SOLR-17160: Core admin async ID status, 10k limit and time expire (apache#2304)

Core Admin "async" request status tracking is no longer capped at 100; it's 10k.
Statuses are now removed 5 minutes after the read of a completed/failed status.
Helps collection async backup/restore and other operations scale to 100+ shards.

Co-authored-by: David Smiley <dsmiley@salesforce.com>

Author: 2 people

solr/CHANGES.txt

@@ -150,6 +150,10 @@ Improvements
 
 * SOLR-16198: Introduce tabbed sections again in the Ref Guide.  (Christos Malliaridis via Eric Pugh)
 
+* SOLR-17160: Core Admin "async" request status tracking is no longer capped at 100; it's 10k.
+  Statuses are now removed 5 minutes after the read of a completed/failed status.  Helps collection
+  async backup/restore and other operations scale to 100+ shards.  (Pierre Salagnac, David Smiley)
+
 Optimizations
 ---------------------
 * SOLR-17257: Both Minimize Cores and the Affinity replica placement strategies would over-gather

solr/core/src/java/org/apache/solr/handler/admin/CoreAdminHandler.java

@@ -21,20 +21,23 @@
 import static org.apache.solr.security.PermissionNameProvider.Name.CORE_EDIT_PERM;
 import static org.apache.solr.security.PermissionNameProvider.Name.CORE_READ_PERM;
 
+import com.github.benmanes.caffeine.cache.Cache;
+import com.github.benmanes.caffeine.cache.Caffeine;
+import com.github.benmanes.caffeine.cache.Expiry;
+import com.github.benmanes.caffeine.cache.Ticker;
 import java.io.File;
 import java.lang.invoke.MethodHandles;
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.Iterator;
-import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.concurrent.Callable;
 import java.util.concurrent.ExecutorService;
+import java.util.concurrent.TimeUnit;
 import org.apache.solr.api.AnnotatedApi;
 import org.apache.solr.api.Api;
 import org.apache.solr.api.JerseyResource;
@@ -47,6 +50,7 @@
 import org.apache.solr.common.params.CoreAdminParams;
 import org.apache.solr.common.params.ModifiableSolrParams;
 import org.apache.solr.common.params.SolrParams;
+import org.apache.solr.common.util.EnvUtils;
 import org.apache.solr.common.util.ExecutorUtil;
 import org.apache.solr.common.util.NamedList;
 import org.apache.solr.common.util.SolrNamedThreadFactory;
@@ -427,11 +431,19 @@ default boolean isExpensive() {
   }
 
   public static class CoreAdminAsyncTracker {
-    private static final int MAX_TRACKED_REQUESTS = 100;
+    /**
+     * Max number of requests we track in the Caffeine cache. This limit is super high on purpose,
+     * we're not supposed to hit it. This is just a protection to grow in memory too much when
+     * receiving an abusive number of admin requests.
+     */
+    private static final int MAX_TRACKED_REQUESTS =
+        EnvUtils.getPropertyAsInteger("solr.admin.async.max", 10_000);
+
     public static final String RUNNING = "running";
     public static final String COMPLETED = "completed";
     public static final String FAILED = "failed";
-    public final Map<String, Map<String, TaskObject>> requestStatusMap;
+
+    private final Cache<String, TaskObject> requestStatusCache; // key by ID
 
     // Executor for all standard tasks (the ones that are not flagged as expensive)
     // We always keep 50 live threads
@@ -440,33 +452,59 @@ public static class CoreAdminAsyncTracker {
             50, new SolrNamedThreadFactory("parallelCoreAdminAPIBaseExecutor"));
 
     // Executor for expensive tasks
-    // We keep the number number of max threads very low to have throttling for expensive tasks
+    // We keep the number of max threads very low to have throttling for expensive tasks
     private ExecutorService expensiveExecutor =
         ExecutorUtil.newMDCAwareCachedThreadPool(
             5,
             Integer.MAX_VALUE,
             new SolrNamedThreadFactory("parallelCoreAdminAPIExpensiveExecutor"));
 
