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Process supervision shell for daemontools, perp, s6 and runit

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// repository documentation

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# NAME

svsh - Process supervision shell for daemontools/perp/s6/runit

# SYNOPSIS

svsh \[OPTIONS\]

Options:

--basedir=BASEDIR (-d)   Service directory (on which supervisor was started).
    --suite=SUITE     (-s)   Supervision suite managing the directory (perp, s6 or runit).
    --bindir=BINDIR   (-b)   Directory where the supervisor is installed (e.g. /usr/sbin). Optional.
    --collapse        (-c)   Collapse numbered services into one line.

Example:

svsh --suite perp --basedir /etc/services
    svsh --suite runit --basedir /var/services restart nginx

# DESCRIPTION

![screenshot](https://ido50.github.io/Svsh/screenshot.png)

`svsh` is a command line shell for process supervision suites of the [daemontools](http://cr.yp.to/daemontools.html) family. Currently, it supports
daemontools, [perp](http://b0llix.net/perp/), [s6](http://www.skarnet.org/software/s6/index.html)
and [runit](http://smarden.org/runit/). It provides a unified interface allowing easy inspection
and manipulation of services (i.e. processes) managed by supported supervision suites.

`svsh` does not require any configurations or changes to your suite's service directories;
just point it at a base directory and you immediately get a usable shell, listing all
services and their statuses, and accepting commands to perform on them.

The shell provides a very simple syntax that is easy to remember, far simpler than the
particular syntax of the underlying supervision suite. Instead of having to execute
`perpctl -b /services q nginx` to restart an `nginx` service running from `/services/nginx`,
just execute `restart nginx`. Couldn't be simpler. Want to send a `HUP` signal to all
services whose names begin with `"worker"`? just execute `signal hup worker*`.

`svsh` is inspired by [supervisord](http://www.supervisord.org/)'s `supervisorctl` shell. I've
attempted to provide a similar syntax and feature set.

# OPTIONS

## -s, --suite

The supervision suite managing the base directory. Either `daemontools`, `perp`,
`s6` or `runit`. If not provided, the `SVSH_SUITE` environment variable will
be checked. An error will be raised if no suite is defined.

## -d, --basedir

Base directory of services supervised by the supervision suite. If not provided,
the `SVSH_BASE` environment variable will be checked, and if not set, the default
base directory of the selected suite will be used. Check the documentation of
the specific suite class for its default directory. If no directory is found,
an error will be raised.

## -b, --bindir

If the supervision suite's tools are not in the environment `PATH` variable,
you can provide the directory where they are located (e.g. `/usr/local/bin`).

## -c, --collapse

Collapse multi-process services to one line in `status`. See ["COLLAPSE"](#collapse)
for more details. This can be changed from inside the shell too.

# COMMANDS

The following commands are provided by `svsh`. Note that some suites do not
support all commands.

## status

Prints a list of all services, their statuses (up, down, etc.), uptimes (or
downtimes) and process IDs. This command is automatically executed upon
initialization of the shell.

## start service, ...

Starts a list of one or more services, if they are not already up.

svsh> start nginx haproxy

## stop service, ...

Stops a list of one or more services. The services stopped will not be restarted.

svsh> stop nginx haproxy

## restart service, ...

Restarts a list of one or more services. Generally, this means sending a QUIT signal
to the services, which _should_ cause them to shutdown and be restarted by the
supervisor.

svsh> restart nginx haproxy

## signal sig service, ...

Send a UNIX signal to a list of one or more services. The name of the signal can
be lowercase or uppercase, and may include the prefix `"SIG"`.

svsh> signal term nginx
        svsh> signal SIGUSR1 haproxy

## rescan

_Alias: update_.

Causes the supervision suite to rescan the base directory for new or removed services.

## fg service

"Moves" a service to the foreground, so that its output streams (at least standard output,
possibly standard error) are printed on screen. In reality, it determines where the process'
log file is located, and tails it with `tail -f`. See ["LOG INSPECTION"](#log-inspection) for more details, as this
is a complicated subject.

svsh> fg nginx

## terminate

_Alias: shutdown_.

Terminate the supervision suite. This will cause all services managed by the supervisor to
terminate as well.

## toggle option

Toggles a shell option on or off. Currently, only the `collapse` option is supported. The
`status` command will be automatically called after toggling the option.

svsh> toggle collapse

## help \[ command \]

Prints help information. Can also provide information about specific commands.

svsh> help signal

## quit

_Alias: exit_.

Quits the shell.

