CODEWITHSUNDEEP
elixirphoenix-frameworkgen-server
Cashmere
Cashmere

Reputation: 11

Genserver Phoenix Issue

I am getting data from an endpoint as a list, assume they are unique id's I attempt to start a GenServer process for each of them but the processes are terminated as soon they are started but the error is unclear, I cant seem to find what is killing the process, here is my sample code below and error trying to debug. NB ("I can however start a process with a single transaction", also when I call Enum. each() with the id's and attempt to start the GenServer in the command line it works successfully ). what exactly is happening when the list comes from an endpoint because the can be printed clearly and the processes started successfully but they are terminated immediately also?.

def new(conn, %{"hashes" => [_ | _] = hashes}) do
    # Enum.each the list of hashes call hash fn on each hash
    # needs more debugging the function is glitching "some processes failing"
    hashes
    |>Enum.each(fn hash ->  call_hash(conn,hash) end)  #research more queing calls?
  end


  defp call_hash(conn,hash) do
    with {:ok, _} <- GenServer.start_link(TransactionSubscriptionHandler, %{hash: 
  String.to_atom(hash)}, name: String.to_atom(hash))
        #  {:ok, %{status: 200}} <- BlockNative.subscribe_transaction(hash)
         do
         json(conn,%{status: "Ok"})
        else
     _ -> conn |> put_status(400) |> json(%{status: "Failed"})
  end

  end

input

"hashes": [
        "0x04b08ab13d51613975cd5035cebb52d5f574137c42902a5b1147f953f1895c6a",
        "0x2285dfeafe2eae5846fe66bd9631f2d258c1d5b32702649153c9073a3a4ec8ad"
    ]

output from the command line

[info] POST /api/transaction
[debug] Processing with VhsWeb.TransactionController.new/2
  Parameters: %{"hashes" => ["0x04b08ab13d51613975cd5035cebb52d5f574137c42902a5b1147f953f1895c6a", "0x2285dfeafe2eae5846fe66bd9631f2d258c1d5b32702649153c9073a3a4ec8ad"]}
  Pipelines: [:api]
{:ok, #PID<0.597.0>}
[info] Sent 200 in 2ms
{:ok, #PID<0.598.0>}
[info] Sent 200 in 2ms
[error] Ranch listener VhsWeb.Endpoint.HTTP had connection process started with :cowboy_clear:start_link/4 at #PID<0.594.0> exit with reason: {:function_clause, [{:cowboy_http, :commands, [{:state, #PID<0.471.0>, VhsWeb.Endpoint.HTTP, #Port<0.22>, :ranch_tcp, :undefined, %{env: %{dispatch: [{:_, [], [{:_, [], Phoenix.Endpoint.Cowboy2Handler, {VhsWeb.Endpoint, []}}]}]}, stream_handlers: [:cowboy_telemetry_h, :cowboy_stream_h]}, "", %{}, {{127, 0, 0, 1}, 34624}, {{127, 0, 0, 1}, 4000}, :undefined, #Reference<0.3145460136.2965635073.81437>, 2, {:ps_request_line, 0}, :infinity, 1, :done, 100, [{:stream, 1, {:cowboy_telemetry_h, {:state, {:cowboy_stream_h, {:state, :undefined, VhsWeb.Endpoint.HTTP, #PID<0.595.0>, :undefined, :undefined, :undefined, :undefined, 0, :fin, "", 180, :undefined, ...}}, #Function<0.122385210/1 in :cowboy_telemetry_h."-fun.metrics_callback/1-">, :undefined, %{body_length: 180, cert: :undefined, has_body: true, headers: %{"accept" => "*/*", "accept-encoding" => "gzip, deflate, br", "connection" => "keep-alive", "content-length" => "180", "content-type" => "application/json", "host" => "localhost:4000", "postman-token" => "ad48096e-c775-4f82-a860-a4d4b4286c9c", "user-agent" => "PostmanRuntime/7.26.8"}, host: "localhost", method: "POST", path: "/api/transaction", peer: {{127, 0, 0, ...}, 34624}, pid: #PID<0.594.0>, port: 4000, qs: "", ref: VhsWeb.Endpoint.HTTP, ...}, "200 OK", %{"cache-control" => "max-age=0, private, must-revalidate", "content-length" => "15", "content-type" => "application/json; charset=utf-8", "date" => "Mon, 03 May 2021 20:41:43 GMT", "server" => "Cowboy", "x-request-id" => "FnupLbYol1vbVZsAAABE"}, VhsWeb.Endpoint.HTTP, -576460686234141769, :undefined, -576460686234115433, -576460686234115433, -576460686203746015, -576460686203746015, %{#PID<0.595.0> => %{spawn: -576460686234129902}}, [], 180, ...}}, "POST", :"HTTP/1.1", :undefined, :undefined, 0, []}], [{:child, #PID<0.595.0>, 1, 5000, :undefined}]}, 1, [{:response, "200 OK", %{"cache-control" => "max-age=0, private, must-revalidate", "content-length" => "15", "content-type" => "application/json; charset=utf-8", "date" => "Mon, 03 May 2021 20:41:43 GMT", "server" => "Cowboy", "x-request-id" => "FnupLbYol1vbVZsAAABE"}, ["{\"", [[] | "status"], "\":", [34, [[] | "Ok"], 34], 125]}]], [file: '/home/edwin/dev/phoenix-projects/vhs/deps/cowboy/src/cowboy_http.erl', line: 922]}, {:cowboy_http, :loop, 1, [file: '/home/edwin/dev/phoenix-projects/vhs/deps/cowboy/src/cowboy_http.erl', line: 231]}, {:proc_lib, :init_p_do_apply, 3, [file: 'proc_lib.erl', line: 226]}]}

Upvotes: 1

Views: 274

Answers (1)

Aleksei Matiushkin
Aleksei Matiushkin

Reputation: 121010

Many processes have nothing to do with the issue. Here is the simplified code that would raise the same error.

def new(conn, _),
  do: ["1", "2"] |> Enum.each(&call_hash(conn, &1))

defp call_hash(conn, _) do
  json(conn, %{status: "Ok"})
end

That said, you are trying to send many responses to the single POST request, which obviously fails, because conn gets terminated after the first one response is sent.

Upvotes: 1

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