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helix-playground/README.md

Using Apache Helix To Perform Distributed Task Execution in Apache Airavata

Introduction

This project is a playground to test Apache Helix's task execution framework. Apache Helix is a generic cluster management framework, which allows one to build highly scalable and fault tolerant distributed systems. It provides a range of functionalities, including:

  • Automatic assignment of resources (task executors) and it’s partitions (parallelism of resources) to nodes in the cluster.
  • Detecting failure of nodes in the cluster, and taking appropriate actions to recover them back.
  • Cluster management – adding nodes and resources to cluster dynamically, load balancing.
  • Ability to define an IDEAL STATE for a node – and defining STATE transitions in case the state for a node deviates from the IDEAL one.

Apart from these, Helix also provides out-of-the-box APIs to perform Distributed Task Execution. Some of the concepts Helix uses are ideal to our Airavata task execution use-case. These concepts include:

  • Tasks – actual runnable logic executors (eg: job submission, data staging, etc). Tasks return a TaskResult object which contains the state of the task once completed. These include, COMPLETED, FAILED, FATAL_FAILED. Difference between FAILED and FATAL_FAILED, is that FAILED tasks are re-run by Helix (threshold can be set), whereas FATAL_FAILED tasks are not.
  • Jobs – A combination of tasks, without dependencies; i.e. if there are > 1 tasks, they are run in parallel across workers.
  • Workflow – A combination of jobs arranged in a DAG. In a ONE-TIME workflow, once all jobs are completed, the workflow ends. In a RECURRING workflow, you can schedule workflows to run periodically.
  • Job Queues – Another type of workflow, but never ends – keeps accepting new incoming jobs. Ends only when user terminates it.

helix-task-framework

  • Helix also allows users to share data (key-value pairs) across Tasks/Jobs/Workflows. The content stored at workflow layer can shared by different jobs belong to this workflow. Similarly content persisted at job layer can shared by different tasks nested in this job.
  • Helix provides APIs to POLL either a JOB or WORKFLOW to reach a particular state.

Some core concepts used in Helix which are important to know:

  • Participant – Is a node in a Helix cluster (a.k.a. an instance or worker), which host resources (a.k.a. tasks).
  • Controller – Is a node in a Helix cluster that monitors and controls the Participant nodes. The controller is responsible for checking if the state of a participant node matches the IDEAL state, and if not, perform STATE TRANSITIONS in order to bring that node back to IDEAL state.
  • State Model & State Transitions – Helix allows developers to define what state a participant node needs to be, in order to declare it healthy. Example, in an ONLINE-OFFLINE state model, a node is healthy if it is in ONLINE state; whereas if it goes OFFLINE (for any reason), we can define TRANSITION actions to bring it back ONLINE.
  • Cluster – Contains participants and controller nodes. One can define the State model for a cluster.

More details about Apache Helix can be found on their website http://helix.apache.org{:target=“_blank”}.

How can Helix be used in Airavata??

Assuming we use Helix just to perform distributed task execution, I have the following in mind:

  • Create Helix Tasks (by implementing the Task interface) for each of our job-submission, data-staging, etc. These tasks are called resources.
  • Create Participant nodes (a.k.a. workers) to hold these resources. Helix allows us to create resource partitions, such that if we need a Task to run in parallel across workers, we can set the num_partitions > 1 for that resource.
  • Define a StateModel, either an OnlineOffline or MasterSlave, and necessary state transitions. With state transitions we can control the behavior of the participant nodes.
  • Create a WORKFLOW to execute a single experiment. This workflow will contain DAG necessary to run that experiment.
  • Create a long running QUEUE to keep accepting in-coming experiment requests. Each new experiment request will result in creation of a new JOB to be added to this queue – this job will contain one task – which is to create and run the workflow (mentioned in bullet above).

Building this Project

This project uses Apache Maven to build the artifacts. Run the following command to make sure the project builds successfully.

$ mvn clean install

Running the Prototype

Open the project in an IDE of your choice. Open the HelixClusterManager.java class. You can control the number of participant nodes (workers) in the cluster by updating the numWorkers field in the main method.

