Extendable command line utility for sysadmins
An extendable utility with plugins for doing everything with self-defined hosts/hostgroups, utilizing API of your environment, with parallel ssh out of the box.
Destroying all your databases at once has never been this simple!
swk pssh ^mysql 'sudo rm -rf /var/lib/mysql'
(yeah, you really shouldn’t do that in production environment. Unless you’re angry and desperate.)
If you’re using swk older than v0.0.4a13, please update to the latest version. There’s a whole lot of bugfixes every week, as development’s in progress, thus I’ve included auto check for updates function. It runs once a day when you run swk, and outputs to stderr if newer version is available. You can turn it off by setting ‘check_for_updates’ to anything but ‘yes’ in swk.ini .
What can it do?
The basic idea is: you specify what to do (a command), a list of hosts or hostgroups to do that with, and additional arguments if needed (depends on what you want to do). You can easily define your own commands through the plugin interface, as well as your own hostgroup parsers (usually they’ll just ask some API in your environment about which hosts are included in provided hostgroup). Basic Foreman, Zabbix API and ssh functions are supported out of the box.
Please note that this is not fabric (though it uses paramiko, both are marvellous pieces of software), and this is not pssh (it uses its own way of parallelling ssh sessions, and its own output handling). This utility is designed to work in small environments and perform ad-hoc operations, it’s very easy to use (not harder than shell) and to configure, it has no learning curve, and it provides a way to execute quick-and-dirty commands on a lot of hosts at hand. You may think of it as of a version of ansible -a that requires very little effort to get usable in your infrastructure (writing parsers to get advantage of tools dividing your hosts to hostgroups) or no effort at all if you happen to use Foreman, Zabbix or third-party host grouping tools.
pip install swk
If you need plugins for casp, Foreman or Zabbix, also run
pip install swk-casp pip install swk-foreman pip install swk-zabbix
Upon first execution `swk`` will create ~/.swk directory, where you should find swk.ini configuration file, and that’s used to store shell mode command history, program’s log, various plugins’ cache, etc.
Please note that you should use python3.3+ for shell mode to work. Everything else should work with python2.7.6+. You probably may have to update pip and setuptools (pip install --upgrade pip setuptools). You also may have to do all of these with sudo, or fall into your virtualenv if you use one.
Typical usage looks like
swk pssh "%hostgroup1[ [-]^hostgroup2 .. host1 [-]host2]" uptime
which executes uptime on all the hosts over ssh in parallel fashion.
%, ^ and other non-alphabetical characters are treated as hostgroup modifiers which indicate which parser should expand a given hostgroup into a host list. hyphen (-) in front of hostgroup or a host means that hostgroup or host will be excluded from resulting list. A host may be a simple regex (no * quantificator or anychar (.), no lookahead/lookbehinds), swk will generate strings that match it and use it as hosts. If you’re excluding hosts that aren’t included yet, nothing happens. Hostlist is expanded from left to right. Example:
swk pssh "^g1 -host" echo Yay
will execute echo Yay in parallel fashion on each host that’s in zabbix hostgroup g1 except hosts host1, host2, host3 and host4.
Available and bundled plugins
From the box, swk supports: - running commands over ssh (ssh and pssh commands), copying files over ssh to multiple hosts (dist command, recursive and without preserving times by default), copying files from multiple hosts over ssh (gather) - and just displaying results of hostlist expansion (dr for ‘dry-run’)
By installing additional packages named swk-<plugin_name>, you also get - expanding zabbix hostgroups (^ modifier), listing, adding and removing maintenance periods in Zabbix (lsmntnce, addmntnce and rmmntnce commands) - expanding casp hostgroups (% modifier), special ALL hostgroup expanding to all the hosts - getting and setting hosts environments in Foreman (getenv and setenv commands), getting, adding and removing classes linked to hosts and hostgroups (getcls, addcls, rmcls, getgcls, addgcls, rmgcls respectively), searching hosts and hostgroups based on given criteria (srch and srchg), listing available classes (lscls) and describing hosts (desc).
To install them, please refer to Installation section above. Also, please read Usage notes below before using.
Don’t forget to make changes to your swk.ini before using plugins (credentials/urls and such).
Hopefully, there are more plugins coming.
Imagine that you need to grep all your frontend nginx logs for string ‘/api/do_something’. Your frontend hostnames are frontend00, frontend01, …, frontend99. You could use something like
swk pssh frontend[0-9][0-9] grep '/api/do_something' /var/log/nginx/access.log
You can interrupt the command execution at any moment with Ctrl-C.
