Verify metrics using reporter approach

[kkrugler]

From the Flink mailing list:

+1 to using reporters.

You will have to explicitly pass a configuration with the reporter settings to the environment via StreamExecutionEnvironment#createLocalEnvironment(int, Configuration).

The reporter can verify registrations/values and pass this information back to the main test thread through a static field (for simplicity).

[Schmed]

I assume you haven't done anything on this yet, @vmagotra, so I'm going to take a crack at it.

I'm hoping this will lead the way toward a unit test for Sync up the total active urls value with state in UrlDbFunction (as @kkrugler suggested via a comment on Try using stream harness support for unit testing).

[Schmed]

For some reason, I'm getting the following failure when running locally (master + one unit test class I added):

schmed-mb-air-2:flink-1.5.2 schmed$ ./bin/flink run ~/Projects/flink-crawler/target/flink-crawler-tool-1.0-SNAPSHOT.jar -commoncrawl 2017-22 -cachedir ~/Downloads/flink-crawler/common-crawl-cache -seedurls ~/Downloads/flink-crawler/common-crawl-seed-urls.txt -forcecrawldelay 0 -maxcontentsize 100000 -outputfile ~/Downloads/flink-crawler/common-crawl-content.txt
Starting execution of program
Error running CrawlTool: Could not load the TypeInformation for the class 'org.apache.hadoop.io.Writable'. You may be missing the 'flink-hadoop-compatibility' dependency.
java.lang.RuntimeException: Could not load the TypeInformation for the class 'org.apache.hadoop.io.Writable'. You may be missing the 'flink-hadoop-compatibility' dependency.
at org.apache.flink.api.java.typeutils.TypeExtractor.createHadoopWritableTypeInfo(TypeExtractor.java:2140)
at org.apache.flink.api.java.typeutils.TypeExtractor.privateGetForClass(TypeExtractor.java:1759)
at org.apache.flink.api.java.typeutils.TypeExtractor.privateGetForClass(TypeExtractor.java:1701)
at org.apache.flink.api.java.typeutils.TypeExtractor.createTypeInfoWithTypeHierarchy(TypeExtractor.java:956)
at org.apache.flink.api.java.typeutils.TypeExtractor.createSubTypesInfo(TypeExtractor.java:1176)
at org.apache.flink.api.java.typeutils.TypeExtractor.createTypeInfoWithTypeHierarchy(TypeExtractor.java:889)
at org.apache.flink.api.java.typeutils.TypeExtractor.createTypeInfoFromInputs(TypeExtractor.java:969)
at org.apache.flink.api.java.typeutils.TypeExtractor.privateCreateTypeInfo(TypeExtractor.java:831)
at org.apache.flink.api.java.typeutils.TypeExtractor.getUnaryOperatorReturnType(TypeExtractor.java:625)
at org.apache.flink.api.java.typeutils.TypeExtractor.getFlatMapReturnTypes(TypeExtractor.java:191)
at org.apache.flink.streaming.api.datastream.DataStream.flatMap(DataStream.java:594)
at com.scaleunlimited.flinkcrawler.topology.CrawlTopologyBuilder.build(CrawlTopologyBuilder.java:412)
at com.scaleunlimited.flinkcrawler.tools.CrawlTool.run(CrawlTool.java:121)
at com.scaleunlimited.flinkcrawler.tools.CrawlTool.main(CrawlTool.java:68)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.apache.flink.client.program.PackagedProgram.callMainMethod(PackagedProgram.java:528)
at org.apache.flink.client.program.PackagedProgram.invokeInteractiveModeForExecution(PackagedProgram.java:420)
at org.apache.flink.client.program.ClusterClient.run(ClusterClient.java:404)
at org.apache.flink.client.cli.CliFrontend.executeProgram(CliFrontend.java:785)
at org.apache.flink.client.cli.CliFrontend.runProgram(CliFrontend.java:279)
at org.apache.flink.client.cli.CliFrontend.run(CliFrontend.java:214)
at org.apache.flink.client.cli.CliFrontend.parseParameters(CliFrontend.java:1025)
at org.apache.flink.client.cli.CliFrontend.lambda$main$9(CliFrontend.java:1101)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:422)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1836)
at org.apache.flink.runtime.security.HadoopSecurityContext.runSecured(HadoopSecurityContext.java:41)
at org.apache.flink.client.cli.CliFrontend.main(CliFrontend.java:1101)