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LittleHorse CLI

lhctl is the LittleHorse CLI. It allows you to manage metadata in your system, observe and analyze your WfRuns, and also perform rudimentary actions such as running a WfRun.

Create Metadata

The lhctl deploy command allows you to create metadata such as WfSpec, TaskDef, UserTaskDef, and ExternalEventDef.

The syntax of the command is as follows:

lhctl deploy {wfSpec,taskDef,externalEventDef} <file>

The <file> parameter is expected to be a JSON-formatted printout of the corresponding protobuf. If your file is in the binary form, you can deploy using the --proto flag.

The following creates a simple TaskDef:

-> cat <<EOF > /tmp/taskDef.json
"name": "my-task",
"inputVars": [{
"type": "STR",
"name": "my-input-var"

-> lhctl deploy taskDef /tmp/taskDef.json
"code": "OK",
"result": {
"name": "my-task",
"inputVars": [
"type": "STR",
"name": "my-input-var",
"required": false
"createdAt": "2023-04-18T18:54:23.263Z"

The same syntax can be used for creating WfSpec, UserTaskDef, and ExternalEventDef objects.

View Objects

The lhctl get command allows you to inspect the state of an API Object; lhctl search allows you to find the ID's of API Object which match certain criteria; and lhctl list allows you to retrieve multiple API Objects at one time.

The following sections describe how to interact with each type of API Object.

Common Notes

In lhctl search, there are two global flags:

  • bookmark
  • limit

The limit flag is quite self-explanatory as it simply limits the number of results for a request.

All lhctl search responses have an optional bookmark field, which is a base64-encoded pagination token. If all results that match the search have been returned, then no bookmark is provided. Otherwise, if you wish to retrieve more results starting from where you left off, just pass in the provided bookmark by copying and pasting the base64-encoded data.


WfSpecs are versioned objects, meaning that their ID comprises a name and a version. When a new WfSpec is created with the same name as an older one, it gets an incremented version number and lives in the API as its own separate object.

You can retrieve the latest WfSpec named foo by doing:

lhctl get wfSpec foo

You can retrieve a list of all WfSpecs named foo by doing:

-> lhctl search wfSpec --name foo
"results": [
"name": "foo",
"version": 0
"name": "foo",
"version": 1

To get an old version (eg. 0) of a WfSpec named foo, you can:

lhctl get wfSpec foo --v 0


To get a WfRun with id <my-wf-id> you can:

lhctl get wfRun <my-wf-id>

Specific WfSpec Version

You can search for WfRuns by providing the name and version of the WfSpec and the status of the WfRun. For example, if you want to find all failed WfRun's from the foo WfSpec, version 9, you would do the following:

lhctl search wfRun --wfSpecName foo --wfSpecVersion 9 --status ERROR

By wfSpecName and status

You can search for WfRuns by providing the name of the WfSpec and the status of the WfRun. This retrieves results from all versions of the WfSpec:

lhctl search wfRun --wfSpecName foo --status ERROR

By wfSpecName

If you only specify --wfSpecName, WfRuns with any status and any version of the provided WfSpec are returned:

lhctl search wfRun --wfSpecName foo

By Time

Every flavor of lhctl search wfRun shown above also allows you to filter based on the time that the WfRun was launched via the following options:

  • --earliestMinutesAgo: Only show WfRuns more recent than this configuration.
  • --latestMinutesAgo: only show WfRun's less recent than this configuration.

For example, to find all workflows started between 10 and 15 minutes ago that are in the COMPLETED state, we would do:

lhctl search wfRun --wfSpecName foo --status COMPLETED --earliestMinutesAgo 15 --latestMinutesAgo 10


A NodeRun has a composite ID consisting of the wfRunId, threadRunNumber, and position.

To get all NodeRun associated to an specific WfRun:

lhctl list nodeRun <wfRunId>

Get an simplified response as follows:

lhctl search nodeRun --wfRunId <my-wf-id>

Use lhctl get nodeRun to find an specific NodeRun, The syntax for this is as follows:

lhctl get nodeRun <wfRunId> <threadRunNumber> <position>

To get the second (zero-indexed) NodeRun for the entrypoint thread (Thread Run 0) of the WfRun with id 123foo, you can:

lhctl get nodeRun 123foo 0 2

TaskDef and ExternalEventDef

The lhctl syntax for TaskDef and ExternalEventDef is identical. You can get a specific TaskDef or ExternalEventDef by its name using:

lhctl get taskDef <name>

You can list all TaskDefs or ExternalEventDefs as follows:

lhctl search externalEventDef

You can search TaskDefs and ExternalEventDefs with prefixes as follows:

lhctl search taskDef --prefix some-pref


A TaskRun is a running instance of a Task in LittleHorse. A TaskRun is associated with a TaskDef.

To retrieve all TaskRun's associated with a TaskDef, use the following command:

lhctl search taskRun --taskDefName <TaskDefName>

You can also filter TaskRuns by specifying a particular TaskRun status:

lhctl search taskRun --taskDefName <TaskDefName> --status <TaskRunStatus>

Possible values for the status parameter are as follows:


Just like lhctl search wfRun, each flavor of lhctl search taskRun shown above also allows you to filter based on the time that the taskRun was scheduled via the following options:

  • --earliestMinutesAgo: Only show TaskRuns more recent than this configuration.
  • --latestMinutesAgo: only show TaskRun's less recent than this configuration.

