Every web request received by Acquia Cloud is assigned a unique request ID, which is set in the HTTP header
X-Request-ID. The HTTP request ID can help you diagnose problems by correlating log entries for a given web request across multiple log sources. Even on a busy website, the HTTP Request ID in the log files makes it very easy to correlate various log entries with each other. Having the HTTP Request ID in the PHP error log is particularly useful, because it enables you to identify the specific page request that generated the PHP error, making it much easier to reproduce and ultimately fix the bug causing it.
The HTTP Request ID is recorded in all logs directly related to the request, including the Apache access log, Drupal request log, Varnish request log, and even the PHP error log. All of these log files include the HTTP request ID with the
The unique HTTP request ID is assigned when the request first arrives at Acquia Cloud, and is preserved from that point onward. Alternatively, you can provide your own
X-Request-ID header and Acquia Cloud will use it instead. An HTTP request ID is 20 to 200 characters long and can include the characters a-z (lowercase), A-Z (uppercase), 0-9, + (plus sign), / (slash mark), = (equal sign), or - (minus sign).
Web requests can access the HTTP request ID using the
HTTP_X_REQUEST_ID environment variable. In PHP, that is
$_ENV['HTTP_X_REQUEST_ID']. For more information, see Using environment variables in Drupal code and Drush commands.