Kill abandoned external servers started during Yaml Tests (#3152)

This adds a static constructor that will find all processes matching the
directory for external servers and kill them.
This is most important when running/debugging locally, if you stop the
debugger, or SIGKILL, there will be a bunch of processes left behind.
This changes it so that we will kill them the next time you run the
test.

Author: ScottDugas

yaml-tests/src/main/java/com/apple/foundationdb/relational/yamltests/YamlTestExtension.java

@@ -31,7 +31,6 @@
 import com.apple.foundationdb.relational.yamltests.configs.YamlTestConfig;
 import com.apple.foundationdb.relational.yamltests.server.ExternalServer;
 import com.google.common.collect.Iterables;
-import com.google.common.collect.Streams;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.junit.jupiter.api.Assertions;
@@ -109,14 +108,19 @@ public void beforeAll(final ExtensionContext context) throws Exception {
     @SuppressWarnings("PMD.UnnecessaryLocalBeforeReturn") // It complains about the local variable `e` being returned
     public void afterAll(final ExtensionContext context) throws Exception {
         final Optional<Exception> exception =
-                Streams.stream(Iterables.concat(testConfigs, maintainConfigs)).map(config -> {
-                    try {
-                        config.afterAll();
-                        return null;
-                    } catch (Exception e) {
-                        return e;
-                    }
-                }).filter(Objects::nonNull).findFirst();
+                Stream.concat(
+                        // if beforeAll fails in certain places, or isn't run, testConfigs and/or maintainConfigs could
+                        // be null
+                        Objects.requireNonNullElse(testConfigs, List.<YamlTestConfig>of()).stream(),
+                        Objects.requireNonNullElse(maintainConfigs, List.<YamlTestConfig>of()).stream())
+                        .map(config -> {
+                            try {
+                                config.afterAll();
+                                return null;
+                            } catch (Exception e) {
+                                return e;
+                            }
+                        }).filter(Objects::nonNull).findFirst();
         for (ExternalServer server : servers) {
             try {
                 server.stop();

yaml-tests/src/main/java/com/apple/foundationdb/relational/yamltests/server/ExternalServer.java

@@ -26,6 +26,7 @@
 
 import java.io.File;
 import java.io.IOException;
+import java.util.Arrays;
 import java.util.List;
 import java.util.Objects;
 import java.util.jar.Attributes;
@@ -66,6 +67,25 @@ public ExternalServer(File serverJar, final int grpcPort, final int httpPort) {
         this.httpPort = httpPort;
     }
 
+    static {
+        final String serverPath = Objects.requireNonNull(System.getProperty(EXTERNAL_SERVER_PROPERTY_NAME));
+        // kill all existing processes
+        ProcessHandle.allProcesses().filter(process ->
+                process.info().arguments().map(arguments ->
+                                Arrays.stream(arguments).anyMatch(argument ->
+                                        argument.startsWith(serverPath)))
+                        .orElse(false) &&
+                        process.info().command().map(command ->
+                                        command.endsWith("/java"))
+                                .orElse(false))
+                .forEach(process -> {
+                    if (logger.isInfoEnabled()) {
+                        logger.info("Killing existing server: pid=" + process.pid() + " " + process.info());
+                    }
+                    process.destroy();
+                });
+    }
+
     /**
      * Get the port to use when connecting.
      *