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From "Chris Trezzo (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (YARN-5767) Fix the order that resources are cleaned up from the local Public/Private caches
Date Fri, 21 Oct 2016 23:06:58 GMT

     [ https://issues.apache.org/jira/browse/YARN-5767?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Chris Trezzo updated YARN-5767:
-------------------------------
    Description: 
If you look at {{ResourceLocalizationService#handleCacheCleanup}}, you can see that public
resources are added to the {{ResourceRetentionSet}} first followed by private resources:
{code:java}
private void handleCacheCleanup(LocalizationEvent event) {
  ResourceRetentionSet retain =
    new ResourceRetentionSet(delService, cacheTargetSize);
  retain.addResources(publicRsrc);
  if (LOG.isDebugEnabled()) {
    LOG.debug("Resource cleanup (public) " + retain);
  }
  for (LocalResourcesTracker t : privateRsrc.values()) {
    retain.addResources(t);
    if (LOG.isDebugEnabled()) {
      LOG.debug("Resource cleanup " + t.getUser() + ":" + retain);
    }
  }
  //TODO Check if appRsrcs should also be added to the retention set.
}
{code}

Unfortunately, if we look at {{ResourceRetentionSet#addResources}} we see that this means
public resources are deleted first until the target cache size is met:
{code:java}
public void addResources(LocalResourcesTracker newTracker) {
  for (LocalizedResource resource : newTracker) {
    currentSize += resource.getSize();
    if (resource.getRefCount() > 0) {
      // always retain resources in use
      continue;
    }
    retain.put(resource, newTracker);
  }
  for (Iterator<Map.Entry<LocalizedResource,LocalResourcesTracker>> i =
         retain.entrySet().iterator();
       currentSize - delSize > targetSize && i.hasNext();) {
    Map.Entry<LocalizedResource,LocalResourcesTracker> rsrc = i.next();
    LocalizedResource resource = rsrc.getKey();
    LocalResourcesTracker tracker = rsrc.getValue();
    if (tracker.remove(resource, delService)) {
      delSize += resource.getSize();
      i.remove();
    }
  }
}
{code}

The result of this is that resources in the private cache are only deleted in the cases where:
# The cache size is larger than the target cache size and the public cache is empty.
# The cache size is larger than the target cache size and everything in the public cache is
being used by a running container.

For clusters that primarily use the public cache (i.e. make use of the shared cache), this
means that the most commonly used resources can be deleted before old resources in the private
cache. Furthermore, the private cache can continue to grow over time causing more and more
churn in the public cache.

Additionally, the same problem exists within the private cache. Since resources are added
to the retention set on a user by user basis, resources will get cleaned up one user at a
time in the order that privateRsrc.values() returns the LocalResourcesTracker. So if user1
has 10MB in their cache and user2 has 100MB in their cache and the target size of the cache
is 50MB, user1 could potentially have their entire cache removed before anything is deleted
from the user2 cache.

  was:
If you look at {{ResourceLocalizationService#handleCacheCleanup}}, you can see that public
resources are added to the {{ResourceRetentionSet}} first followed by private resources:
{code:java}
private void handleCacheCleanup(LocalizationEvent event) {
  ResourceRetentionSet retain =
    new ResourceRetentionSet(delService, cacheTargetSize);
  retain.addResources(publicRsrc);
  if (LOG.isDebugEnabled()) {
    LOG.debug("Resource cleanup (public) " + retain);
  }
  for (LocalResourcesTracker t : privateRsrc.values()) {
    retain.addResources(t);
    if (LOG.isDebugEnabled()) {
      LOG.debug("Resource cleanup " + t.getUser() + ":" + retain);
    }
  }
  //TODO Check if appRsrcs should also be added to the retention set.
}
{code}

Unfortunately, if we look at {{ResourceRetentionSet#addResources}} we see that this means
public resources are deleted first until the target cache size is met:
{code:java}
public void addResources(LocalResourcesTracker newTracker) {
  for (LocalizedResource resource : newTracker) {
    currentSize += resource.getSize();
    if (resource.getRefCount() > 0) {
      // always retain resources in use
      continue;
    }
    retain.put(resource, newTracker);
  }
  for (Iterator<Map.Entry<LocalizedResource,LocalResourcesTracker>> i =
         retain.entrySet().iterator();
       currentSize - delSize > targetSize && i.hasNext();) {
    Map.Entry<LocalizedResource,LocalResourcesTracker> rsrc = i.next();
    LocalizedResource resource = rsrc.getKey();
    LocalResourcesTracker tracker = rsrc.getValue();
    if (tracker.remove(resource, delService)) {
      delSize += resource.getSize();
      i.remove();
    }
  }
}
{code}

