Depo v1.6.0 Depo.DB
A DB is a GenServer that manages an open database connection and a cache of prepared SQL statements.
Summary
Functions
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 theGenServer
; 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 :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 callingSupervisor.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
.