Avoiding Dynlink and Config Files

One may not want to use a configuration file (because lacking a file-system or so) and/or dynamic linking of plugins (because dynamic-linking can be problematic).

It is possible! This document shows how.

Plugins

Plugins can be compiled to “good old-school” libraries:

tmp_dir=/tmp/with_dummy_plugin
mkdir -p $tmp_dir
cp src/test/dummy_plugin.ml $tmp_dir
ocamlfind opt  -package ketrew -thread -c  $tmp_dir/dummy_plugin.ml -o $tmp_dir/dummy_plugin.cmx

And can be linked-in directly with src/app/main.ml:

cp src/app/main.ml $tmp_dir
ocamlfind opt -package ketrew -thread -linkpkg -I $tmp_dir $tmp_dir/dummy_plugin.cmx $tmp_dir/main.ml -o $tmp_dir/new_ketrew_app
$tmp_dir/new_ketrew_app --help=plain

We can run the plugin user to add a workflow:

cp src/test/dummy_plugin_user.ml $tmp_dir
ocamlfind opt -package ketrew -thread -linkpkg -I $tmp_dir $tmp_dir/dummy_plugin.cmx $tmp_dir/dummy_plugin_user.ml -o $tmp_dir/my_workflow
$tmp_dir/my_workflow "du -sh $HOME"

We can run the workflow (type 'q' when done):

$tmp_dir/new_ketrew_app run loop

And explore to the target, to call the custom query:

$tmp_dir/new_ketrew_app interact

(choose the target, 's' for “show-status”, '1' for “display date”).

Configuration

The function Ketrew_command_line.run_main can take an ~override_configuration parameter, which can be created with Ketrew_configuration.{create,create_server} (c.f. Ketrew_command_line and Ketrew_configuration).

See the example in src/test/preconfigured_main.ml, here is how to compile it:

tmp_dir=/tmp/with_preconfiguration
mkdir -p $tmp_dir
cp src/test/preconfigured_main.ml $tmp_dir
ocamlfind opt -package ketrew -thread -linkpkg $tmp_dir/preconfigured_main.ml -o $tmp_dir/new_ketrew_app
$tmp_dir/new_ketrew_app print-configuration

We can check that no configuration file is read with

export KETREW_CONFIGURATION=/some/unknown/path/that/really/does/not/exist

The “normal” ketrew fails:

ketrew pc

[ketrew: ERROR]
    Error: Exception while reading
    "/some/unknown/path/that/really/does/not/exist":
    Unix.Unix_error(Unix.ENOENT, "open",
    "/some/unknown/path/that/really/does/not/exist")

The new one succeeds:

$tmp_dir/new_ketrew_app print-configuration

[ketrew]
    From user-overriden:
    * Database: "/tmp/somepath"
    * Unix-failure does not turn into target failure
    * Debug-level: 42
    * Client with colors
    * Timeout-upper-bound: 60. seconds
    * Plugins:
        * OCamlfind package: "lwt.react"
        * OCamlfind package: "lwt.unix"
    Server:
        Authorized tokens: Some "/tmp/tokens"
        Listen: TLS:4242 (Certificate: "somecert.pem",
            Key: "somekey.pem")
        Return-error-messages: false

Command Line “Sub-commands”

One can also even add their own sub-commands to the command-line parsing: this is also in the example src/test/preconfigured_main.ml.

Ketrew: Alternative CLI Application

Contents

Menu

Avoiding Dynlink and Config Files

Plugins

Configuration

Command Line “Sub-commands”