添加Capacity调度器的源码注释

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/capacity/LeafQueue.java

@@ -1123,6 +1123,16 @@ private ConcurrentMap<String, CachedUserLimit> getUserLimitCache(
     }
   }
 
+  /**
+   * 分配资源到子队列的逻辑。
+   * @param clusterResource the resource of the cluster.
+   * @param candidates {@link CandidateNodeSet} the nodes that are considered
+   *                   for the current placement.
+   * @param currentResourceLimits how much overall resource of this queue can use.
+   * @param schedulingMode Type of exclusive check when assign container on a
+   * NodeManager, see {@link SchedulingMode}.
+   * @return
+   */
   @Override
   public CSAssignment assignContainers(Resource clusterResource,
       CandidateNodeSet<FiCaSchedulerNode> candidates,
@@ -1135,6 +1145,7 @@ public CSAssignment assignContainers(Resource clusterResource,
           + " #applications=" + orderingPolicy.getNumSchedulableEntities());
     }
 
+    // 是否允许抢占。
     setPreemptionAllowed(currentResourceLimits, candidates.getPartition());
 
     // Check for reserved resources, try to allocate reserved container first.
@@ -1228,6 +1239,7 @@ public CSAssignment assignContainers(Resource clusterResource,
       if (!cul.canAssign && Resources.fitsIn(appReserved, cul.reservation)) {
         userAssignable = false;
       } else {
+        // 资源分配到用户
         userAssignable = canAssignToUser(clusterResource, application.getUser(),
             userLimit, application, candidates.getPartition(),
             currentResourceLimits);

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/capacity/ParentQueue.java

@@ -626,7 +626,7 @@ public CSAssignment assignContainers(Resource clusterResource,
         break;
       }
 
-      // Schedule
+      // Schedule , 开始给子队列分配资源。
       CSAssignment assignedToChild = assignContainersToChildQueues(
           clusterResource, candidates, resourceLimits, schedulingMode);
       assignment.setType(assignedToChild.getType());
@@ -834,6 +834,7 @@ private CSAssignment assignContainersToChildQueues(Resource cluster,
           getResourceLimitsOfChild(childQueue, cluster, limits.getNetLimit(),
               candidates.getPartition());
 
+      // 分配资源到队列
       CSAssignment childAssignment = childQueue.assignContainers(cluster,
           candidates, childLimits, schedulingMode);
       if(LOG.isDebugEnabled()) {

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/capacity/allocator/RegularContainerAllocator.java

@@ -423,7 +423,7 @@ private ContainerAllocation assignContainersOnNode(Resource clusterResource,
     ContainerAllocation allocation;
     NodeType requestLocalityType = null;
 
-    // Data-local
+    // Data-local 优先分配local。
     PendingAsk nodeLocalAsk =
         application.getPendingAsk(schedulerKey, node.getNodeName());
     if (nodeLocalAsk.getCount() > 0) {
@@ -439,7 +439,7 @@ private ContainerAllocation assignContainersOnNode(Resource clusterResource,
       }
     }
 
-    // Rack-local
+    // Rack-local 在Rack-local 分配
     PendingAsk rackLocalAsk =
         application.getPendingAsk(schedulerKey, node.getRackName());
     if (rackLocalAsk.getCount() > 0) {
@@ -466,7 +466,7 @@ private ContainerAllocation assignContainersOnNode(Resource clusterResource,
       }
     }
 
-    // Off-switch
+    // Off-switch 检查不限制
     PendingAsk offSwitchAsk =
         application.getPendingAsk(schedulerKey, ResourceRequest.ANY);
     if (offSwitchAsk.getCount() > 0) {
@@ -922,7 +922,7 @@ public CSAssignment assignContainers(Resource clusterResource,
         return CSAssignment.SKIP_ASSIGNMENT;
       }
       
-      // Schedule in priority order
+      // Schedule in priority order 按照优先级顺序分配资源
       for (SchedulerRequestKey schedulerKey : application.getSchedulerKeys()) {
         ContainerAllocation result = allocate(clusterResource, candidates,
             schedulingMode, resourceLimits, schedulerKey, null);