The output after running the program should look as follows:

Starting helix manager for cluster [ HelixDemoCluster ], on ZK server [ localhost:2199 ], with [ 3 ] workers, having [ 1] partitions.
0    [main] WARN  org.apache.helix.manager.zk.ZKHelixAdmin  - Root directory exists.Cleaning the root directory:/HelixDemoCluster
Successfully created helix cluster: HelixDemoCluster, with [ 1 ] partitions.
Successfully started participant node: HelixDemoParticipant_0, on cluster: HelixDemoCluster
Successfully started participant node: HelixDemoParticipant_1, on cluster: HelixDemoCluster
Successfully started participant node: HelixDemoParticipant_2, on cluster: HelixDemoCluster
548  [pool-1-thread-3] WARN  org.apache.helix.healthcheck.ParticipantHealthReportTask  - ParticipantHealthReportTimerTask already stopped
548  [pool-1-thread-2] WARN  org.apache.helix.healthcheck.ParticipantHealthReportTask  - ParticipantHealthReportTimerTask already stopped
548  [pool-1-thread-1] WARN  org.apache.helix.healthcheck.ParticipantHealthReportTask  - ParticipantHealthReportTimerTask already stopped
631  [pool-1-thread-1] WARN  org.apache.helix.manager.zk.CallbackHandler  - Skip processing callbacks for listener: org.apache.helix.messaging.handling.HelixTaskExecutor@fc497fe, path: /HelixDemoCluster/INSTANCES/HelixDemoParticipant_0/MESSAGES, expected types: [CALLBACK, FINALIZE] but was INIT
631  [pool-1-thread-3] WARN  org.apache.helix.manager.zk.CallbackHandler  - Skip processing callbacks for listener: org.apache.helix.messaging.handling.HelixTaskExecutor@7bd93e51, path: /HelixDemoCluster/INSTANCES/HelixDemoParticipant_2/MESSAGES, expected types: [CALLBACK, FINALIZE] but was INIT
631  [pool-1-thread-2] WARN  org.apache.helix.manager.zk.CallbackHandler  - Skip processing callbacks for listener: org.apache.helix.messaging.handling.HelixTaskExecutor@3bcaa92a, path: /HelixDemoCluster/INSTANCES/HelixDemoParticipant_1/MESSAGES, expected types: [CALLBACK, FINALIZE] but was INIT
Successfully added resources to cluster: HelixDemoCluster
736  [Thread-17] WARN  org.apache.helix.manager.zk.CallbackHandler  - Skip processing callbacks for listener: org.apache.helix.messaging.handling.HelixTaskExecutor@3046372e, path: /HelixDemoCluster/CONTROLLER/MESSAGES, expected types: [CALLBACK, FINALIZE] but was INIT
737  [Thread-17] WARN  org.apache.helix.manager.zk.CallbackHandler  - Skip processing callbacks for listener: org.apache.helix.controller.GenericHelixController@629ae1fd, path: /HelixDemoCluster/CONFIGS/PARTICIPANT, expected types: [CALLBACK, FINALIZE] but was INIT
737  [Thread-17] WARN  org.apache.helix.manager.zk.CallbackHandler  - Skip processing callbacks for listener: org.apache.helix.controller.GenericHelixController@629ae1fd, path: /HelixDemoCluster/INSTANCES/HelixDemoParticipant_2/CURRENTSTATES/15ca80eae2e02bd, expected types: [CALLBACK, FINALIZE] but was INIT
737  [Thread-17] WARN  org.apache.helix.manager.zk.CallbackHandler  - Skip processing callbacks for listener: org.apache.helix.controller.GenericHelixController@629ae1fd, path: /HelixDemoCluster/INSTANCES/HelixDemoParticipant_1/CURRENTSTATES/15ca80eae2e02be, expected types: [CALLBACK, FINALIZE] but was INIT
737  [Thread-17] WARN  org.apache.helix.manager.zk.CallbackHandler  - Skip processing callbacks for listener: org.apache.helix.controller.GenericHelixController@629ae1fd, path: /HelixDemoCluster/INSTANCES/HelixDemoParticipant_0/CURRENTSTATES/15ca80eae2e02bf, expected types: [CALLBACK, FINALIZE] but was INIT
737  [Thread-17] WARN  org.apache.helix.manager.zk.CallbackHandler  - Skip processing callbacks for listener: org.apache.helix.controller.GenericHelixController@629ae1fd, path: /HelixDemoCluster/INSTANCES/HelixDemoParticipant_0/MESSAGES, expected types: [CALLBACK, FINALIZE] but was INIT
737  [Thread-17] WARN  org.apache.helix.manager.zk.CallbackHandler  - Skip processing callbacks for listener: org.apache.helix.controller.GenericHelixController@629ae1fd, path: /HelixDemoCluster/INSTANCES/HelixDemoParticipant_1/MESSAGES, expected types: [CALLBACK, FINALIZE] but was INIT
