Opening as a PCEP bug as this happens during Beryllium PCEP performance suite [0], but this may also be a Controller (or even Yangtools) bug.

(Title of BGPCEP-267 looks similar, but symptoms are completely different there.)

This does not happen in PCEP functional suite. One possible difference is that the function suite uses XML data, while the performance suite uses JSON data.
The same performance suite is passing on Lithium snapshot builds.

There are only two suspicious warnings in karaf.log (even though the suite sends 65535 requests), between INFO about device connecting and WARN when device is killed (not shown here, original at [1]):

2016-01-11 23:18:19,665 | WARN | CommitFutures-3 | PingPongTransactionChain | 116 - org.opendaylight.controller.sal-broker-impl - 1.3.0.SNAPSHOT | Submitting transaction PingPongTransaction

while PingPongTransaction

is still running
2016-01-11 23:22:31,049 | WARN | ssionScavenger-3 | teInvalidatingHashSessionManager | 160 - org.ops4j.pax.web.pax-web-jetty - 3.1.4 | Timing out for 1 session(s) with id o1upfcm3jyz01lil98gaojr9u

This Bug is reported against the "Submitting transaction" warning. If the suite failure has a different cause, it should be opened as a separate Bug.

The http responses itself are more informative, as they include an exception:

com.google.common.util.concurrent.UncheckedExecutionException: java.lang.NullPointerException
at com.google.common.cache.LocalCache$Segment.get(LocalCache.java:2203)
at com.google.common.cache.LocalCache.get(LocalCache.java:3937)
at com.google.common.cache.LocalCache.getOrLoad(LocalCache.java:3941)
at com.google.common.cache.LocalCache$LocalLoadingCache.get(LocalCache.java:4824)
at com.google.common.cache.LocalCache$LocalLoadingCache.getUnchecked(LocalCache.java:4830)
at org.opendaylight.yangtools.yang.data.codec.gson.JSONCodecFactory.codecFor(JSONCodecFactory.java:140)
at org.opendaylight.yangtools.yang.data.codec.gson.JsonParserStream.translateValueByType(JsonParserStream.java:223)
at org.opendaylight.yangtools.yang.data.codec.gson.JsonParserStream.setValue(JsonParserStream.java:116)
at org.opendaylight.yangtools.yang.data.codec.gson.JsonParserStream.read(JsonParserStream.java:124)
at org.opendaylight.yangtools.yang.data.codec.gson.JsonParserStream.read(JsonParserStream.java:183)
at org.opendaylight.yangtools.yang.data.codec.gson.JsonParserStream.read(JsonParserStream.java:183)
at org.opendaylight.yangtools.yang.data.codec.gson.JsonParserStream.parse(JsonParserStream.java:86)
at org.opendaylight.netconf.sal.rest.impl.JsonNormalizedNodeBodyReader.readFrom(JsonNormalizedNodeBodyReader.java:131)
at org.opendaylight.netconf.sal.rest.impl.JsonNormalizedNodeBodyReader.readFrom(JsonNormalizedNodeBodyReader.java:71)
at org.opendaylight.netconf.sal.rest.impl.JsonNormalizedNodeBodyReader.readFrom(JsonNormalizedNodeBodyReader.java:52)
at com.sun.jersey.spi.container.ContainerRequest.getEntity(ContainerRequest.java:488)
at com.sun.jersey.server.impl.model.method.dispatch.EntityParamDispatchProvider$EntityInjectable.getValue(EntityParamDispatchProvider.java:123)
at com.sun.jersey.server.impl.inject.InjectableValuesProvider.getInjectableValues(InjectableValuesProvider.java:46)
at com.sun.jersey.server.impl.model.method.dispatch.AbstractResourceMethodDispatchProvider$EntityParamInInvoker.getParams(AbstractResourceMethodDispatchProvider.java:153)
at com.sun.jersey.server.impl.model.method.dispatch.AbstractResourceMethodDispatchProvider$TypeOutInvoker._dispatch(AbstractResourceMethodDispatchProvider.java:183)
at com.sun.jersey.server.impl.model.method.dispatch.ResourceJavaMethodDispatcher.dispatch(ResourceJavaMethodDispatcher.java:75)
at com.sun.jersey.server.impl.uri.rules.HttpMethodRule.accept(HttpMethodRule.java:302)
at com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:147)
at com.sun.jersey.server.impl.uri.rules.ResourceObjectRule.accept(ResourceObjectRule.java:100)
at com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:147)
at com.sun.jersey.server.impl.uri.rules.RootResourceClassesRule.accept(RootResourceClassesRule.java:84)
at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1511)
at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1442)
at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1391)
at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1381)
at com.sun.jersey.spi.container.servlet.WebComponent.service(WebComponent.java:416)
at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:538)
at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:716)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:668)
at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:684)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1496)