     public CoreAdminAsyncTracker() {
-      HashMap<String, Map<String, TaskObject>> map = new HashMap<>(3, 1.0f);
-      map.put(RUNNING, Collections.synchronizedMap(new LinkedHashMap<>()));
-      map.put(COMPLETED, Collections.synchronizedMap(new LinkedHashMap<>()));
-      map.put(FAILED, Collections.synchronizedMap(new LinkedHashMap<>()));
-      requestStatusMap = Collections.unmodifiableMap(map);
+      this(
+          Ticker.systemTicker(),
+          TimeUnit.MINUTES.toNanos(
+              EnvUtils.getPropertyAsLong("solr.admin.async.timeout.minutes", 60L)),
+          TimeUnit.MINUTES.toNanos(
+              EnvUtils.getPropertyAsLong("solr.admin.async.timeout.completed.minutes", 5L)));
+    }
+
+    /**
+     * @param runningTimeoutNanos The time-to-keep for tasks in the RUNNING state.
+     * @param completedTimeoutNanos The time-to-keep for tasks in the COMPLETED or FAILED state
+     *     after the status was polled.
+     */
+    CoreAdminAsyncTracker(Ticker ticker, long runningTimeoutNanos, long completedTimeoutNanos) {
+
+      TaskExpiry expiry = new TaskExpiry(runningTimeoutNanos, completedTimeoutNanos);
+      requestStatusCache =
+          Caffeine.newBuilder()
+              .ticker(ticker)
+              .maximumSize(MAX_TRACKED_REQUESTS)
+              .expireAfter(expiry)
+              .build();
     }
 
     public void shutdown() {
       ExecutorUtil.shutdownAndAwaitTermination(standardExecutor);
       ExecutorUtil.shutdownAndAwaitTermination(expensiveExecutor);
     }
 
-    public Map<String, TaskObject> getRequestStatusMap(String key) {
-      return requestStatusMap.get(key);
+    public TaskObject getAsyncRequestForStatus(String key) {
+      TaskObject task = requestStatusCache.getIfPresent(key);
+
+      if (task != null && !RUNNING.equals(task.status) && !task.polledAfterCompletion) {
+        task.polledAfterCompletion = true;
+        // At the first time we retrieve the status of a completed request, do a second lookup in
+        // the cache. This is necessary to update the TTL of this request in the cache.
+        // Unfortunately, we can't force the expiration time to be refreshed without a lookup.
+        requestStatusCache.getIfPresent(key);
+      }
+
+      return task;
     }
 
     public void submitAsyncTask(TaskObject taskObject) throws SolrException {
-      ensureTaskIdNotInUse(taskObject.taskId);
-      addTask(RUNNING, taskObject);
+      addTask(taskObject);
 
       Runnable command =
           () -> {
@@ -497,42 +535,26 @@ public void submitAsyncTask(TaskObject taskObject) throws SolrException {
       }
     }
 
-    /** Helper method to add a task to a tracking type. */
-    private void addTask(String type, TaskObject o, boolean limit) {
-      synchronized (getRequestStatusMap(type)) {
-        if (limit && getRequestStatusMap(type).size() == MAX_TRACKED_REQUESTS) {
-          String key = getRequestStatusMap(type).entrySet().iterator().next().getKey();
-          getRequestStatusMap(type).remove(key);
-        }
-        addTask(type, o);
-      }
-    }
-
-    private void addTask(String type, TaskObject o) {
-      synchronized (getRequestStatusMap(type)) {
-        getRequestStatusMap(type).put(o.taskId, o);
-      }
-    }
-
-    /** Helper method to remove a task from a tracking map. */
-    private void removeTask(String map, String taskId) {
-      synchronized (getRequestStatusMap(map)) {
-        getRequestStatusMap(map).remove(taskId);
-      }
-    }
-
-    private void ensureTaskIdNotInUse(String taskId) throws SolrException {
-      if (getRequestStatusMap(RUNNING).containsKey(taskId)
-          || getRequestStatusMap(COMPLETED).containsKey(taskId)
-          || getRequestStatusMap(FAILED).containsKey(taskId)) {
+    private void addTask(TaskObject taskObject) {
+      // Ensure task ID is not already in use
+      TaskObject taskInCache =
+          requestStatusCache.get(
+              taskObject.taskId,
+              n -> {
+                taskObject.status = RUNNING;
+                return taskObject;
+              });
+
+      // If we get a different task instance, it means one was already in the cache with the
+      // same name. Just reject the new one.
+      if (taskInCache != taskObject) {
         throw new SolrException(
             ErrorCode.BAD_REQUEST, "Duplicate request with the same requestid found.");
       }
     }
 
     private void finishTask(TaskObject taskObject, boolean successful) {
-      removeTask(RUNNING, taskObject.taskId);
-      addTask(successful ? COMPLETED : FAILED, taskObject, true);
+      taskObject.status = successful ? COMPLETED : FAILED;
     }
 
