erlang.paris Meetup / June 29th 2015, Paris / André Graf (@der_graf)

VerneMQ - A distributed MQTT message broker developed in Erlang

Intro

- André Graf, Co-Founder at Erl.io (2012)- Programming in Erlang since 2008- Basel Switzerland

@der_graf

Simple Publish/Subscribe protocol over TCP/IP that utilizes

a centralized message broker

MQTT

Different use cases…

MQTT

https://www.flickr.com/mmmavocado/

https://www.flickr.com/photos/christianhaugen

https://www.flickr.com/photos/janitors

Different use cases… ...but similar requirements.

MQTT

constrained devices in constrained environments

MQTT

| different QoS Levels | small header sizes (min 2B)| durable sessions| last will testament

MQTT

Some MQTT Facts

- Current Spec Version 3.1.1- open OASIS Standard since 2014- Invented 1998 at IBM and Arcom

VerneMQ Architecture from a bird’s eye perspective

Erlang VM

ninenines/ranch

ninenines/cowboy

vmq_server

vmq_plugin

helium/eleveldb

helium/plumtree

uwiger/jobsvmq_commonsfeuerlabs/exometer_core

vmq_passwd

vmq_acl

vmq_bridge

vmq_systree

vmq_snmp

vmq_graphite

larshesel/vmq_elixir

erlio/vernemq release project

basho/nodepackage

basho/cuttlefish

basho/clique

rebar/rebar3

vmq_reg_trie<<gen_server>>

3 processes / MQTT connection

vmq_server

vmq_session<<gen_fsm>>

vmq_ranch<<ranch_protocol>>

vmq_queue<<gen_fsm>>start_link start_link

vmq_reg<<gen_server>>

vmq_reg_sup<<supervisor>>

vmq_reg_trie<<gen_server>>

monitor

ETSETS

vmq_reg_trie<<gen_server>>

vmq_server

vmq_session<<gen_fsm>>

vmq_ranch<<ranch_protocol>> sync

vmq_reg<<gen_server>>

vmq_reg_sup<<supervisor>>

vmq_reg_trie<<gen_server>>

ETS

vmq_session<<gen_fsm>>

vmq_ranch<<ranch_protocol>>

vmq_queue<<gen_fsm>>async batch/async

matchfold

MQTT publish example

TCP Conn Client A

TCP Conn Client BETS

PUB/a/b/c

SUB/a/b/+

Clustering VerneMQ

Distribution

What is ACTIVELY distributed?

| Subscriber Data

| Online Messages

| Cluster Status Information

| ...

Distribution

What is NOT distributed?

| offline messages (future)

Distributing Subscriber Data

- Initially using Mnesia- Move to Plumtree/LevelDB

Paradigm Shift:

Consistent -> eventual Consistent

Distributing online Messages

- Initially over Erlang Distribution layer- Move to own communication layer

- buffering in case of ‘nodedown’s- batching requests for higher throughput

Extending VerneMQ

erlio/vmq_plugin

%% iterates over all Plugins serving the Hook 'HookName'

vmq_plugin:all(HookName :: atom(), HookArgs :: [any()]).

%% iterates over all Plugins serving the Hook 'HookName'

%% until one returns 'ok' | {'ok', any()}

vmq_plugin:all_till_ok(HookName :: atom(), HookArgs :: [any()]).

%% calls the top priority Plugin that serves the Hook 'HookName'

vmq_plugin:only(HookName :: atom(), HookArgs :: [any()]).

erlio/vmq_plugin

%% enabling an OTP Application Pluginvmq_plugin_mgr:enable_plugin(Application :: atom()).

%% in Application.app.src{env, [

{vmq_plugin_hooks, [

{HookName, Module, Function, Arity, []}

...

]}

]}

erlio/vmq_plugin

Available Hooks:

- auth_on_register/5- auth_on_publish/6- auth_on_subscribe/3- on_register/3- on_publish/6- on_subscribe/3- on_deliver/6 (planned)

erlio/vmq_plugin

Available Hooks:

- msg_store_write_sync/2- msg_store_write_async/2- msg_store_delete_sync/1- msg_store_delete_async/1- msg_store_fold/2- msg_store_read/1

erlio/vmq_plugin

Checkout vmq_plugin and the Demo Plugin App

https://github.com/erlio/vmq_plugin

https://github.com/dergraf/vernemq_demo_plugin

To Sum Up

- MQTT is a great Protocol for various use cases (monitoring/metering/mobile/..)

- VerneMQ brings scalability and powerful extensibility to the MQTT world.

- Erl.io provides support and development services for VerneMQ

http://verne.mq | http://erl.io@der_graf | @vernemq | @erlio_basel

Merci Beaucoup!Je suis content de répondre a vos questions.

References

https://verne.mq

http://mqtt.org

https://github.com/erlio/vernemq

https://github.com/erlio/vmq_plugin

https://github.com/dergraf/vernemq_demo_plugin

https://github.com/helium/plumtree

http://asc.di.fct.unl.pt/~jleitao/pdf/srds07-leitao.pdf

https://groups.google.com/forum/#!topic/mqtt/c1dlCdA5eOc