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Custom XHProf run IDs

December 21st, 2014 Leave a comment Go to comments

XHProf is an awesome tool, but ships with a very annoying restriction out of the box. It names the run IDs in a cryptic randomized fashion (which makes sense - should be no collisions, and there's no "good" default way to name them otherwise.)

The good news however is that it does support custom run IDs to be named in the save_run() method. Awesome! Except for an odd "bug" or "feature" - a custom run ID won't display in the runs UI if it has non-hex characters in it (see the end of this post for information about that.)

This makes profiling specific requests a lot easier - you can put in a unique query string parameter and see it come up in the run ID, if the URL isn't already obvious. You could also simply define a standard query string parameter for your users/developers to use instead of the entire [scrubbed] URL as a run ID. Since I run a multi-tenant development server with a bunch of developers each having the ability to have a bunch of unique hostnames, it makes the most sense to use every piece of the URL for the run ID.

To start using custom XHProf run IDs, enable XHProf the standard way, at the earliest point in your application (at the top of the front-controller index.php, for example):

if (isset($_GET['xhprof']) && !empty($_SERVER['XHPROF_ROOT']) ) {
  include_once $_SERVER['XHPROF_ROOT'] . '/xhprof_lib/utils/xhprof_lib.php';
  include_once $_SERVER['XHPROF_ROOT']. '/xhprof_lib/utils/xhprof_runs.php';
  xhprof_enable(XHPROF_FLAGS_CPU | XHPROF_FLAGS_MEMORY);
}

The key to the custom naming is is when it saves the run output. In this example, I made a simple function to take the URL, remove all special characters and change them into dashes and remove any repetitive "dashing", and assign that as the third parameter to the save_runs() method, which is the "run ID" name.

if (isset($_GET['xhprof']) && !empty($_SERVER['XHPROF_ROOT'])) {
  function _make_xhprof_run_id() {
    if (isset($_SERVER['HTTPS'])) {
      $run_id = 'https-';
    }
    else {
      $run_id = 'http-';
    }
    $run_id .= urldecode($_SERVER['HTTP_HOST'] . '/' . $_SERVER['REQUEST_URI']) . '-' . microtime(TRUE);
    $run_id = trim(preg_replace('|([^A-Za-z0-9])|', '-', $run_id), '-');
    while (strstr($run_id, '--')) {
      $run_id = str_replace('--' , '-', $run_id);
    }
    return $run_id;
  }
  $xhprof_data = xhprof_disable();
  $xhprof_runs = new XHProfRuns_Default();
  $run_id = $xhprof_runs->save_run($xhprof_data, 'xhprof_testing', _make_xhprof_run_id()); 
}

If you wanted to use a simple query string parameter, I would still use the same type of safeguards so that the filename comes out in a sane way (no high ASCII or other characters which the filesystem wouldn't handle well) - for example, using the "run_id" parameter (I haven't tested this code, but it *should* work :))

if (isset($_GET['xhprof']) && !empty($_SERVER['XHPROF_ROOT'])) {
  function _make_xhprof_run_id() {
    // return null and it will handle it like usual
    if (!isset($_GET['run_id'])) {
      return null;
    }
    $run_id = trim(preg_replace('|([^A-Za-z0-9])|', '-', urldecode($_GET['run_id']) . '-' . microtime(TRUE)), '-');
    while (strstr($run_id, '--')) {
      $run_id = str_replace('--' , '-', $run_id);
    }
    return $run_id;
  }
  $xhprof_data = xhprof_disable();
  $xhprof_runs = new XHProfRuns_Default();
  $run_id = $xhprof_runs->save_run($xhprof_data, 'xhprof_testing', _make_xhprof_run_id()); 
}

NOTE: Both of these methods require one thing to be fixed on the display side. Currently, the XHProf display UI that comes with the stock package *will* list all the XHProf runs, but won't load them if there's non-hex characters in the run ID. I don't know why this naming limitation is being forced. I've filed a bug[1] for now to ask why, or to propose removing the restriction (ideally) - however, for now I've commented out those three lines and everything seems to work fine so far.

[1] https://github.com/phacility/xhprof/issues/58

Categories: PHP
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