such as periodically scheduled work. To illustrate:
const tracer = require('@google-cloud/trace-agent').start();
// ...
app.get('/', (req, res) => {
// We are in an automatically created root span corresponding to a request's
// lifecycle. Here, we can manually create and use a child span to track the
// time it takes to open a file.
const readFileSpan = tracer.createChildSpan({ name: 'fs.readFile' });
fs.readFile('/some/file', 'utf8', (err, data) => {
readFileSpan.endSpan();
res.send(data);
});
});
// For any significant work done _outside_ of the request lifecycle, use
// runInRootSpan.
tracer.runInRootSpan({ name: 'init' }, rootSpan => {
// ...
// Be sure to call rootSpan.endSpan().
});
For any of the web frameworks for which we provide built-in plugins, a root span is automatically started whenever an incoming request is received (in other words, all middleware already runs within a root span). If you wish to record a span outside of any of these frameworks, any traced code must run within a root span that you create yourself.
Calling the start function returns an instance of Tracer, which provides an interface for tracing:
const tracer = require('@google-cloud/trace-agent').start();
It can also be retrieved by subsequent calls to get elsewhere:
// after start() is called
const tracer = require('@google-cloud/trace-agent').get();
A Tracer object is guaranteed to be returned by both of these calls, even if the agent is disabled.
A fully detailed overview of the Tracer object is available here.
The Trace Agent automatically patches well-known modules to insert calls to functions that start, label, and end spans to measure latency of RPCs (such as mysql, redis, etc.) and incoming requests (such as express, hapi, etc.). As each RPC is typically performed on behalf of an incoming request, we must make sure that this association is accurately reflected in span data. To provide a uniform, generalized way of keeping track of which RPC belongs to which incoming request, we rely on async_hooks to keep track of the "trace context" across asynchronous boundaries.
async_hooks works well in most cases. However, it does have some limitations that can prevent us from being able to properly propagate trace context:
async_hooks API has issues tracking context around await-ed "thenables" (rather than real promises). Requests originating from the body of a then implementation in such a user-space "thenable" may not get traced. This is largely an unconventional case but is present in the knex module, which monkeypatches the Bluebird Promise's prototype to make database calls. If you are using knex (esp. the raw function), see #946 for more details on whether you are affected, as well as a suggested workaround.unsupported
The Trace Agent does not support bundled server code, so bundlers like webpack or @zeit/ncc will not work.
Samples are in the samples/ directory. Each sample's README.md has instructions for running its sample.
| Sample | Source Code | Try it |
|---|---|---|
| App | source code |  |
| Snippets | source code | |
The Cloud Trace Node.js Client API Reference documentation also contains samples.
Our client libraries follow the Node.js release schedule. Libraries are compatible with all current active and maintenance versions of Node.js. If you are using an end-of-life version of Node.js, we recommend that you update as soon as possible to an actively supported LTS version.
Google's client libraries support legacy versions of Node.js runtimes on a best-efforts basis with the following warnings:
Client libraries targeting some end-of-life versions of Node.js are available, and
can be installed through npm dist-tags.
The dist-tags follow the naming convention legacy-(version).
For example, npm install @google-cloud/trace-agent@legacy-8 installs client libraries
for versions compatible with Node.js 8.
This library follows Semantic Versioning.
This library is considered to be in preview. This means it is still a work-in-progress and under active development. Any release is subject to backwards-incompatible changes at any time.
More Information: Google Cloud Platform Launch Stages
Contributions welcome! See the Contributing Guide.
Please note that this README.md, the samples/README.md,
and a variety of configuration files in this repository (including .nycrc and tsconfig.json)
are generated from a central template. To edit one of these files, make an edit
to its templates in
directory.
Apache Version 2.0
See LICENSE
8.0.0 (2024-02-07)
FAQs
Node.js Support for StackDriver Trace
The npm package @google-cloud/trace-agent receives a total of 92,816 weekly downloads. As such, @google-cloud/trace-agent popularity was classified as popular.
We found that @google-cloud/trace-agent demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 1 open source maintainer collaborating on the project.
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