Build: Allow preserving shared dir (#24962)

This adds an option to `ClusterConfiguration` to preserve the
`shared` directory when starting up a new cluster and switches
the `qa:full-cluster-restart` tests to use it rather than
disable the clean shared task.

Relates to #24846

buildSrc/src/main/groovy/org/elasticsearch/gradle/test/ClusterConfiguration.groovy

@@ -76,6 +76,14 @@ class ClusterConfiguration {
         " " + "-Xmx" + System.getProperty('tests.heap.size', '512m') +
         " " + System.getProperty('tests.jvm.argline', '')
 
+    /**
+     * Should the shared environment be cleaned on cluster startup? Defaults
+     * to {@code true} so we run with a clean cluster but some tests wish to
+     * preserve snapshots between clusters so they set this to true.
+     */
+    @Input
+    boolean cleanShared = true
+
     /**
      * A closure to call which returns the unicast host to connect to for cluster formation.
      *

buildSrc/src/main/groovy/org/elasticsearch/gradle/test/ClusterFormationTasks.groovy

@@ -54,14 +54,24 @@ class ClusterFormationTasks {
      */
     static List<NodeInfo> setup(Project project, String prefix, Task runner, ClusterConfiguration config) {
         File sharedDir = new File(project.buildDir, "cluster/shared")
-        // first we remove everything in the shared cluster directory to ensure there are no leftovers in repos or anything
-        // in theory this should not be necessary but repositories are only deleted in the cluster-state and not on-disk
-        // such that snapshots survive failures / test runs and there is no simple way today to fix that.
-        Task cleanup = project.tasks.create(name: "${prefix}#prepareCluster.cleanShared", type: Delete, dependsOn: config.dependencies) {
-            delete sharedDir
-            doLast {
-                sharedDir.mkdirs()
-            }
+        Object startDependencies = config.dependencies
+        /* First, if we want a clean environment, we remove everything in the
+         * shared cluster directory to ensure there are no leftovers in repos
+         * or anything in theory this should not be necessary but repositories
+         * are only deleted in the cluster-state and not on-disk such that
+         * snapshots survive failures / test runs and there is no simple way
+         * today to fix that. */
+        if (config.cleanShared) {
+          Task cleanup = project.tasks.create(
+            name: "${prefix}#prepareCluster.cleanShared",
+            type: Delete,
+            dependsOn: startDependencies) {
+              delete sharedDir
+              doLast {
+                  sharedDir.mkdirs()
+              }
+          }
+          startDependencies = cleanup
         }
         List<Task> startTasks = []
         List<NodeInfo> nodes = []
@@ -103,7 +113,7 @@ class ClusterFormationTasks {
             }
             NodeInfo node = new NodeInfo(config, i, project, prefix, elasticsearchVersion, sharedDir)
             nodes.add(node)
-            Task dependsOn = startTasks.empty ? cleanup : startTasks.get(0)
+            Object dependsOn = startTasks.empty ? startDependencies : startTasks.get(0)
             startTasks.add(configureNode(project, prefix, runner, dependsOn, node, config, distro, nodes.get(0)))
         }
 

qa/full-cluster-restart/build.gradle

@@ -66,6 +66,7 @@ for (Version version : indexCompatVersions) {
     clusterName = 'full-cluster-restart'
     numNodes = 2
     dataDir = { nodeNum -> oldClusterTest.nodes[nodeNum].dataDir }
+    cleanShared = false // We want to keep snapshots made by the old cluster!
   }
 
   tasks.getByName("${baseName}#upgradedClusterTestRunner").configure {
@@ -78,13 +79,6 @@ for (Version version : indexCompatVersions) {
     dependsOn = [upgradedClusterTest]
   }
 
-  /* Delay this change because the task we need to modify isn't created until
-   * after projects are evaluated. */
-  gradle.projectsEvaluated {
-    // Disable cleaning the repository so we can test loading a snapshot
-    tasks.getByName("${baseName}#upgradedClusterTestCluster#prepareCluster.cleanShared").enabled = false
-  }
-
   bwcTest.dependsOn(versionBwcTest)
 }