µTask is an automation engine built for the cloud. It is:
- simple to operate: only a postgres DB is required
- secure: all data is encrypted, only visible to authorized users
- extensible: you can develop custom actions in golang
µTask allows you to model business processes in a declarative yaml format. Describe a set of inputs and a graph of actions and their inter-dependencies: µTask will asynchronously handle the execution of each action, working its way around transient errors and keeping an encrypted, auditable trace of all intermediary states until completion.
- Real-world examples
- Quick Start
- Operating in production
- Configuration
- Authoring Task Templates
- Extending µTask with plugins
- Contributing
- License
Here are a few real-world examples that can be implemented with µTask:
A new ingress is created on the production kubernetes cluster. A hook triggers a µTask template that:
- generates a private key
- requests a new certificate
- meets the certificate issuer's challenges
- commits the resulting certificate back to the cluster
A new member joins the team. The team leader starts a task specifying the new member's name, that:
- asks the new team member to generate an SSH key pair and copy the public key in a µTask-generated form
- registers the public SSH key centrally
- creates accounts on internal services (code repository, CI/CD, internal PaaS, ...) for the new team member
- triggers another task to spawn a development VM
- sends a welcome email full of GIFs
The payments API receives a request that requires an asynchronous antifraud check. It spawns a task on its companion µTask instance that:
- calls a first risk-assessing API which returns a number
- if the risk is low, the task succeeds immediately
- otherwise it calls a SaaS antifraud solution API which returns a score
- if the score is good, the task succeeds
- if the score is very bad, the task fails
- if it is in between, it triggers a human investigation step where an operator can enter a score in a µTask-generated form
- when it is done, the task sends an event to the payments API to notify of the result
The payments API keeps a reference to the running workflow via its task ID. Operators of the payments API can follow the state of current tasks by requesting the µTask instance directly. Depending on the payments API implementation, it may allow its callers to follow a task's state.
Download our latest install script, setup your environment and launch your own local instance of µTask.
mkdir utask && cd utask
wget https://github.com/ovh/utask/releases/latest/download/install-utask.sh
sh install-utask.sh
docker-compose upAll the configuration for the application is found in the environment variables in docker-compose.yaml. You'll see that basic auth is setup for user admin with password 1234. Try logging in with this user on the graphical dashboard: http://localhost:8081/ui/dashboard.
You can also explore the API schema: http://localhost:8081/unsecured/spec.json.
Request a new task:
Get an overview of all tasks:
Get a detailed view of a running task:
Browse available task templates:
Alternatively, you can clone this repository and build the µTask binary:
make allThe folder you created in the previous step is meant to become a git repo where you version your own task templates and plugins. Re-download and run the latest install script to bump your version of µTask.
You'll deploy your version of µTask by building a docker image based on the official µTask image, which will include your extensions. See the Dockerfile generated during installation.
µTask is designed to run a task scheduler and perform the task workloads within a single runtime: work is not delegated to external agents. Multiple instances of the application will coordinate around a single postgres database: each will be able to determine independently which tasks are available. When an instance of µTask decides to execute a task, it will take hold of that task to avoid collisions, then release it at the end of an execution cycle.
A task will keep running as long as its steps are successfully executed. If a task's execution is interrupted before completion, it will become available to be re-collected by one of the active instances of µTask. That means that execution might start in one instance and resume on a different one.
- Generate a new key with symmecrypt, with the 'storage' label.
- Add it to your configuration items. The library will take all keys into account and use the latest possible key, falling back to older keys when finding older data.
- Set your API in maintenance mode (env var or command line arg, see config below): all write actions will be refused when you reboot the API.
- Reboot API.
- Make a POST request on the /key-rotate endpoint of the API.
- All data will be encrypted with the latest key, you can delete older keys.
- De-activate maintenance mode.
- Reboot API.
