I use the following code to check the server status of a certain game server to see if the game server is online.
begin
sock = Socket.new(Socket::AF_INET, Socket::SOCK_STREAM, 0)
sockaddr = Socket.sockaddr_in(game_server.gameserver_port, game_server.gameserver_hostname)
sock.connect(sockaddr)
server_status.status = 1
rescue
server_status.status = 0
end
However it seems that the code blindly hangs up on the line without proceeding anywhere sock.connect(sockaddr) and does not throw an error when there's no services listening on that port. Is there a better way to do this in Ruby?
Could timeout be a good solution?
require 'timeout'
begin
timeout(5) do
# socket stuff...
end
rescue Timeout::Error
puts "Timed out!"
end
Related
I have a TCPserver that I made in ruby, the server seems to work, I can see that two or more clients can connect and be served by the server, but, they sometime get stuck (as in need to wait for the other client to disconnect or just get unresponsive), usually after the "pass_ok" bit, When connecting only with one client I don't see this issue.
Here is my code:
def self.main_server
begin
server = TCPServer.open(#port)
rescue Exception => e
CoreLogging.syslog_error("Cant start server: #{e}")
end
#main_pid = Process.pid
# Main Loop
Thread.abort_on_exception = true
while true
Thread.fork(server.accept) do |client|
#client = client
sock_domain, remote_port, remote_hostname, remote_ip = #client.peeraddr # Get some info on the incoming connection
CoreLogging.syslog_error("Got new connection from #{#client.peeraddr[3]} Handeled by Thread: #{Thread.current}") # Log incoming connection
#client.puts "Please enter password: " # Password testing (later will be from a config file or DB)
action = #client.gets(4096).chomp # get client password response 'chomp' is super important
if action == #password
# what to do when password is right
pass_ok
Thread.exit
else
# what to do when password is wrong
pass_fail
Thread.exit
end
end
begin
CoreLogging.syslog_error("Thread Ended (SOFT)")
rescue Exception => e
CoreLogging.syslog_error("Thread was killed (HARD)")
end
end
end
I'll leave it here for future reference and hope someone in a close situation will find it useful.
The issue was the global #client variable, which got overwritten every new thread and then inherited to the subclasses inside the thread.
using a local client variable (without the '#') got it to work as supposed.
I have a 2 part question on reading from sockets and how is it managed on Ruby servers like Unicorn or Mongrel
I've learnt that to read from a socket is different from reading a file and that there are no distinct EOF message sent and the data is an endless stream. So how do you know when to stop reading? My TCPServer for example in this case when I hit my server by accessing http://localhost:9799 from a browser, it hangs after there is no more data to read and it won't throw the EOFError either.
require 'socket'
READ_CHUNK = 1024
socket = Socket.new(Socket::AF_INET, Socket::SOCK_STREAM)
addr = Socket.pack_sockaddr_in(9799, '127.0.0.1')
socket.bind(addr)
socket.listen(Socket::SOMAXCONN)
socket.setsockopt(:SOCKET, :REUSEADDR, true)
puts "Server is listening on port = 9799"
loop do
connection, addr_info = socket.accept
data_buffer = ""
loop do
begin
connection.read_nonblock(READ_CHUNK, data_buffer)
puts "Buffer = #{data_buffer}"
rescue Errno::EAGAIN => e
IO.select([connection])
retry
rescue EOFError
break
end
end
connection.write("HTTP/1.1 200 \r\n")
connection.write("Content-Type: text/html\r\n")
connection.write("Status 200 \r\n")
connection.write("Connection: close \r\n")
connection.write("Hello World \r\n")
connection.close
end
I'd like to know whats the best practice/standard approach used by Ruby servers. I see the Unicorn uses read_nonblock from kgio library and mongrel uses readpartial (I'm not sure about these but going through the code this is what I feel is the approach adopted.) Even with checks for \r\n how does the server know the input is complete.
