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From "Joseph Wu (JIRA)" <j...@apache.org>
Subject [jira] [Created] (MESOS-6285) Agents may OOM during recovery if there are too many tasks or executors
Date Thu, 29 Sep 2016 20:18:20 GMT
Joseph Wu created MESOS-6285:
--------------------------------

             Summary: Agents may OOM during recovery if there are too many tasks or executors
                 Key: MESOS-6285
                 URL: https://issues.apache.org/jira/browse/MESOS-6285
             Project: Mesos
          Issue Type: Bug
    Affects Versions: 1.0.1
            Reporter: Joseph Wu


On an test cluster, we encountered a degenerate case where running the example {{long-lived-framework}}
for over a week would render the agent un-recoverable.  

The {{long-lived-framework}} creates one custom {{long-lived-executor}} and launches a single
task on that executor every time it receives an offer from that agent.  Over a week's worth
of time, the framework manages to launch some 400k tasks (short sleeps) on one executor. 
During runtime, this is not problematic, as each completed task is quickly rotated out of
the agent's memory (and checkpointed to disk).

During recovery, however, the agent reads every single task into memory, which leads to slow
recovery; and often results in the agent being OOM-killed before it finishes recovering.

To repro this condition quickly:
1) Apply this patch to the {{long-lived-framework}}:
{code}
diff --git a/src/examples/long_lived_framework.cpp b/src/examples/long_lived_framework.cpp
index 7c57eb5..1263d82 100644
--- a/src/examples/long_lived_framework.cpp
+++ b/src/examples/long_lived_framework.cpp
@@ -358,16 +358,6 @@ private:
   // Helper to launch a task using an offer.
   void launch(const Offer& offer)
   {
-    int taskId = tasksLaunched++;
-    ++metrics.tasks_launched;
-
-    TaskInfo task;
-    task.set_name("Task " + stringify(taskId));
-    task.mutable_task_id()->set_value(stringify(taskId));
-    task.mutable_agent_id()->MergeFrom(offer.agent_id());
-    task.mutable_resources()->CopyFrom(taskResources);
-    task.mutable_executor()->CopyFrom(executor);
-
     Call call;
     call.set_type(Call::ACCEPT);
 
@@ -380,7 +370,23 @@ private:
     Offer::Operation* operation = accept->add_operations();
     operation->set_type(Offer::Operation::LAUNCH);
 
-    operation->mutable_launch()->add_task_infos()->CopyFrom(task);
+    // Launch as many tasks as possible in the given offer.
+    Resources remaining = Resources(offer.resources()).flatten();
+    while (remaining.contains(taskResources)) {
+      int taskId = tasksLaunched++;
+      ++metrics.tasks_launched;
+
+      TaskInfo task;
+      task.set_name("Task " + stringify(taskId));
+      task.mutable_task_id()->set_value(stringify(taskId));
+      task.mutable_agent_id()->MergeFrom(offer.agent_id());
+      task.mutable_resources()->CopyFrom(taskResources);
+      task.mutable_executor()->CopyFrom(executor);
+
+      operation->mutable_launch()->add_task_infos()->CopyFrom(task);
+
+      remaining -= taskResources;
+    }
 
     mesos->send(call);
   }
{code}

2) Run a master, agent, and {{long-lived-framework}}.  On a 1 CPU, 1 GB agent + this patch,
it should take about 10 minutes to build up sufficient task launches.

3) Restart the agent and watch it flail during recovery.



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