Supervisor 3.0 Beta 2

A client/server system that allows its users to control a number of processes on UNIX-like operating systems

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What's new in Supervisor 3.0 Beta 2:

  • The behavior of the program option user has changed. In all previous versions, if supervisord failed to switch to the user, a warning would be sent to the stderr log but the child process would still be spawned. This means that a mistake in the config file could result in a child process being unintentionally spawned as root. Now, supervisord will not spawn the child unless it was able to successfully switch to the user. Thanks to Igor Partola for reporting this issue.
  • If a user specified in the config file does not exist on the system, supervisord will now print an error and refuse to start.
  • Reverted a change to logging introduced in 3.0b1 that was intended to allow multiple processes to log to the same file with the rotating log handler. The implementation caused supervisord to crash during reload and to leak file handles. Also, since log rotation options are given on a per-program basis, impossible configurations could be created (conflicting rotation options for the same file). Given this and that supervisord now has syslog support, it was decided to remove this feature. A warning was added to the documentation that two processes may not log to the same file.
  • Fixed a bug where parsing command= could cause supervisord to crash if shlex.split() fails, such as a bad quoting. Patch by Scott Wilson.
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3.2/5 17
Chris McDonough
ROOT \ System \ Monitoring
Supervisor is a client/server system that allows its users to control a number of processes on UNIX-like operating systems. It was inspired by the following:

- It is often inconvenient to need to write "rc.d" scripts for every single process instance. rc.d scripts are a great lowest-common-denominator form of process initialization/autostart/management, but they can be painful to write and maintain. Additionally, rc.d scripts cannot automatically restart a crashed process and many programs do not restart themselves properly on a crash. Supervisord starts processes as its subprocesses, and can be configured to automatically restart them on a crash. It can also automatically be configured to start processes on its own invocation.
- It's often difficult to get accurate up/down status on processes on UNIX. Pidfiles often lie. Supervisord starts processes as subprocesses, so it always knows the true up/down status of its children and can be queried conveniently for this data.
- Users who need to control process state often need only to do that. They don't want or need full-blown shell access to the machine on which the processes are running. Supervisorctl allows a very limited form of access to the machine, essentially allowing users to see process status and control supervisord-controlled subprocesses by emitting "stop", "start", and "restart" commands from a simple shell or web UI.
- Users often need to control processes on many machines. Supervisor provides a simple, secure, and uniform mechanism for interactively and automatically controlling processes on groups of machines.
- Processes which listen on "low" TCP ports often need to be started and restarted as the root user (a UNIX misfeature). It's usually the case that it's perfectly fine to allow "normal" people to stop or restart such a process, but providing them with shell access is often impractical, and providing them with root access or sudo access is often impossible. It's also (rightly) difficult to explain to them why this problem exists. If supervisord is started as root, it is possible to allow "normal" users to control such processes without needing to explain the intricacies of the problem to them.
- Processes often need to be started and stopped in groups, sometimes even in a "priority order". It's often difficult to explain to people how to do this. Supervisor allows you to assign priorities to processes, and allows user to emit commands via the supervisorctl client like "start all", and "restart all", which starts them in the preassigned priority order. Additionally, processes can be grouped into "process groups" and a set of logically related processes can be stopped and started as a unit.otification system was added.

Last updated on September 12th, 2012


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