The only dependency for µTask is a Postgres database server. The minimum version for the Postgres database is 9.5
The µTask binary accepts the following arguments as binary args or env var. All are optional and have a default value:
init-path: the directory from where initialization plugins (see "Developing plugins") are loaded in *.so form (default:./init)plugins-path: the directory from where action plugins (see "Developing plugins") are loaded in *.so form (default:./plugins)templates-path: the directories where yaml-formatted task templates are loaded from, can be a colon separated list (default:./templates)functions-path: the directory where yaml-formatted functions templates are loaded from (default:./functions)region: an arbitrary identifier, to aggregate a running group of µTask instances (commonly containers), and differentiate them from another group, in a separate region (default:default)http-port: the port on which the HTTP API listents (default:8081)debug: a boolean flag to activate verbose logs (default:false)maintenance-mode: a boolean to switch API to maintenance mode (default:false)
Checkout the µTask config keys and files README.
The vanilla version of µTask doesn't handle authentication by itself, it is meant to be placed behind a reverse proxy that provides a username through the "x-remote-user" http header. A username found there will be trusted as is, and used for authorization purposes (admin actions, task resolution, etc...).
For development purposes, an optional basic-auth configstore item can be provided to define a mapping of usernames and passwords. This is not meant for use in production.
Extending this basic authentication mechanism is possible by developing an "init" plugin, as described below.
Every task state change can be notified to a notification backend. µTask implements three differents notification backends: Slack, Opsgenie, and generic webhooks.
Default payload that will be sent for generic webhooks are:
task_state_update notifications:
{
"message": "string",
"notification_type": "task_state_update",
"task_id": "public_task_uuid",
"title": "task title string",
"state": "current task state",
"template": "template_name",
"requester": "optional",
"resolver": "optional",
"steps": "14/20",
"potential_resolvers": "user1,user2,admin",
"resolution_id": "optional,public_resolution_uuid",
"tags": "{\"tag1\":\"value1\"}"
}task_step_update notifications:
{
"message": "string",
"notification_type": "task_step_update",
"task_id": "public_task_uuid",
"title": "task title string",
"state": "current task state",
"template": "template_name",
"step_name": "string",
"step_state": "string",
"requester": "string",
"resolver": "string",
"steps": "14/20",
"resolution_id": "public_resolution_uuid",
"tags": "{\"tag1\":\"value1\"}"
}task_validation notifications:
{
"message": "string",
"notification_type": "task_validation",
"task_id": "public_task_uuid",
"title": "task title string",
"state": "TODO",
"template": "template_name",
"requester": "optional",
"potential_resolvers": "user1,user2,admin",
"tags": "{\"tag1\":\"value1\"}"
}Notification backends can be configured in the global µTask configuration, as described here.
Checkout the µTask examples directory.
A process that can be executed by µTask is modelled as a task template: it is written in yaml format and describes a sequence of steps, their interdepencies, and additional conditions and constraints to control the flow of execution.
The user that creates a task is called requester, and the user that executes it is called resolver. Both can be the same user in some scenarios.
A user can be allowed to resolve a task in four ways:
- the user is included in the global configuration's list of
admin_usernames - the user is included in the task's template list of
allowed_resolver_usernames - the user is in a group that is included in the task's template list of
allowed_resolver_groups - the user is included in the task
resolver_usernameslist
µTask uses the go templating engine in order to introduce dynamic values during a task's execution. As you'll see in the example template below, template handles can be used to access values from different sources. Here's a summary of how you can access values through template handles:
.input.[INPUT_NAME]: the value of an input provided by the task's requester.resolver_input.[INPUT_NAME]: the value of an input provided by the task's resolver.step.[STEP_NAME].output.foo: fieldfoofrom the output of a named step.step.[STEP_NAME].metadata.HTTPStatus: fieldHTTPStatusfrom the metadata of a named step.step.[STEP_NAME].children: the collection of results from a 'foreach' step.step.[STEP_NAME].error: error message from a failed step.step.[STEP_NAME].state: current state of the given step.step.[STEP_NAME].max_retries: max retries of the given step.step.[STEP_NAME].try_count: try count of the given step.config.[CONFIG_ITEM].bar: fieldbarfrom a config item (configstore, see above).iterator.foo: fieldfoofrom the iterator in a loop (seeforeachsteps below).pre_hook.output.foo: fieldfoofrom the output of the step's pre-hook (see pre-hooks).pre_hook.metadata.HTTPStatus: fieldHTTPStatusfrom the metadata of the step's pre-hook (see pre-hooks).function_args.[ARG_NAME]: argument that needs to be given in the conifguration section to the function (seefunctionsbelow)
