YARN-8930. CGroup-based strict container memory enforcement does not work with CGroupElasticMemoryController (haibochen via rkanter)

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/linux/resources/CGroupsMemoryResourceHandlerImpl.java

@@ -34,9 +34,6 @@
 import java.io.File;
 import java.util.ArrayList;
 import java.util.List;
-import java.util.Optional;
-
-import static org.apache.hadoop.yarn.server.nodemanager.containermanager.linux.resources.CGroupsHandler.CGROUP_PARAM_MEMORY_OOM_CONTROL;
 
 /**
  * Handler class to handle the memory controller. YARN already ships a
@@ -174,26 +171,4 @@ public List<PrivilegedOperation> postComplete(ContainerId containerId)
   public List<PrivilegedOperation> teardown() throws ResourceHandlerException {
     return null;
   }
-
-  @Override
-  public Optional<Boolean> isUnderOOM(ContainerId containerId) {
-    try {
-      String status = cGroupsHandler.getCGroupParam(
-          CGroupsHandler.CGroupController.MEMORY,
-          containerId.toString(),
-          CGROUP_PARAM_MEMORY_OOM_CONTROL);
-      if (LOG.isDebugEnabled()) {
-        LOG.debug("cgroups OOM status for " + containerId + ": " + status);
-      }
-      if (status.contains(CGroupsHandler.UNDER_OOM)) {
-        LOG.warn("Container " + containerId + " under OOM based on cgroups.");
-        return Optional.of(true);
-      } else {
-        return Optional.of(false);
-      }
-    } catch (ResourceHandlerException e) {
-      LOG.warn("Could not read cgroups" + containerId, e);
-    }
-    return Optional.empty();
-  }
 }

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/linux/resources/MemoryResourceHandler.java

@@ -20,18 +20,8 @@
 
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.classification.InterfaceStability;
-import org.apache.hadoop.yarn.api.records.ContainerId;
-
-import java.util.Optional;
 
 @InterfaceAudience.Private
 @InterfaceStability.Unstable
 public interface MemoryResourceHandler extends ResourceHandler {
-  /**
-   * check whether a container is under OOM.
-   * @param containerId the id of the container
-   * @return empty if the status is unknown, true is the container is under oom,
-   *         false otherwise
-   */
-  Optional<Boolean> isUnderOOM(ContainerId containerId);
 }

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/monitor/ContainersMonitorImpl.java

@@ -22,7 +22,6 @@
 import com.google.common.base.Preconditions;
 import org.apache.hadoop.yarn.exceptions.YarnException;
 import org.apache.hadoop.yarn.server.nodemanager.containermanager.linux.resources.CGroupElasticMemoryController;
-import org.apache.hadoop.yarn.server.nodemanager.containermanager.linux.resources.MemoryResourceHandler;
 import org.apache.hadoop.yarn.server.nodemanager.containermanager.linux.resources.ResourceHandlerModule;
 import org.apache.hadoop.yarn.server.nodemanager.metrics.NodeManagerMetrics;
 import org.slf4j.Logger;
@@ -52,7 +51,6 @@
 import java.util.Arrays;
 import java.util.Map;
 import java.util.Map.Entry;
-import java.util.Optional;
 import java.util.concurrent.ConcurrentHashMap;
 
 /**
@@ -699,32 +697,19 @@ private void checkLimit(ContainerId containerId, String pId,
                             ProcessTreeInfo ptInfo,
                             long currentVmemUsage,
                             long currentPmemUsage) {
-      Optional<Boolean> isMemoryOverLimit = Optional.empty();
+      if (strictMemoryEnforcement && !elasticMemoryEnforcement) {
+        // When cgroup-based strict memory enforcement is used alone without
+        // elastic memory control, the oom-kill would take care of it.
+        // However, when elastic memory control is also enabled, the oom killer
+        // would be disabled at the root yarn container cgroup level (all child
+        // cgroups would inherit that setting). Hence, we fall back to the
+        // polling-based mechanism.
+        return;
+      }
+      boolean isMemoryOverLimit = false;
       String msg = "";
       int containerExitStatus = ContainerExitStatus.INVALID;
 
-      if (strictMemoryEnforcement && elasticMemoryEnforcement) {
-        // Both elastic memory control and strict memory control are enabled
-        // through cgroups. A container will be frozen by the elastic memory
-        // control mechanism if it exceeds its request, so we check for this
-        // here and kill it. Otherwise, the container will not be killed if
-        // the node never exceeds its limit and the procfs-based
-        // memory accounting is different from the cgroup-based accounting.
-
-        MemoryResourceHandler handler =
-            ResourceHandlerModule.getMemoryResourceHandler();
-        if (handler != null) {
-          isMemoryOverLimit = handler.isUnderOOM(containerId);
-          containerExitStatus = ContainerExitStatus.KILLED_EXCEEDED_PMEM;
-          msg = containerId + " is under oom because it exceeded its" +
-              " physical memory limit";
-        }
-      } else if (strictMemoryEnforcement || elasticMemoryEnforcement) {
-        // if cgroup-based memory control is enabled
-        isMemoryOverLimit = Optional.of(false);
-      }
-
-      if (!isMemoryOverLimit.isPresent()) {
       long vmemLimit = ptInfo.getVmemLimit();
       long pmemLimit = ptInfo.getPmemLimit();
       // as processes begin with an age 1, we want to see if there
@@ -745,7 +730,7 @@ && isProcessTreeOverLimit(containerId.toString(),
             formatUsageString(currentVmemUsage, vmemLimit,
                 currentPmemUsage, pmemLimit),
             pId, containerId, pTree, delta);
-          isMemoryOverLimit = Optional.of(true);
+        isMemoryOverLimit = true;
         containerExitStatus = ContainerExitStatus.KILLED_EXCEEDED_VMEM;
       } else if (isPmemCheckEnabled()
           && isProcessTreeOverLimit(containerId.toString(),
@@ -762,12 +747,11 @@ && isProcessTreeOverLimit(containerId.toString(),
             formatUsageString(currentVmemUsage, vmemLimit,
                 currentPmemUsage, pmemLimit),
             pId, containerId, pTree, delta);
-          isMemoryOverLimit = Optional.of(true);
+        isMemoryOverLimit = true;
         containerExitStatus = ContainerExitStatus.KILLED_EXCEEDED_PMEM;
       }
-      }
 
