Taskmaster

My Taskmaster projet for the 42 School cursus, a Supervisord like process manager make in C++ 20.

Getting started

You need to compile the project with make.

You will have two binaries, a daemon named taskmasterd and a client 'shell' named taskmasterctl to communicate with the daemon.

Usage

taskmasterd: run a set of applications as daemons

Usage: ./taskmasterd [options]

Options:
  -c, --configuration <file> Specify configuration file
  -n, --nodaemon           Run in foreground (do not daemonize)
  -s, --silent             Suppress output to stdout/stderr
  -h, --help               Display this help and exit
  -v, --version            Display version information and exit

If no configuration file is specified, taskmasterd will try to find a file named taskmaster.conf the following directories:

• /etc
• /etc/taskmaster
• /usr/local/etc/taskmaster
• current working directory

taskmasterctl: control applications run by taskmasterd from the cmd line

Usage: ./taskmasterctl [options] [action [arguments]]

Options:
  -i, --interactive        start an interactive shell after executing commands
  -h, --help               Display this help and exit

action [arguments] -- see below

Actions are commands like "tail" or "stop".  If -i is specified or no action is
specified on the command line, a "shell" interpreting actions typed
interactively is started.  Use the action "help" to find out about available
actions.

Features

Table of contents

• unix_server
  • file
  • chmod
  • chown
• taskmasterd
  • logfile
  • pidfile
  • logfile_maxbytes
  • umask
  • user
  • directory
  • environment
• program:*
  • numprocs
  • autostart
  • startsecs
  • startretries
  • autorestart
  • exitcodes
  • stopsignal
  • stopwaitsecs
  • stopasgroup
  • killasgroup
  • user
  • stdout_logfile
  • stderr_logfile
  • environment
  • directory
  • umask

Documentation

Based on Supervisord documentation ;)

[unix_server]

file

A path to a UNIX domain socket on which supervisor will listen for requests. taskmasterctl uses custom protocol to communicate with taskmasterd over this port.

Default: AUTO

Required: No

chmod

Change the UNIX permission mode bits of the UNIX domain socket to this value at startup.

Default: 0700

Required: No

chown

Change the user and group of the socket file to this value. May be a UNIX username (e.g. max) or a UNIX username and group separated by a colon (e.g. max:wheel).

Default: Use the username and group of the user who starts taskmasterd

Required: No

[taskmasterd]

logfile

The path to the activity log of the taskmasterd process.

Default: $CWD/taskmasterd.log

Required: No

logfile_maxbytes

The maximum number of bytes that may be consumed by the activity log file before it is rotated (suffix multipliers like “KB”, “MB”, and “GB” can be used in the value). Set this value to 0 to indicate an unlimited log size.

Default: 50MB

Required: No

pidfile

The location in which taskmasterd keeps its pid file.

Default: $CWD/taskmasterd.pid

Required: No

umask

The umask of the taskmasterd process.

Default: 022

Required: No

user

Instruct taskmasterd to switch users to this UNIX user account before doing any meaningful processing. The user can only be switched if taskmasterd is started as the root user.

Default: do not switch users

Required: No

directory

When taskmasterd daemonizes, switch to this directory.

Default: do not cd

Required: No

environment

A list of key/value pairs in the form KEY="val",KEY2="val2" that will be placed in the environment of all child processes. This does not change the environment of taskmasterd itself. Values containing non-alphanumeric characters should be quoted (e.g. KEY="val:123",KEY2="val,456"). Otherwise, quoting the values is optional but recommended. Note that subprocesses will inherit the environment variables of the shell used to start taskmasterd except for the ones overridden here and within the program’s environment option

[program]

command

The command that will be run when this program is started. The command should be either absolute (e.g. /path/to/programname). Programs can accept arguments, e.g. /path/to/program foo bar. The command line can use double quotes to group arguments with spaces in them to pass to the program, e.g. /path/to/program/name -p "foo bar". Controlled programs should themselves not be daemons, as taskmasterd assumes it is responsible for daemonizing its subprocesses.

Default: no values

Required: Yes

numprocs

Taskmaster will start as many instances of this program as named by numprocs.

Default: 1

Required: No

autostart

If true, this program will start automatically when taskmasterd is started.

