Bryan Hunt (binarytemple) binarytemple-external

Erlang and Named Pipes

The intention of this post is to provide a solution (with examples) to a somewhat uncommon issue in Erlang. I hate searching for answers to the same problems over and over, and I had a hard time finding answers to this particular problem, so I wrote it all down once I figured it out. If one day you decide to read and write data through fifo's (named pipes) and then decide you want to read or write the other end of the pipe from Erlang, this post is for you.

The Problem

I wanted to read and write to a fifo from a C/C++ app and have an Erlang app communicate over the other end of that fifo. Put simply, Erlang doesn't really support what I was trying to do. You cannot just file:open/2 a fifo, or any special device for that matter, in Erlang and expect it to work. This is documented in Erlang's FAQ.

The Solution! ... ???

Put

API

Starting: https://github.com/basho/riak_kv/blob/1.4.2/src/riak_kv_wm_object.erl#L619
We create a new riak_object and populate the various fields with the headers, metadata supplied by the client.
Big suprise, we eventually call riak_client:put: https://github.com/basho/riak_kv/blob/1.4.2/src/riak_client.erl#L143
If/when the client returns any errors these are handled in handle_common_errors and it is nice to return human readable errors to client :)

Riak_client

API

###HTTP

Entry point for all object operations: https://github.com/basho/riak_kv/blob/1.4.2/src/riak_kv_wm_object.erl

delete_resource/2 takes RequestData(Request header, ex: vclock) and Context(Record containing: Bucket, Key, Client): https://github.com/basho/riak_kv/blob/1.4.2/src/riak_kv_wm_object.erl#L888

	defmodule GCM.Pusher do
	use GenStage
	# The maximum number of requests Firebase allows at once per XMPP connection
	@max_demand 100

	defstruct [
	:producer,
	:producer_from,
	:fcm_conn_pid,
	:pending_requests,

	defmodule GCM.PushCollector do
	use GenStage

	# Client

	def push(pid, push_requests) do
	GenServer.cast(pid, {:push, push_requests})
	end

	# Server

	ERLFLAGS= -pa $(CURDIR)/.eunit -pa $(CURDIR)/ebin -pa $(CURDIR)/deps/*/ebin

	PROJECT_PLT=$(CURDIR)/.project_plt

	# =============================================================================
	# Verify that the programs we need to run are installed on this system
	# =============================================================================
	ERL = $(shell which erl)

	ifeq ($(ERL),)

	(add-to-list 'load-path (file-truename "<PATH>/projmake-mode"))
	(require 'projmake-mode)
	(defun projmake-mode-hook ()
	(projmake-mode)
	(projmake-search-load-project))

	(add-hook 'erlang-mode-hook 'projmake-mode-hook)

	{erl_opts, [debug_info, {parse_transform, lager_transform}]}.

	{deps, [
	{pbkdf2, {git, "git://github.com/marianoguerra/erlang-pbkdf2-no-history", {branch, "master"}}},
	{exometer_core, {git, "git://github.com/basho/exometer_core.git", {branch, "th/correct-dependencies"}}},
	{riak_core, {git, "git://github.com/basho/riak_core", {branch, "develop"}}}
	]}.

	{relx, [{release, { ricor , "0.1.0"},
	[ricor,

	This is unsupported by Basho, but you can build Basho's flavor of Erlang and Riak on Raspberry Pis.

	#!/bin/bash

	sudo kextunload -b com.apple.iokit.BroadcomBluetoothHostControllerUSBTransport
	sudo kextload -b com.apple.iokit.BroadcomBluetoothHostControllerUSBTransport