com.hazelcast.jet

## Interface Job

-     public interface Job

  A Jet computation job created by submitting a `DAG` or `Pipeline`. Once submitted, Jet starts executing the job automatically.
  Since:
    3.0

- - ### Method Summary

    All Methods Instance Methods Abstract Methods Default Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `cancel()` Makes a request to cancel this job and returns.
    `JobStateSnapshot` | `cancelAndExportSnapshot(String name)` Exports and saves a state snapshot with the given name, and then cancels the job without processing any more data after the barrier (graceful cancellation).
    `JobStateSnapshot` | `exportSnapshot(String name)` Exports a state snapshot and saves it under the given name.
    `JobConfig` | `getConfig()` Returns the configuration this job was submitted with.
    `CompletableFuture<Void>` | `getFuture()` Gets the future associated with the job.
    `long` | `getId()` Returns the ID of this job.
    `default String` | `getIdString()` Returns the string representation of this job's ID.
    `JobMetrics` | `getMetrics()` Returns a snapshot of the current values of all job-specific metrics.
    `default String` | `getName()` Returns the name of this job or `null` if no name was supplied.
    `JobStatus` | `getStatus()` Returns the current status of this job.
    `long` | `getSubmissionTime()` Returns the time when the job was submitted to the cluster.
    `default void` | `join()` Waits for the job to complete and throws an exception if the job completes with an error.
    `void` | `restart()` Gracefully stops the current execution and schedules a new execution with the current member list of the Jet cluster.
    `void` | `resume()` Resumes a suspended job.
    `void` | `suspend()` Gracefully suspends the current execution of the job.

- - ### Method Detail

    - #### getId

          long getId()

      Returns the ID of this job.
      Throws:
        `IllegalStateException` - if the job has not started yet, and thus has no ID.

    - #### getIdString

          @Nonnull
          default String getIdString()

      Returns the string representation of this job's ID.

    - #### getConfig

          @Nonnull
          JobConfig getConfig()

      Returns the configuration this job was submitted with. Changes made to the returned config object will not have any affect.

    - #### getName

          @Nullable
          default String getName()

      Returns the name of this job or `null` if no name was supplied.

      Jobs can be named through `JobConfig.setName(String)` prior to submission.

    - #### getSubmissionTime

          long getSubmissionTime()

      Returns the time when the job was submitted to the cluster.

      The time is assigned by reading `System.currentTimeMillis()` of the master member that executes the job for the first time. It doesn't change on restart.

    - #### getStatus

          @Nonnull
          JobStatus getStatus()

      Returns the current status of this job.

    - #### getMetrics

          @Nonnull
          JobMetrics getMetrics()

      Returns a snapshot of the current values of all job-specific metrics.

      While the job is running the metric values are updated periodically (see `metrics collection interval`), assuming that both `global metrics collection` and `per job metrics collection` are enabled. Otherwise empty metrics will be returned.

      Keep in mind that the collections may occur at different times on each member, metrics from various members aren't from the same instant.

      When a job is restarted (or resumed after being previously suspended) the metrics are reset too, their values will reflect only updates from the latest execution of the job.

      Once a job stops executing (successfully, after a failure, cancellation, or temporarily while suspended) the metrics will have their most recent values (i.e. the last metric values from the moment before the job completed), assuming that `metrics storage` was enabled. Otherwise empty metrics will be returned.

      Since:
        3.2

    - #### getFuture

          @Nonnull
          CompletableFuture<Void> getFuture()

      Gets the future associated with the job. The returned future is not cancellable. To cancel the job, the `cancel()` method should be used.
      Throws:
        `IllegalStateException` - if the job has not started yet.

    - #### join

          default void join()

      Waits for the job to complete and throws an exception if the job completes with an error. Does not return if the job gets suspended. Never returns for streaming (unbounded) jobs, unless they fail or are cancelled.

      Shorthand for `job.getFuture().join()`.

      Throws:
        `CancellationException` - if the job was cancelled

    - #### restart

          void restart()

      Gracefully stops the current execution and schedules a new execution with the current member list of the Jet cluster. Can be called to manually make use of added members, if auto scaling is disabled. Only a running job can be restarted; a suspended job must be resumed.

      Conceptually this call is equivalent to `suspend()` & `resume()`.

      Throws:
        `IllegalStateException` - if the job is not running, for example it has already completed, is not yet running, is already restarting, suspended etc.

