[STORM-3339] Port all the AtomicReference to ConcurrentHashMap for Nimbus

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 2.0.0
• Component/s: storm-core
• Assignee: Danny Chen
• Reporter: Danny Chen
• Due: 16/Feb/19
• Created: 16/Feb/19 12:23
• Updated: 22/Mar/19 20:10

Description

Now for many concurrent access resource in Nimbus.java, we use AtomicReference to make them multi thread safe. The resources summarized below:

1. heartbeatsCache
2. schedulingStartTimeNs
3. idToSchedStatus
4. nodeIdToResources
5. idToWorkerResources
6. idToExecutors

The 1, 4, 5 and 6 may grows huge if we have hundreds of topologies on cluster, when we update AtomicReference, actually we passed in a Function and use compareAndSet to update the whole val to the new returned by the Function, in that case, we must do a reference copy and merge the changes, which seems not necessary.

I think the reason to use AtomicReference is a legacy from old Clojure code, we can replace them totally with ConcurrentHashMap which supported better performance.