Suppose your servers are named a bit more sophisticated, like frontend01, frontend02, …, frontend25. This command would do the trick (note the quotes around host expression):
swk pssh 'frontend([0-1][0-9]|2[0-5]) -frontend00' grep '/api/do_something' /var/log/nginx/access.log
You can always verify if you did the host expression right:
swk dr 'frontend([0-1][0-9]|2[0-5]) -frontend00'
frontend01 frontend02 <...skipped...> frontend24 frontend25
Suppose you also have servers backend01, backend02, …, backend10, and you want to run uptime on both frontends and backends. Try this one:
swk pssh 'frontend([0-1][0-9]|2[0-5]) -frontend00 backend(0[1-9]|10)' uptime
Now imagine you have to execute a certain script named test.sh on those 25 frontends locally. First, copy it to target hosts:
swk dist 'frontend([0-1][0-9]|2[0-5]) -frontend00' ./my_scripts/test.sh /usr/share/
and then execute it:
swk pssh 'frontend([0-1][0-9]|2[0-5]) -frontend00' /usr/share/test.sh
Imagine you need to do something with nginx logs locally on your computer (say, a simple statistics calculation). You can gather all the logs to your machine with one command:
swk gather 'frontend([0-1][0-9]|2[0-5]) -frontend00' /var/log/nginx/access.log ./nginx-logs-from-production
This will create ‘nginx-logs-from-production’ directory in your current working directory, and copy over all the access.log files, appending a suffix so you can tell from which host each log has been copied.
Say you have a Zabbix installation in your environment, and all the frontends are in ‘frontend’ hostgroup. You can do the same as above using zabbix hostgroup expansion (note that zabbix module is disabled by default. More on that in Available plugins section above)
swk gather ^frontend /var/log/nginx/access.log ./nginx-logs-from-production
You probably already have some cli tools for finding hosts falling under some search criteria. Suppose you have a tool that’s called my_awesome_tool which returns some hostnames on call, like this:
$ my_awesome_tool host1 host2 host3
If you want to use your tools as a source for hostlists for swk, you can achieve this in two ways:
swk pssh "`my_awesome_tool`" uptime
my_awesome_tool | swk pssh - uptime
where - instead of host expression indicates that swk reads from stdin.
Imagine that you have Foreman installation and you need to set all the frontends’ environments to ‘development’ (note that you still use ^ here, so host expansion mechanism works with Zabbix hostgroups)
swk setenv ^frontend development
…or add to frontend Foreman hostgroup your brand new nginx::verbose_access_logs Puppet class
swk addgcls frontend nginx::verbose_access_logs
Note: if you have several Foreman hostgroups named the same, but different hierarchically (for example, debian/mysql and mysql), getgcls, addgcls and rmgcls will work with the first group returned by Foreman API.
You can also get description on an existing host:
swk desc myhost
[myhost.example_domain.com]: Hostgroup: mysql OS: Debian 7.9 IP: 192.168.1.1 Resource: myhypervisor Env: production Comment: my favorite host!
Or search hosts by a given criteria (Foreman doesn’t support everything for a search criterias). There are several short keywords for convenience now: hg for hostgroup, cls for class, env for environment and os for OS family (Debian, RedHat etc). Specifying several implies AND logic:
swk srch cls=my_awesome_puppet_class
This way you can combine swk invocations in something really fun like
swk pssh "`swk srch cls=my_awesome_puppet_class`" reboot
Remember to use and escape quotes when needed!
swk pssh ^mysql mysql -e 'show variables like "read_only"' won’t work (due to shell quote processing, it represents mysql -e show variables like "read only"), but
swk pssh ^mysql "mysql -e 'show variables like \"read_only\"'" will.
You can get more info on available parsers, commands and arguments by running swk -h .
If you need to change your default SSH user, parallel processes count, API credentials or such, take a look at swk.ini file located at ~/.swk .
If you run swk without any arguments, it starts in shell mode. Like this:
trueneu$ swk swk>
You can do absolutely all the same like in command line mode, but in shell mode you don’t need to think about quote escaping in tricky commands, because the arguments are treated literally even if not quoted.
For example, that ugly mysql example above would look like this in shell mode:
swk> pssh ^mysql mysql -e 'show variables like "read_only"'
Additionally, you may call any system utility from inside swk shell via sys command or even omit sys:
swk> pssh ^mysql mysql -e 'show variables like "%format%"' | grep innodb
It also supports history through hist command, etc. To get help on any command, issue help <command> or help without arguments to get an overview.
Please note that shell mode doesn’t support backticks yet, so if you need to feed a hostlist to swk from somewhere, you should use stdin approach:
swk> srch cls=my_awesome_class | pssh - reboot
Commands, hostgroup modifiers and parsers code are defined through swk plugins. They can be connected to the main program in three ways: being included in main package under swk/plugins dir, having a defined swk_plugin entry point in their setup.py and installed or just being put in one of plugins_directories dir from swk.ini file.
