nerves_runtime v0.6.2 Nerves.Runtime.LogTailer

Collects operating system-level messages from /dev/log and /proc/kmsg, forwarding them to Logger with an appropriate level to match the syslog priority parsed out of the message.

You can disable this feature (e.g. for testing) by configuring the following option:

# config.exs
config :nerves_runtime, enable_syslog: false

Link to this section Summary

Functions

Returns a specification to start this module under a supervisor

Invoked when the server is started. start_link/3 or start/3 will block until it returns

Parse out the syslog facility, severity, and message (including the timestamp and host) from a syslog-formatted string

type must be :syslog or :kmsg to indicate which log to tail with this process. They’re managed by separate processes, both to isolate failures and to simplify the handling of messages being sent back from the ports

Link to this section Types

Link to this type type()
type() :: :syslog | :kmsg

Link to this section Functions

Link to this function child_spec(arg)

Returns a specification to start this module under a supervisor.

See Supervisor.

Link to this function init(map)
init(%{type: :syslog | :kmsg, enabled: boolean()}) ::
  {:ok, %{type: atom(), port: port(), buffer: binary()}} | :ignore

Invoked when the server is started. start_link/3 or start/3 will block until it returns.

args is the argument term (second argument) passed to start_link/3.

Returning {:ok, state} will cause start_link/3 to return {:ok, pid} and the process to enter its loop.

Returning {:ok, state, timeout} is similar to {:ok, state} except handle_info(:timeout, state) will be called after timeout milliseconds if no messages are received within the timeout.

Returning {:ok, state, :hibernate} is similar to {:ok, state} except the process is hibernated before entering the loop. See c:handle_call/3 for more information on hibernation.

Returning :ignore will cause start_link/3 to return :ignore and the process will exit normally without entering the loop or calling c:terminate/2. If used when part of a supervision tree the parent supervisor will not fail to start nor immediately try to restart the GenServer. The remainder of the supervision tree will be (re)started and so the GenServer should not be required by other processes. It can be started later with Supervisor.restart_child/2 as the child specification is saved in the parent supervisor. The main use cases for this are:

  • The GenServer is disabled by configuration but might be enabled later.
  • An error occurred and it will be handled by a different mechanism than the Supervisor. Likely this approach involves calling Supervisor.restart_child/2 after a delay to attempt a restart.

Returning {:stop, reason} will cause start_link/3 to return {:error, reason} and the process to exit with reason reason without entering the loop or calling c:terminate/2.

Callback implementation for GenServer.init/1.

Link to this function parse_syslog_message(data)
parse_syslog_message(binary()) ::
  %{facility: atom(), severity: atom(), message: binary()}
  | {:error, :not_syslog_format}

Parse out the syslog facility, severity, and message (including the timestamp and host) from a syslog-formatted string.

Link to this function start_link(type)
start_link(:syslog | :kmsg) :: {:ok, pid()}

type must be :syslog or :kmsg to indicate which log to tail with this process. They’re managed by separate processes, both to isolate failures and to simplify the handling of messages being sent back from the ports.