The result of this is that resources in the private cache are only deleted in the cases where
the cache size is larger than the target cache size and the public cache is empty, or everything
in the public cache is being used by a running container. For clusters that primarily use
the public cache (i.e. make use of the shared cache), this means that the most commonly used
resources can be deleted before old resources in the private cache. Furthermore, the private
cache can continue to grow over time causing more and more churn in the public cache.

Additionally, the same problem exists within the private cache. Since resources are added
to the retention set on a user by user basis, resources will get cleaned up one user at a
time in the order that privateRsrc.values() returns the LocalResourcesTracker. So if user1
has 10MB in their cache and user2 has 100MB in their cache and the target size of the cache
is 50MB, user1 could potentially have their entire cache removed before anything is deleted
from the user2 cache.


> Fix the order that resources are cleaned up from the local Public/Private caches
> --------------------------------------------------------------------------------
>
>                 Key: YARN-5767
>                 URL: https://issues.apache.org/jira/browse/YARN-5767
>             Project: Hadoop YARN
>          Issue Type: Bug
>    Affects Versions: 2.6.0, 2.7.0, 3.0.0-alpha1
>            Reporter: Chris Trezzo
>            Assignee: Chris Trezzo
>
> If you look at {{ResourceLocalizationService#handleCacheCleanup}}, you can see that public
resources are added to the {{ResourceRetentionSet}} first followed by private resources:
> {code:java}
> private void handleCacheCleanup(LocalizationEvent event) {
>   ResourceRetentionSet retain =
>     new ResourceRetentionSet(delService, cacheTargetSize);
>   retain.addResources(publicRsrc);
>   if (LOG.isDebugEnabled()) {
>     LOG.debug("Resource cleanup (public) " + retain);
>   }
>   for (LocalResourcesTracker t : privateRsrc.values()) {
>     retain.addResources(t);
>     if (LOG.isDebugEnabled()) {
>       LOG.debug("Resource cleanup " + t.getUser() + ":" + retain);
>     }
>   }
>   //TODO Check if appRsrcs should also be added to the retention set.
> }
> {code}
> Unfortunately, if we look at {{ResourceRetentionSet#addResources}} we see that this means
public resources are deleted first until the target cache size is met:
> {code:java}
> public void addResources(LocalResourcesTracker newTracker) {
>   for (LocalizedResource resource : newTracker) {
>     currentSize += resource.getSize();
>     if (resource.getRefCount() > 0) {
>       // always retain resources in use
>       continue;
>     }
>     retain.put(resource, newTracker);
>   }
>   for (Iterator<Map.Entry<LocalizedResource,LocalResourcesTracker>> i =
>          retain.entrySet().iterator();
>        currentSize - delSize > targetSize && i.hasNext();) {
>     Map.Entry<LocalizedResource,LocalResourcesTracker> rsrc = i.next();
>     LocalizedResource resource = rsrc.getKey();
>     LocalResourcesTracker tracker = rsrc.getValue();
>     if (tracker.remove(resource, delService)) {
>       delSize += resource.getSize();
>       i.remove();
>     }
>   }
> }
> {code}
> The result of this is that resources in the private cache are only deleted in the cases
where:
> # The cache size is larger than the target cache size and the public cache is empty.
> # The cache size is larger than the target cache size and everything in the public cache
is being used by a running container.
> For clusters that primarily use the public cache (i.e. make use of the shared cache),
this means that the most commonly used resources can be deleted before old resources in the
private cache. Furthermore, the private cache can continue to grow over time causing more
and more churn in the public cache.
> Additionally, the same problem exists within the private cache. Since resources are added
to the retention set on a user by user basis, resources will get cleaned up one user at a
time in the order that privateRsrc.values() returns the LocalResourcesTracker. So if user1
has 10MB in their cache and user2 has 100MB in their cache and the target size of the cache
is 50MB, user1 could potentially have their entire cache removed before anything is deleted
from the user2 cache.



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