737  [Thread-17] WARN  org.apache.helix.manager.zk.CallbackHandler  - Skip processing callbacks for listener: org.apache.helix.controller.GenericHelixController@629ae1fd, path: /HelixDemoCluster/INSTANCES/HelixDemoParticipant_2/MESSAGES, expected types: [CALLBACK, FINALIZE] but was INIT
737  [Thread-17] WARN  org.apache.helix.manager.zk.CallbackHandler  - Skip processing callbacks for listener: org.apache.helix.controller.GenericHelixController@629ae1fd, path: /HelixDemoCluster/LIVEINSTANCES, expected types: [CALLBACK, FINALIZE] but was INIT
737  [Thread-17] WARN  org.apache.helix.manager.zk.CallbackHandler  - Skip processing callbacks for listener: org.apache.helix.controller.GenericHelixController@629ae1fd, path: /HelixDemoCluster/IDEALSTATES, expected types: [CALLBACK, FINALIZE] but was INIT
737  [Thread-17] WARN  org.apache.helix.manager.zk.CallbackHandler  - Skip processing callbacks for listener: org.apache.helix.controller.GenericHelixController@629ae1fd, path: /HelixDemoCluster/CONTROLLER, expected types: [CALLBACK, FINALIZE] but was INIT
Successfully started the controller node: HelixDemoController, on cluster: HelixDemoCluster
Successfully started the helix cluster manager (admin), on cluster: HelixDemoCluster
Submitting Workflow for DagType: TYPE_A
839  [ZkClient-EventThread-33-localhost:2199] WARN  org.apache.helix.ConfigAccessor  - No config found at /HelixDemoCluster/CONFIGS/RESOURCE/HelixTask_A
844  [ZkClient-EventThread-33-localhost:2199] WARN  org.apache.helix.ConfigAccessor  - No config found at /HelixDemoCluster/CONFIGS/RESOURCE/HelixTask_C
846  [ZkClient-EventThread-33-localhost:2199] WARN  org.apache.helix.ConfigAccessor  - No config found at /HelixDemoCluster/CONFIGS/RESOURCE/HelixTask_D
849  [ZkClient-EventThread-33-localhost:2199] WARN  org.apache.helix.ConfigAccessor  - No config found at /HelixDemoCluster/CONFIGS/RESOURCE/HelixTask_B
OnlineOfflineStateModelFactory.onBecomeOnlineFromOffline():HelixDemoParticipant_0 transitioning from OFFLINE to ONLINE for HelixTask_C HelixTask_C_0
OnlineOfflineStateModelFactory.onBecomeOnlineFromOffline():HelixDemoParticipant_0 transitioning from OFFLINE to ONLINE for HelixTask_A HelixTask_A_0
OnlineOfflineStateModelFactory.onBecomeOnlineFromOffline():HelixDemoParticipant_0 transitioning from OFFLINE to ONLINE for HelixTask_D HelixTask_D_0
OnlineOfflineStateModelFactory.onBecomeOnlineFromOffline():HelixDemoParticipant_0 transitioning from OFFLINE to ONLINE for HelixTask_B HelixTask_B_0
Started workflow for DagType: TYPE_A, in cluster: HelixDemoCluster
BLAH WKFLW: WorkflowContext, {START_TIME=1498159501322}{}{}
HelixTaskA | callbackContext: org.apache.helix.task.TaskCallbackContext@2e4d5c35
HelixTaskA | Inside run(), sleeping for 2 secs
HelixTaskA | Inside addToUserStore()
HelixTaskA | Returning status : COMPLETED.
BLAH WKFLW: WorkflowContext, {START_TIME=1498159501322, STATE=IN_PROGRESS}{JOB_STATES={helix_workflow_helix_job_a=IN_PROGRESS}}{}
BLAH WKFLW: WorkflowContext, {START_TIME=1498159501322, STATE=IN_PROGRESS}{JOB_STATES={helix_workflow_helix_job_a=COMPLETED}}{}
HelixTaskB | callbackContext: org.apache.helix.task.TaskCallbackContext@351b6cb3
HelixTaskB | Returning status FAILED, Helix will retry this task. Retry count: 1
BLAH WKFLW: WorkflowContext, {START_TIME=1498159501322, STATE=IN_PROGRESS}{JOB_STATES={helix_workflow_helix_job_a=COMPLETED, helix_workflow_helix_job_b=IN_PROGRESS}}{}
HelixTaskB | callbackContext: org.apache.helix.task.TaskCallbackContext@40decb7c
HelixTaskB | Returning status FAILED, Helix will retry this task. Retry count: 2
BLAH WKFLW: WorkflowContext, {START_TIME=1498159501322, STATE=IN_PROGRESS}{JOB_STATES={helix_workflow_helix_job_a=COMPLETED, helix_workflow_helix_job_b=IN_PROGRESS}}{}
HelixTaskB | callbackContext: org.apache.helix.task.TaskCallbackContext@38a77770
HelixTaskB | After 2 retries, Inside run(), sleeping for 2 secs