    - #### suspend

          void suspend()

      Gracefully suspends the current execution of the job. The job's status will become `JobStatus.SUSPENDED`. To resume the job, call `resume()`.

      You can suspend a job even if it's not configured for snapshotting. Such a job will resume with empty state, as if it has just been started.

      This call just initiates the suspension process and doesn't wait for it to complete. Suspension starts with creating a terminal state snapshot. Should the terminal snapshot fail, the job will suspend anyway, but the previous snapshot (if there was one) won't be deleted. When the job resumes, its processing starts from the point of the last snapshot.

      NOTE: if the cluster becomes unstable (a member leaves or similar) while the job is in the process of being suspended, it may end up getting immediately restarted. Call `getStatus()` to find out and possibly try to suspend again.

      Throws:
        `IllegalStateException` - if the job is not running

    - #### resume

          void resume()

      Resumes a suspended job. The job will resume from the last known successful snapshot, if there is one.

      If the job is not suspended, it does nothing.

    - #### cancel

          void cancel()

      Makes a request to cancel this job and returns. The job will complete after its execution has stopped on all the nodes. If the job is already suspended, Jet will delete its runtime resources and snapshots and it won't be able to resume again.

      NOTE: if the cluster becomes unstable (a member leaves or similar) while the job is in the process of cancellation, it may end up getting restarted after the cluster has stabilized and won't be cancelled. Call `getStatus()` to find out and possibly try to cancel again.

      The job status will be `JobStatus.FAILED` after cancellation, `join()` will throw a `CancellationException`.

      See `cancelAndExportSnapshot(String)` to cancel with a terminal snapshot.

      Throws:
        `IllegalStateException` - if the cluster is not in a state to restart the job, for example when coordinator member left and new coordinator did not yet load job's metadata.

    - #### cancelAndExportSnapshot

          JobStateSnapshot cancelAndExportSnapshot(String name)

      Exports and saves a state snapshot with the given name, and then cancels the job without processing any more data after the barrier (graceful cancellation). It's similar to `suspend()` followed by a `cancel()`, except that it won't process any more data data after the snapshot.

      You can use the exported snapshot as a starting point for a new job. The job doesn't need to execute the same Pipeline as the job that created it, it must just be compatible with its state data. To achieve this, use `JobConfig.setInitialSnapshotName(String)`.

      If the terminal snapshot fails, Jet will suspend this job instead of cancelling it.

      You can call this method for a suspended job, too: in that case it will export the last successful snapshot and cancel the job.

      The method call will block until it has fully exported the snapshot, but may return before the job has stopped executing.

      For more information about "exported state" see `exportSnapshot(String)`.

      The job status will be `JobStatus.FAILED` after cancellation, `join()` will throw a `CancellationException`.

      Parameters:
        `name` - name of the snapshot. If name is already used, it will be overwritten
      Throws:
        `JetException` - if the job is in an incorrect state: completed, cancelled or is in the process of restarting or suspending.

    - #### exportSnapshot

          JobStateSnapshot exportSnapshot(String name)

      Exports a state snapshot and saves it under the given name. You can start a new job using the exported state using `JobConfig.setInitialSnapshotName(String)`.

      The snapshot will be independent from the job that created it. Jet won't automatically delete the IMap it is exported into. You must manually call snapshot.destroy() to delete it. If your state is large, make sure you have enough memory to store it.

      If a snapshot with the same name already exists, it will be overwritten. If a snapshot is already in progress for this job (either automatic or user-requested), the requested one will wait and start immediately after the previous one completes. If a snapshot with the same name is requested for two jobs at the same time, their data will likely be damaged (similar to two processes writing to the same file).

      You can call this method on a suspended job: in that case it will export the last successful snapshot. You can also export the state of non-snapshotted jobs (those with `ProcessingGuarantee.NONE`).

      If you issue any graceful job-control actions such as a graceful member shutdown or suspending a snapshotted job while Jet is exporting a snapshot, they will wait in a queue for this snapshot to complete. Forceful job-control actions will interrupt the export procedure.

      You can access the exported state map using `JetInstance.getJobStateSnapshot(String)`.

      The method call will block until it has fully exported the snapshot.

      Parameters:
        `name` - name of the snapshot. If name is already used, it will be overwritten
      Throws:
        `JetException` - if the job is in an incorrect state: completed, cancelled or is in the process of restarting or suspending.

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