The following templating functions are available:
| Name | Description | Reference |
|---|---|---|
Golang |
Builtin functions from Golang text template | Doc |
Sprig |
Extended set of functions from the Sprig project | Doc |
field |
Equivalent to the dot notation, for entries with forbidden characters | {{field `config` `foo.bar`}} |
fieldFrom |
Equivalent to the dot notation, for entries with forbidden characters. It takes the previous template expression as source for the templating values. Example: ```{{ {"foo.foo":"bar"} |
fromJson |
eval |
Evaluates the value of a template variable | {{eval `var1`}} |
evalCache |
Evaluates the value of a template variable, and cache for future usage (to avoid further computation) | {{evalCache `var1`}} |
fromJson |
Decodes a JSON document into a structure. If the input cannot be decoded as JSON, the function will return an empty string | {{fromJson `{"a":"b"}`}} |
mustFromJson |
Similar to fromJson, but will return an error in case the JSON is invalid. A common usecase consists of returning a JSON stringified data structure from a JavaScript expression (object, array), and use one of its members in the template. Example: {{(eval `myExpression` | fromJson).myArr}} or {{(eval `myExpression` | fromJson).myObj}} |
{{mustFromJson `{"a":"b"}`}} |
name: a short unique human-readable identifierdescription: sentence-long description of intentlong_description: paragraph-long basic documentationdoc_link: URL for external documentation about the tasktitle_format: templateable text, generates a title for a task based on this templateresult_format: templateable map, used to generate a final result object from data collected during execution
allowed_resolver_groups: a list of groups with the right to resolve a task based on this templateallowed_resolver_usernames: a list of usernames with the right to resolve a task based on this templateallow_all_resolver_usernames: boolean (default: false): when true, any user can execute a task based on this templateauto_runnable; boolean (default: false): when true, the task will be executed directly after being created, IF the requester is an accepted resolver orallow_all_resolver_usernamesis trueblocked: boolean (default: false): no tasks can be created from this templatehidden: boolean (default: false): the template is not listed on the API, it is concealed to regular usersretry_max: int (default: 100): maximum amount of consecutive executions of a task based on this template, before being blocked for manual reviewtags: templatable map, used to filter tasks (see tags)
When creating a new task, a requester needs to provide parameters described as a list of objects under the inputs property of a template. Additional parameters can be requested from a task's resolver user: those are represented under the resolver_inputs property of a template.
An input's definition allows to define validation constraints on the values provided for that input. See example template above.
name: unique name, used to access the value provided by the task's requesterdescription: human readable description of the input, meant to give context to the task's requesterregex: (optional) a regular expression that the provided value must matchlegal_values: (optional) a list of possible values accepted for this inputcollection: boolean (default: false) a list of values is accepted, instead of a single valuetype: (string|number|bool) (default: string) the type of data acceptedoptional: boolean (default: false) the input can be left emptydefault: (optional) a value assigned to the input if left empty
A template variable is a named holder of either:
- a fixed value
- a JavaScript expression evaluated on the fly.
See the example template above to see variables in action. The expression in a variable can contain template handles to introduce values dynamically (from executed steps, for instance), like a step's configuration.
The JavaScript evaluation is done using otto.
Tags are a map of strings property of a task. They will be used in the task listing to search for some tasks using filters. With tags, uTask can be used as a task backend by others APIs.
Tags values are expected to be a string: it support all uTask templating on values. To remove a tag from a task, use the empty value "".
tags:
customer: "{{.input.customer_id}}"
type: "billing"In this example, tag customer will be templated from the task inputs, and allow others APIs to search all the tasks for a given customer.
Tags can be added to a task:
- from the template definition of the task
- while creating a task, requester can input custom tags
- during the execution, using the
tagbuiltin plugin
A step is the smallest unit of work that can be performed within a task. At is's heart, a step defines an action: several types of actions are available, and each type requires a different configuration, provided as part of the step definition. The state of a step will change during a task's resolution process, and determine which steps become eligible for execution. Custom states can be defined for a step, to fine-tune execution flow (see below).
