PassengerPreStart / prespawn fails for apps not reachable via 127.0.0.1

[FooBarWidget]

From svnmnt on September 15, 2013 15:02:16

What steps will reproduce the problem?

1. configure virtual host example.com which is only reachable on public IP and not on 127.0.0.1
2. add "PassengerPreStart http(s?)://example.com"
3. restart apache
4. rails app is not prestarted

alternative way:

1. from above
2. run "ruby prespawn http://example.com " from the command line

What is the expected output? What do you see instead?

I expect, that the app would have been prestarted. I see a "Connection refused" error. Details are given below.

What version of Phusion Passenger are you using? Which version of Rails? On what operating system?

Passenger Version: 4.0.17 Rails: 4.0.0 OS: FreeBSD 8.2 Please provide any additional information below. The httpd-error.log shows:

[...]/gems/passenger-4.0.17/helper-scripts/prespawn:105:in `initialize': Connection refused - connect(2) (Errno::ECONNREFUSED)
        from [...]/gems/passenger-4.0.17/helper-scripts/prespawn:105:in `new'
        from [...]/gems/passenger-4.0.17/helper-scripts/prespawn:105:in `connect'
        from [...]/gems/passenger-4.0.17/helper-scripts/prespawn:112:in `connect'
        from [...]/gems/passenger-4.0.17/helper-scripts/prespawn:86:in `socket'
        from [...]/gems/passenger-4.0.17/helper-scripts/prespawn:90:in `head_request'
        from [...]/gems/passenger-4.0.17/helper-scripts/prespawn:145:in `<main>'

The problem is that the connection is made to host '127.0.0.1' which is hard coded in the prespawn script. I've attached a patch which uses request_host instead of 127.0.0.1 for the connection.

Attachment: prespawn_fix.diff

Original issue: http://code.google.com/p/phusion-passenger/issues/detail?id=949

[FooBarWidget]

From honglilai on September 16, 2013 04:38:42

This fix is not the proper way to do it. If the host name in request_host points to a load balancer, or a DNS entry with multiple IP addresses, or generally not the local host, then it won't work properly.

A better way would be for Passenger to parse the web server config file and to truly pre-start processes instead of using the current make-an-internal-request-to-the-web-server route.

For now, you can solve this problem locally by sending a request to the correct IP address manually.

[danowar2k]

This just appeared in my Nginx+Passenger Redmine application. I don't listen to 127.0.0.1 and configure nginx via Passenger or rather via Passengerfile.json. I can only set "address" to a single address. Any pointers how I can avoid this error? Add something to nginx.conf? Anywhere else?

[CamJN]

You can track the progress on this issue at: https://github.com/phusion/passenger/tree/prespawn_non_localhost

[HOSTED-POWER]

Hello,

The "progress article" is no longer valid it seems.

Was this ever fixed? We're suffering from this too and don't see why this limitation is imposed :(

Something to override the behavior at least would be terrific!

[CamJN]

It's not fixed yet, unfortunately. The limitation is due to us not knowing to which ip passenger is bound to in apache and nginx integration modes.

[HOSTED-POWER]

Why not simply have an option to resolve the hostname? :)

[CamJN]

We don't do that because the dns resolution for a hostname might point to a load balancer not the server passenger is installed on.

[HOSTED-POWER]

Thanks for feedback, but it could at least be provided as an option, it would help us so much :)

[jgosmann]

Why not an option to specify the IP address explicitly to be used in establishing the connection?

[mzagar]

Modified prespawn script to try to connect to @uri.host if 127.0.0.1 and ::1 both failed, works for me nicely. If this is bad for some reason would it help to introduce support for another uri scheme - ie http_ip://192.168.1.2/ - which would basically say 'ok, i know what i'm doing, let me' and provide me with the option I need (potentially checking that this is indeed ip interface on this machine)?

Current prespawn script i'm using:

class TCPPrespawnLocation < PrespawnLocation
  def request_port
    @uri.port
  end

  def connect
    TCPSocket.new('127.0.0.1', request_port)
  rescue Errno::ECONNREFUSED
    begin
      TCPSocket.new('::1', request_port)
    rescue Errno::ECONNREFUSED
      TCPSocket.new(@uri.host, request_port)
    end
  end
end

then in my prestart I put IP on which nginx is listening on:

passenger_pre_start http://<ip>/;