Local

class torchx.schedulers.local_scheduler.LocalScheduler(session_name: str, image_provider_class: Callable[[torchx.specs.api.RunConfig], torchx.schedulers.local_scheduler.ImageProvider], cache_size: int = 100, extra_paths: Optional[List[str]] = None)

Schedules on localhost. Containers are modeled as processes and certain properties of the container that are either not relevant or that cannot be enforced for localhost runs are ignored. Properties that are ignored:

1. Resource requirements

2. Resource limit enforcements

3. Retry policies

4. Retry counts (no retries supported)

5. Deployment preferences

Scheduler support orphan processes cleanup on receiving SIGTERM or SIGINT. The scheduler will terminate the spawned processes.

This is exposed via the schedulers local_cwd and local_docker.

• local_docker runs the provided app via the local docker runtime using the specified images in the AppDef. Docker must be installed. This provides the closest environment to schedulers that natively use Docker such as Kubernetes.

• local_cwd runs the provided app relative to the current working directory and ignores the images field for faster iteration and testing purposes.

Note

The orphan cleanup only works if LocalScheduler is instantiated from the main thread.

Note

Use this scheduler sparingly since an application that runs successfully on a session backed by this scheduler may not work on an actual production cluster using a different scheduler.

Feature	Scheduler Support
Fetch Logs	✔️
Distributed Jobs	LocalScheduler supports multiple replicas but all replicas will execute on the local host.
Cancel Job	✔️
Describe Job	✔️

close() → None

Only for schedulers that have local state! Closes the scheduler freeing any allocated resources. Once closed, the scheduler object is deemed to no longer be valid and any method called on the object results in undefined behavior.

This method should not raise exceptions and is allowed to be called multiple times on the same object.

Note

Override only for scheduler implementations that have local state (torchx/schedulers/local_scheduler.py). Schedulers simply wrapping a remote scheduler’s client need not implement this method.

describe(app_id: str) → Optional[torchx.schedulers.api.DescribeAppResponse]

Describes the specified application.

Returns

AppDef description or None if the app does not exist.

log_iter(app_id: str, role_name: str, k: int = 0, regex: Optional[str] = None, since: Optional[datetime.datetime] = None, until: Optional[datetime.datetime] = None, should_tail: bool = False) → Iterable[str]

Returns an iterator to the log lines of the k``th replica of the ``role. The iterator ends end all qualifying log lines have been read.

If the scheduler supports time-based cursors fetching log lines for custom time ranges, then the since, until fields are honored, otherwise they are ignored. Not specifying since and until is equivalent to getting all available log lines. If the until is empty, then the iterator behaves like tail -f, following the log output until the job reaches a terminal state.

The exact definition of what constitutes a log is scheduler specific. Some schedulers may consider stderr or stdout as the log, others may read the logs from a log file.

Behaviors and assumptions:

1. Produces an undefined-behavior if called on an app that does not exist The caller should check that the app exists using exists(app_id) prior to calling this method.

2. Is not stateful, calling this method twice with same parameters returns a new iterator. Prior iteration progress is lost.

3. Does not always support log-tailing. Not all schedulers support live log iteration (e.g. tailing logs while the app is running). Refer to the specific scheduler’s documentation for the iterator’s behavior.

3.1 If the scheduler supports log-tailing, it should be controlled

by``should_tail`` parameter.

4. Does not guarantee log retention. It is possible that by the time this method is called, the underlying scheduler may have purged the log records for this application. If so this method raises an arbitrary exception.

5. If should_tail is True, the method only raises a StopIteration exception when the accessible log lines have been fully exhausted and the app has reached a final state. For instance, if the app gets stuck and does not produce any log lines, then the iterator blocks until the app eventually gets killed (either via timeout or manually) at which point it raises a StopIteration.

   If should_tail is False, the method raises StopIteration when there are no more logs.

6. Need not be supported by all schedulers.

7. Some schedulers may support line cursors by supporting __getitem__ (e.g. iter[50] seeks to the 50th log line).

Returns

An Iterator over log lines of the specified role replica

Raises

NotImplementedError – if the scheduler does not support log iteration

run_opts() → torchx.specs.api.runopts

Returns the run configuration options expected by the scheduler. Basically a --help for the run API.

schedule(dryrun_info: torchx.specs.api.AppDryRunInfo[torchx.schedulers.local_scheduler.PopenRequest]) → str

Same as submit except that it takes an AppDryRunInfo. Implementors are encouraged to implement this method rather than directly implementing submit since submit can be trivially implemented by:

dryrun_info = self.submit_dryrun(app, cfg)
return schedule(dryrun_info)

Image Providers

class torchx.schedulers.local_scheduler.ImageProvider

Manages downloading and setting up an on localhost. This is only needed for LocalhostScheduler since typically real schedulers will do this on-behalf of the user.

abstract fetch(image: str) → str

Pulls the given image and returns a path to the pulled image on the local host or empty string if no op

get_cwd(image: str) → Optional[str]

Returns the absolute path of the mounted img directory. Used as a working directory for starting child processes.

get_entrypoint(img_root: str, role: torchx.specs.api.Role) → str

Returns the location of the entrypoint.

get_replica_param(img_root: str, role: torchx.specs.api.Role, stdout: Optional[str] = None, stderr: Optional[str] = None) → torchx.schedulers.local_scheduler.ReplicaParam

Given the role replica’s specs returns ReplicaParam holder which hold the arguments to eventually pass to subprocess.Popen to actually invoke and run each role’s replica. The img_root is expected to be the return value of self.fetch(role.image). Since the role’s image need only be fetched once (not for each replica) it is expected that the caller call the fetch method once per role and call this method for each role.num_replicas.

class torchx.schedulers.local_scheduler.DockerImageProvider(cfg: torchx.specs.api.RunConfig)

Calls into docker CLI to pull and run the specified image.

Example

fetch(Image(name="pytorch/pytorch:latest")) pulls docker image, returns “” get_command(image="pytorch/pytorch:latest", ..) return docker run ...

fetch(image: str) → str

Pulls the given image and returns a path to the pulled image on the local host or empty string if no op

get_replica_param(img_root: str, role: torchx.specs.api.Role, stdout: Optional[str] = None, stderr: Optional[str] = None) → torchx.schedulers.local_scheduler.ReplicaParam

Given the role replica’s specs returns ReplicaParam holder which hold the arguments to eventually pass to subprocess.Popen to actually invoke and run each role’s replica. The img_root is expected to be the return value of self.fetch(role.image). Since the role’s image need only be fetched once (not for each replica) it is expected that the caller call the fetch method once per role and call this method for each role.num_replicas.

class torchx.schedulers.local_scheduler.CWDImageProvider(cfg: torchx.specs.api.RunConfig)

Similar to LocalDirectoryImageProvider however it ignores the image name and uses the current working directory as the image path.

Example:

1. fetch(Image(name="/tmp/foobar")) returns os.getcwd()

2. fetch(Image(name="foobar:latest")) returns os.getcwd()

fetch(image: str) → str

Pulls the given image and returns a path to the pulled image on the local host or empty string if no op

get_cwd(image: str) → Optional[str]

Returns the absolute path of the mounted img directory. Used as a working directory for starting child processes.

get_entrypoint(img_root: str, role: torchx.specs.api.Role) → str

Returns the location of the entrypoint.