跨不同流程使用Elixir ETS

我试图围绕ETS实现一个非常简单的示例，但没有取得多大成功。我想让多个

worker

进程写入ETS表，然后让一个（不同的）读卡器进程定期检索值作为总和。我似乎无法在没有崩溃的情况下插入到表中，而读取器在执行时返回零…这是我的代码，非常感谢收到的任何帮助：

主管

模块：

defmodule Stackex do
  use Application

  @noOfWriters 1

  def start(_type, _args) do
    import Supervisor.Spec, warn: false

    Stackex.Reader.start_link
    Stackex.Table.start_link

    opts = [strategy: :one_for_one, name: Stackex.Supervisor]

    children =
      for i <- 1..@noOfWriters do
        worker(Stackex.Writer, [i], id: i)
      end

    Supervisor.start_link(children, opts)

  end
end

defmodule Stackex.Writer do
  use GenServer

  def start_link(id) do
    GenServer.start_link(__MODULE__,{id})
  end

  def init({id}) do
    state = %{writer_id: id, value: value}
    schedule_work()
    {:ok, state}
  end

  def handle_info(:update, state) do
    Stackex.Table.add_kvp(state)
    update = %{writer_id: state.writer_id, value: value}
    schedule_work()
    {:noreply, update}
  end

  defp value do
    :random.seed(:erlang.now())
    :random.uniform(10) 
  end

  defp schedule_work() do
    Process.send_after(self, :update, 1000)
  end
end

defmodule Stackex.Table do
  use GenServer

  def start_link do
    GenServer.start_link(__MODULE__,[], name: __MODULE__)
  end

  def init do
    {:ok, :ets.new(:table, [:set, :named_table])}
  end

  #Client API
  def add_kvp(update) do
    GenServer.cast __MODULE__, {:load, update}
  end

  def get_kvp_sum do
    GenServer.call __MODULE__, {:sum}
  end

  ###### Server Callback Functions ########

  def handle_cast({:load, update}, state) do
    %{writer_id: key, value: value} = update
    {:noreply, :ets.insert(:table, {key, value})}
  end

  #Return total system load
  def handle_call({:sum}, _from, state) do
    sum = :ets.foldl(fn({{_,v}, acc}) -> v + acc end, 0, :table)
    {:reply, sum, state}
  end
end

defmodule Stackex.Reader do
  use GenServer

  def start_link do
    GenServer.start_link(__MODULE__, [], name: __MODULE__)
  end

  def init do
    schedule_update
    {:ok, nil}
  end

  def handle_info(:update) do
    sum = Stackex.Table.get_kvp_sum
    IO.puts("Sum #{sum}")

    schedule_update
    {:noreply, nil}
  end

  defp schedule_update do
    Process.send_after(self, :update, 2000)
  end
end

表

模块：

defmodule Stackex do
  use Application

  @noOfWriters 1

  def start(_type, _args) do
    import Supervisor.Spec, warn: false

    Stackex.Reader.start_link
    Stackex.Table.start_link

    opts = [strategy: :one_for_one, name: Stackex.Supervisor]

    children =
      for i <- 1..@noOfWriters do
        worker(Stackex.Writer, [i], id: i)
      end

    Supervisor.start_link(children, opts)

  end
end

defmodule Stackex.Writer do
  use GenServer

  def start_link(id) do
    GenServer.start_link(__MODULE__,{id})
  end

  def init({id}) do
    state = %{writer_id: id, value: value}
    schedule_work()
    {:ok, state}
  end

  def handle_info(:update, state) do
    Stackex.Table.add_kvp(state)
    update = %{writer_id: state.writer_id, value: value}
    schedule_work()
    {:noreply, update}
  end

  defp value do
    :random.seed(:erlang.now())
    :random.uniform(10) 
  end

  defp schedule_work() do
    Process.send_after(self, :update, 1000)
  end
end

defmodule Stackex.Table do
  use GenServer

  def start_link do
    GenServer.start_link(__MODULE__,[], name: __MODULE__)
  end

  def init do
    {:ok, :ets.new(:table, [:set, :named_table])}
  end

  #Client API
  def add_kvp(update) do
    GenServer.cast __MODULE__, {:load, update}
  end

  def get_kvp_sum do
    GenServer.call __MODULE__, {:sum}
  end

  ###### Server Callback Functions ########

  def handle_cast({:load, update}, state) do
    %{writer_id: key, value: value} = update
    {:noreply, :ets.insert(:table, {key, value})}
  end

