KAFKA-1714: Fix gradle wrapper bootstrapping

.gitignore

@@ -34,8 +34,7 @@ Vagrantfile.local
 config/server-*
 config/zookeeper-*
 core/data/*
-gradle/wrapper/*
-gradlew
+gradle/wrapper/*.jar
 gradlew.bat
 
 results

README.md

@@ -2,20 +2,12 @@ Apache Kafka
 =================
 See our [web site](http://kafka.apache.org) for details on the project.
 
-You need to have [Gradle](http://www.gradle.org/installation) and [Java](http://www.oracle.com/technetwork/java/javase/downloads/index.html) installed.
-
-Kafka requires Gradle 5.0 or higher.
+You need to have [Java](http://www.oracle.com/technetwork/java/javase/downloads/index.html) installed.
 
 Java 8 should be used for building in order to support both Java 8 and Java 11 at runtime.
 
 Scala 2.12 is used by default, see below for how to use a different Scala version or all of the supported Scala versions.
 
-### First bootstrap and download the wrapper ###
-    cd kafka_source_dir
-    gradle
-
-Now everything else will work.
-
 ### Build a jar and run it ###
     ./gradlew jar
 

gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,19 @@
+#
+# Copyright 2017 the original author or authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-5.0-all.zip
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists

wrapper.gradle

@@ -17,9 +17,108 @@
  * under the License.
  */
 
-defaultTasks 'downloadWrapper'
+// This file contains tasks for the gradle wrapper generation.
 
-task downloadWrapper(type: Wrapper) {
-    description = "Download the gradle wrapper and requisite files. Overwrites existing wrapper files."
+// Ensure the wrapper script is generated based on the version defined in the project
+// and not the version installed on the machine running the task.
+// Read more about the wrapper here: https://docs.gradle.org/current/userguide/gradle_wrapper.html
+wrapper {
     gradleVersion = project.gradleVersion
-}
+    distributionType = Wrapper.DistributionType.ALL
+}
+
+def licenseString = """#
+# Copyright 2017 the original author or authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License."""
+
+// Custom task to inject support for downloading the gradle wrapper jar if it doesn't exist.
+// This allows us to avoid checking in the jar to our repository.
+// Additionally adds a license header to the wrapper while editing the file contents.
+task bootstrapWrapper() {
+    // In the doLast block so this runs when the task is called and not during project configuration.
+    doLast {
+        def wrapperBasePath = "\$APP_HOME/gradle/wrapper"
+        def wrapperJarPath = wrapperBasePath + "/gradle-wrapper.jar"
+
+        // Add a trailing zero to the version if needed.
+        def fullVersion = project.gradleVersion.count(".") == 1 ? "${project.gradleVersion}.0" : versions.gradle
+        // Leverages the wrapper jar checked into the gradle project on github because the jar isn't
+        // available elsewhere. Using raw.githubusercontent.com instead of github.com because
+        // github.com servers deprecated TLSv1/TLSv1.1 support some time ago, so older versions
+        // of curl (built against OpenSSL library that doesn't support TLSv1.2) would fail to
+        // fetch the jar.
+        def wrapperBaseUrl = "https://raw.githubusercontent.com/gradle/gradle/v$fullVersion/gradle/wrapper"
+        def wrapperJarUrl = wrapperBaseUrl + "/gradle-wrapper.jar"
+
+        def bootstrapString = """
+      # Loop in case we encounter an error.
+      for attempt in 1 2 3; do
+        if [ ! -e $wrapperJarPath ]; then
+          if ! curl -s -S --retry 3 -L -o "$wrapperJarPath" "$wrapperJarUrl"; then
+            rm -f "$wrapperJarPath"
+            # Pause for a bit before looping in case the server throttled us.
+            sleep 5
+            continue
+          fi
+        fi
+      done
+      """.stripIndent()
+
+        def wrapperScript = wrapper.scriptFile
+        def wrapperLines = wrapperScript.readLines()
+        wrapperScript.withPrintWriter { out ->
+            def licenseWritten = false
+            def bootstrapWritten = false
+            wrapperLines.each { line ->
+                // Print the wrapper bootstrap before the first usage of the wrapper jar.
+                if (!bootstrapWritten && line.contains("gradle-wrapper.jar")) {
+                    out.println(bootstrapString)
+                    bootstrapWritten = true
+                }
+                out.print(line)
+                // Print the licence after the shebang.
+                if(!licenseWritten && line.contains("#!/usr/bin/env sh")) {
+                    out.println()
+                    out.print(licenseString)
+                    licenseWritten = true
+                }
+                out.println() // New Line
+            }
+        }
+    }
+}
+wrapper.finalizedBy bootstrapWrapper
+
+// Custom task to add a license header to the gradle-wrapper.properties file.
+task bootstrapWrapperProperties() {
+    // In the doLast block so this runs when the task is called and not during project configuration.
+    doLast {
+        def wrapperProperties = wrapper.propertiesFile
+        def wrapperLines = wrapperProperties.readLines()
+        wrapperProperties.withPrintWriter { out ->
+            // Print the license
+            out.println(licenseString)
+            wrapperLines.each { line ->
+                out.println(line)
+            }
+        }
+    }
+}
+wrapper.finalizedBy bootstrapWrapperProperties
+
+// Remove the generated batch file since we don't test building in the Windows environment.
+task removeWindowsScript(type: Delete) {
+    delete "$rootDir/gradlew.bat"
+}
+wrapper.finalizedBy removeWindowsScript