Could explain how this should be done (and I think gets is not the approach - its with read, readpartial, read_nonblock).
2). I would really appreciate a few lines on how this is achieved in servers like unicorn or passenger
Thank you.
It's done in unicorn here
https://github.com/defunkt/unicorn/blob/master/lib/unicorn/http_request.rb#L69-L71
There is add_parse method(read the comments above methods)
https://github.com/defunkt/unicorn/blob/master/ext/unicorn_http/unicorn_http.rl#L760-L778
Also take a look at some explanations here http://www.ruby-forum.com/topic/2267632#1014288
Here is your working code using http_parser.rb https://gist.github.com/4136962
gem install http_parser.rb
require 'socket'
require "http/parser"
READ_CHUNK = 1024 * 4
socket = Socket.new(Socket::AF_INET, Socket::SOCK_STREAM)
addr = Socket.pack_sockaddr_in(9799, '127.0.0.1')
socket.bind(addr)
socket.listen(Socket::SOMAXCONN)
socket.setsockopt(:SOCKET, :REUSEADDR, true)
puts "Server is listening on port = 9799"
loop do
connection, addr_info = socket.accept
parser = Http::Parser.new
begin
data = connection.readpartial(READ_CHUNK)
puts "Buffer = #{data}"
parser << data
end until parser.headers
connection.write("HTTP/1.1 200 \r\n")
connection.write("Content-Type: text/html\r\n")
connection.write("Status 200 \r\n")
connection.write("Connection: close \r\n")
connection.write("\r\n\r\n")
connection.write("Hello World \r\n")
connection.close
end
I have a circumstance where my server may close TCPServer and restart, saving all the users to a file, and immediately reloading them; their connections do not sever.
The problem is I can't seem to reinitialize their streams.
When we restart (and attempt to maintain connections), I reinitialize TCPServer, and load my array of connected users – Since these each have an existing socket address, stored as <TCPSocket:0x00000000000000>, can I reinitialize these addresses with TCPServer?
Normally, each user connects and is accepted:
$nCS = TCPServer.new(HOST, PORT)
begin
while socket = $nCS.accept
Thread.new( socket ) do |sock|
begin
d = User.new(sock)
while sock.gets
szIn = $_.chomp
DBG( "Received '" + szIn + "' from Client " + sock.to_s )
d.parseInput( szIn )
end
rescue => e
$stdout.puts "ERROR: Caught error in Client Thread: #{e} \r\n #{e.backtrace.to_s.gsub(",", ",\r\n")}"
sock.write("Sorry, an error has occurred, and you have been disconnected."+EOL+"Please try again later."+EOL)
d.closeConnection
end
end
end
rescue => e
$stdout.puts "ERROR: Caught error in Server Thread: #{e} \r\n #{e.backtrace.to_s.gsub(",", ",\r\n")}"
exit
end
To give it a command to hot reboot, we use exec('./main --copyover') to flag that a copy over is occurring.
If $connected holds an array of all users, and each user has a socket, how do I reinitialize the socket that was open before the restart (assuming the other end is still connected)?
I suspect that using exec("./main", "--copyover", *$nCS, *$connected) is getting me closer, since this simply replaces the process, and should maintain the files (not close them).
You can't. The socket is only valid for the lifetime of the process: it is closed by the OS when the process exits. That in turn invalidates the connection, so the other end is not still connected.
How to Hot-Reboot a TCPServer in Ruby
Hot-Rebooting (aka Copyover) is a process by which an administrator can reload the application (along with any new changes made since last boot) without losing the client connections. This is useful in managing customer expectations as the application does not need to suffer severe downtime and disruption if in use.
What I propose below may not be the best practice, but it's functioning and perhaps will guide others to a similar solution.
