The main interface between an ApplicationMaster
and the ResourceManager
.
The ApplicationMaster
uses this interface to provide a list of {@link ResourceRequest} and returns unused {@link Container} allocated toit via {@link AllocateRequest}. Optionally, the ApplicationMaster
can also blacklist resources which it doesn't want to use.
This also doubles up as a heartbeat to let the ResourceManager
know that the ApplicationMaster
is alive. Thus, applications should periodically make this call to be kept alive. The frequency depends on {@link YarnConfiguration#RM_AM_EXPIRY_INTERVAL_MS} which defaults to{@link YarnConfiguration#DEFAULT_RM_AM_EXPIRY_INTERVAL_MS}.
The ResourceManager
responds with list of allocated {@link Container}, status of completed containers and headroom information for the application.
The ApplicationMaster
can use the available headroom (resources) to decide how to utilized allocated resources and make informed decisions about future resource requests.
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