@InterfaceAudience.Public @InterfaceStability.Unstable public class ApplicationMaster extends Object
This class is meant to act as an example on how to write yarn-based application masters.
The ApplicationMaster is started on a container by the ResourceManager
's launcher.
The first thing that the ApplicationMaster
needs to do is to connect and register itself with
the ResourceManager
. The registration sets up information within the ResourceManager
regarding what host:port the ApplicationMaster is listening on to provide any form of functionality to a client
as well as a tracking url that a client can use to keep track of status/job history if needed.
The ApplicationMaster
needs to send a heartbeat to the ResourceManager
at regular intervals
to inform the ResourceManager
that it is up and alive. The AMRMProtocol.allocate(org.apache.hadoop.yarn.api.protocolrecords.AllocateRequest)
to the
ResourceManager
from the ApplicationMaster
acts as a heartbeat.
For the actual handling of the job, the ApplicationMaster
has to request the
ResourceManager
via AllocateRequest
for the required no. of containers using ResourceRequest
with the necessary resource specifications such as node location, computational (memory/disk/cpu) resource requirements.
The ResourceManager
responds with an AllocateResponse
that informs the ApplicationMaster
of the set of newly allocated containers, completed containers as well as current state of available resources.
For each allocated container, the ApplicationMaster
can then set up the necessary launch context via
ContainerLaunchContext
to specify the allocated container id, local resources required by the executable,
the environment to be setup for the executable, commands to execute, etc. and submit a StartContainerRequest
to the ContainerManager
to launch and execute the defined commands on the given allocated container.
The ApplicationMaster
can monitor the launched container by either querying the ResourceManager
using AMRMProtocol.allocate(org.apache.hadoop.yarn.api.protocolrecords.AllocateRequest)
to get updates on completed containers or via the ContainerManager
by querying for the status of the allocated container's ContainerId
.
After the job has been completed, the ApplicationMaster
has to send a FinishApplicationMasterRequest
to the ResourceManager
to inform it that the ApplicationMaster
has been completed.
public ApplicationMaster() throws Exception
Exception
public boolean init(String[] args) throws org.apache.commons.cli.ParseException, IOException
args
- Command line argsorg.apache.commons.cli.ParseException
IOException
public boolean run() throws org.apache.hadoop.yarn.exceptions.YarnRemoteException
org.apache.hadoop.yarn.exceptions.YarnRemoteException
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