Get unique worker/thread/process/request ID in PHP

Question

In multi-threaded environments (like most web platforms) I often include some sort of thread ID to the logs of my apps. This enables me to tell exactly what log entry came from which request/thread, when there are multiple requests at once which are simultaneously writing to the same log.

In .NET/C#, this can be done by the formatters of log4net, which by default include the current thread's ManagedThreadId (a number) or Name (a given name). These properties uniquely identify a thread (see for example: How to log correct context with Threadpool threads using log4net?

In PHP, I have not found anything similar (I asked Google, PHP docs and SO). Does it exist?

Answer 1

Up until recently, I used apache_getenv("UNIQUE_ID"), and it worked perfectly with a crc32 or another hash function.

Nowadays I'm just using the following, in order to remove dependency on Apache and this mod.

$uniqueid = sprintf("%08x", abs(crc32($_SERVER['REMOTE_ADDR'] . $_SERVER['REQUEST_TIME'] . $_SERVER['REMOTE_PORT'])));

It's unique enough to understand which logs belong to which request. If you need more precision, you can use other hash functions.

Hope this helps.

Answer 2

zend_thread_id():

int zend_thread_id ( void ) 

This function returns a unique identifier for the current thread.

Although:

This function is only available if PHP has been built with ZTS (Zend Thread Safety) support and debug mode (--enable-debug).

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You could also try yo call mysql_thread_id(), when you use that API for your database access (or mysqli::$thread_id when using mysqli).

Answer 3

PHP does not seem to have a function for this available, but your web server might be able to pass the identifier via environment variables. There is for example an Apache module called "mod_unique_id"[1] which generates a unique identifier for each request and stores it as an environment variables. If the variable is present, it should be visible via $_SERVER['unique_id'] [2]

"Pure PHP" solution could be to write a script that generates suitable random identifier, stores it via define("unique_id", val) and then use auto_prepend_file [3] option in php.ini to include this in every script that executes. This way the unique id would be created when the request starts processing and it would be available during the processing of the request.

• [1] http://httpd.apache.org/docs/current/mod/mod_unique_id.html
• [2] http://forums.devshed.com/php-development-5/server-unique-id-questions-163269.html
• [3] http://www.php.net/manual/en/ini.core.php#ini.auto-prepend-file

Answer 4

I've seen getmypid() used for this purpose, but it seems to behave differently on different systems. In some cases the ID is unique to each request, but on others it's shared.

So, you're probably better of going with one of the other answers to ensure portability.