spring-cloud-gateway: WeightCalculatorWebFilter NPE

when we use jmeter send 650 request to gateway, it always throw this exception as follow:

Failed to handle request [GET http://xxxxxxxxxx]
java.lang.NullPointerException: null
	at java.util.concurrent.ConcurrentHashMap.putVal(ConcurrentHashMap.java:1011)
	at java.util.concurrent.ConcurrentHashMap.put(ConcurrentHashMap.java:1006)
	at org.springframework.cloud.gateway.filter.WeightCalculatorWebFilter.lambda$filter$2(WeightCalculatorWebFilter.java:187)
	at java.util.concurrent.ConcurrentHashMap.forEach(ConcurrentHashMap.java:1597)
	at org.springframework.cloud.gateway.filter.WeightCalculatorWebFilter.filter(WeightCalculatorWebFilter.java:175)
	at org.springframework.web.server.handler.DefaultWebFilterChain.lambda$filter$0(DefaultWebFilterChain.java:76)
	at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:45)
	at reactor.core.publisher.MonoPeekTerminal.subscribe(MonoPeekTerminal.java:61)
	at reactor.core.publisher.MonoPeekFuseable.subscribe(MonoPeekFuseable.java:74)
	at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:53)
	at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:53)
	at reactor.core.publisher.MonoOnErrorResume.subscribe(MonoOnErrorResume.java:44)
	at reactor.core.publisher.MonoOnErrorResume.subscribe(MonoOnErrorResume.java:44)
	at reactor.core.publisher.MonoOnErrorResume.subscribe(MonoOnErrorResume.java:44)
	at reactor.core.publisher.Mono.subscribe(Mono.java:3080)
	at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.drain(MonoIgnoreThen.java:172)
	at reactor.core.publisher.MonoIgnoreThen.subscribe(MonoIgnoreThen.java:56)
	at reactor.core.publisher.MonoPeekFuseable.subscribe(MonoPeekFuseable.java:70)
	at reactor.core.publisher.MonoPeekTerminal.subscribe(MonoPeekTerminal.java:61)
	at reactor.ipc.netty.channel.ChannelOperations.applyHandler(ChannelOperations.java:380)
	at reactor.ipc.netty.http.server.HttpServerOperations.onHandlerStart(HttpServerOperations.java:398)
	at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:163)
	at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:404)
	at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:313)
	at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:884)
	at java.lang.Thread.run(Thread.java:748)
2019-01-19 16:00:31.280 [reactor-http-server-epoll-5] ERROR o.s.b.a.w.r.error.DefaultErrorWebExceptionHandler - Failed to handle request [GET http://gateway.facethink.com/auth/oauth/token?grant_type=client_credentials&client_id=test-client-3&client_secret=123456]
java.lang.NullPointerException: null
	at java.util.concurrent.ConcurrentHashMap.putVal(ConcurrentHashMap.java:1011)
	at java.util.concurrent.ConcurrentHashMap.put(ConcurrentHashMap.java:1006)
	at org.springframework.cloud.gateway.filter.WeightCalculatorWebFilter.lambda$filter$2(WeightCalculatorWebFilter.java:187)
	at java.util.concurrent.ConcurrentHashMap.forEach(ConcurrentHashMap.java:1597)
	at org.springframework.cloud.gateway.filter.WeightCalculatorWebFilter.filter(WeightCalculatorWebFilter.java:175)
	at org.springframework.web.server.handler.DefaultWebFilterChain.lambda$filter$0(DefaultWebFilterChain.java:76)
	at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:45)
	at reactor.core.publisher.MonoPeekTerminal.subscribe(MonoPeekTerminal.java:61)
	at reactor.core.publisher.MonoPeekFuseable.subscribe(MonoPeekFuseable.java:74)
	at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:53)
	at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:53)
	at reactor.core.publisher.MonoOnErrorResume.subscribe(MonoOnErrorResume.java:44)
	at reactor.core.publisher.MonoOnErrorResume.subscribe(MonoOnErrorResume.java:44)
	at reactor.core.publisher.MonoOnErrorResume.subscribe(MonoOnErrorResume.java:44)
	at reactor.core.publisher.Mono.subscribe(Mono.java:3080)
	at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.drain(MonoIgnoreThen.java:172)
	at reactor.core.publisher.MonoIgnoreThen.subscribe(MonoIgnoreThen.java:56)
	at reactor.core.publisher.MonoPeekFuseable.subscribe(MonoPeekFuseable.java:70)
	at reactor.core.publisher.MonoPeekTerminal.subscribe(MonoPeekTerminal.java:61)
	at reactor.ipc.netty.channel.ChannelOperations.applyHandler(ChannelOperations.java:380)
	at reactor.ipc.netty.http.server.HttpServerOperations.onHandlerStart(HttpServerOperations.java:398)
	at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:163)
	at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:404)
	at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:313)
	at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:884)
	at java.lang.Thread.run(Thread.java:748)

I don’t know why ? our version is

<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-gateway</artifactId>
<version>2.0.0.RELEASE</version>