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Elixir Z-Wave library
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lib/grizzly/zipgateway/sapi_monitor.ex
defmodule Grizzly.ZIPGateway.SAPIMonitor do
@moduledoc false
use GenServer
alias Grizzly.StatusReporter
@type option ::
{:period, pos_integer()}
| {:threshold, pos_integer()}
| {:status_reporter, (StatusReporter.serial_api_status() -> :ok) | {module(), atom()}}
| {:name, GenServer.name()}
# There must be THRESHOLD retransmissions within the last PERIOD milliseconds for
# the SAPI status to be considered unresponsive. This prevents occasional SAPI
# blips from accumulating and causing a false positive unresponsive status.
@default_period :timer.seconds(30)
@default_threshold 5
@spec retransmission(GenServer.name()) :: :ok
def retransmission(name \\ __MODULE__) do
GenServer.call(name, :retransmission)
end
@spec status(GenServer.name()) :: StatusReporter.serial_api_status()
def status(name \\ __MODULE__) do
GenServer.call(name, :status)
end
@spec reset(GenServer.name()) :: :ok
def reset(name \\ __MODULE__) do
GenServer.call(name, :reset)
end
@spec start_link([option()]) :: GenServer.on_start()
def start_link(opts \\ []) do
name = Keyword.get(opts, :name, __MODULE__)
default_period = Application.get_env(:grizzly, :sapi_monitor_period, @default_period)
default_threshold = Application.get_env(:grizzly, :sapi_monitor_threshold, @default_threshold)
period = Keyword.get(opts, :period, default_period)
threshold = Keyword.get(opts, :threshold, default_threshold)
status_reporter = Keyword.get(opts, :status_reporter)
GenServer.start_link(
__MODULE__,
[period: period, threshold: threshold, status_reporter: status_reporter],
name: name
)
end
@impl GenServer
def init(opts) do
period = Keyword.fetch!(opts, :period)
threshold = Keyword.fetch!(opts, :threshold)
status_reporter = Keyword.get(opts, :status_reporter)
state = %{
period: period,
threshold: threshold,
status_reporter: status_reporter,
retransmissions: [],
status: :ok,
check_timer: nil
}
notify_status_reporter(status_reporter, :ok)
{:ok, state}
end
@impl GenServer
def handle_call(:retransmission, _from, state) do
state = %{
state
| retransmissions: [System.monotonic_time(:millisecond) | state.retransmissions]
}
{:reply, :ok, update(state)}
end
def handle_call(:status, _from, state) do
state = update(state)
{:reply, state.status, state}
end
def handle_call(:reset, _from, state) do
state = %{state | retransmissions: []}
{:reply, :ok, update(state)}
end
@impl GenServer
def handle_info(:check, state) do
{:noreply, update(state)}
end
defp update(state) do
state = %{state | retransmissions: drop_old(state.retransmissions, state.period)}
if length(state.retransmissions) >= state.threshold do
state
|> set_status(:unresponsive)
|> clear_timer()
|> schedule_check()
else
set_status(state, :ok)
end
end
defp set_status(state, new_status) do
maybe_notify_status_reporter(state, new_status)
%{state | status: new_status}
end
defp clear_timer(state) do
case state.check_timer do
nil ->
state
check_timer ->
_ = Process.cancel_timer(check_timer, info: false)
%{state | check_timer: nil}
end
end
defp schedule_check(state) do
# If there are any retransmissions in the current state, set a new timer to
# check again in PERIOD + 10 milliseconds
ref = Process.send_after(self(), :check, state.period + 10)
%{state | check_timer: ref}
end
# If status has not changed, do not notify
defp maybe_notify_status_reporter(%{status: status}, status), do: :ok
defp maybe_notify_status_reporter(state, new_status) do
notify_status_reporter(state.status_reporter, new_status)
end
defp notify_status_reporter(status_reporter, status) do
cond do
is_function(status_reporter, 1) ->
status_reporter.(status)
is_atom(status_reporter) and
function_exported?(status_reporter, :serial_api_status, 1) ->
status_reporter.serial_api_status(status)
true ->
:ok
end
:ok
end
# Drop retransmissions older than PERIOD milliseconds
defp drop_old(retransmissions, period) do
Enum.reject(retransmissions, fn timestamp ->
System.monotonic_time(:millisecond) - timestamp > period
end)
end
end