Lack of PID uniqueness in container environments makes prometheus_multiproc difficult to use

In environments where each container is running in its own PID namespace, multiple instances of the same container will quickly result in (silently) conflicting file names as any my-favorite-server.py process will likely have the same low, single or double digit PID in each of the multiple containers. As a result, the different processes will attempt to mmap the same file in the shared multiprocess metric directory, and various scary errors that aren't always easy to understand the root cause will occur.

It would be beneficial if something in addition to the PID was used to help ensure uniqueness across the files in the PROMETHEUS_MULTIPROC_DIR, or if a string could be passed in at initialization time to be embedded in the file names, such as a container or pod name, or another value determined by the application.

Inizia tracciando il modo in cui prometheus_multiproc assegna i nomi ai file in PROMETHEUS_MULTIPROC_DIR e il modo in cui ricava i nomi dagli ID dei processi. Confronta il comportamento tra più container che condividono la directory, quindi determina un meccanismo di unicità o un valore di inizializzazione adatto all’issue. Il lavoro è completato quando i processi dei container concorrenti non causano più conflitti durante il mmap degli stessi file e il caso di errore rilevante è coperto dai test.