Thread Safety in KafkaServer.scala

["Grant Overby (groverby)" <gr...@cisco.com>]

KafkaServer.scala is using 3 AtomicBooleans (startupComplete, isShuttingDown, isStartingUp) as locks around the broker lifecycle. This strategy doesn’t appear to be thread safe, which I assume is the goal.

Consider two threads, A and B, calling startup() and execution occurring as:

Thread A progresses to the first line inside the if (canStartup) block.
Thread B progresses past if(startupComplete.get), but does not progress to setting canStartup.
Thread A completes startup()
Thread B resumes from previous location and sets canStartup to true.

Similar situations allow concurrent execution of startup() and shutdown().

It seems none of this is likely to happen.

Given the infrequency of calls to startup() and shutdown(), could a simple lock work in place of the three AtomicBooleans?



Fair warning: Take this with a grain of salt. Today is my first read through Kafka source and my scala fu is weak.


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Grant Overby
Software Engineer
Cisco.com<http://www.cisco.com/>
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