Options accepted by constructor.
Human-readable, unique name for this daemon, e.g. "Sphinx search server". This identifier will be used in some error messages. On some platforms, it will be used for concurrency control: on such platforms, no two DaemonController objects will operate on the same identifier on the same time.
Command to start the daemon. This must be a a String, e.g. "mongrel_rails start -e production", or a Proc which returns a String.
If the value is a Proc, and the before_start option is given too, then
the start_command Proc is guaranteed to be called after the before_start
Proc is called.
This is subject to a timeout, see start_timeout and Stop flow.
Command used to check whether the daemon can be connected to. It is also used to ensure that #start only returns when the daemon can be connected to.
Value may be a command string. This command must exit with an exit code of 0 if the daemon can be successfully connected to, or exit with a non-0 exit code on failure.
Value may also be an Array which specifies the socket address of the daemon. It must be in one of the following forms:
[:tcp, host_name, port][:unix, filename]
Value may also be a Proc, which returns an expression that evaluates to
true (indicating that the daemon can be connected to) or false (failure).
If the Proc raises Errno::ECONNREFUSED, Errno::ENETUNREACH, Errno::ETIMEDOUT
Errno::ECONNRESET, Errno::EINVAL or Errno::EADDRNOTAVAIL then that also
means that the daemon cannot be connected to.
NOTE: if the ping command returns an object which responds to
#close, then that method will be called on it.
This makes it possible to specify a ping command such as
lambda { TCPSocket.new('localhost', 1234) }, without having to worry
about closing it afterwards.
Any exceptions raised by #close are ignored.
PID file that the daemon will write to. Used to check whether the daemon is running.
Log file that the daemon will write to. It will be consulted to see whether the daemon has printed any error messages during startup.
Lock file to use for serializing concurrent daemon management operations.
Command to stop the daemon with, e.g. "/etc/rc.d/nginx stop".
If no stop command is given (i.e., nil), then will stop the daemon
by sending signals to the PID written in the PID file. See
Stop flow for how that works.
Command to restart the daemon with, e.g. "/etc/rc.d/nginx restart". If
no restart command is given (i.e. nil), then DaemonController will
restart the daemon by calling #stop and #start.
This may be a Proc. It will be called just before running the start command. The Proc call is not subject to the start timeout.
Maximum amount of time (seconds) that #start may take to start the daemon. Since #start also waits until the daemon can be connected to, that wait time is counted as well. If the daemon does not start in time, then #start will raise an exception and also stop the daemon. See also Stop flow for how that works.
Maximum amount of time (seconds) to wait for the daemon to terminate after sending SIGTERM during the start timeout flow. If the daemon does not terminate within this time, it will be forcefully terminated with SIGKILL. See Stop flow for more details.
Maximum amount of time (seconds) that #stop may take to stop the daemon. Since #stop also waits until the daemon is no longer running, that wait time is counted as well. If the daemon does not stop in time, then #stop will raise an exception and force stop the daemon.
See Stop flow for al overview of the entire stopping flow.
Once a daemon has gone into the background, it will become difficult to know for certain whether it is still initializing or whether it has failed and exited, until it has written its PID file. Suppose that it failed with an error after daemonizing but before it has written its PID file; not many system administrators want to wait 30 seconds (the default start timeout) to be notified of whether the daemon has terminated with an error.
An alternative way to check whether the daemon has terminated with an error, is by checking whether its log file has been recently updated. If, after the daemon has started, the log file hasn't been updated for the amount of seconds given by this option, then the daemon is assumed to have terminated with an error.
Time interval (seconds) between pinging attempts (see ping_command) when waiting
for the daemon to start.
Signal to send to the daemon when attempting to stop it gracefully during #stop
(regular stop flow). This is only used when no stop_command is provided.
See Stop flow for more details.
If the stop_command option is given, then normally daemon_controller will always execute this command upon calling #stop. But if dont_stop_if_pid_file_invalid is given, then daemon_controller will not do that if the PID file does not contain a valid number.
Normally daemon_controller will wait until the daemon has daemonized into the background, in order to capture any errors that it may print on stdout or stderr before daemonizing. However, if the daemon doesn't support daemonization for some reason, then setting this option to true will cause daemon_controller to do the daemonization for the daemon.
Upon spawning the daemon, daemon_controller will normally close all file descriptors except stdin, stdout and stderr. However if there are any file descriptors you want to keep open, specify the IO objects here. This must be an array of IO objects.
This must be a Hash. The hash will contain the environment variables available to be made available to the daemon. Hash keys must be Strings, not Symbols.