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https://issues.apache.org/jira/browse/YARN-2027?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13998912#comment-13998912
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Bikas Saha commented on YARN-2027:
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Yes. If strict node locality is needed then the rack should not be specified.
If the rack is specified then it will allow relaxing locality up to the rack
but no further.
> YARN ignores host-specific resource requests
> --------------------------------------------
>
> Key: YARN-2027
> URL: https://issues.apache.org/jira/browse/YARN-2027
> Project: Hadoop YARN
> Issue Type: Bug
> Components: resourcemanager, scheduler
> Affects Versions: 2.4.0
> Environment: RHEL 6.1
> YARN 2.4
> Reporter: Chris Riccomini
>
> YARN appears to be ignoring host-level ContainerRequests.
> I am creating a container request with code that pretty closely mirrors the
> DistributedShell code:
> {code}
> protected def requestContainers(memMb: Int, cpuCores: Int, containers: Int)
> {
> info("Requesting %d container(s) with %dmb of memory" format (containers,
> memMb))
> val capability = Records.newRecord(classOf[Resource])
> val priority = Records.newRecord(classOf[Priority])
> priority.setPriority(0)
> capability.setMemory(memMb)
> capability.setVirtualCores(cpuCores)
> // Specifying a host in the String[] host parameter here seems to do
> nothing. Setting relaxLocality to false also doesn't help.
> (0 until containers).foreach(idx => amClient.addContainerRequest(new
> ContainerRequest(capability, null, null, priority)))
> }
> {code}
> When I run this code with a specific host in the ContainerRequest, YARN does
> not honor the request. Instead, it puts the container on an arbitrary host.
> This appears to be true for both the FifoScheduler and the CapacityScheduler.
> Currently, we are running the CapacityScheduler with the following settings:
> {noformat}
> <configuration>
> <property>
> <name>yarn.scheduler.capacity.maximum-applications</name>
> <value>10000</value>
> <description>
> Maximum number of applications that can be pending and running.
> </description>
> </property>
> <property>
> <name>yarn.scheduler.capacity.maximum-am-resource-percent</name>
> <value>0.1</value>
> <description>
> Maximum percent of resources in the cluster which can be used to run
> application masters i.e. controls number of concurrent running
> applications.
> </description>
> </property>
> <property>
> <name>yarn.scheduler.capacity.resource-calculator</name>
>
> <value>org.apache.hadoop.yarn.util.resource.DefaultResourceCalculator</value>
> <description>
> The ResourceCalculator implementation to be used to compare
> Resources in the scheduler.
> The default i.e. DefaultResourceCalculator only uses Memory while
> DominantResourceCalculator uses dominant-resource to compare
> multi-dimensional resources such as Memory, CPU etc.
> </description>
> </property>
> <property>
> <name>yarn.scheduler.capacity.root.queues</name>
> <value>default</value>
> <description>
> The queues at the this level (root is the root queue).
> </description>
> </property>
> <property>
> <name>yarn.scheduler.capacity.root.default.capacity</name>
> <value>100</value>
> <description>Samza queue target capacity.</description>
> </property>
> <property>
> <name>yarn.scheduler.capacity.root.default.user-limit-factor</name>
> <value>1</value>
> <description>
> Default queue user limit a percentage from 0.0 to 1.0.
> </description>
> </property>
> <property>
> <name>yarn.scheduler.capacity.root.default.maximum-capacity</name>
> <value>100</value>
> <description>
> The maximum capacity of the default queue.
> </description>
> </property>
> <property>
> <name>yarn.scheduler.capacity.root.default.state</name>
> <value>RUNNING</value>
> <description>
> The state of the default queue. State can be one of RUNNING or STOPPED.
> </description>
> </property>
> <property>
> <name>yarn.scheduler.capacity.root.default.acl_submit_applications</name>
> <value>*</value>
> <description>
> The ACL of who can submit jobs to the default queue.
> </description>
> </property>
> <property>
> <name>yarn.scheduler.capacity.root.default.acl_administer_queue</name>
> <value>*</value>
> <description>
> The ACL of who can administer jobs on the default queue.
> </description>
> </property>
> <property>
> <name>yarn.scheduler.capacity.node-locality-delay</name>
> <value>40</value>
> <description>
> Number of missed scheduling opportunities after which the
> CapacityScheduler
> attempts to schedule rack-local containers.
> Typically this should be set to number of nodes in the cluster, By
> default is setting
> approximately number of nodes in one rack which is 40.
> </description>
> </property>
> </configuration>
> {noformat}
> Digging into the code a bit (props to [~jghoman] for finding this), we have a
> theory as to why this is happening. It looks like
> RMContainerRequestor.addContainerReq adds three resource requests per
> container request: data-local, rack-local, and any:
> {code}
> protected void addContainerReq(ContainerRequest req) {
> // Create resource requests
> for (String host : req.hosts) {
> // Data-local
> if (!isNodeBlacklisted(host)) {
> addResourceRequest(req.priority, host, req.capability);
> }
> }
> // Nothing Rack-local for now
> for (String rack : req.racks) {
> addResourceRequest(req.priority, rack, req.capability);
> }
> // Off-switch
> addResourceRequest(req.priority, ResourceRequest.ANY, req.capability);
> }
> {code}
> The addResourceRequest method, in turn, calls addResourceRequestToAsk, which
> in turn calls ask.add(remoteRequest):
> {code}
> private void addResourceRequestToAsk(ResourceRequest remoteRequest) {
> // because objects inside the resource map can be deleted ask can end up
> // containing an object that matches new resource object but with different
> // numContainers. So exisintg values must be replaced explicitly
> if(ask.contains(remoteRequest)) {
> ask.remove(remoteRequest);
> }
> ask.add(remoteRequest);
> }
> {code}
> The problem is that the "ask" variable is a TreeSet:
> {code}
> private final Set<ResourceRequest> ask = new TreeSet<ResourceRequest>(
> new
> org.apache.hadoop.yarn.api.records.ResourceRequest.ResourceRequestComparator());
> {code}
> The ResourceRequestComparator sorts the TreeSet according to:
> {code}
> public int compare(ResourceRequest r1, ResourceRequest r2) {
> // Compare priority, host and capability
> int ret = r1.getPriority().compareTo(r2.getPriority());
> if (ret == 0) {
> String h1 = r1.getResourceName();
> String h2 = r2.getResourceName();
> ret = h1.compareTo(h2);
> }
> if (ret == 0) {
> ret = r1.getCapability().compareTo(r2.getCapability());
> }
> return ret;
> }
> {code}
> The first thing to note is that our resource requests all have the same
> priority, so the TreeSet is really sorted by resource name (host/rack). The
> resource names that are added as part of addContainerReq are host, rack, and
> any, which is denoted as "\*" (see above). The problem with this is that the
> TreeSet is going to sort the resource requests with the "\*" request first,
> even if the host request was added first in addContainerReq.
> {code}
> > import java.util.TreeSet
> > val set = new TreeSet[String]
> set: java.util.TreeSet[String] = []
> > set.add("eat1-app")
> > set
> res3: java.util.TreeSet[String] = [eat1-app]
> > set.add("*")
> > set
> res5: java.util.TreeSet[String] = [*, eat1-app]
> {code}
> From here on out, it seems to me that anything interacting with the "ask"
> TreeSet (including the allocation requests) will be using the most general
> resource request, not the most specific.
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