Rabbitmq (#277)

* some stuff about rabbitmq

* recept for ipsec with PSK

* spelling

* links to AMQP some notes on plugins

* major rewrite

* further work

* config and installation notes

* learn to spell, better indentation, better line lenght

* better language

* moving to a different branch

* better refs

* added link to slideshares

* removed some redundant links to rabbitmq

* fixed some typos

application_components_201.rst

@@ -1,11 +1,114 @@
 Application Components 201
 **************************
 
+Message Queue Systems
+======================
+In a distributed system a Message Queue Systems can provide a basic infrastructure to higher level functions like
+
+ * decoupling processes or hosts from each other
+ * parallel processes execution
+ * distribute events and information like changes to data, entries from logfiles and statistics for monitoring and notification
+ * data-streaming and file-transfers to multiple hosts via multicast and unicast
+ * replace polling mechanism with an event orientated system
+ * network wide accessible job queues
+ * message rerouting on failure / escalation schemes
+ * verification of results ( best of three )
+ * asynchronous remote procedure calls
+ * network wide mutex
+ * network or distributed system wide message bus
+
+Message Queue Systems are more like peer2peer networks then client-server applications.
+They can be split up into message brokers and routers or brokerless message queuing systems. [0MQ]_
+A message as understood by the system is everything that can be represented as a bytestream.
+Properties like type and timestamp may are added to message. [Bok]_
+
+.. [Bok] http://sardes.inrialpes.fr/papers/files/Bouchenak08a.pdf
+.. [0MQ] https://en.wikipedia.org/wiki/%C3%98MQ
+
+
+Further Readings
+----------------
+
+ * http://c2.com/cgi/wiki?MessageQueuingArchitectures
+ * https://en.wikipedia.org/wiki/Message-oriented_middleware and https://en.wikipedia.org/wiki/Message_oriented_middleware
+ * https://en.wikipedia.org/wiki/Queueing_theory
+ * https://en.wikipedia.org/wiki/Message_queue
+ * http://www.slideshare.net/mwillbanks/art-of-message-queues
+
 Message Brokers
 ===============
+Message brokers represent a message queue systems that relies on a central system to route messages to its destination.
+Messages are send to exchanges and received from queues.
+Queues resists on the broker, also some protocols implement a client site queue for multipart transactions and prefetching.
+Message Brokers tend to become a critical system in an otherwise distributed environment.
+
 
 RabbitMQ
 --------
+RabbitMQ_ is an open source Message Broker written in erlang.
+Its queuing protocol is the Advance Message Queuing Protocol. [wiki]_  [specs]_ 
+It provides plugins for different queuing protocols like STOMP and advanced setups.
+Installations scale from single host as an applicationmessagebus, to multi cluster installations in different networks.
+Messages are send to different type of exchanges.
+While Direct, Fanout, Topic and Header Exchanges are part of the core system, others plugins are rooted in the community. 
+No prior understanding of the erlang programming language is needed to setup, configure and operate the message broker.
+The documentation on the projects homepage reads a fair amount of different configurations with explanations.
+
+To setup a cluster a minimum of two nodes is required.
+All nodes of a cluster must be in the same IP network segment.
+It is possible to send huge messages via AMQP to a RabbitMQ node.
+The maximum message size is limited by the amount of available RAM on the node.
+Depending on the durability of a message and the policy of queues, the messages are synchronized to other nodes.
+A disc-node ensures a message is stored to a disc before delivering.
+Memory based nodes provide a much higher message throughput.
+To establish an encrypted communication between nodes, IPSec or TLS can be used.
+Authentication is possible via an internal database, LDAP, SASL and PKI client certificates.
+With a PKI in place consumers and publisher can share the same authorization.
+No preshared password among all processes is needed, but different private keys are mandatory.
+This is accomplished by using the commonname of the dn in the x509 client certificate as username.
+Different applications can be separated by the concept of virtual hosts in a similar way the Apache web server does.
+Configuration is provided by webGUI or commandline tools.
+Programming libraries and tools for a wide range of environments are available.
+
+The installation from the Debian repository leads to a configuration with a single host.
+Similar installation instructions are provided for Windows, Solaris and other operation systems.
+
+.. code-block:: bash
+
+  curl 'https://www.rabbitmq.com/rabbitmq-signing-key-public.asc' | sudo apt-key add -
+  echo 'deb http://www.rabbitmq.com/debian/ testing main' | sudo tee /etc/sources.d/rabbitmq.list
+  sudo apt-get update
+  sudo apt-get upgrade
+  sudo apt-get install rabbitmq-server
+
+To backup and restore configuration data the management plugin should be configured.
+
+.. code-block:: none
+
+  { rabbitmq_management, [
+      {  listener, [ { port, 15672 },
+                     { ssl, true },
+                     { ssl_opts, [ { cacertfile, "/etc/ssl/certs/cacert.crt" },
+                                   { certfile,   "/etc/ssl/certs/node1.crt" },
+                                   { keyfile,    "/etc/ssl/private/node1.key" } ]}
+                   ]} // configured listener
+  ]} // configured rabbitmq_management
+  ]. // EOC
+
+.. code-block:: console
+
+  rabbitmqadmin export rabbit.config
+  rabbitmqadmin -q import rabbit.config
+
+Show a detailed report about queues, users and connections
+
+.. code-block:: console
+
+  rabbitmqctl report
+
+.. _RabbitMQ: https://www.rabbitmq.com
+.. [wiki] https://en.wikipedia.org/wiki/AMQP
+.. [specs] http://www.amqp.org/resources/download
 
 Apache ActiveMQ
 ---------------