Default: true

Required: No

startsecs

The total number of seconds which the program needs to stay running after a startup to consider the start successful (moving the process from the STARTING state to the RUNNING state). Set to 0 to indicate that the program needn’t stay running for any particular amount of time.

Even if a process exits with an “expected” exit code (see exitcodes), the start will still be considered a failure if the process exits quicker than startsecs.

Default: 1

Required: No

startretries

The number of serial failure attempts that taskmasterd will allow when attempting to start the program before giving up and putting the process into an FATAL state.

After each failed restart, process will be put in BACKOFF state and each retry attempt will take increasingly more time.

Default: 3

Required: No

autorestart

Specifies if taskmasterd should automatically restart a process if it exits when it is in the RUNNING state. May be one of false, unexpected, or true. If false, the process will not be autorestarted. If unexpected, the process will be restarted when the program exits with an exit code that is not one of the exit codes associated with this process’ configuration (see exitcodes). If true, the process will be unconditionally restarted when it exits, without regard to its exit code.

autorestart controls whether taskmasterd will autorestart a program if it exits after it has successfully started up (the process is in the RUNNING state).

taskmasterd has a different restart mechanism for when the process is starting up (the process is in the STARTING state). Retries during process startup are controlled by startsecs and startretries.

Default: unexpected

Required: No

exitcodes

The list of “expected” exit codes for this program used with autorestart. If the autorestart parameter is set to unexpected, and the process exits in any other way than as a result of a taskmaster stop request, taskmasterd will restart the process if it exits with an exit code that is not defined in this list.

Default: 0

Required: No

stopsignal

The signal used to kill the program when a stop is requested. This can be specified using the signal’s name or its number. It is normally one of: TERM, HUP, INT, QUIT, KILL, USR1, or USR2.

Default: TERM

Required: No

stopwaitsecs

The number of seconds to wait for the child process to end after the program has been sent a stopsignal. If this number of seconds elapses, taskmasterd will attempt to kill it with a final SIGKILL.

Default: 10

Required: No

stopasgroup

If true, the flag causes supervisor to send the stop signal to the whole process group and implies killasgroup is true. This is useful for programs, such as Flask in debug mode, that do not propagate stop signals to their children, leaving them orphaned.

Default: false

Required: No

killasgroup

If true, when resorting to send SIGKILL to the program to terminate it send it to its whole process group instead, taking care of its children as well, useful e.g with Python programs using multiprocessing.

Default: false

Required: No

user

Instruct taskmasterd to use this UNIX user account as the account which runs the program. The user can only be switched if taskmasterd is run as the root user. If taskmasterd can’t switch to the specified user, the program will not be started.

Default: do not switch users

Required: No

stdout_logfile

Put process stdout output in this file. If stdout_logfile is unset, taskmaster will automatically choose a file location.

Default: auto

Required: No

stderr_logfile

Put process stderr output in this file. If stderr_logfile is unset, taskmaster will automatically choose a file location.

Default: auto

Required: No

environment

A list of key/value pairs in the form KEY="val",KEY2="val2" that will be placed in the environment of all child processes. This does not change the environment of taskmasterd itself. Values containing non-alphanumeric characters should be quoted (e.g. KEY="val:123",KEY2="val,456"). Otherwise, quoting the values is optional but recommended. Note that subprocesses will inherit the environment variables of the shell used to start taskmasterd except for the ones overridden here and within the program’s environment option

Default: no extra environment

Required: No

directory

A file path representing a directory to which taskmasterd should temporarily chdir before exec’ing the child.

Default: No chdir (inherit taskmaster’s)

Required: No

umask

An octal number (e.g. 002, 022) representing the umask of the process.

Default: No special umask (inherit taskmaster’s)

Required: No

Signal Handlers

The taskmaster daemon handles several signals to control its behavior:

• SIGTERM: taskmasterd and all its subprocesses will shut down. This may take several seconds.
• SIGINT: taskmasterd and all its subprocesses will shut down. This may take several seconds.
• SIGQUIT: taskmasterd and all its subprocesses will shut down. This may take several seconds.
• SIGHUP: taskmasterd will stop all processes, reload the configuration from the first config file it finds, and start all processes.
• SIGUSR2: taskmasterd will close and reopen the main activity log and all child log files.