A sequence of ordered steps constitutes the entire workload of a task. Steps are ordered by declaring dependencies between each other. A step declares its dependencies as a list of step names on which it waits, meaning that a step's execution will be on hold until its dependencies have been resolved. More details about dependencies.
The flow of this sequence can further be controlled with conditions on the steps: a condition is a clause that can be run before or after the step's action. A condition can either be used:
- to skip a step altogether
- to analyze its outcome and override the engine's default behaviour
Several conditions can be specified.
Unless final is set to true, they are all evaluated in order. If multiple conditions evaluate to true, they will be applied sequentially. Once a condition is applied, the next condition is evaluated using the new context (i.e. using the new state value of steps that got updated). If multiple conditions are evaluated to true and are changing the same step state value, then the last condition to evaluate as true will be the one that will change the state step for real.
A condition is composed of:
- a
type(skip or check) - a list of
ifassertions (value,operator,expected) which all have to be true (AND on the collection), - a
thenobject to impact the state of steps (thisrefers to the current step) - a
finalboolean, defaulting tofalse. When set totrue, it prevents the evaluation of the next conditions if this one is evaluated totrue - an optional
messageto convey the intention of the condition, making it easier to inspect tasks
Here's an example of a skip condition. The value of an input is evaluated to determine the result: if the value of runType is dry, the createUser step will not be executed, its state will be set directly to DONE.
inputs:
- name: runType
description: Run this task with/without side effects
legal_values: [dry, wet]
steps:
createUser:
description: Create new user
action:
... etc...
conditions:
- type: skip
if:
- value: '{{.input.runType}}'
operator: EQ
expected: dry
then:
this: DONE
message: Dry run, skip user creationHere's an example of a check condition. Here the return of an http call is inspected: a 404 status will put the step in a custom NOT_FOUND state. The default behavior would be to consider any 4xx status as a client error, which blocks execution of the task. The check condition allows you to consider this situation as normal, and proceed with other steps that take the NOT_FOUND state into account (creating the missing resource, for instance).
steps:
getUser:
description: Get user
custom_states: [NOT_FOUND]
action:
type: http
configuration:
url: http://example.org/user/{{.input.id}}
method: GET
conditions:
- type: check
if:
- value: '{{.step.getUser.metadata.HTTPStatus}}'
operator: EQ
expected: '404'
then:
this: NOT_FOUND
message: User {{.input.id}} not found
createUser:
description: Create the user
dependencies: ["getUser:NOT_FOUND"]
action:
type: http
configuration:
url: http://example.org/user
method: POST
body: |-
{"user_id":"{{.input.id}}"}A condition can use one of the following operators:
EQ: equalNE: not equalGT: greater thanLT: less thanGE: greater or equalLE: less than or equalREGEXP: match a regexpNOTREGEXP: doesn't match a regexpIN: found in a list of valuesNOTIN: not found in a list of values
Note that the operators IN and NOTIN expect a list of acceptable values in the field value, instead of a single one. You can specify the separator character to use to split the values of the list using the field list_separator (default: ,). Each value of the list will be trimmed of its leading and trailing white spaces before comparison.
name: a unique identifierdescription: a human readable sentence to convey the step's intentaction: the actual task the step executes, see Actionforeach: see Loopspre_hook: an action that can be executed before the actual action of the stepdependencies: a list of step names on which this step waits before runningidempotent: a boolean indicating if this step is safe to be replayed in case of uTask instance crashjson_schema: a JSON-Schema object to validate the step outputresources: a list of resources that will be used by this step to apply some rate-limiting (see resources)custom_states: a list of personnalised allowed state for this step (can be assigned to the state's step usingconditions)retry_pattern: (seconds,minutes,hours) define on what temporal order of magnitude the re-runs of this step should be spread (default =seconds)resources: a list of resources that will be used during the step execution, to control and limit the concurrent execution of the step (more information in the resources section).