HelixTaskB | Inside getFromUserStore()
HelixTaskB | Retrieved from UserStore : Gourav Shenoy
HelixTaskB | Returning status : COMPLETED.
BLAH WKFLW: WorkflowContext, {START_TIME=1498159501322, STATE=IN_PROGRESS}{JOB_STATES={helix_workflow_helix_job_a=COMPLETED, helix_workflow_helix_job_b=IN_PROGRESS}}{}
BLAH WKFLW: WorkflowContext, {START_TIME=1498159501322, STATE=IN_PROGRESS}{JOB_STATES={helix_workflow_helix_job_a=COMPLETED, helix_workflow_helix_job_b=COMPLETED}}{}
HelixTaskC | callbackContext: org.apache.helix.task.TaskCallbackContext@36cf68e3
HelixTaskC | Inside run(), sleeping for 2 secs
HelixTaskC | Inside getFromUserStore()
HelixTaskC | Retrieved from UserStore : Gourav Shenoy
HelixTaskC | Returning status : COMPLETED.
BLAH WKFLW: WorkflowContext, {START_TIME=1498159501322, STATE=IN_PROGRESS}{JOB_STATES={helix_workflow_helix_job_a=COMPLETED, helix_workflow_helix_job_b=COMPLETED, helix_workflow_helix_job_c=IN_PROGRESS}}{}
BLAH WKFLW: WorkflowContext, {START_TIME=1498159501322, STATE=IN_PROGRESS}{JOB_STATES={helix_workflow_helix_job_a=COMPLETED, helix_workflow_helix_job_b=COMPLETED, helix_workflow_helix_job_c=COMPLETED, helix_workflow_helix_job_d=IN_PROGRESS}}{}
HelixTaskD | callbackContext: org.apache.helix.task.TaskCallbackContext@79cba411
HelixTaskD | Inside run(), sleeping for 2 secs
HelixTaskD | Inside getFromUserStore()
HelixTaskD | Retrieved from UserStore : Gourav Shenoy
HelixTaskD | Returning status : COMPLETED.
1890 [Thread-19] WARN  org.apache.helix.task.TaskRebalancer  - Idealstate for resource helix_workflow_helix_job_a does not exist.
BLAH WKFLW: WorkflowContext, {FINISH_TIME=1498159502302, START_TIME=1498159501322, STATE=COMPLETED}{JOB_STATES={helix_workflow_helix_job_a=COMPLETED, helix_workflow_helix_job_b=COMPLETED, helix_workflow_helix_job_c=COMPLETED, helix_workflow_helix_job_d=COMPLETED}}{}
Successfully completed workflow for Dag: TYPE_A
*** Exiting System ***
1900 [Thread-19] WARN  org.apache.helix.task.TaskRebalancer  - Idealstate for resource helix_workflow_helix_job_b does not exist.
1910 [Thread-19] WARN  org.apache.helix.task.TaskRebalancer  - Idealstate for resource helix_workflow_helix_job_c does not exist.
1931 [Thread-19] ERROR org.apache.helix.task.JobRebalancer  - Job configuration is NULL for helix_workflow_helix_job_d
1939 [Thread-19] WARN  org.apache.helix.model.IdealState  - Resource key:helix_workflow_helix_job_d_0 does not have a pre-computed preference list.
HelixManager Admin disconnecting from cluster: HelixDemoCluster
6211 [Thread-6] WARN  org.apache.helix.participant.statemachine.StateModel  - Default reset method invoked. Either because the process longer own this resource or session timedout
6212 [Thread-6] WARN  org.apache.helix.participant.statemachine.StateModel  - Default reset method invoked. Either because the process longer own this resource or session timedout
6212 [Thread-6] WARN  org.apache.helix.participant.statemachine.StateModel  - Default reset method invoked. Either because the process longer own this resource or session timedout
6212 [Thread-6] WARN  org.apache.helix.participant.statemachine.StateModel  - Default reset method invoked. Either because the process longer own this resource or session timedout
6214 [Thread-6] WARN  org.apache.helix.participant.statemachine.StateModel  - Default reset method invoked. Either because the process longer own this resource or session timedout
6214 [Thread-6] WARN  org.apache.helix.participant.statemachine.StateModel  - Default reset method invoked. Either because the process longer own this resource or session timedout
6214 [Thread-6] WARN  org.apache.helix.participant.statemachine.StateModel  - Default reset method invoked. Either because the process longer own this resource or session timedout
6214 [Thread-6] WARN  org.apache.helix.participant.statemachine.StateModel  - Default reset method invoked. Either because the process longer own this resource or session timedout