StartTask Class

A Task which is run when a Node joins a Pool in the Azure Batch service, or when the Compute Node is rebooted or reimaged.

Batch will retry Tasks when a recovery operation is triggered on a Node. Examples of recovery operations include (but are not limited to) when an unhealthy Node is rebooted or a Compute Node disappeared due to host failure. Retries due to recovery operations are independent of and are not counted against the maxTaskRetryCount. Even if the maxTaskRetryCount is 0, an internal retry due to a recovery operation may occur. Because of this, all Tasks should be idempotent. This means Tasks need to tolerate being interrupted and restarted without causing any corruption or duplicate data. The best practice for long running Tasks is to use some form of checkpointing. In some cases the StartTask may be re-run even though the Compute Node was not rebooted. Special care should be taken to avoid StartTasks which create breakaway process or install/launch services from the StartTask working directory, as this will block Batch from being able to re-run the StartTask.

All required parameters must be populated in order to send to Azure.

Inheritance

msrest.serialization.Model

StartTask

Constructor

StartTask(*, command_line: str, container_settings=None, resource_files=None, environment_settings=None, user_identity=None, max_task_retry_count: int = None, wait_for_success: bool = None, **kwargs)

Parameters

Name	Description
command_line Required	str Required. The command line does not run under a shell, and therefore cannot take advantage of shell features such as environment variable expansion. If you want to take advantage of such features, you should invoke the shell in the command line, for example using "cmd /c MyCommand" in Windows or "/bin/sh -c MyCommand" in Linux. If the command line refers to file paths, it should use a relative path (relative to the Task working directory), or use the Batch provided environment variable (https://docs.microsoft.com/en-us/azure/batch/batch-compute-node-environment-variables).
container_settings Required	TaskContainerSettings The settings for the container under which the StartTask runs. When this is specified, all directories recursively below the AZ_BATCH_NODE_ROOT_DIR (the root of Azure Batch directories on the node) are mapped into the container, all Task environment variables are mapped into the container, and the Task command line is executed in the container. Files produced in the container outside of AZ_BATCH_NODE_ROOT_DIR might not be reflected to the host disk, meaning that Batch file APIs will not be able to access those files.
resource_files Required	list[ResourceFile] Files listed under this element are located in the Task's working directory.
environment_settings Required	list[EnvironmentSetting]
user_identity Required	UserIdentity The user identity under which the StartTask runs. If omitted, the Task runs as a non-administrative user unique to the Task.
max_task_retry_count Required	int The maximum number of times the Task may be retried. The Batch service retries a Task if its exit code is nonzero. Note that this value specifically controls the number of retries. The Batch service will try the Task once, and may then retry up to this limit. For example, if the maximum retry count is 3, Batch tries the Task up to 4 times (one initial try and 3 retries). If the maximum retry count is 0, the Batch service does not retry the Task. If the maximum retry count is -1, the Batch service retries the Task without limit, however this is not recommended for a start task or any task. The default value is 0 (no retries).
wait_for_success Required	bool Whether the Batch service should wait for the StartTask to complete successfully (that is, to exit with exit code 0) before scheduling any Tasks on the Compute Node. If true and the StartTask fails on a Node, the Batch service retries the StartTask up to its maximum retry count (maxTaskRetryCount). If the Task has still not completed successfully after all retries, then the Batch service marks the Node unusable, and will not schedule Tasks to it. This condition can be detected via the Compute Node state and failure info details. If false, the Batch service will not wait for the StartTask to complete. In this case, other Tasks can start executing on the Compute Node while the StartTask is still running; and even if the StartTask fails, new Tasks will continue to be scheduled on the Compute Node. The default is true.

Keyword-Only Parameters

Name	Description
command_line Required
container_settings Required
resource_files Required
environment_settings Required
user_identity Required
max_task_retry_count Required
wait_for_success Required

Methods

as_dict	Return a dict that can be JSONify using json.dump. Advanced usage might optionally use a callback as parameter: Key is the attribute name used in Python. Attr_desc is a dict of metadata. Currently contains 'type' with the msrest type and 'key' with the RestAPI encoded key. Value is the current value in this object. The string returned will be used to serialize the key. If the return type is a list, this is considered hierarchical result dict. See the three examples in this file: attribute_transformer full_restapi_key_transformer last_restapi_key_transformer If you want XML serialization, you can pass the kwargs is_xml=True.
deserialize	Parse a str using the RestAPI syntax and return a model.
enable_additional_properties_sending
from_dict	Parse a dict using given key extractor return a model. By default consider key extractors (rest_key_case_insensitive_extractor, attribute_key_case_insensitive_extractor and last_rest_key_case_insensitive_extractor)
is_xml_model
serialize	Return the JSON that would be sent to azure from this model. This is an alias to as_dict(full_restapi_key_transformer, keep_readonly=False). If you want XML serialization, you can pass the kwargs is_xml=True.
validate	Validate this model recursively and return a list of ValidationError.

as_dict

Return a dict that can be JSONify using json.dump.

Advanced usage might optionally use a callback as parameter:

Key is the attribute name used in Python. Attr_desc is a dict of metadata. Currently contains 'type' with the msrest type and 'key' with the RestAPI encoded key. Value is the current value in this object.

The string returned will be used to serialize the key. If the return type is a list, this is considered hierarchical result dict.

See the three examples in this file:

• attribute_transformer

• full_restapi_key_transformer

• last_restapi_key_transformer

If you want XML serialization, you can pass the kwargs is_xml=True.

as_dict(keep_readonly=True, key_transformer=<function attribute_transformer>, **kwargs)

Parameters

Name	Description
key_transformer	<xref:function> A key transformer function.
keep_readonly	default value: True

Returns

Type	Description
dict	A dict JSON compatible object

deserialize

Parse a str using the RestAPI syntax and return a model.

deserialize(data, content_type=None)

Parameters

Name	Description
data Required	str A str using RestAPI structure. JSON by default.
content_type	str JSON by default, set application/xml if XML. default value: None

Returns

Type	Description
	An instance of this model

Exceptions

Type	Description
DeserializationError if something went wrong

enable_additional_properties_sending

enable_additional_properties_sending()

from_dict

Parse a dict using given key extractor return a model.

By default consider key extractors (rest_key_case_insensitive_extractor, attribute_key_case_insensitive_extractor and last_rest_key_case_insensitive_extractor)

from_dict(data, key_extractors=None, content_type=None)

Parameters

Name	Description
data Required	dict A dict using RestAPI structure
content_type	str JSON by default, set application/xml if XML. default value: None
key_extractors	default value: None

Returns

Type	Description
	An instance of this model

Exceptions

Type	Description
DeserializationError if something went wrong

is_xml_model

is_xml_model()

serialize

Return the JSON that would be sent to azure from this model.

This is an alias to as_dict(full_restapi_key_transformer, keep_readonly=False).

If you want XML serialization, you can pass the kwargs is_xml=True.

serialize(keep_readonly=False, **kwargs)

Parameters

Name	Description
keep_readonly	bool If you want to serialize the readonly attributes default value: False

Returns

Type	Description
dict	A dict JSON compatible object

validate

Validate this model recursively and return a list of ValidationError.

validate()

Returns

Type	Description
list	A list of validation error