The action field of a step defines the actual workload to be performed. It consists of at least a type chosen among the registered action plugins, and a configuration fitting that plugin. See below for a detailed description of builtin plugins. For information on how to develop your own action plugins, refer to this section.
When an action's configuration is repeated across several steps, it can be factored by defining base_configurations at the root of the template. For example:
base_configurations:
postMessage:
method: POST
url: http://message.board/newThis base configuration can then be leveraged by any step wanting to post a message, with different bodies:
steps:
sayHello:
description: Say hello on the message board
action:
type: http
base_configuration: postMessage
configuration:
body: Hello
sayGoodbye:
description: Say goodbye on the message board
dependencies: [sayHello]
action:
type: http
base_configuration: postMessage
configuration:
body: GoodbyeThese two step definitions are the equivalent of:
steps:
sayHello:
description: Say hello on the message board
action:
type: http
configuration:
body: Hello
method: POST
url: http://message.board/new
sayGoodbye:
description: Say goodbye on the message board
dependencies: [sayHello]
action:
type: http
configuration:
body: Goodbye
method: POST
url: http://message.board/newThe output of an action can be enriched by means of an output. For example, in a template with an input field named id, value 1234 and a call to a service which returns the following payload:
{
"name": "username"
}The following action definition:
steps:
getUser:
description: Prefix an ID received as input, return both
action:
type: http
output:
strategy: merge
format:
id: "{{.input.id}}"
configuration:
method: GET
url: http://directory/user/{{.input.id}}Will render the following output, a combination of the action's raw output and the output:
{
"id": "1234",
"name": "username"
}All the strategies available are:
merge: data informatmust be a dict and will be merged with the output of the action (e.g. ahead)template: the action will return exactly the data informatthat can be templated (see Value Templating)
Browse builtin actions
| Plugin name | Description | Documentation |
|---|---|---|
echo |
Print out a pre-determined result | Access plugin doc |
http |
Make an http request | Access plugin doc |
subtask |
Spawn a new task on µTask | Access plugin doc |
notify |
Dispatch a notification over a registered channel | Access plugin doc |
apiovh |
Make a signed call on OVH's public API (requires credentials retrieved from configstore, containing the fields endpoint, appKey, appSecret, consumerKey, more info here) |
Access plugin doc |
ssh |
Connect to a remote system and run commands on it | Access plugin doc |
email |
Send an email | Access plugin doc |
ping |
Send a ping to an hostname Warn: This plugin will keep running until the count is done | Access plugin doc |
script |
Execute a script under scripts folder |
Access plugin doc |
tag |
Add tags to the current running task | Access plugin doc |
callback |
Use callbacks to manage your tasks life-cycle | Access plugin doc |
The pre_hook field of a step can be set to define an action that is executed before the step's action. This field supports all the same fields as the action. It aims to fetch data for the execution of the action that can change over time and needs to be fetched at every retry, such as OTPs. All the result values of the pre-hook are available under the templating variable .pre_hook.
doSomeAuthPost:
pre_hook:
type: http
configuration:
method: "GET"
url: "https://example.org/otp"
action:
type: http
configuration:
method: "POST"
url: "https://example.org/doSomePost"
headers:
X-Otp: "{{ .pre_hook.output }}"Functions are abstraction of the actions to define a behavior that can be re-used in templates. They act like a plugin but are pre-declared in dedicated directory functions. They can have arguments that need to be given in the configuration section of the action and can be used in the declaration of the function by accessing the templating variables under .function_args.