     /**
@@ -546,6 +568,13 @@ public static class TaskObject {
       final Callable<SolrQueryResponse> task;
       public String rspInfo;
       public Object operationRspInfo;
+      private volatile String status;
+
+      /**
+       * Flag set to true once the task is complete (can be in error) and the status was polled
+       * already once. Once set, the time we keep the task status is shortened.
+       */
+      private volatile boolean polledAfterCompletion;
 
       public TaskObject(
           String taskId, String action, boolean expensive, Callable<SolrQueryResponse> task) {
@@ -574,6 +603,42 @@ public Object getOperationRspObject() {
       public void setOperationRspObject(SolrQueryResponse rspObject) {
         this.operationRspInfo = rspObject.getResponse();
       }
+
+      public String getStatus() {
+        return status;
+      }
+    }
+
+    /**
+     * Expiration policy for Caffeine cache. Depending on whether the status of a completed task was
+     * already retrieved, we return {@link #runningTimeoutNanos} or {@link #completedTimeoutNanos}.
+     */
+    private static class TaskExpiry implements Expiry<String, TaskObject> {
+
+      private final long runningTimeoutNanos;
+      private final long completedTimeoutNanos;
+
+      private TaskExpiry(long runningTimeoutNanos, long completedTimeoutNanos) {
+        this.runningTimeoutNanos = runningTimeoutNanos;
+        this.completedTimeoutNanos = completedTimeoutNanos;
+      }
+
+      @Override
+      public long expireAfterCreate(String key, TaskObject task, long currentTime) {
+        return runningTimeoutNanos;
+      }
+
+      @Override
+      public long expireAfterUpdate(
+          String key, TaskObject task, long currentTime, long currentDuration) {
+        return task.polledAfterCompletion ? completedTimeoutNanos : runningTimeoutNanos;
+      }
+
+      @Override
+      public long expireAfterRead(
+          String key, TaskObject task, long currentTime, long currentDuration) {
+        return task.polledAfterCompletion ? completedTimeoutNanos : runningTimeoutNanos;
+      }
     }
   }
 }

solr/core/src/java/org/apache/solr/handler/admin/api/GetNodeCommandStatus.java

@@ -18,14 +18,14 @@
 
 import static org.apache.solr.handler.admin.CoreAdminHandler.CoreAdminAsyncTracker.COMPLETED;
 import static org.apache.solr.handler.admin.CoreAdminHandler.CoreAdminAsyncTracker.FAILED;
-import static org.apache.solr.handler.admin.CoreAdminHandler.CoreAdminAsyncTracker.RUNNING;
 
 import jakarta.inject.Inject;
 import org.apache.solr.client.api.endpoint.GetNodeCommandStatusApi;
 import org.apache.solr.client.api.model.GetNodeCommandStatusResponse;
 import org.apache.solr.common.params.CoreAdminParams;
 import org.apache.solr.core.CoreContainer;
 import org.apache.solr.handler.admin.CoreAdminHandler;
+import org.apache.solr.handler.admin.CoreAdminHandler.CoreAdminAsyncTracker.TaskObject;
 import org.apache.solr.jersey.PermissionName;
 import org.apache.solr.request.SolrQueryRequest;
 import org.apache.solr.response.SolrQueryResponse;
@@ -51,25 +51,24 @@ public GetNodeCommandStatus(
   public GetNodeCommandStatusResponse getCommandStatus(String requestId) {
     ensureRequiredParameterProvided(CoreAdminParams.REQUESTID, requestId);
     var requestStatusResponse = new GetNodeCommandStatusResponse();
-    if (coreAdminAsyncTracker.getRequestStatusMap(RUNNING).containsKey(requestId)) {
-      requestStatusResponse.status = RUNNING;
-    } else if (coreAdminAsyncTracker.getRequestStatusMap(COMPLETED).containsKey(requestId)) {
-      requestStatusResponse.status = COMPLETED;
-      requestStatusResponse.response =
-          coreAdminAsyncTracker.getRequestStatusMap(COMPLETED).get(requestId).getRspObject();
-      requestStatusResponse.response =
-          coreAdminAsyncTracker
-              .getRequestStatusMap(COMPLETED)
-              .get(requestId)
-              .getOperationRspObject();
-    } else if (coreAdminAsyncTracker.getRequestStatusMap(FAILED).containsKey(requestId)) {
-      requestStatusResponse.status = FAILED;
-      requestStatusResponse.response =
-          coreAdminAsyncTracker.getRequestStatusMap(FAILED).get(requestId).getRspObject();
-    } else {
+
+    TaskObject taskObject = coreAdminAsyncTracker.getAsyncRequestForStatus(requestId);
+    String status = taskObject != null ? taskObject.getStatus() : null;
+
+    if (status == null) {
       requestStatusResponse.status = "notfound";
       requestStatusResponse.msg = "No task found in running, completed or failed tasks";
+    } else {
+      requestStatusResponse.status = status;
+
+      if (status.equals(COMPLETED)) {
+        requestStatusResponse.response = taskObject.getRspObject();
+        requestStatusResponse.response = taskObject.getOperationRspObject();
+      } else if (status.equals(FAILED)) {
+        requestStatusResponse.response = taskObject.getRspObject();
+      }
     }
+
     return requestStatusResponse;
   }
 }