Profiling HTTP Requests with the CLI

Blackfire lets you profile HTTP requests like web pages, web service calls, or API calls.

To get started, check that you have Blackfire installed correctly on the server hosting the website you want to profile.

Profiling an HTTP request means instrumenting the project’s code. Blackfire is apart from many other profilers because of two main differences:

  • Blackfire automatically instruments your code when needed, so you don’t need to change your code;
  • Blackfire does nothing when you are not profiling a request (the overhead is then almost zero), so it is safe to deploy Blackfire on production servers, even for heavy-traffic projects.

This cookbook describes how to profile from the command line interface. You can also profile web applications from a browser.

Profiling Simple HTTP Requests

Profiling an HTTP request can be done on the command line thanks to the blackfire utility.

The easiest way to profile an HTTP request is to use the curl sub-command of the blackfire utility. It accepts the same arguments and options as the regular curl utility:

blackfire curl


Recommended: To explicitly define which environment the profile must be sent to, use the --env=<ENV_UUID> parameter.

v2.14.0+ of the unified Agent and Client: when no target environment is specified, the Agent uses the BLACKFIRE_SERVER_ID environment variable to determine where to send the profile.

When no target environment is specified or implicitly discovered, the profile is sent to the personal sandbox environment of the user whose personal credentials (BLACKFIRE_CLIENT_ID and BLACKFIRE_CLIENT_TOKEN) were used. Only that user can then access the profile from /my/profiles.

To explicitly specify your personal sandbox environment, use --env="My Environment"

You can get a list of options available for the curl sub-command:

blackfire help curl

To get more accurate results, take several samples of the request via the --samples option (we recommend you to use this option only for “safe” HTTP requests like GET requests):

blackfire --samples 10 curl

At the end of the request, blackfire outputs the URL where the profile can be found (hide it by passing the -q option.)

JSON Output

You can integrate Blackfire results into your tools by using the --json option to get a JSON representation of a profile:

blackfire --json curl


The JSON output is displayed on STDOUT, while the regular output (e.g. progress, profile summary…) is displayed on STDERR.

The resources consumed are available under the envelope entry; keys are the cost dimensions:

  • pmu: Peak Memory Usage (in bytes);
  • nw: Network (in bytes);
  • wt: Wall Clock Time (in microseconds);
  • cpu: CPU time (in microseconds);
  • io: I/O time (in microseconds).

Profiling non-GET Requests, Ajax, and More

Profiling non-GET requests or requests which need some specific HTTP headers is no different as blackfire curl supports all cURL options:

blackfire curl -XPOST

Profiling Part of an HTTP Call

Blackfire automatically instruments your code, but sometimes, you might want to focus the profiling on only part of the code. That’s possible when opting for manual instrumentation via the PHP SDK.

After instrumenting your code, use the blackfire utility as above to profile your application. When not using Blackfire, all calls are converted to no-ops.

Profiling all Requests While you Browse Requires Development/Production

Profiling POST requests, Ajax requests, and API calls can be done via the “Profile all Requests” link in the browser extension.

When profiling from a browser, select “Profile all requests”, then “Record!”. Blackfire will instrument all requests until you click on the “Stop” button in the pop-over.

A pop-over window will open at the bottom right of your screen, where all profiled requests will be listed.

All PHP requests which have been profiled will be shown on your dashboard.