Add benchmarking tests (close #300)

build.gradle

@@ -218,3 +218,4 @@ signing {
         println 'Used useInMemoryPgpKeys()'
     }
 }
+

examples/benchmarking/BenchmarkingREADME.md

@@ -0,0 +1,24 @@
+## Benchmarking results
+
+This benchmarking module is provided for maintainers, allowing them to check that their changes have not degraded performance. It uses the Java microbenchmarking harness, JMH.
+
+The benchmark test measures the time taken to track one event. Note that this does not include the time for the event to be processed and sent, which happens asynchronously.
+
+To run the test, navigate to this folder and run:
+
+```bash
+$ ./gradlew build
+$ ./gradlew jmh
+```
+
+The tracker version is set in the `build.gradle` file. Change the specified version to benchmark a different tracker version. 
+```groovy
+dependencies {
+    jmh 'com.snowplowanalytics:snowplow-java-tracker:0.11.0'
+}
+```
+Note that you may also need to edit the `TrackerBenchmark` `closeThreads()` code. Versions from 0.12.0 onwards must call a different method. This is explained in in-line comments.
+
+### Results
+See this PR for discussion of benchmarking results: https://github.com/snowplow/snowplow-java-tracker/pull/301
+

examples/benchmarking/build.gradle

@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2014-2021 Snowplow Analytics Ltd. All rights reserved.
+ *
+ * This program is licensed to you under the Apache License Version 2.0,
+ * and you may not use this file except in compliance with the Apache License Version 2.0.
+ * You may obtain a copy of the Apache License Version 2.0 at http://www.apache.org/licenses/LICENSE-2.0.
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the Apache License Version 2.0 is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the Apache License Version 2.0 for the specific language governing permissions and limitations there under.
+ */
+
+import org.gradle.api.tasks.JavaExec
+
+plugins {
+    id 'java'
+    id "me.champeau.jmh" version "0.6.6"
+}
+
+group 'com.snowplowanalytics'
+version '1.0'
+
+repositories {
+    mavenLocal {
+        content {
+            includeGroup "com.snowplowanalytics"
+        }
+    }
+    mavenCentral()
+}
+
+
+dependencies {
+    jmh 'com.snowplowanalytics:snowplow-java-tracker:0.10.1'
+}
+

examples/benchmarking/gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,5 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.1-bin.zip
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists

examples/benchmarking/settings.gradle

@@ -0,0 +1,2 @@
+rootProject.name = 'benchmarking'
+