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    dyconf can be used to generate a dynamically updated configuration from a template. It can also launch processes whenever a change is detected.

    dyconf is a tool, not a library. It is best suited to run inside a docker container.

    TL;DR you can find a working sample in consul-haproxy-dyconf.

    How does this compare to consul-template or confd?

    • dyconf is not tied to a specific backend. You can use it with ZooKeeper, etcd, ... or your own REST services.
    • It uses node.js so you have access to npm modules.
    • dyconf uses lodash templates which, if you know JavaScript, might be easier to grok than the golang text templates that are used by confd and consul-template.

    Install from npm

    npm install dyconf -g


    usage: dyconf -config=FILE [OPTIONS]
      -config   path to the template configuration
      -dump     dumps the generated template to the console
      -q        quiet, no logs

    When you launch dyconf you need to specify -config=FILE, all other parameters are passed to the controller.


    The Hjson configuration defines the following settings:

    • controller: path to the JavaScript controller (see below)
    • outputFile: configuration file to write to
    • refreshInterval: refresh interval in seconds unless handled by the controller
    • syslog: set to true to run a syslog server and print to the console (useful with the docker logs command)
    • logFile: path to a logfile to tail and print to the console (similar to syslog above)
    • startup: a shell script to run at startup
    • reload: a shell script to run whenever the configuration changes
    • shutdown: a shell script to run at when the process is terminated
    • template: inline template that will produce the output file

    The controller can define additional settings.

    dyconf uses lodash.template.


    The controller is a JavaScript module that is executed by dyconf.

    All controller functions are passed a context that contains:

    • args: CLI options (object)
    • argv: CLI arguments (array)
    • config: the template configuration
    • log: logging function
    • helpText: the standard help text (to append in init)

    The module needs to export:


    function init(ctx, showHelp)

    init can be used to

    • evaluate commandline arguments,
    • create server connections (if any) or
    • show CLI help if showHelp is set.

    Return true to continue, false to exit.


    function fetchData(ctx)

    Use fetchData to collect data required for the template.

    Return a promise with the data that will be passed to the template.

    start (optional)

    function start(ctx, update)

    Starts the update process. If start is not supplied a fixed interval (refreshInterval) will be used.

    You can use start to watch for changes. Call update to trigger fetchData and to create/refresh the output file.


    The Hello World source is available in the sample folder.


    #hjson (go to for details)
      # define the controller that fetches the configuration and produces the content for outputFile
      controller: controller.js
      outputFile: /tmp/test.txt
      # refresh interval in seconds
      refreshInterval: 5
      # start a syslog server listening on port 514 (use rfc5424)
      # can be used to redirect logs for Docker
      syslog: false
      # logfile to tail to the console (can be "")
      # can be used like syslog for Docker
      logFile: ""
      # run on start/restart
        # prepare, configure files or run any required processes
        # here you would launch the main process (e.g. haproxy)
        # for the sample we only show the outputFile
        cat /tmp/test.txt
      # reload a new configuration
        # here you would tell the main process (e.g. haproxy)
        # to reload it's configuration
        # for the sample we only show the outputFile
        echo ---
        cat /tmp/test.txt
      # run on shutdown
        # here you would kill the main process
      # define the template to generate the outputFile
      `random` was generated by the code in controller.js
        <% [ "World", "Human" ].forEach(name => {
        %>Hello <%=name%>!
        <% }); %>
        In a real world scenario this file would contain the configuration generated by dyconf.
        Today's random value is <%=random%>!


    // if you `require` any libraries you can add them to package.json &
    // run `npm i` in the directory that contains this file.
    var max;
    // init runs at startup to configure options and initialize prerequisites
    function init(ctx, showHelp) {
      var args=ctx.args;
      if (showHelp || ctx.argv.length>0) {
        console.error("usage: -max=#");
        console.error("  -max      max random sample value");
        return false;
      return true;
    // fetchData can be used to query an external service (like consul)
    // it needs to return a data structure that will be used to generate the template
    function fetchData(ctx) {
      return new Promise((resolve, reject) => resolve(Math.random()*max))
        .then(x => ({ random: x }));
    // start the update process (optional)
    // can be used to implement a watch on a service
    function start(ctx, update) {
      setInterval(update, 1000);
      init: init,
      fetchData: fetchData,
      start: start,


    npm i dyconf

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