  #Return total system load
  def handle_call({:sum}, _from, state) do
    sum = :ets.foldl(fn({{_,v}, acc}) -> v + acc end, 0, :table)
    {:reply, sum, state}
  end
end

defmodule Stackex.Reader do
  use GenServer

  def start_link do
    GenServer.start_link(__MODULE__, [], name: __MODULE__)
  end

  def init do
    schedule_update
    {:ok, nil}
  end

  def handle_info(:update) do
    sum = Stackex.Table.get_kvp_sum
    IO.puts("Sum #{sum}")

    schedule_update
    {:noreply, nil}
  end

  defp schedule_update do
    Process.send_after(self, :update, 2000)
  end
end

读卡器

模块：

defmodule Stackex do
  use Application

  @noOfWriters 1

  def start(_type, _args) do
    import Supervisor.Spec, warn: false

    Stackex.Reader.start_link
    Stackex.Table.start_link

    opts = [strategy: :one_for_one, name: Stackex.Supervisor]

    children =
      for i <- 1..@noOfWriters do
        worker(Stackex.Writer, [i], id: i)
      end

    Supervisor.start_link(children, opts)

  end
end

defmodule Stackex.Writer do
  use GenServer

  def start_link(id) do
    GenServer.start_link(__MODULE__,{id})
  end

  def init({id}) do
    state = %{writer_id: id, value: value}
    schedule_work()
    {:ok, state}
  end

  def handle_info(:update, state) do
    Stackex.Table.add_kvp(state)
    update = %{writer_id: state.writer_id, value: value}
    schedule_work()
    {:noreply, update}
  end

  defp value do
    :random.seed(:erlang.now())
    :random.uniform(10) 
  end

  defp schedule_work() do
    Process.send_after(self, :update, 1000)
  end
end

defmodule Stackex.Table do
  use GenServer

  def start_link do
    GenServer.start_link(__MODULE__,[], name: __MODULE__)
  end

  def init do
    {:ok, :ets.new(:table, [:set, :named_table])}
  end

  #Client API
  def add_kvp(update) do
    GenServer.cast __MODULE__, {:load, update}
  end

  def get_kvp_sum do
    GenServer.call __MODULE__, {:sum}
  end

  ###### Server Callback Functions ########

  def handle_cast({:load, update}, state) do
    %{writer_id: key, value: value} = update
    {:noreply, :ets.insert(:table, {key, value})}
  end

  #Return total system load
  def handle_call({:sum}, _from, state) do
    sum = :ets.foldl(fn({{_,v}, acc}) -> v + acc end, 0, :table)
    {:reply, sum, state}
  end
end

defmodule Stackex.Reader do
  use GenServer

  def start_link do
    GenServer.start_link(__MODULE__, [], name: __MODULE__)
  end

  def init do
    schedule_update
    {:ok, nil}
  end

  def handle_info(:update) do
    sum = Stackex.Table.get_kvp_sum
    IO.puts("Sum #{sum}")

    schedule_update
    {:noreply, nil}
  end

  defp schedule_update do
    Process.send_after(self, :update, 2000)
  end
end

---

在回答标题中的问题时，当您调用

：ets.new/2

但是根据您发布的代码，您没有多个进程访问您的表。只有一个

Stackex.Table

genserver已启动。看起来您甚至不需要它是一个

：命名的_表

，因为您只需在

状态

变量中传递pid，而对代码的更改很少

看起来您的直接问题是您将错误的变量传递给了

add_kvp

方法（

state

而不是

update

）