Returns a specification to start this module under a supervisor.

See Supervisor.

Invoked in some cases to retrieve a formatted version of the GenServer status.

This callback can be useful to control the appearance of the status of the GenServer. For example, it can be used to return a compact representation of the GenServer’s state to avoid having large state terms printed.

• one of :sys.get_status/1 or :sys.get_status/2 is invoked to get the status of the GenServer; in such cases, reason is :normal

• the GenServer terminates abnormally and logs an error; in such cases, reason is :terminate

pdict_and_state is a two-elements list [pdict, state] where pdict is a list of {key, value} tuples representing the current process dictionary of the GenServer and state is the current state of the GenServer.

Callback implementation for GenServer.format_status/2.

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 {:ok, state, {:continue, continue}} is similar to {:ok, state} except that immediately after entering the loop the c:handle_continue/2 callback will be invoked with the value continue as first argument.

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 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.