[KAFKA-4286] metric reporter may hit NullPointerException during shutdown

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.10.0.0
• Fix Version/s: 0.10.2.0
• Component/s: core
• Assignee: Xavier Léauté
• Reporter: Jun Rao
• Created: 10/Oct/16 17:22
• Updated: 09/Dec/16 15:04
• Resolved: 09/Dec/16 15:04

Description

When we shut down a broker, our metric reporter could throw the following exception.
java.lang.NullPointerException
at kafka.network.Processor$$anon$2.value(SocketServer.scala:392)
at kafka.network.Processor$$anon$2.value(SocketServer.scala:390)

This is because we report Yammer metric like the following and we de-register the underlying Kafka metric when shutting down the socket server.
newGauge("IdlePercent",
new Gauge[Double] {
def value =

{ metrics.metrics().get(metrics.metricName("io-wait-ratio", "socket-server-metrics", metricTags)).value() }

},
metricTags.asScala
)