[CASSANDRA-2333] Clean up thread pool and queue sizes

• Type: Bug
• Status: Resolved
• Priority: Low
• Resolution: Fixed
• Fix Version/s: 0.7.5
• Severity: Low
• Assignee: Jonathan Ellis
• Reporter: Jonathan Ellis

Authors

Jonathan Ellis

Reviewers

Brandon Williams

• Created: 15/Mar/11 18:11
• Updated: 16/Apr/19 09:33
• Resolved: 23/Mar/11 16:22

Description

Most of Cassandra assumes that ThreadPoolExecutor handles tasks by starting with Core threads, adding threads up to Max as tasks arrive, then queuing any additional. This is not correct:

    If fewer than corePoolSize threads are running, the Executor always prefers adding a new thread rather than queuing.
    If corePoolSize or more threads are running, the Executor always prefers queuing a request rather than adding a new thread.
    If a request cannot be queued, a new thread is created unless this would exceed maximumPoolSize, in which case, the task will be rejected.

CASSANDRA-2178 fixed this in one place but made it worse by default since most people run with a single data dir, meaning as soon as you have multiple CFs flushing (or a single one with indexes) then you will start blocking writes.