[HADOOP-9086] Enforce process singleton rules through an exclusive write lock on a file, not a pid file +kill -0,

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Won't Fix
• Affects Version/s: 1.1.1, 2.0.3-alpha
• Component/s: scripts, util

Environment

Unix/Linux.

• Assignee: Unassigned
• Reporter: Steve Loughran
• Created: 23/Nov/12 11:08
• Updated: 10/Mar/15 03:44
• Resolved: 10/Mar/15 03:44

Description

the hadoop-daemon.sh script (and other liveness monitors) probe the existence of a daemon service by a kill -0 of a process id picked up from a pid file.
This is flawed

1. pid file locations may change with installations.
2. Linux and Unix recycle pids, leading to false positives -the scripts think the process is running, when another process is.
3. doesn't work on windows.

Having the processes acquire an exclusive write-lock on a known file would delegate lock management and implicitly liveness to the OS itself. when the process dies, the lock is relased (on Unixes)

Issue Links

• is related to: HADOOP-9085 start namenode failure,bacause pid of namenode pid file is other process pid or thread id before start namenode