Speed up ci/e2e builds (#3130)

* Make use of multi-thread builds of maven

* Bump up maven version to get rid of parallel build bug

* Apply the same to E2E tests

* Apply the same to JavaDoc task

* Revert E2E settings

* Add maven tuning opts

* Increase maven fork process memory

.mvn/wrapper/maven-wrapper.properties

-distributionUrl=https://repo.maven.apache.org/maven2/org/apache/maven/apache-maven/3.5.4/apache-maven-3.5.4-bin.zip
\ No newline at end of file
+distributionUrl=https://repo.maven.apache.org/maven2/org/apache/maven/apache-maven/3.6.1/apache-maven-3.6.1-bin.zip

Jenkinsfile

@@ -28,6 +28,10 @@ pipeline {
         timeout time: 60, unit: 'MINUTES'
     }
 
+    environment {
+        MAVEN_OPTS = '-XX:+TieredCompilation -XX:TieredStopAtLevel=1 -XX:+CMSClassUnloadingEnabled -XX:+UseConcMarkSweepGC -XX:-UseGCOverheadLimit -Xmx3g'
+    }
+
     stages {
         stage('Install & Test') {
             parallel {
@@ -60,8 +64,10 @@ pipeline {
 
                         stage('Test & Report') {
                             steps {
-                                sh './mvnw -P"agent,backend,ui,dist,CI-with-IT" org.jacoco:jacoco-maven-plugin:0.8.3:prepare-agent clean install org.jacoco:jacoco-maven-plugin:0.8.3:report coveralls:report'
-                                sh './mvnw javadoc:javadoc -Dmaven.test.skip=true'
+                                // separate lightweight checks that don't support parallel run
+                                sh './mvnw checkstyle:check apache-rat:check'
+                                sh './mvnw -Dcheckstyle.skip -Drat.skip -T2 -Dmaven.compile.fork -Dmaven.compiler.maxmem=3072 -P"agent,backend,ui,dist,CI-with-IT" org.jacoco:jacoco-maven-plugin:0.8.3:prepare-agent clean install org.jacoco:jacoco-maven-plugin:0.8.3:report coveralls:report'
+                                sh './mvnw -DskipTests -Dcheckstyle.skip -Drat.skip -T 2C javadoc:javadoc'
                             }
                         }
                     }

Jenkinsfile-E2E

@@ -25,6 +25,10 @@ pipeline {
         jdk 'JDK 1.8 (latest)'
     }
 
+    environment {
+        MAVEN_OPTS = '-XX:+TieredCompilation -XX:TieredStopAtLevel=1 -XX:+CMSClassUnloadingEnabled -XX:+UseConcMarkSweepGC -XX:-UseGCOverheadLimit -Xmx3g'
+    }
+
     stages {
         stage('Checkout Source Code') {
             steps {
@@ -36,7 +40,11 @@ pipeline {
 
         stage('Prepare Distribution Package') {
             steps {
-                sh './mvnw -DskipTests clean package'
+                // although these checks are done in ci-it, since they are lightweight/cheap
+                // we're using them as a barrier here to filter out some invalid PRs (fast-fail)
+                // thus save unnecessary E2E builds(which is expensive)
+                sh './mvnw checkstyle:check apache-rat:check'
+                sh './mvnw -Dcheckstyle.skip -Drat.skip -T2 -Dmaven.compile.fork -Dmaven.compiler.maxmem=3072 -DskipTests clean package'
                 sh 'tar -zxf dist/apache-skywalking-apm-bin.tar.gz -C dist'
             }
         }