Ketrew: Keep Track of Experimental Workflows
- An OCaml library providing an EDSL API to define complex and convoluted workflows (interdependent steps/programs using a lot of data, with many parameter variations, running on different hosts with various schedulers).
- A client-server application to interact with these workflows. The engine at heart of the server takes care of orchestrating workflows, and keeps track of everything that succeeds, fails, or gets lost.
See also the documentation for various releases.
If you have any questions, you may submit an issue, or join the authors on the public “Slack” channel of the Hammer Lab:
Build & Install
See the specific documentation on building and installing. TL;DR for OCaml hackers:
opam switch 4.03.0 opam install [postgresql] [tls] ketrew
Ketrew is very flexible and hence may seem difficult to understand and setup at first. Let's get a minimal setup ready and a workflow running on it.
alias kdc='./tools/docker-compose/kdc.sh' kdc config --services
Let's get a Ketrew server with a PostgreSQL database and a Coclobas scheduler talking to each other:
kdc up -d
Check that everything is running:
Check the Ketrew server status:
curl http://127.0.0.1:8123/hello || echo 'Not ready'
After a minute or two you can check that everything is setup by visiting the Ketrew UI: http://127.0.0.1:8123/gui?token=nekot:
At any moment you can take everything down with:
Or use other inspection commands:
We can now create a Ketrew client configuration, please choose a directory:
and initialize Ketrew there:
ketrew init --configuration-path $KETREW_ROOT \ --just-client http://127.0.0.1:8123/gui?token=nekot
ketrew submit sub-command can create one-command workflows (uses the
ketrew submit \ --wet-run --tag 1st-workflow --tag command-line \ --daemonize /tmp/KT,'du -sh $HOME'
The job will appear on the WebUI and you can inspect/restart/kill it.
If you don't like Web UI's you can use the text-based UI:
$ ketrew interact [ketrew] Main menu Press a single key: * [q]: Quit * [v]: Toggle verbose * [s]: Display current status * [l]: Loop displaying the status * [k]: Kill targets * [e]: The Target Explorer™
As you can see, just from the command line, you can use
ketrew submit to
launch daemonized tasks. To go further we need to use Ketrew's EDSL.
The EDSL: Defining Workflows
The EDSL is an OCaml library where functions are used to build a workflow
Ketrew.Client.submit_workflow is used to submit that
datastructure to the engine.
A workflow is a graph of “workflow-nodes” (sometimes called “targets”).
There are three kinds of links (edges) between nodes:
depends_on: nodes that need to be ensured or satisfied before a node can start,
on_failure_activate: nodes that will be activated if the node fails, and
on_success_activate: nodes that will be activated only after a node succeeds.
Ketrew.EDSL.workflow_node function documentation for details. Any
OCaml program can use the EDSL (script, compiled, or even inside the
toplevel). See the documentation of the EDSL API (
A Quick Taste
You can run these commands for example in
opam install utop).
Load the Ketrew library to build and submit workflows:
#use "topfind";; #thread;; #require "ketrew";;
Globally tell the Ketrew client to get its configuration from the file created above:
let () = Unix.putenv "KETREW_CONFIGURATION" (Sys.getenv "HOME" ^ "/tmp/kclient-config/configuration.ml");;
Submit an “empty” workflow-node to Ketrew (i.e. a node that does not do nor ensure anything):
let () = let open Ketrew.EDSL in workflow_node without_product ~name:"Mostly Empty Node" |> Ketrew.Client.submit_workflow;;
Submit a node mostly equivalent to the one submitted from the command-line
ketrew submit --daemonize ...):
let () = let open Ketrew.EDSL in workflow_node without_product ~name:"Equivalent to the Command Line one" ~make:( daemonize ~using:`Python_daemon ~host:Host.(parse "/tmp/KT") Program.(sh "du -sh $HOME") ) ~tags:["not-1st-workflow"; "not-command-line"] |> Ketrew.Client.submit_workflow;;
Run a command, in a docker container scheduler by the Coclobas server (also
#require "coclobas.ketrew_backend";; let () = let open Ketrew.EDSL in workflow_node without_product ~name:"Uses a docker image to run some commands" ~make:( (* We use a different “backend”: *) Coclobas_ketrew_backend.Plugin.local_docker_program ~tmp_dir:"/tmp/secotrec-local-shared-temp" ~base_url:"http://coclo:8082" ~image:"ubuntu" Program.( (* sh "sudo mkdir -m 777 -p /cloco-kube/playground" && *) sh "echo User" && sh "whoami" && sh "echo Host" && sh "hostname" && sh "echo Machine" && sh "uname -a" && exec ["sleep"; "42"] ) ) ~tags:["using-coclobas"; "from-utop"] |> Ketrew.Client.submit_workflow;;
The Ketrew WebUI should look like this:
The following script extends the previous examples with the capability to send emails upon the success or failure of your command.
#use "topfind" #thread #require "ketrew" let run_command_with_daemonize ~cmd ~email = let module KEDSL = Ketrew.EDSL in (* Where to run stuff: *) let host = KEDSL.Host.tmp_on_localhost in (* A node that Ketrew will activate after cmd completes, on its success or failure. *) let email_target ~success = let msg_string = if success then "succeeded" else "failed" in let e_program = KEDSL.Program.shf "echo \"'%s' %s\" | mail -s \"Status update\" %s" cmd msg_string email in let e_process = KEDSL.daemonize ~using:`Python_daemon ~host e_program in KEDSL.workflow_node KEDSL.without_product ~name:("email result " ^ msg_string) ~make:e_process in (* The function `KEDSL.workflow_node` creates a node in the workflow graph. The value `KEDSL.without_product` means this node does not “produce” anything, it is like a `.PHONY` target in `make`. *) KEDSL.workflow_node KEDSL.without_product ~name:"daemonized command with email notification" ~make:( (* A “program” is a datastructure representing an “extended shell script”. *) let program = KEDSL.Program.sh cmd in KEDSL.daemonize ~host ~using:`Python_daemon program ) ~edges:[ KEDSL.on_success_activate (email_target true); KEDSL.on_failure_activate (email_target false); ] let () = (* Grab the command line arguments. *) let cmd = Sys.argv.(1) in let email = Sys.argv.(2) in (* Create the workflow with the first argument of the command line: *) let workflow = run_command_with_daemonize ~cmd ~email in (* Then, `Client.submit_workflow` is the only function that “does” something, it submits the constructed workflow to the engine: *) Ketrew.Client.submit_workflow workflow
You can run this script from the shell with
export KETREW_CONFIGURATION=$HOME/kclient-config/configuration.ml ocaml daemonize_workflow.ml 'du -sh $HOME' firstname.lastname@example.org
Checking in with the GUI, we'll have a few new nodes, here is an example of
execution where the daemonized program does not know about the
Where to Go Next
- To write workflows for Ketrew see:
- examples of more and more complicated
- the documentation of the
- examples of more and more complicated workflows:
- To configure Ketrew use the configuration file documentation.
- You may want to “extend” Ketrew with new ways of running “long-running"
computations: see the documentation
on plugins, and the examples in the
Ketrew.Lsfor in the tests:
- You may want to extend Ketrew, or preconfigure it, without configuration files or dynamically loaded libraries: just create your own comand-line app.
- If you are using Ketrew in server mode, you may want to know about the commands that the server can understand as it listens on a Unix-pipe.
- You may want to call out directly to the HTTP API
ketrewas a client).
- If you want to help or simply to understand Ketrew see
the development documentation, and have
a look at the modules like
It's Apache 2.0.