A TaskRun has a composite id consisting of the id of its WfRun, and a taskGuid. To get a TaskRun, you can use:

lhctl get taskRun <wfRunId> <taskGuid>

# This is equivalent:
lhctl get taskRun <wfRunId>/<taskGuid>


A UserTaskRun is an instance of a UserTaskDef in LittleHorse, in which a human is assigned a Task and the WfRun blocks until that Task is completed. The ID of a UserTaskRun is a composite ID consisting of the ID of the WfRun and a Guid.

To get a UserTaskRun, you can run:

lhctl get userTaskRun <wfRunId> <userTaskGuid>

You can search for UserTaskRun's with multiple combinations of flags. Supported flags for a UserTaskRun search are:

  • --earliestMinutesAgo
  • --latestMinutesAgo
  • --userTaskStatus, which is the status of the UserTaskRun. Valid values are:
    • DONE
  • --userId, or the ID of the User to whom the Task is assigned.
  • --userGroup, or the ID of the User Group to whom the Task is assigned.
  • --userTaskDefName, or the name of the UserTaskDef that the Task comes from.


A UserTaskDef is equivalent to a TaskDef but for UserTaskRuns instead of TaskRuns. To find all UserTaskDefs, you can:

lhctl search userTaskDef

# By Prefix
lhctl search userTaskDef --prefix some-prefix-

You can get a userTaskDef as follows:

lhctl get userTaskDef my-user-task-def

# optionally specify version. If version not set, defaults to latest.
lhctl get userTaskDef my-user-task-def --v 2

You can delete a UserTaskDef as follows:

lhctl delete userTaskDef my-user-task-def 2  # version is required


An ExternalEvent has a composite ID consisting of:

  • The associated wfRunId.
  • The name of the ExternalEventDef.
  • A unique guid for that ExternalEvent instance.

To get an ExternalEvent, you can:

lhctl search externalEvent <wfRunId> <externalEventDefName> <guid>

You can list all ExternalEvents for a given wfRunId via the following:

lhctl search externalEvent --wfRunId <wfRunId>


A Variable has a composite ID consisting of:

  • The associated wfRunId.
  • The threadRunNumber of the owning ThreadRun.
  • The name of the Variable.

You can get a specific variable via:

lhctl get variable <wfRunId> <threadRunNumber> <name>

You can list all Variables for a given WfRun via:

lhctl search variable --wfRunId <wfRunId>

You can search for Variables with a certain value (not supported for JSON_OBJ, BYTES, and JSON_ARR variables). You must pass in the Variable name, the type, and the value. For example, to search for email-address variable's with the value, you would:

lhctl search variable --varType STR --value '' --name email-address

Supported variable types for searching are:

  • STR
  • INT
  • BOOL


The LittleHorse CLI lets you view metrics in a rudimentary manner. It is recommended to use the Admin Dashboard to better visualize these metrics; however, you can still view metrics through the CLI.

LittleHorse exposes two types of metrics: "Task Metrics", which are aggregated by TaskDef, and "Workflow Metrics", which are aggregated by WfSpec.

Metrics are collected and aggregated on tumbling time windows. There are three sizes of windows which you can use:

  • MINUTES_5,
  • HOURS_2, and
  • DAYS_1.

To get the last 10 windows of size MINUTES_5 of metrics for the foo-task TaskDef, you can:

lhctl taskDefMetrics foo-task MINUTES_5 10

To get the last 5 windows of size DAYS_1 for the second version of the foo-wf WfSpec, you can:

lhctl wfSpecMetrics foo-wf 2 DAYS_1 5

Manage WfRuns

lhctl allows you to perform basic actions around running, stopping, and resuming WfRuns and also creating ExternalEvents.

Run a WfRun

You can run a WfRun using the lhctl run command. The syntax is:

lhctl run <wfSpecName> ...args

All positional arguments after the WfSpec Name are interpreted as pairs of {Variable Name, Variable Value}. The variable values are intelligently deserialized to their appropriate types; for example, if var 'foo' is of type 'JSON_OBJ', then the argument '{"bar":"baz"}' will be unmarshalled as a JSON object.

To run the "my-workflow" WfSpec with two input parameters,

  • foo set to the Json Object {"bar":"baz"}
  • my-int set to 123

you can:

lhctl run my-workflow foo '{"bar":"baz"}' my-int 123

You can also set the ID of the WfRun using the --wfRunId flag. Note that there can only be one WfRun with a given ID. This can be used to guarantee idempotence.

Stop and Resume a WfRun

You can use:

lhctl stop wfRun <wfRunId>

to stop a WfRun, and then resume it with:

lhctl resume wfRun <wfRunId>

You can optionally stop or resume a child thread (without affecting the entrypoint ThreadRun) by using the --threadRunNumber argument.

Post an ExternalEvent

lhctl postEvent allows you to post an ExternalEvent of a specified Event Type and Variable Type to a WfRun. Specifying the Variable Type for the external event is currently required as ExternalEventDef's currently do not carry Schema information (this will change in a future release). The payload is deserialized according to the type. JSON objects should be provided as a string; BYTES objects should be b64-encoded.

To send an External Event of type my-event with a String value "my-event-content" to the WfRun given by id "my-wf-id", you can:

lhctl postEvent my-wf-id my-event STR my-event-content

As a refresher, the valid variable types in LittleHorse are:

  • STR
  • INT
  • BOOL

You can optionally specify the --guid flag to guarantee idempotence of this request, as only one ExternalEvent can exist with the same guid, wfRunId, and externalEventDefName.

You can optionally assign the ExternalEvent to a specific NodeRun or ThreadRun using the --nodeRunPosition and --threadRunNumber flags, respectively. The --nodeRunPosition flag is only valid if the --threadRunNumber flag is also set.