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# frozen_string_literal: true
require "socket"
# SdNotify is a pure-Ruby implementation of sd_notify(3). It can be used to
# notify systemd about state changes. Methods of this package are no-op on
# non-systemd systems (eg. Darwin).
#
# The API maps closely to the original implementation of sd_notify(3),
# therefore be sure to check the official man pages prior to using SdNotify.
#
# @see https://www.freedesktop.org/software/systemd/man/sd_notify.html
module SdNotify
# Exception raised when there's an error writing to the notification socket
class NotifyError < RuntimeError; end
READY = "READY=1"
RELOADING = "RELOADING=1"
STOPPING = "STOPPING=1"
STATUS = "STATUS="
ERRNO = "ERRNO="
MAINPID = "MAINPID="
WATCHDOG = "WATCHDOG=1"
FDSTORE = "FDSTORE=1"
def self.ready(unset_env=false)
notify(READY, unset_env)
end
def self.reloading(unset_env=false)
notify(RELOADING, unset_env)
end
def self.stopping(unset_env=false)
notify(STOPPING, unset_env)
end
# @param status [String] a custom status string that describes the current
# state of the service
def self.status(status, unset_env=false)
notify("#{STATUS}#{status}", unset_env)
end
# @param errno [Integer]
def self.errno(errno, unset_env=false)
notify("#{ERRNO}#{errno}", unset_env)
end
# @param pid [Integer]
def self.mainpid(pid, unset_env=false)
notify("#{MAINPID}#{pid}", unset_env)
end
def self.watchdog(unset_env=false)
notify(WATCHDOG, unset_env)
end
def self.fdstore(unset_env=false)
notify(FDSTORE, unset_env)
end
# @param [Boolean] true if the service manager expects watchdog keep-alive
# notification messages to be sent from this process.
#
# If the $WATCHDOG_USEC environment variable is set,
# and the $WATCHDOG_PID variable is unset or set to the PID of the current
# process
#
# @note Unlike sd_watchdog_enabled(3), this method does not mutate the
# environment.
def self.watchdog?
wd_usec = ENV["WATCHDOG_USEC"]
wd_pid = ENV["WATCHDOG_PID"]
return false if !wd_usec
begin
wd_usec = Integer(wd_usec)
rescue
return false
end
return false if wd_usec <= 0
return true if !wd_pid || wd_pid == $$.to_s
false
end
# Notify systemd with the provided state, via the notification socket, if
# any.
#
# Generally this method will be used indirectly through the other methods
# of the library.
#
# @param state [String]
# @param unset_env [Boolean]
#
# @return [Fixnum, nil] the number of bytes written to the notification
# socket or nil if there was no socket to report to (eg. the program wasn't
# started by systemd)
#
# @raise [NotifyError] if there was an error communicating with the systemd
# socket
#
# @see https://www.freedesktop.org/software/systemd/man/sd_notify.html
def self.notify(state, unset_env=false)
sock = ENV["NOTIFY_SOCKET"]
return nil if !sock
ENV.delete("NOTIFY_SOCKET") if unset_env
begin
Addrinfo.unix(sock, :DGRAM).connect do |s|
s.close_on_exec = true
s.write(state)
end
rescue StandardError => e
raise NotifyError, "#{e.class}: #{e.message}", e.backtrace
end
end
end
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