Mistral/DSLv1

Mistral DSL specification
Version 0.1 (NOT SUPPORTED SINCE April 2015)

Main objects

 * Namespace
 * Action
 * Workflow
 * Task
 * Trigger

Namespaces
Contains a list of namespaces grouping custom (ad-hoc) actions. For example, it's possible to create namespace "Nova" that would provide actions "createVM", "deleteVM" and similar for VM management in OpenStack.

Attributes
All attributes are inside main keys of Namespaces - namespaces names. Attributes of an individual namespace are:
 * class - currently Mistral supports the following action classes out of the box: std.http, std.mistral_http, std.echo, std.email, std.ssh, this is an optional attribute
 * base-parameters - dictionary depending on type of the namespace, this parameter is optional. Values of these parameters apply to all actions inside the namespace. For example for std.http it can contain url, method, body and headers.
 * actions - list of actions provided by this namespace.

YAML example:
Namespaces: Nova: class: std.http base-parameters: method: GET actions: create-vm: ......      delete-vm: .....

Action
A function provided by specific namespace.

Attributes

 * name - action name (string without space, mandatory attribute).
 * base-parameters - dictionary whose structure is defined by action class (or namespace class if defined). For std.http class it contains url, method, body and headers according to HTTP protocol specification.
 * parameters - list containing parameter names which should or could be specified in task. This attribute is optional and used only for documenting purposes.
 * output - dictionary-transformer for action output to send this output next to task. Keys of this dictionary will be included in task result, values are pure YAQL or inline YAQL expressions per key which define how the specific output should be retrieved from raw output (from action). See more about YAQL at https://pypi.python.org/pypi/yaql/0.3

YAML example:
create-vm: base-parameters: url: servers parameters: - name - server_name output: vm_id: $.content.server.id

Attributes

 * tasks - list of tasks in this workflow, each task represents a computational step in the workflow.

YAML example:
Workflow: tasks: create-vms: .....     attache-volumes: .....

Task
Represents a step in workflow, for example creating the VM

Attributes

 * action - name of action to perform
 * requires - list of tasks which should be execute before this tasks, or list of task names as a keys and condition as a value, this is optional parameter
 * parameters - actual parameters for the task, each value can be either some number, string etc, or YAQL expression to retrieve value from task context
 * on-success - task which will be scheduled on execution after current task has finished with state 'SUCCESS'
 * on-error - task which will be scheduled on execution after current task has finished with state 'ERROR'
 * on-finish - task which will be scheduled on execution after current task has finished

YAML example:
create-vm: action: Nova.create-vm parameters: image_id: $.image_id flavor_id: 42 requires: task2: '$.value2 = 123' task4: '$.value4 = 122' on-success: task3

Triggers
Using triggers it is possible to run workflows according to specific rules: periodically setting a cron (http://en.wikipedia.org/wiki/Cron) pattern or on external events like ceilometer alarm.

Attributes

 * type - can be PERIODIC, CEILOMETER_ALARM
 * tasks - list of tasks which should be execute on trigger
 * parameters - list of task parameters

YAML example:
triggers: backup-vm: type: periodic tasks: [create_backup, delete_old_backup] parameters: cron-pattern: 1 0 * * *

This example requires the following properties provided in execution context:

 * 1) - nova_url  ## url to Nova service, e.g. http://0.0.0.0:8774/v3
 * 2) - server_name ## Name you want to give to new instance
 * 3) - image_id  ## image id from Glance service
 * 4) - flavor_id ## flavor id - type of instance hardware
 * 5) - ssh_username ## username of your VM
 * 6) - ssh_password ## password to your VM
 * 7) - admin_email ## email address to send notifications to
 * 8) - from_email ## email address to send notifications from
 * 9) - smtp_server ## SMTP server to use for sending emails (e.g. smtp.gmail.com:587)
 * 10) - smtp_password ## password to connect to SMTP server

