[ZOOKEEPER-890] C client invokes watcher callbacks multiple times

• Type: Bug
• Status: Resolved
• Priority: Critical
• Resolution: Not A Problem
• Affects Version/s: 3.3.1
• Component/s: c client

Environment

Mac OS X 10.6.5

• Assignee: Unassigned
• Reporter: Austin Bennett
• Created: 07/Oct/10 07:53
• Updated: 13/Oct/10 17:11
• Resolved: 13/Oct/10 17:11

Description

Code using the C client assumes that watcher callbacks are called exactly once. If the watcher is called more than once, the process will likely overwrite freed memory and/or crash.

collect_session_watchers (zk_hashtable.c) gathers watchers from active_node_watchers, active_exist_watchers, and active_child_watchers without removing them. This results in watchers being invoked more than once.

Test code is attached that reproduces the bug, along with a proposed patch.

Issue Links

• duplicates: ZOOKEEPER-888 c-client / zkpython: Double free corruption on node watcher