Attempt to fix recent hiccup of official maven repo

Author: shunping

buildSrc/build.gradle.kts

@@ -15,6 +15,25 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+import java.net.HttpURLConnection
+import java.net.URL
+
+fun checkMavenCentralAccessibility(): Boolean {
+  val testUrl = "https://repo.maven.apache.org/maven2/org/slf4j/slf4j-api/1.7.2/slf4j-api-1.7.2.pom"
+  return try {
+    val connection = URL(testUrl).openConnection() as HttpURLConnection
+    connection.requestMethod = "HEAD"
+    connection.connectTimeout = 2000
+    connection.readTimeout = 2000
+    connection.useCaches = false
+    connection.responseCode == 200
+  } catch (e: Exception) {
+    false
+  }
+}
+
+val isMavenAccessible = checkMavenCentralAccessibility()
+val mavenCentralMirrorUrl = "https://maven-central.storage-api.googleapis.com/repos/central/data/"
 
 // Plugins for configuring _this build_ of the module
 plugins {
@@ -25,7 +44,13 @@ plugins {
 
 // Define the set of repositories required to fetch and enable plugins.
 repositories {
-  maven { url = uri("https://plugins.gradle.org/m2/") }
+  if (isMavenAccessible) {
+    maven { url = uri("https://plugins.gradle.org/m2/") }
+  } else {
+    logger.lifecycle("Maven Central is not accessible. Falling back to Google Maven Mirror for buildSrc.")
+    maven { url = uri(mavenCentralMirrorUrl) }
+    maven { url = uri("https://plugins.gradle.org/m2/") }
+  }
   maven {
     url = uri("https://repo.spring.io/plugins-release/")
     content { includeGroup("io.spring.gradle") }

buildSrc/src/main/groovy/org/apache/beam/gradle/Repositories.groovy

@@ -19,9 +19,32 @@
 package org.apache.beam.gradle
 
 import org.gradle.api.Project
+import java.net.HttpURLConnection
+import java.net.URL
 
 class Repositories {
 
+  private static Boolean isMavenAccessible = null
+
+  static synchronized boolean checkMavenCentral() {
+    if (isMavenAccessible != null) {
+      return isMavenAccessible
+    }
+    def testUrl = "https://repo.maven.apache.org/maven2/org/slf4j/slf4j-api/1.7.2/slf4j-api-1.7.2.pom"
+    try {
+      def url = new URL(testUrl)
+      def connection = (HttpURLConnection) url.openConnection()
+      connection.requestMethod = "HEAD"
+      connection.connectTimeout = 2000
+      connection.readTimeout = 2000
+      connection.useCaches = false
+      isMavenAccessible = (connection.responseCode == 200)
+    } catch (Exception e) {
+      isMavenAccessible = false
+    }
+    return isMavenAccessible
+  }
+
   static void register(Project project) {
 
     project.repositories {
@@ -36,7 +59,12 @@ class Repositories {
         return
       }
 
-      mavenCentral()
+      if (checkMavenCentral()) {
+        mavenCentral()
+      } else {
+        project.logger.lifecycle "Maven Central is not accessible. Redirecting to Google Maven Mirror."
+        maven { url "https://maven-central.storage-api.googleapis.com/repos/central/data/" }
+      }
       mavenLocal()
 
       // For Confluent Kafka dependencies
@@ -68,8 +96,12 @@ class Repositories {
     project.offlineDependencies {
       repositories {
         mavenLocal()
-        mavenCentral()
-        maven { url "https://plugins.gradle.org/m2/" }
+        if (checkMavenCentral()) {
+          mavenCentral()
+          maven { url "https://plugins.gradle.org/m2/" }
+        } else {
+          maven { url "https://maven-central.storage-api.googleapis.com/repos/central/data/" }
+        }
         maven { url "https://repo.spring.io/plugins-release" }
         maven { url "https://packages.confluent.io/maven/" }
         maven { url project.offlineRepositoryRoot }

settings.gradle.kts

@@ -18,6 +18,26 @@
 import com.gradle.enterprise.gradleplugin.internal.extension.BuildScanExtensionWithHiddenFeatures
 
 pluginManagement {
+    val isMavenAccessible = try {
+        val connection = java.net.URL("https://repo.maven.apache.org/maven2/org/slf4j/slf4j-api/1.7.2/slf4j-api-1.7.2.pom").openConnection() as java.net.HttpURLConnection
+        connection.requestMethod = "HEAD"
+        connection.connectTimeout = 2000
+        connection.readTimeout = 2000
+        connection.useCaches = false
+        connection.responseCode == 200
+    } catch (e: Exception) {
+        false
+    }
+    val mavenCentralMirrorUrl = "https://maven-central.storage-api.googleapis.com/repos/central/data/"
+
+    repositories {
+        if (isMavenAccessible) {
+            gradlePluginPortal()
+        } else {
+            maven { url = uri(mavenCentralMirrorUrl) }
+            gradlePluginPortal()
+        }
+    }
     plugins {
         id("org.javacc.javacc") version "4.0.3" // enable the JavaCC parser generator
     }