name: ovh::request
description: Execute a call to the ovh API
pre_hook:
type: http
configuration:
method: "GET"
url: https://api.ovh.com/1.0/auth/time
action:
type: http
configuration:
headers:
- name: X-Ovh-Signature
value: '{{ printf "%s+%s+%s+%s%s+%s+%v" .config.apiovh.applicationSecret .config.apiovh.consumerKey .function_args.method .config.apiovh.basePath .function_args.path .function_args.body .pre_hook.output | sha1sum | printf "$1$%s"}}'
- name: X-Ovh-Timestamp
value: "{{ .pre_hook.output }}"
- name: X-Ovh-Consumer
value: "{{ .config.apiovh.consumerKey }}"
- name: X-Ovh-Application
value: "{{ .config.apiovh.applicationKey }}"
method: "{{ .function_args.method }}"
url: "{{.config.apiovh.basePath}}{{ .function_args.path }}"
body: "{{ .function_args.body }}"This function can be used in a template like this:
steps:
getService:
description: Get Service
action:
type: ovh::request
configuration:
path: "{{.input.path}}"
method: GET
body: ""Dependencies can be declared on a step, to indicate what requirements should be met before the step can actually run. A step can have multiple dependencies, which will all have to be met before the step can start running.
A dependency can be qualified with a step's state (stepX:stateY, it depends on stepX, finishing in stateY). If omitted, then DONE is assumed.
There are two different kinds of states: builtin and custom. Builtin states are provided by uTask and include: TODO, RUNNING, DONE, CLIENT_ERROR, SERVER_ERROR, FATAL_ERROR, CRASHED, PRUNE, TO_RETRY, AFTERRUN_ERROR. Additionally, a step can define custom states via its custom_states field. These custom states provide a way for the step to express that it ran successfully, but the result may be different from the normal expected case (e.g. a custom state NOT_FOUND would let the rest of the workflow proceed, but may trigger additional provisioning steps).
A dependency (stepX:stateY) can be on any of stepX's custom states, along with DONE (builtin). These are all considered final (uTask will not touch that step anymore, it has been run to completion). Conversely, other builtin states (CLIENT_ERROR, ...) may not be used in a dependency, since those imply a transient state and the uTask engine still has work to do on these.
If you wish to declare a dependency on something normally considered as a CLIENT_ERROR (e.g. GET HTTP returns a 404), you can write a check condition to inspect your step result, and change it to a custom state instead (meaning an alternative termination, see the NOT_FOUND example)
It is possible that a dependency will never match the expected state. For example, step1 is in DONE state, and step2 has a dependency declared as step1:NOT_FOUND: it means that step2 requires that step1 finishes its execution with state NOT_FOUND. In that case, step2 will never be allowed to run, as step1 finished with state DONE. To remedy this, uTask will remove step2 from the workflow by setting its state to the special state PRUNE. Any further step depending on step2 will also be pruned, removing entire alternative execution branches. This allows crossroads patterns, where a step may be followed by two mutually exclusive branches (one for DONE, one for ALTERNATE_STATE_XXX). (Note: PRUNE may also be used in conditions to manually eliminate entire branches of execution)
A special qualifier that can be used as a dependency state is ANY (stepX:ANY). ANY matches all custom states and DONE, and it also does not get PRUNE'd recursively if stepX is set to PRUNE. This is used mostly for sequencing, either when the actual result of the step does not matter, but its timing does; or to reconcile mutually exclusive branches in a diamond pattern (using e.g. the coalesce templating function to mix optional step results).
For example, step2 can declare a dependency on step1 in the following ways:
step1: wait forstep1to be in stateDONE(could also be written asstep1:DONE)step1:DONE,ALREADY_EXISTS: wait forstep1to be either in stateDONEorALREADY_EXISTSstep1:ANY: wait forstep1to be in any "final" state, ie. it cannot keep running
A step can be configured to take a json-formatted collection as input, in its foreach property. It will be executed once for each element in the collection, and its result will be a collection of each iteration. This scheme makes it possible to chain several steps with the foreach property.
For the following step definition (note json-format of foreach):
steps:
prefixStrings:
description: Process a collection of strings, adding a prefix
foreach: '[{"id":"a"},{"id":"b"},{"id":"c"}]'
action:
type: echo
configuration:
output:
prefixed: pre-{{.iterator.id}}The following output can be expected to be accessible at {{.step.prefixStrings.children}}
[
{
"output": {
"prefixed": "pre-a"
},
"metadata": {},
"state": "DONE"
},
{
"output": {
"prefixed": "pre-b"
},
"metadata": {},
"state": "DONE"
},
{
"output": {
"prefixed": "pre-c"
},
"metadata": {},
"state": "DONE"
}
]It contains all the output, metadata and state of the different iterations, coming from the foreach loop.
