db4de12767
This allows you to specify a custom prefix, or a tmp prefix which is chosen automatically.
14 KiB
#mgmt
##mgmt by James ####Available from: ####https://github.com/purpleidea/mgmt/
####This documentation is available in: Markdown or PDF format.
####Table of Contents
- Overview
- Project description - What the project does
- Setup - Getting started with mgmt
- Features - All things mgmt can do
- Usage/FAQ - Notes on usage and frequently asked questions
- Reference - Detailed reference
- Examples - Example configurations
- Development - Background on module development and reporting bugs
- Authors - Authors and contact information
##Overview
The mgmt tool is a next generation config management prototype. It's not yet
ready for production, but we hope to get there soon. Get involved today!
##Project Description
The mgmt tool is a distributed, event driven, config management tool, that supports parallel execution, and librarification to be used as the management foundation in and for, new and existing software.
For more information, you may like to read some blog posts from the author:
- Next generation config mgmt
- Automatic edges in mgmt
- Automatic grouping in mgmt
- Automatic clustering in mgmt
There is also an introductory video available. Older videos and other material is available.
##Setup
During this prototype phase, the tool can be run out of the source directory.
You'll probably want to use ./run.sh run --file examples/graph1.yaml to
get started. Beware that this can cause data loss. Understand what you're
doing first, or perform these actions in a virtual environment such as the one
provided by Oh-My-Vagrant.
##Features
This section details the numerous features of mgmt and some caveats you might need to be aware of.
###Autoedges
Automatic edges, or AutoEdges, is the mechanism in mgmt by which it will automatically create dependencies for you between resources. For example, since mgmt can discover which files are installed by a package it will automatically ensure that any file resource you declare that matches a file installed by your package resource will only be processed after the package is installed.
####Controlling autoedges
Though autoedges is likely to be very helpful and avoid you having to declare all dependencies explicitly, there are cases where this behaviour is undesirable.
Some distributions allow package installations to automatically start the
service they ship. This can be problematic in the case of packages like MySQL
as there are configuration options that need to be set before MySQL is ever
started for the first time (or you'll need to wipe the data directory). In
order to handle this situation you can disable autoedges per resource and
explicitly declare that you want my.cnf to be written to disk before the
installation of the mysql-server package.
You can disable autoedges for a resource by setting the autoedge key on
the meta attributes of that resource to false.
####Blog post
You can read the introductory blog post about this topic here: https://ttboj.wordpress.com/2016/03/14/automatic-edges-in-mgmt/
###Autogrouping
Automatic grouping or AutoGroup is the mechanism in mgmt by which it will automatically group multiple resource vertices into a single one. This is particularly useful for grouping multiple package resources into a single resource, since the multiple installations can happen together in a single transaction, which saves a lot of time because package resources typically have a large fixed cost to running (downloading and verifying the package repo) and if they are grouped they share this fixed cost. This grouping feature can be used for other use cases too.
You can disable autogrouping for a resource by setting the autogroup key on
the meta attributes of that resource to false.
####Blog post
You can read the introductory blog post about this topic here: https://ttboj.wordpress.com/2016/03/30/automatic-grouping-in-mgmt/
###Automatic clustering
Automatic clustering is a feature by which mgmt automatically builds, scales, and manages the embedded etcd cluster which is compiled into mgmt itself. It is quite helpful for rapidly bootstrapping clusters and avoiding the extra work to setup etcd.
If you prefer to avoid this feature. you can always opt to use an existing etcd
cluster that is managed separately from mgmt by pointing your mgmt agents at it
with the --seeds variable.
####Blog post
You can read the introductory blog post about this topic here: https://ttboj.wordpress.com/2016/06/20/automatic-clustering-in-mgmt/
###Remote ("agent-less") mode
Remote mode is a special mode that lets you kick off mgmt runs on one or more
remote machines which are only accessible via SSH. In this mode the initiating
host connects over SSH, copies over the mgmt binary, opens an SSH tunnel, and
runs the remote program while simultaneously passing the etcd traffic back
through the tunnel so that the initiators etcd cluster can be used to exchange
resource data.
The interesting benefit of this architecture is that multiple hosts which can't connect directly use the initiator to pass the important traffic through to each other. Once the cluster has converged all the remote programs can shutdown leaving no residual agent.
This mode can also be useful for bootstrapping a new host where you'd like to have the service run continuously and as part of an mgmt cluster normally.
####Blog post
An introductory blog post about this topic will follow soon.
##Usage and frequently asked questions (Send your questions as a patch to this FAQ! I'll review it, merge it, and respond by commit with the answer.)
###Why did you start this project?