You can find some working plugins there mentioned above, as well as dummy examples in swk_plugins_examples . Further help can be found in swk.classes, which you MUST import when defining your own command and/or parser modules.
For example, if you use Nagios in your environment, you can create a parser that will expand a Nagios hostgroup into a hostlist, or a command that will take a Nagios hostgroup and do something with it using Nagios API (say, downtime it or something). Information that’s used for modules to work (such as authentication information for various APIs) may (and should) be stored in config named swk.ini.
Shell mode parsing details
When in shell mode, every argument starting with the third to the end of the line is passed literally even if not quoted, backslashes being escaped, and then it’s shlexed down to a list respectful to quotes. It sounds a little bit confusing at first, but it has its benefits. You do not need to escape backslash character, and you don’t need the outer level of quoting when ssh`ing this way.
Please note that these rules work only for swk commands. Everything else is passed as you’d expect.
Trade-offs: - you may have to implement your own argument parsing in command plugins for them to work correctly (using a whitespace or something else as a delimiter). - you have to escape chaining/io redirection characters for those to be passed as arguments to commmand instead of work locally. For example, ssh remote echo ABC > file creates file on local machine, but ssh remote echo ABC \> file does the same on remote.
Why did I do this and why you may need this?
I did it simply because there was no such instruments in my environment, and I needed them from time to time. As a side note, I hate GUIs and web interfaces for everything that shouldn’t be necessary visualized (like UML or statistic charts). And I just can’t accept that I need to make 10 mouse clicks to change a host’s environment in Foreman when I know hostname and environment name exactly. So swiss-knife is a simple instrument to make simple operations and its functionality can be extended rather easily.
There’s a few possible reasons you’ll find it useful: - You are a system administrator. If you’re not, it’s doubtfully can be useful for you in any way - You hate clicking GUIs just like me, and your GUI instrument(s) has an API you could use - There’s no such an instrument in your environment: it’s either de-centralized and/or you don’t use configuration management software and its tools heavily - You’d like to glue altogether all the stuff you use in your environment to classify or group hosts and you know a little bit of python
Known issues and notes
As this is an alpha version under development, author wouldn’t recommend to think of swk as of a reliable tool suitable for running important, potentially destructive tasks. i.e. restarting/reinstalling important services, seding mission critical configs, etc. Always double-check command’s result on one host before applying it to whole production, use dr command.
No compatibility with future versions is guaranteed yet.
casp is a nice piece of software written by my former colleague Stan E. Putrya. It’s not yet released to opensource, but I’m sure it will eventually.
swk uses a small part of yolk3k package by Rob Cakebread (sources can be found on github, distribution on pypi) to handle self-update noticing mechanics. You can turn new version checking off by modifying swk.ini parameter ‘check_for_updates’ to anything but ‘yes’.
It should work on python2.7.6+, python3.3+.
currently, host cannot start with non-alphanumerical character. This breaks using something like (host|hos)123 as a host expression as left bracket will be treated as a hostgroup modifier.
ssh module needs a running ssh-agent with private keys added, or private keys need to remain password free
username for ssh specified in swk.ini will override your current username and username from .ssh/config if present
Ctrl-C works poorly when pssh’ing (providing you unneeded tracebacks from multiprocessing)
interactive user input is NOT supported when running a command
if you have several Foreman hostgroups named the same, but different hierarchically (for example, debian/mysql and mysql), getgcls, addgcls and rmgcls will work with the first group returned by Foreman API.
using dist and gather commands has a little trick: if you want the name expansion to be done at the remote side instead of local by your shell when not in swk shell mode, quote it.
Foreman srch routines may work not as you expect, because swk relies completely on Foreman’s API. For example, swk srch cls!=myclass won’t give neither any useful results nor error, but this is how API is designed. To check if your query really works, try it in the web interface first.
if a parser doesn’t return any hosts, its job is considered failed and desired command doesn’t start
all the information needed to run a command is added to class attributes, more info on that in swk_classes
all the information you’ve mentioned in config is also added to class attributes. Section must be named the same as the class that is being configured for this to work; [Main] section is for swk program
in order to be supported in update checker, your package should have a version.py file with __version__ string determining package version.
for swk-casp plugin: requests
for swk-zabbix plugin: pyzabbix
for swk-foreman plugin: python-foreman
Please do! Don’t forget to exclude sensitive details from swk.ini, if any.
Pavel “trueneu” Gurkov, 2016
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