Namespaces: Nova: # Nova actions for creating VM, retrieving IP and VM deleting. class: std.http actions: createVM: base-parameters: url: '{$.nova_url}/{$.project_id}/servers' method: POST headers: X-Auth-Token: $.auth_token Content-Type: application/json body: server: name: $.server_name imageRef: $.image_id flavorRef: $.flavor_id output: vm_id: $.content.server.id     getIP: base-parameters: url: '{$.nova_url}/{$.project_id}/servers/{$.vm_id}' method: GET headers: X-Auth-Token: $.auth_token output: vm_ip: "$.content.server.addresses.novanetwork.where($.'OS-EXT-IPS:type' = 'floating')[0].addr" deleteVM: base-parameters: url: '{$.nova_url}/{$.project_id}/servers/{$.vm_id}' method: DELETE headers: X-Auth-Token: $.auth_token output: status: $.status Server: actions: # HTTP request to the server. calcSumm: class: std.http base-parameters: url: 'http://{$.vm_ip}:5000/summ' method: POST body: arguments: $.arguments output: summ_result: $.content.result Ssh: class: std.ssh base-parameters: host: $.vm_ip username: $.username password: $.password actions: # Simple SSH command. waitSSH: base-parameters: cmd: 'ls -l' # SSH command to run the server. runServer: base-parameters: cmd: 'nohup python ~/web_app.py > web_app.log &' Workflow: tasks: # Create a VM (request to Nova). createVM: action: Nova.createVM parameters: server_name: $.server_name image_id: $.image_id flavor_id: $.flavor_id nova_url: $.nova_url project_id: $.project_id auth_token: $.auth_token publish: vm_id: vm_id on-success: waitForIP on-error: sendCreateVMError # Wait till the VM is assigned with IP address (request to Nova). waitForIP: action: Nova.getIP retry: count: 10 delay: 10 publish: vm_ip: vm_ip parameters: nova_url: $.nova_url project_id: $.project_id auth_token: $.auth_token vm_id: $.vm_id on-success: waitSSH on-error: sendCreateVMError # Wait till operating system on the VM is up (SSH command). waitSSH: action: Ssh.waitSSH retry: count: 10 delay: 10 parameters: username: $.ssh_username password: $.ssh_password vm_ip: $.vm_ip on-success: runServer on-error: sendCreateVMError # When SSH is up, we are able to run the server on VM (SSH command). runServer: action: Ssh.runServer parameters: vm_ip: $.vm_ip username: $.ssh_username password: $.ssh_password on-success: calcSumm on-error: sendCreateVMError # Send HTTP request on server and calc the result. calcSumm: action: Server.calcSumm retry: count: 10 delay: 1 parameters: arguments: - 32         - 45          - 23        vm_ip: $.vm_ip publish: result: summ_result on-finish: sendResultEmail # In case of createVM error send e-mail with error message. sendResultEmail: action: std.email parameters: params: to: [$.admin_email] subject: Workflow result body: | Workflow result of execution {$.__execution.id} is {$.result} -- Thanks, Mistral Team. settings: smtp_server: $.smtp_server from: $.from_email password: $.smtp_password on-finish: deleteVM # In case of createVM error send e-mail with error message. sendCreateVMError: action: std.email parameters: params: to: [$.admin_email] subject: Workflow error body: | Failed to create a VM in execution {$.__execution.id} -- Thanks, Mistral Team. settings: smtp_server: $.smtp_server from: $.from_email password: $.smtp_password on-finish: deleteVM # Destroy the VM (request to Nova). deleteVM: action: Nova.deleteVM parameters: nova_url: $.nova_url project_id: $.project_id auth_token: $.auth_token vm_id: $.vm_id

Initial execution context
{   "nova_url": , "image_id": , "flavor_id": , "server_name": , "ssh_username": , "ssh_password": , "admin_email": , "from_email": , "smtp_server": , "smtp_password": , }

When a workflow starts Mistral also adds execution information into the context so the context looks like the following:

{   "nova_url": TBD, "image_id": TBD, "image_id": , "flavor_id": , "server_name": , "ssh_username": , "ssh_password": , "admin_email": , "from_email": <from_email>, "smtp_server": <smtp_server>, "smtp_password": <smtp_password>, "__execution": { "id": "234234", "workbook_name" : "my_workbook", "project_id": "ghfgsdfasdfasdf" "auth_token": "sdfljsdfsdf-234234234", "trust_id": "oiretoilkjsdfglkjsdfglkjsdfg" } }