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CrawlerExample.Queue do | |
use GenServer | |
#client | |
def start_link(opts \\ []) do | |
GenServer.start_link(__MODULE__, nil, opts) | |
end | |
def load_from_file(file_path) do | |
GenServer.cast(__MODULE__, {:load_state_from_disk, file_path}) | |
end | |
def push(url) when is_binary(url) do | |
GenServer.cast(__MODULE__, {:push, [url, 0]}) | |
end | |
def push(url, depth) when is_binary(url) and is_integer(depth) do | |
GenServer.cast(__MODULE__, {:push, [url, depth]}) | |
end | |
def pop() do | |
GenServer.call(__MODULE__, :pop) | |
end | |
#server | |
@impl true | |
def init(_init_arg) do | |
schedule_write_to_disk(5000) | |
{:ok, :queue.new} | |
end | |
@impl true | |
def handle_info(:schedule_write_to_disk, state) do | |
current_state = :queue.to_list(state) | |
state_json = Poison.encode!(current_state) | |
File.write("/tmp/crawler_state.json", state_json) | |
schedule_write_to_disk(interval) | |
end | |
@impl true | |
def handle_cast({:load_state_from_disk, file_path}, _) do | |
contents = File.read!(file_path) | |
from_json = Poison.decode!(contents) | |
{:noreply, :queue.from_list(from_json)} | |
end | |
def handle_cast({:push, [url, depth]}, state) do | |
new_state = :queue.in(state, [url, depth]) | |
{:noreply, new_state} | |
end | |
@impl true | |
def handle_call(:pop, _, state) do | |
{val, new_queue} = :queue.out(state) | |
{:reply, val, new_queue} | |
end | |
defp schedule_write_to_disk(interval), do: :erlang.send_after(interval, self(), :schedule_write_to_disk) | |
end |
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