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How to use Erlang releases with Kazoo

Kazoo is bundled and shipped as an Erlang release. This means Erlang/OTP's and Kazoo's code are mixed together under _rel/, thus creating a standalone Kazoo.

relx builds the release using

  • rel/relx.config.script (this file in fact generates rel/relx.config)
  • rel/vm.args has all the BEAM VM arguments used for running the release
  • rel/sys.config (or /etc/kazoo/app.config when present) which defines environment values for Erlang apps.

Information on Erlang releases and live-updates:

Makefile commands

All the following commands have to be run from the root directory of the Kazoo repository.

Build the release

make build-release

Creates rel/relx.config, the file Relx uses then to generate the release under _rel.

This folder contains two binaries under _rel/kazoo/bin: kazoo and kazoo-$VSN. These are the exact same binary.

Node types

The release can be spawned as either one of the following node types:

  • ecallmgr: when booting, the VM will start the ecallmgr application and its dependencies
  • kazoo_apps: when booting, the VM will start the kazoo_apps application and its dependencies

Once booted, the node listens to its assigned ports, writes to the system logs, does everything Kazoo did when it wasn't a release. Releases add no scoping nor sandboxing capabilities.

REL is the Makefile variable that stipulates the node type of the starting release. It defaults to kazoo_apps and is used as if calling erl with -name option set to $(REL)@$(hostname).

Start a node

Once built, start a release in "attached mode":

make release

Which is equivalent to

ACT=console REL=kazoo_apps make release

There are different ways to start/stop a release (set the Makefile ACT variable accordingly):

  • console (default value): starts a node killable with ^G q
  • start: creates a pipe that can be connected to later with the command attach
  • attach: show the REPL of a start-ed node
  • stop
  • foreground

For local development you will likely use console. In production you will want start or foreground.

The Erlang VM calls fsync on every line of output in start mode, so foreground might be better for your use cases.

To open a console with a node started with foreground, use remote_console.

Service a production node

If the ecallmgr died, this would start another VM:

REL=ecallmgr ACT=start  make release

When troubleshooting, this attaches a REPL to the running faulty ecallmgr node:

REL=ecallmgr ACT=attach make release

This gracefully stops an ecallmgr node:

REL=ecallmgr ACT=stop   make release

Read a release's cookie from Kazoo's configuration

REL=kazoo_apps make read-release-cookie

This hits /etc/kazoo/config.ini or the file at $KAZOO_CONFIG and reads the cookie value for release REL.

Note: the release does not even need to be started!