-      if (isMemoryOverLimit.isPresent() && isMemoryOverLimit.get()) {
+      if (isMemoryOverLimit) {
         // Virtual or physical memory over limit. Fail the container and
         // remove
         // the corresponding process tree

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/test/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/linux/resources/TestCGroupsMemoryResourceHandlerImpl.java

@@ -31,9 +31,6 @@
 import org.junit.Assert;
 
 import java.util.List;
-import java.util.Optional;
-
-import static org.apache.hadoop.yarn.server.nodemanager.containermanager.linux.resources.CGroupsHandler.CGROUP_PARAM_MEMORY_OOM_CONTROL;
 import static org.mockito.Mockito.*;
 
 /**
@@ -244,45 +241,4 @@ public void testOpportunistic() throws Exception {
         .updateCGroupParam(CGroupsHandler.CGroupController.MEMORY, id,
             CGroupsHandler.CGROUP_PARAM_MEMORY_HARD_LIMIT_BYTES, "1024M");
   }
-
-  @Test
-  public void testContainerUnderOom() throws Exception {
-    Configuration conf = new YarnConfiguration();
-    conf.setBoolean(YarnConfiguration.NM_PMEM_CHECK_ENABLED, false);
-    conf.setBoolean(YarnConfiguration.NM_VMEM_CHECK_ENABLED, false);
-
-    cGroupsMemoryResourceHandler.bootstrap(conf);
-
-    ContainerId containerId = mock(ContainerId.class);
-    when(containerId.toString()).thenReturn("container_01_01");
-
-    when(mockCGroupsHandler.getCGroupParam(
-        CGroupsHandler.CGroupController.MEMORY,
-        containerId.toString(),
-        CGROUP_PARAM_MEMORY_OOM_CONTROL)).thenReturn(CGroupsHandler.UNDER_OOM);
-    Optional<Boolean> outOfOom =
-        cGroupsMemoryResourceHandler.isUnderOOM(containerId);
-    Assert.assertTrue("The container should be reported to run under oom",
-        outOfOom.isPresent() && outOfOom.get().equals(true));
-
-    when(mockCGroupsHandler.getCGroupParam(
-        CGroupsHandler.CGroupController.MEMORY,
-        containerId.toString(),
-        CGROUP_PARAM_MEMORY_OOM_CONTROL)).thenReturn("");
-    outOfOom = cGroupsMemoryResourceHandler.isUnderOOM(containerId);
-    Assert.assertTrue(
-        "The container should not be reported to run under oom",
-        outOfOom.isPresent() && outOfOom.get().equals(false));
-
-    when(mockCGroupsHandler.getCGroupParam(
-        CGroupsHandler.CGroupController.MEMORY,
-        containerId.toString(),
-        CGROUP_PARAM_MEMORY_OOM_CONTROL)).
-        thenThrow(new ResourceHandlerException());
-    outOfOom = cGroupsMemoryResourceHandler.isUnderOOM(containerId);
-    Assert.assertFalse(
-        "No report of the oom status should be available.",
-        outOfOom.isPresent());
-
-  }
 }

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-site/src/site/markdown/NodeManagerCGroupsMemory.md

@@ -20,8 +20,6 @@ YARN has multiple features to enforce container memory limits. There are three t
 2. Strict memory control kills each container that has exceeded its limits. It is using the OOM killer capability of the cgroups Linux kernel feature.
 3. Elastic memory control is also based on cgroups. It allows bursting and starts killing containers only, if the overall system memory usage reaches a limit.
 
-If you use 2. or 3. feature 1. is disabled.
-
 Strict Memory Feature
 ---------------------
 
@@ -131,3 +129,13 @@ Configure the cgroups prerequisites mentioned above.
 `yarn.nodemanager.resource.memory.enforced` should be `false`
 
 `yarn.nodemanager.pmem-check-enabled` or `yarn.nodemanager.vmem-check-enabled` should be `true`. If swapping is turned off the former should be set, the latter should be set otherwise.
+
+
+Configuring elastic memory control and strict container memory enforcement through cgroups
+------------------------------------------
+ADVANCED ONLY
+Elastic memory control and strict container memory enforcement can be enabled at the same time to allow Node Manager to over-allocate itself.
+However, elastic memory control changes how strict container memory enforcement through cgroups is performed. Elastic memory control
+disables the oom killer on the root yarn container cgroup. The oom killer setting overrides that of individual container cgroups, so individual
+containers won't be killed by the oom killer when they go over their memory limit. The strict container memory enforcement in this case falls
+back to the polling-based mechanism.