This output can be then passed to another step in json format:
foreach: '{{.step.prefixStrings.children | toJson}}'It's possible to configure the strategy used to run each elements:
parallel(default): each elements will be run in parallel to maximize throughputsequence: will run each element when the previous one is done, to ensure the sequence between elements.
It can be declared in the template like this:
foreach_strategy: "sequence"When writing skip conditions on loops, an additional property foreach can be added. It can have two values:
children: default value. If no value is set, this value is used. The condition will be run on every iteration of the foreach loop;parent: the condition will be run on the step itself before creating its children.
For example:
foreach: '{{.step.aPreviousStep.output.ids | toJson}}'
action:
type: echo
configuration:
output:
url: '{{ .iterator }}'
conditions:
- type: skip
foreach: children # <- this line can be omitted
if:
- value: '{{ .iterator }}'
operator: EQ
expected: '{{ .step.something.output.dontTouchId }}'
then:
this: PRUNEwill be run on every children and skip the child by pruning it the condition is true. And
foreach: '{{.step.aPreviousStep.output.ids | toJson}}'
action:
type: echo
configuration:
output:
url: '{{ .iterator }}'
conditions:
- type: skip
foreach: parent
if:
- value: '{{ step.previousCheck.output.result }}'
operator: EQ
expected: 'already_done'
then:
this: PRUNEwill be run before creating any children, by pruning the parent.
Resources are a way to restrict the concurrency factor of operations, to control the throughput and avoid dangerous behavior (e.g. flooding the targets).
High level view:
- For each action to execute, a list of target
resourcesis determined. (see later) - In the µTask configuration, numerical limits can be set to each resource label. This acts as a semaphore, allowing a certain number of concurrent slots for the given resource label. If no limit is set for a resource label, the previously mentionned target resources have no effect. Limits are declared in the
resource_limitsproperty.
The target resources for a step can be defined in its YAML definition, using the resources property.
steps:
foobar:
description: A dummy step, that should not execute in parallel
resources: ["myLimitedResource"]
action:
type: echo
configuration:
output:
foobar: fuzzAlternatively, some target resources are determined automatically by µTask Engine:
- When a task is run, the resource
template:my-template-nameis used automatically. - When a step is run, the plugin in charge of the execution automatically generates a list of resources. This includes generic resources such as
socket,url:www.example.org,fork... allowing the µTask administrator to set-up generic limits such as"socket": 48or"url:www.example.org": 1.
Each builtin plugins declares resources which can be discovered using the README of the plugin (example for http plugin).
Declared resource_limits must be positive integers. When a step is executed, if the number of concurrent executions is reached, the µTask Engine will wait for a slot to be released. If the resource is limited to the 0 value, then the step will not be executed and is set to TO_RETRY state, it will be run once the instance allows the execution of its resources. The default time that µTask Engine will wait for a resource to become available is 1 minute, but it can be configured using the resource_acquire_timeout property.
A JSON-schema file is available to validate the syntax of task templates and functions, it's available in files hack/template-schema.json and hack/function-schema.json.
Validation can be performed at writing time if you are using a modern IDE or editor.
- Install official µTask extension.
- Ctrl+P, then type
ext install ovh.vscode-utask
- Ctrl+P, then type
Code snippets are available in this repository to be used for task template editing: hack/templates.code-snippets
To use them inside your repository, copy the templates.code-snippets file into your .vscode workspace folder.
Available snippets:
- template
- variable
- input
- step
µTask is extensible with golang plugins compiled in *.so format. Two kinds of plugins exist:
- action plugins, that you can re-use in your task templates to implement steps
- init plugins, a way to customize the authentication mechanism of the API, and to draw data from different providers of the configstore library
The installation script for utask creates a folder structure that will automatically package and build your code in a docker image, with your plugins ready to be loaded by the main binary at boot time. Create a separate folder for each of your plugins, within either the plugins or the init folders.
Action plugins allow you to extend the kind of work that can be performed during a task. An action plugin has a name, that will be referred to as the action type in a template. It declares a configuration structure, a validation function for the data received from the template as configuration, and an execution function which performs an action based on valid configuration.
