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require 'fcgi'
require 'logger'
require 'dispatcher'
class RailsFCGIHandler
SIGNALS = {
'HUP' => :reload,
'TERM' => :graceful_exit,
'USR1' => :graceful_exit
}
attr_reader :when_ready
attr_reader :processing
attr_accessor :log_file_path
attr_accessor :gc_request_period
# Initialize and run the FastCGI instance, passing arguments through to new.
def self.process!(*args, &block)
new(*args, &block).process!
end
# Initialize the FastCGI instance with the path to a crash log
# detailing unhandled exceptions (default RAILS_ROOT/log/fastcgi.crash.log)
# and the number of requests to process between garbage collection runs
# (default nil for normal GC behavior.) Optionally, pass a block which
# takes this instance as an argument for further configuration.
def initialize(log_file_path = nil, gc_request_period = nil)
@when_ready = nil
@processing = false
self.log_file_path = log_file_path || "#{RAILS_ROOT}/log/fastcgi.crash.log"
self.gc_request_period = gc_request_period
# Yield for additional configuration.
yield self if block_given?
# Safely install signal handlers.
install_signal_handlers
# Start error timestamp at 11 seconds ago.
@last_error_on = Time.now - 11
dispatcher_log(:info, "starting")
end
def process!
# Make a note of $" so we can safely reload this instance.
mark!
# Begin countdown to garbage collection.
run_gc! if gc_request_period
FCGI.each_cgi do |cgi|
# Safely reload this instance if requested.
if when_ready == :reload
run_gc! if gc_request_period
restore!
@when_ready = nil
dispatcher_log(:info, "reloaded")
end
process_request(cgi)
# Break if graceful exit requested.
break if when_ready == :exit
# Garbage collection countdown.
if gc_request_period
@gc_request_countdown -= 1
run_gc! if @gc_request_countdown <= 0
end
end
GC.enable
dispatcher_log(:info, "terminated gracefully")
rescue SystemExit => exit_error
dispatcher_log(:info, "terminated by explicit exit")
rescue Object => fcgi_error
# retry on errors that would otherwise have terminated the FCGI process,
# but only if they occur more than 10 seconds apart.
if !(SignalException === fcgi_error) && Time.now - @last_error_on > 10
@last_error_on = Time.now
dispatcher_error(fcgi_error, "almost killed by this error")
retry
else
dispatcher_error(fcgi_error, "killed by this error")
end
end
private
def logger
@logger ||= Logger.new(@log_file_path)
end
def dispatcher_log(level, msg)
time_str = Time.now.strftime("%d/%b/%Y:%H:%M:%S")
logger.send(level, "[#{time_str} :: #{$$}] #{msg}")
rescue Object => log_error
STDERR << "Couldn't write to #{@log_file_path.inspect}: #{msg}\n"
STDERR << " #{log_error.class}: #{log_error.message}\n"
end
def dispatcher_error(e,msg="")
error_message =
"Dispatcher failed to catch: #{e} (#{e.class})\n" +
" #{e.backtrace.join("\n ")}\n#{msg}"
dispatcher_log(:error, error_message)
end
def install_signal_handlers
SIGNALS.each do |signal, handler_name|
install_signal_handler signal, method("#{handler_name}_handler").to_proc
end
end
def install_signal_handler(signal, handler)
trap signal, handler
rescue ArgumentError
dispatcher_log :warn, "Ignoring unsupported signal #{signal}."
end
def graceful_exit_handler(signal)
if processing
dispatcher_log :info, "asked to terminate ASAP"
@when_ready = :exit
else
dispatcher_log :info, "told to terminate NOW"
exit
end
end
def reload_handler(signal)
@when_ready = :reload
dispatcher_log :info, "asked to reload ASAP"
end
def process_request(cgi)
@processing = true
Dispatcher.dispatch(cgi)
rescue Object => e
raise if SignalException === e
dispatcher_error(e)
ensure
@processing = false
end
def mark!
@features = $".clone
end
def restore!
$".replace @features
Dispatcher.reset_application!
ActionController::Routing::Routes.reload
end
def run_gc!
@gc_request_countdown = gc_request_period
GC.enable; GC.start; GC.disable
end
end
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