at org.eclipse.jetty.servlets.CrossOriginFilter.handle(CrossOriginFilter.java:247)
at org.eclipse.jetty.servlets.CrossOriginFilter.doFilter(CrossOriginFilter.java:210)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1467)
at org.eclipse.jetty.servlets.UserAgentFilter.doFilter(UserAgentFilter.java:82)
at org.eclipse.jetty.servlets.GzipFilter.doFilter(GzipFilter.java:256)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1467)
at org.apache.shiro.web.servlet.ProxiedFilterChain.doFilter(ProxiedFilterChain.java:61)
at org.apache.shiro.web.servlet.AdviceFilter.executeChain(AdviceFilter.java:108)
at org.apache.shiro.web.servlet.AdviceFilter.doFilterInternal(AdviceFilter.java:137)
at org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125)
at org.apache.shiro.web.servlet.ProxiedFilterChain.doFilter(ProxiedFilterChain.java:66)
at org.apache.shiro.web.servlet.AbstractShiroFilter.executeChain(AbstractShiroFilter.java:449)
at org.apache.shiro.web.servlet.AbstractShiroFilter$1.call(AbstractShiroFilter.java:365)
at org.apache.shiro.subject.support.SubjectCallable.doCall(SubjectCallable.java:90)
at org.apache.shiro.subject.support.SubjectCallable.call(SubjectCallable.java:83)
at org.apache.shiro.subject.support.DelegatingSubject.execute(DelegatingSubject.java:383)
at org.apache.shiro.web.servlet.AbstractShiroFilter.doFilterInternal(AbstractShiroFilter.java:362)
at org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1467)
at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:501)
at org.ops4j.pax.web.service.jetty.internal.HttpServiceServletHandler.doHandle(HttpServiceServletHandler.java:69)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:137)
at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:557)
at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:231)
at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1086)
at org.ops4j.pax.web.service.jetty.internal.HttpServiceContext.doHandle(HttpServiceContext.java:240)
at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:429)
at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:193)
at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1020)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:135)
at org.ops4j.pax.web.service.jetty.internal.JettyServerHandlerCollection.handle(JettyServerHandlerCollection.java:75)
at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:116)
at org.eclipse.jetty.server.Server.handle(Server.java:370)
at org.eclipse.jetty.server.AbstractHttpConnection.handleRequest(AbstractHttpConnection.java:494)
at org.eclipse.jetty.server.AbstractHttpConnection.content(AbstractHttpConnection.java:982)
at org.eclipse.jetty.server.AbstractHttpConnection$RequestHandler.content(AbstractHttpConnection.java:1043)
at org.eclipse.jetty.http.HttpParser.parseNext(HttpParser.java:865)
at org.eclipse.jetty.http.HttpParser.parseAvailable(HttpParser.java:235)
at org.eclipse.jetty.server.AsyncHttpConnection.handle(AsyncHttpConnection.java:82)
at org.eclipse.jetty.io.nio.SelectChannelEndPoint.handle(SelectChannelEndPoint.java:696)
at org.eclipse.jetty.io.nio.SelectChannelEndPoint$1.run(SelectChannelEndPoint.java:53)
at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:608)
at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:543)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NullPointerException
at org.opendaylight.yangtools.yang.data.codec.gson.JSONCodecFactory.createFromSimpleType(JSONCodecFactory.java:128)
at org.opendaylight.yangtools.yang.data.codec.gson.JSONCodecFactory.createCodec(JSONCodecFactory.java:106)
at org.opendaylight.yangtools.yang.data.codec.gson.JSONCodecFactory.createReferencedTypeCodec(JSONCodecFactory.java:114)
at org.opendaylight.yangtools.yang.data.codec.gson.JSONCodecFactory.createCodec(JSONCodecFactory.java:100)
at org.opendaylight.yangtools.yang.data.codec.gson.JSONCodecFactory.access$100(JSONCodecFactory.java:37)
at org.opendaylight.yangtools.yang.data.codec.gson.JSONCodecFactory$2.load(JSONCodecFactory.java:74)
at org.opendaylight.yangtools.yang.data.codec.gson.JSONCodecFactory$2.load(JSONCodecFactory.java:63)
at com.google.common.cache.LocalCache$LoadingValueReference.loadFuture(LocalCache.java:3527)
at com.google.common.cache.LocalCache$Segment.loadSync(LocalCache.java:2319)
at com.google.common.cache.LocalCache$Segment.lockedGetOrLoad(LocalCache.java:2282)
at com.google.common.cache.LocalCache$Segment.get(LocalCache.java:2197)
... 79 more

[0] https://jenkins.opendaylight.org/releng/view/bgpcep/job/bgpcep-csit-1node-periodic-throughpcep-only-beryllium/
[1] https://jenkins.opendaylight.org/releng/view/bgpcep/job/bgpcep-csit-1node-periodic-throughpcep-only-beryllium/106/artifact/karaf.log