The Command
I use a particular style of coding that makes use of command tables to find functions and their accessibility. All command functions are prefixed with cmd. I'll clean up the miscellany to improve readability:
def cmdCopyover
#$nCS is the TCPServer object
#$connected holds an array of all users sockets
#--copyover flags that this is a hot reboot.
connected_args = $connected.map do |sock|
sock.close_on_exec = false if sock.respond_to?(:close_on_exec=)
sock.fileno.to_s
end.join(",")
exec('./main.rb', '--copyover', $nCS.fileno.to_s, connected_args)
end
What we're passing are strings; $nCS.fileno.to_s provides us the file descriptor of the main TCPServer object, while connected_args is a comma-delineated list of file descriptors for each user connected. When we restart, ARGV will be an array holding each argument:
ARGV[0] == "--copyover"
ARGV[1] == "5" (Or whatever the file descriptor for TCPServer was)
ARGV[2] == "6,7,8,9" (Example, assuming 4 connected users)
What To Expect When You're Expecting (a Copyover)
Under normal circumstances, we may have a basic server (in main.rb that looks something like this:
puts "Starting Server"
$connected = Array.new
$nCS = TCPServer.new("127.0.0.1",9999)
begin
while socket = $nCS.accept
# NB: Move this loop to its own function, threadLoop()
Thread.new( socket ) do |sock|
begin
while sock.gets
szIn = $_.chomp
#do something with input.
end
rescue => e
puts "ERROR: Caught error in Client Thread: #{e}"
puts #{e.backtrace.to_s.gsub(",", ",\r\n")}"
sock.write("Sorry, an error has occurred, and you have been disconnected."+EOL+"Please try again later."+EOL)
sock.close
end
end
end
rescue => e
puts "Error: Caught Error in Server Thread: #{e}"
puts "#{e.backtrace.to_s.gsub(",", ",\r\n")}"
exit
end
We want to move that main loop to its own function to make it accessible -- our reconnecting users will need to be reinserted in the loop.
So let's get main.rb ready for accepting a hot reboot:
def threadLoop( socket )
Thread.new( socket ) do |sock|
begin
while sock.gets
szIn = $_.chomp
#do something with input.
end
rescue => e
puts "ERROR: Caught error in Client Thread: #{e}"
puts #{e.backtrace.to_s.gsub(",", ",\r\n")}"
sock.write("Sorry, an error has occurred, and you have been disconnected."+EOL+"Please try again later."+EOL)
sock.close
end
end
end
puts "Starting Server"
$connected = Array.new
if ARGV[0] == '--copyover'
$nCS = TCPServer.for_fd( ARGV[1].to_i )
$nCS.close_on_exec = false if $nCS.respond_to?(:close_on_exec=)
connected_args = ARGV[2]
connected_args.split(/,/).map do |sockfd|
$connected << sockfd
$connected.each {|c| threadLoop( c ) }
else
$nCS = TCPServer.new("127.0.0.1",9999)
$nCS.close_on_exec = false if $nCS.respond_to?(:close_on_exec=)
end
begin
while socket = $nCS.accept
threadLoop( socket )
end
rescue => e
puts "Error: Caught Error in Server Thread: #{e}"
puts "#{e.backtrace.to_s.gsub(",", ",\r\n")}"
exit
end
Caveat
My actual usage was a lot more ridiculously complicated, so I did my best to strip out all the garbage; however, I was realizing when I got the end here that you could probably do without $connected (it's a part of a larger system for me). There may be some errors, so please comment if you find them and I'll correct.
Hope this helps anyone who finds it.
I'm trying to write a simple zmq system to replace an http client/server. My client times out when the server is off/unavailable, but does not retry or stop. What am I missing?