Create a new folder within the plugins folder of your utask repo. There, develop a main package that exposes a Plugin variable that implements the TaskPlugin defined in the plugins package:
type TaskPlugin interface {
ValidConfig(baseConfig json.RawMessage, config json.RawMessage) error
Exec(stepName string, baseConfig json.RawMessage, config json.RawMessage, ctx interface{}) (interface{}, interface{}, error)
Context(stepName string) interface{}
PluginName() string
PluginVersion() string
MetadataSchema() json.RawMessage
}The taskplugin package provides helper functions to build a Plugin:
package main
import (
"github.com/ovh/utask/pkg/plugins/taskplugin"
)
var (
Plugin = taskplugin.New("my-plugin", "v0.1", exec,
taskplugin.WithConfig(validConfig, Config{}))
)
type Config struct { ... }
func validConfig(config interface{}) (err error) {
cfg := config.(*Config)
...
return
}
func exec(stepName string, config interface{}, ctx interface{}) (output interface{}, metadata interface{}, err error) {
cfg := config.(*Config)
...
return
}Exec function returns 3 values:
output: an object representing the output of the plugin, that will be usable as{{.step.xxx.output}}in the templating engine.metadata: an object representing the metadata of the plugin, that will be usable as{{.step.xxx.metadata}}in the templating engine.err: an error if the execution of the plugin failed. uTask is based ongithub.com/juju/errorspackage to determine if the returned error is aCLIENT_ERRORor aSERVER_ERROR.
Warning: output and metadata should not be named structures but plain map. Otherwise, you might encounter some inconsistencies in templating as keys could be different before and after marshalling in the database.
Init plugins allow you to customize your instance of µtask by giving you access to its underlying configuration store and its API server.
Create a new folder within the init folder of your utask repo. There, develop a main package that exposes a Plugin variable that implements the InitializerPlugin defined in the plugins package:
type Service struct {
Store *configstore.Store
Server *api.Server
}
type InitializerPlugin interface {
Init(service *Service) error // access configstore and server to customize µTask
Description() string // describe what the initialization plugin does
}As of version v1.0.0, this is meant to give you access to two features:
service.Storeexposes theRegisterProvider(name string, f configstore.Provider)method that allow you to plug different data sources for you configuration, which are not available by default in the main runtimeservice.Serverexposes theWithAuth(authProvider func(*http.Request) (string, error))andWithGroupAuth(groupAuthProvider func(*http.Request) (string, []string, error))methods, where you can provide a custom source of authentication and authorization based on the incoming http requests
If you develop more than one initialization plugin, they will all be loaded in alphabetical order. You might want to provide a default initialization, plus more specific behaviour under certain scenarios.
In order to iterate on feature development, run the utask server plus a backing postgres DB by invoking make run-test-stack-docker in a terminal. Use SIGINT (Ctrl+C) to reboot the server, and SIGQUIT (Ctrl+4) to teardown the server and its DB.
In a separate terminal, rebuild (make re) each time you want to iterate on a code patch, then reboot the server in the terminal where it is running.
To visualize API routes, a swagger-ui interface is available with the docker image, accessible through your browser at http://hostname.example/ui/swagger/.
µTask serves a graphical interface for general use of the tool (dashboard). It is found in the ui folder and has its own Makefile for development purposes.
Run make dev to launch a live-reloading on your machine. The dashboard needs a backing µTask api (see above to run a server).
Run all test suites against an ephemeral postgres DB:
$ make test-dockerYou've developed a new cool feature ? Fixed an annoying bug ? We'll be happy to hear from you! Take a look at CONTRIBUTING.md
The uTask logo is an original artwork under Creative Commons 3.0 license based on a design by Renee French under Creative Commons 3.0 Attributions.
Swagger UI is an open-source software, under Apache 2 license.
For the rest of the code, see LICENSE.
- Contribute: CONTRIBUTING.md
- Report bugs: https://github.com/ovh/utask/issues
- Get latest version: https://github.com/ovh/utask/releases
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