Set Application Limits
To avoid system-thrash due to an unmanageable load -- caused either by malicious users, or by accident -- the Capacity Scheduler enables you to place a static, configurable limit on the total number of concurrently active (both running and pending) applications at any one time.
The limit for running applications in any specific queue is a fraction of this total limit, proportional to its capacity. This is a hard limit, which means that once this limit is reached for a queue, any new applications to that queue will be rejected, and clients will have to wait and retry later. This limit can be explicitly overridden on a per-queue basis with the following configuration property:
absolute-capacity * yarn.scheduler.capacity.maximum-applications
There is another resource limit that can be used to set a maximum percentage of
cluster resources allocated specifically to ApplicationMasters. The
maximum-am-resource-percent property has a default value of
10%, and exists to avoid cross-application deadlocks where significant resources
in the cluster are occupied entirely by the Containers running ApplicationMasters.
This property also indirectly controls the number of concurrent running
applications in the cluster, with each queue limited to a number of running
applications proportional to its capacity.
As with maximum-applications, this limit can also be overridden on a per-queue basis:
All of these limits ensure that no single application, user, or queue can cause catastrophic failure, or monopolize the cluster and cause excessive degradation of cluster performance.