zmq_client.rb (modified version of Han Holl's lazy pirate client from zeromq guide)
require 'rubygems'
require 'zmq'
context = ZMQ::Context.new
socket = context.socket(ZMQ::REQ)
socket.connect('tcp://localhost:5559')
retries = 2
timeout = 10
retries.times do |tries|
message = "Hello #{tries}"
raise("Send: #{message} failed") unless socket.send(message)
puts "Sending string [#{message}]"
if ZMQ.select( [socket], nil, nil, timeout)
message = socket.recv
puts "Received reply [#{message}]"
break
else
puts "timeout"
end
end
socket.close
zmq_broker.rb (modified version of Oleg Sidorov's code found on zeromq guide)
require 'rubygems'
require 'ffi-rzmq'
context = ZMQ::Context.new
frontend = context.socket(ZMQ::ROUTER)
frontend.bind('tcp://*:5559')
poller = ZMQ::Poller.new
poller.register(frontend, ZMQ::POLLIN)
loop do
poller.poll(:blocking)
poller.readables.each do |socket|
if socket === frontend
loop do
socket.recv_string(message = '')
more = socket.more_parts?
puts "#{message}#{more}"
socket.send_string(message, more ? ZMQ::SNDMORE : 0)
break unless more
end
end
end
end
You should get an error Send: #{message} failed as soon as you try to send again after the first timeout, because your 2nd send will happen directly after the 1st send, and the REQ socket enforces that each send must go after (successful, not timeout-ed) recv.
In the lazy pirate pattern, you may need to send several requests before getting a reply. Solution suggested in the 0MQ Guide is to close and reopen the REQ socket after an error. Your client doesn't close/reopen the REQ socket.
You may find helpful the "Lazy Pirate client in Ruby" example from the Guide.
I'm reading lines of input on a TCP socket, similar to this:
class Bla
def getcmd
#sock.gets unless #sock.closed?
end
def start
srv = TCPServer.new(5000)
#sock = srv.accept
while ! #sock.closed?
ans = getcmd
end
end
end
If the endpoint terminates the connection while getline() is running then gets() hangs.
How can I work around this? Is it necessary to do non-blocking or timed I/O?
You can use select to see whether you can safely gets from the socket, see following implementation of a TCPServer using this technique.
require 'socket'
host, port = 'localhost', 7000
TCPServer.open(host, port) do |server|
while client = server.accept
readfds = true
got = nil
begin
readfds, writefds, exceptfds = select([client], nil, nil, 0.1)
p :r => readfds, :w => writefds, :e => exceptfds
if readfds
got = client.gets
p got
end
end while got
end
end
And here a client that tries to break the server:
require 'socket'
host, port = 'localhost', 7000
TCPSocket.open(host, port) do |socket|
socket.puts "Hey there"
socket.write 'he'
socket.flush
socket.close
end
The IO#closed? returns true when both reader and writer are closed.
In your case, the #sock.gets returns nil, and then you call the getcmd again, and this runs in a never ending loop. You can either use select, or close the socket when gets returns nil.
I recommend using readpartial to read from your socket and also catching peer resets:
while true
sockets_ready = select(#sockets, nil, nil, nil)
if sockets_ready != nil
sockets_ready[0].each do |socket|
begin
if (socket == #server_socket)
# puts "Connection accepted!"
#sockets << #server_socket.accept
else
# Received something on a client socket
if socket.eof?
# puts "Disconnect!"
socket.close
#sockets.delete(socket)
else
data = ""
recv_length = 256
while (tmp = socket.readpartial(recv_length))
data += tmp
break if (!socket.ready?)
end
listen socket, data
end
end
rescue Exception => exception
case exception
when Errno::ECONNRESET,Errno::ECONNABORTED,Errno::ETIMEDOUT
# puts "Socket: #{exception.class}"
#sockets.delete(socket)
else
raise exception
end
end
end
end
end
This code borrows heavily from some nice IBM code by M. Tim Jones. Note that #server_socket is initialized by:
#server_socket = TCPServer.open(port)
#sockets is just an array of sockets.
I simply pgrep "ruby" to find the pid, and kill -9 the pid and restart.
If you believe the rdoc for ruby sockets, they don't implement gets. This leads me to believe gets is being provided by a higher level of abstraction (maybe the IO libraries?) and probably isn't aware of socket-specific things like 'connection closed.'
Try using recvfrom instead of gets