Ejournald is an Erlang interface for systemd's journald. It provides advanced write and read support.

Ejournald consists of two parts: the first part is a NIF for the communication with journald, the second is an Erlang application using it.

First, you have to compile the sources in c_src/ using make. You will need the systemd development header for that. Next you can compile the erlang source in src/.

Execute "tetrapak build". If you use tetrapak, you don't need to compile the sources in c_src/, tetrapak will do this for you.

Execute "rebar compile".

Ejournald is intended to provide logging support for journald. Together with lager and the lager_journald_backend it allows to write structured logs with additional metainformation into systemd's journal. Logging directly with ejournald is also possible (via the NIF-API) but it is recommended to use lager. On top of that ejournald provides:

• an Erlang I/O-server for stream-like logging (without lager)
• a high-level API for retrieving logs (possibly by Erlang specific meta information)

The I/O-server is is not capable of reading the journal. It can be used as an IO device together with the erlang io library. Therefore commands like io:format() or io:write() can be used in a very convenient way to write stuff into the journal without using lager.

To test this setup via simply sending error messages from an erlang shell, do the following: Start ejournald:

application:ensure_all_started(ejournald).

{ok,[ejournald]}

Set the handler for the lager backend:

application:set_env(lager, handlers, [{lager_journald_backend, []}]).

Start lager:

lager:start().

Send an error message (which the backend sends to the journal)

lager:log(error, [{pid, self()}, {module, module}, {function, function}, {line, 0}], "hello world").

Then simply check your journal for the corresponding message:

# journalctl

...

Jan 16 13:16:18 tpiadmin-HP-EliteBook-8470p beam.smp[7481]: hello world

See edocs for more information.