I wanted a next generation config management solution that didn't have all of the design flaws or limitations that the current generation of tools do, and no tool existed!
###Why did you use etcd? What about consul?
Etcd and consul are both written in golang, which made them the top two contenders for my prototype. Ultimately a choice had to be made, and etcd was chosen, but it was also somewhat arbitrary. If there is available interest, good reasoning, and patches, then we would consider either switching or supporting both, but this is not a high priority at this time.
###Can I use an existing etcd cluster instead of the automatic embedded servers?
Yes, it's possible to use an existing etcd cluster instead of the automatic,
elastic embedded etcd servers. To do so, simply point to the cluster with the
--seeds variable, the same way you would if you were seeding a new member to
an existing mgmt cluster.
The downside to this approach is that you won't benefit from the automatic elastic nature of the embedded etcd servers, and that you're responsible if you accidentally break your etcd cluster, or if you use an unsupported version.
###Did you know that there is a band named MGMT?
I didn't realize this when naming the project, and it is accidental. After much
anguishing, I chose the name because it was short and I thought it was
appropriately descriptive. If you need a less ambiguous search term or phrase,
you can try using mgmtconfig or mgmt config.
###You didn't answer my question, or I have a question!
It's best to ask on IRC to see if someone can help you. Once we get a big enough community going, we'll add a mailing list. If you don't get any response from the above, you can contact me through my technical blog and I'll do my best to help. If you have a good question, please add it as a patch to this documentation. I'll merge your question, and add a patch with the answer!
##Reference Please note that there are a number of undocumented options. For more information on these options, please view the source at: https://github.com/purpleidea/mgmt/. If you feel that a well used option needs documenting here, please patch it!
###Overview of reference
- Graph definition file: Main graph definition file.
- Command line: Command line parameters.
###Graph definition file graph.yaml is the compiled graph definition file. The format is currently undocumented, but by looking through the examples/ you can probably figure out most of it, as it's fairly intuitive.
###Command line
The main interface to the mgmt tool is the command line. For the most recent
documentation, please run mgmt --help.
####--file <graph.yaml>
Point to a graph file to run.
####--converged-timeout <seconds>
Exit if the machine has converged for approximately this many seconds.
####--max-runtime <seconds>
Exit when the agent has run for approximately this many seconds. This is not
generally recommended, but may be useful for users who know what they're doing.
####--noop
Globally force all resources into no-op mode. This also disables the export to
etcd functionality, but does not disable resource collection, however all
resources that are collected will have their individual noop settings set.
####--remote <graph.yaml>
Point to a graph file to run on the remote host specified within. This parameter
can be used multiple times if you'd like to remotely run on multiple hosts in
parallel.
####--prefix <path>
Specify a path to a custom working directory prefix. This directory will get
created if it does not exist. This usually defaults to /var/lib/mgmt/. This
can't be combined with the --tmp-prefix option. It can be combined with the
--allow-tmp-prefix option.
####--tmp-prefix
If this option is specified, a temporary prefix will be used instead of the
default prefix. This can't be combined with the --prefix option.
####--allow-tmp-prefix
If this option is specified, we will attempt to fall back to a temporary prefix
if the primary prefix couldn't be created. This is useful for avoiding failures
in environments where the primary prefix may or may not be available, but you'd
like to try. The canonical example is when running mgmt with --remote there
might be a cached copy of the binary in the primary prefix, but in case there's
no binary available continue working in a temporary directory to avoid failure.
##Examples For example configurations, please consult the examples/ directory in the git source repository. It is available from:
https://github.com/purpleidea/mgmt/tree/master/examples
Systemd:
See misc/mgmt.service for a sample systemd unit file.
This unit file is part of the RPM.
To specify your custom options for mgmt on a systemd distro:
sudo mkdir -p /etc/systemd/system/mgmt.service.d/
cat > /etc/systemd/system/mgmt.service.d/env.conf <<EOF
# Environment variables:
MGMT_SEEDS=http://127.0.0.1:2379
MGMT_CONVERGED_TIMEOUT=-1
MGMT_MAX_RUNTIME=0
# Other CLI options if necessary.
#OPTS="--max-runtime=0"
EOF
sudo systemctl daemon-reload
##Development
This is a project that I started in my free time in 2013. Development is driven by all of our collective patches! Dive right in, and start hacking! Please contact me if you'd like to invite me to speak about this at your event.
You can follow along on my technical blog.
To report any bugs, please file a ticket at: https://github.com/purpleidea/mgmt/issues.
##Authors
Copyright (C) 2013-2016+ James Shubin and the project contributors
Please see the AUTHORS file for more information.