# ADVANCED FEATURES AND IMPORTANT INFORMATION

## LOG INSPECTION

All of the supported supervision suites do not enforce a logging scheme on managed
services. While all of them provide a logging tool (`daemontools` provides `multilog`,
`perp` provides `tinylog` and `sissylog`; `s6` provides `s6-log`; `runit`
provides `svlogd`), none of them enforce their usage. It is actually not uncommon
among users of these suites to use a logging tool provided by one suite for services
managed by another one. This means it is hard for an external program such as `svsh`
to determine where log files are stored, if at all.

Currently, `svsh` will attempt to find the log file of a service by checking the
pid of the associated log process, and if (and only if) that process is one of the
supported loggers (`multilog`, `tinylog`, `s6-log` or `svlogd`), it will try to find the
file descriptor used by that process under `/proc/<pid>/fd`. As long as your services
are being logged by one of these tools, `svsh` _should_ be able to `tail` their log
files  when the [fg](#fg-service) command is used. However, if the log file is being rotated
while it is being tailed, behavior is currently undefined (will probably stop working until
the command is run again).

## HISTORY

`svsh` provides bash-like history so you can use your up arrow key to cycle back through
past commands, or use `Ctrl+R` to search your history. The history file is saved under
the name `.svsh_history` under the home directory of the running user (`~/.svsh_history`).

Note that history is saved only when the shell is properly terminated, such as with the
[quit](https://metacpan.org/pod/quit) command. `Ctrl+C` will not trigger history saving.

It is highly recommended to install [Term::ReadLine::Gnu](https://metacpan.org/pod/Term%3A%3AReadLine%3A%3AGnu) for proper history support.

## AUTOCOMPLETION

`svsh` provides autocompletion for all its commands. Tap the tab key at any moment while
typing in commands and arguments, and `svsh` will attempt to autocomplete your current
word, or display a list if multiple options are available. Again, [Term::ReadLine::Gnu](https://metacpan.org/pod/Term%3A%3AReadLine%3A%3AGnu)
is recommended for better autocompletion.

## WILDCARDS

`svsh` makes it easy to manipulate multiple services at once. Wildcards are supported
by the `start`, `stop`, `restart` and `signal` commands. If, for example, you have
several services whose names start with "worker", you can stop them all by executing
`stop worker*`. Wildcards are also supported at the beginning of the name, so
`signal term *d` will send a `TERM` signal to all services whose names end with "d".

svsh> status
           process |     status | duration |   pid
          worker-1 |         up |    9813s | 25984
          worker-2 |         up |    9813s | 25976
          worker-3 |         up |    4393s | 2990

svsh> stop worker*

## COLLAPSE

Often times you would like to run a certain service with X number of identical processes.
None of the supervision suites have any mechanism to allow this (none that I
know of at least), apart from creating identical copies of a service directory for every
process needed. While `svsh` can't help you with that, it provides a nice feature for collapsing
these identical services in the output of the ["status"](#status) command to just one line. This can
be very useful with lots of multi-process services.

Currently, `svsh` determines multi-process services if their names are postfixed with a dash
and a number. For example, if you have a service called `worker` that you need 3 processes
of which to run, you can create `worker-1`, `worker-2` and `worker-3` service directories.
If the [collapse](#c-collapse) option is on, `svsh` will collapse all of these into
just one line, under the name `status`.

svsh> status
           process |     status | duration |   pid
          worker-1 |         up |    9813s | 25984
          worker-2 |         up |    9813s | 25976
          worker-3 |         up |    4393s | 2990

svsh> toggle collapse
           process |     status | duration |   pid
            worker |       3 up |    9850s |     -

This feature combines well with the ["WILDCARDS"](#wildcards) feature.

Hopefully, future versions will find a more generic way of identifying multi-process services.

# CONFIGURATION AND ENVIRONMENT

`svsh` requires no configuration files or environment variables.

# DEPENDENCIES

`svsh` depends on the following modules:

- [Moo](https://metacpan.org/pod/Moo)
- [namespace::clean](https://metacpan.org/pod/namespace%3A%3Aclean)
- [Proc::Killall](https://metacpan.org/pod/Proc%3A%3AKillall)
- [Term::ShellUI](https://metacpan.org/pod/Term%3A%3AShellUI)

For proper history and autocompletion support, and generally a better
working shell, it is recommended to install [Term::ReadLine::Gnu](https://metacpan.org/pod/Term%3A%3AReadLine%3A%3AGnu).

# BUGS AND LIMITATIONS

Please report any bugs or feature requests to
[https://github.com/ido50/Svsh/issues](https://github.com/ido50/Svsh/issues).

# AUTHOR

Ido Perlmuter <ido@ido50.net>

Thanks to the guys at the [supervision mailing list](http://skarnet.org/lists.html#supervision),
especially Colin Booth, for helping out with suggestions and information.

# LICENSE AND COPYRIGHT

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

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