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146 lines
5.1 KiB
ReStructuredText
.. _raet:
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==================
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The RAET Transport
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==================
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.. note::
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The RAET transport is in very early development, it is functional but no
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promises are yet made as to its reliability or security.
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As for reliability and security, the encryption used has been audited and
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our tests show that raet is reliable. With this said we are still conducting
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more security audits and pushing the reliability.
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This document outlines the encryption used in RAET
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.. versionadded:: 2014.7.0
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The Reliable Asynchronous Event Transport, or RAET, is an alternative transport
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medium developed specifically with Salt in mind. It has been developed to
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allow queuing to happen up on the application layer and comes with socket
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layer encryption. It also abstracts a great deal of control over the socket
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layer and makes it easy to bubble up errors and exceptions.
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RAET also offers very powerful message routing capabilities, allowing for
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messages to be routed between processes on a single machine all the way up to
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processes on multiple machines. Messages can also be restricted, allowing
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processes to be sent messages of specific types from specific sources
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allowing for trust to be established.
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Using RAET in Salt
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==================
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Using RAET in Salt is easy, the main difference is that the core dependencies
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change, instead of needing pycrypto, M2Crypto, ZeroMQ, and PYZMQ, the packages
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`libsodium`_, libnacl, ioflo, and raet are required. Encryption is handled very cleanly
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by libnacl, while the queueing and flow control is handled by
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ioflo. Distribution packages are forthcoming, but `libsodium`_ can be easily
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installed from source, or many distributions do ship packages for it.
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The libnacl and ioflo packages can be easily installed from pypi, distribution
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packages are in the works.
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Once the new deps are installed the 2014.7 release or higher of Salt needs to
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be installed.
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Once installed, modify the configuration files for the minion and master to
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set the transport to raet:
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``/etc/salt/master``:
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.. code-block:: yaml
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transport: raet
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``/etc/salt/minion``:
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.. code-block:: yaml
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transport: raet
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Now start salt as it would normally be started, the minion will connect to the
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master and share long term keys, which can then in turn be managed via
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salt-key. Remote execution and salt states will function in the same way as
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with Salt over ZeroMQ.
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Limitations
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===========
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The 2014.7 release of RAET is not complete! The Syndic and Multi Master have
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not been completed yet and these are slated for completion in the 2015.5.0
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release.
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Also, Salt-Raet allows for more control over the client but these hooks have
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not been implemented yet, thereforre the client still uses the same system
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as the ZeroMQ client. This means that the extra reliability that RAET exposes
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has not yet been implemented in the CLI client.
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Why?
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====
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Customer and User Request
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-------------------------
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Why make an alternative transport for Salt? There are many reasons, but the
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primary motivation came from customer requests, many large companies came with
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requests to run Salt over an alternative transport, the reasoning was varied,
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from performance and scaling improvements to licensing concerns. These
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customers have partnered with SaltStack to make RAET a reality.
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More Capabilities
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-----------------
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RAET has been designed to allow salt to have greater communication
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capabilities. It has been designed to allow for development into features
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which out ZeroMQ topologies can't match.
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Many of the proposed features are still under development and will be
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announced as they enter proof of concept phases, but these features include
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`salt-fuse` - a filesystem over salt, `salt-vt` - a parallel api driven shell
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over the salt transport and many others.
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RAET Reliability
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================
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RAET is reliable, hence the name (Reliable Asynchronous Event Transport).
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The concern posed by some over RAET reliability is based on the fact that
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RAET uses UDP instead of TCP and UDP does not have built in reliability.
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RAET itself implements the needed reliability layers that are not natively
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present in UDP, this allows RAET to dynamically optimize packet delivery
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in a way that keeps it both reliable and asynchronous.
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RAET and ZeroMQ
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===============
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When using RAET, ZeroMQ is not required. RAET is a complete networking
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replacement. It is noteworthy that RAET is not a ZeroMQ replacement in a
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general sense, the ZeroMQ constructs are not reproduced in RAET, but they are
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instead implemented in such a way that is specific to Salt's needs.
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RAET is primarily an async communication layer over truly async connections,
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defaulting to UDP. ZeroMQ is over TCP and abstracts async constructs within the
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socket layer.
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Salt is not dropping ZeroMQ support and has no immediate plans to do so.
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Encryption
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==========
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RAET uses Dan Bernstein's NACL encryption libraries and `CurveCP`_ handshake.
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The libnacl python binding binds to both `libsodium`_ and tweetnacl to execute
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the underlying cryptography. This allows us to completely rely on an
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externally developed cryptography system.
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Programming Intro
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=================
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.. toctree::
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programming_intro
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.. _libsodium: http://doc.libsodium.org/
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.. _CurveCP: http://curvecp.org/
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