svsh - Process supervision shell for daemontools/perp/s6/runit
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
svsh is a command line shell for process supervision suites of the daemontools family. Currently, it supports
daemontools, perp, s6
and 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's supervisorctl shell. I've
attempted to provide a similar syntax and feature set.
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.
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.
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).
Collapse multi-process services to one line in status. See "COLLAPSE"
for more details. This can be changed from inside the shell too.
The following commands are provided by svsh. Note that some suites do not
support all commands.
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.
Starts a list of one or more services, if they are not already up.
svsh> start nginx haproxy
Stops a list of one or more services. The services stopped will not be restarted.
svsh> stop nginx haproxy
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
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
Alias: update.
Causes the supervision suite to rescan the base directory for new or removed services.
"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" for more details, as this
is a complicated subject.
svsh> fg nginx
Alias: shutdown.
Terminate the supervision suite. This will cause all services managed by the supervisor to terminate as well.
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
Prints help information. Can also provide information about specific commands.
svsh> help signal
Alias: exit.
Quits the shell.
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 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).
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 command. Ctrl+C will not trigger history saving.
It is highly recommended to install Term::ReadLine::Gnu for proper history support.
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
is recommended for better autocompletion.
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*
svsh> status
process | status | duration | pid
worker-1 | down | 2s | -
worker-2 | down | 2s | -
worker-3 | down | 2s | -
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" 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 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" feature.
Hopefully, future versions will find a more generic way of identifying multi-process services.
svsh requires no configuration files or environment variables.
svsh depends on the following modules:
For proper history and autocompletion support, and generally a better working shell, it is recommended to install Term::ReadLine::Gnu.
Please report any bugs or feature requests to https://github.com/ido50/Svsh/issues.
Ido Perlmuter [email protected]
Thanks to the guys at the supervision mailing list, especially Colin Booth, for helping out with suggestions and information.
Copyright (c) 2015-2023, Ido Perlmuter [email protected].
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.