From: Simon Eskildsen <firstname.lastname@example.org>
To: Eric Wong <email@example.com>
Cc: firstname.lastname@example.org, email@example.com
Subject: Re: check_client_connection using getsockopt(2)
Date: Wed, 22 Feb 2017 21:42:04 -0500 [thread overview]
Message-ID: <CAO3HKM6AFH2cg1nxVTCfq6jNshaOZEPgPivdFQGz7ovZzWzKFQ@mail.gmail.com> (raw)
On Wed, Feb 22, 2017 at 8:42 PM, Eric Wong <firstname.lastname@example.org> wrote:
> Simon Eskildsen <email@example.com> wrote:
> <snip> Thanks for the writeup!
> Another sidenote: It seems nginx <-> unicorn is a bit odd
> for deployment in a containerized environment(*).
>> I meant to ask, in Raindrops why do you use the netlink API to get the
>> socket backlog instead of `getsockopt(2)` with `TCP_INFO` to get
>> `tcpi_unacked`? (as described in
>> http://www.ryanfrantz.com/posts/apache-tcp-backlog/) We use this to
>> monitor socket backlogs with a sidekick Ruby daemon. Although we're
>> looking to replace it with a middleware to simplify for Kubernetes.
>> It's one of our main metrics for monitoring performance, especially
>> around deploys.
> The netlink API allows independently-spawned processes to
> monitor others; so it can be system-wide. TCP_INFO requires the
> process doing the checking to also have the socket open.
> I guess this reasoning for using netlink is invalid for containers,
If you namespace the network it's problematic, yeah. I'm considering
right now putting Raindrops in a middleware with the netlink API
inside the container, but it feels weird. That said, if you consider
the alternative of using `getsockopt(2)` on the listening socket, I
don't know how you'd get access to the Unicorn listening socket from a
middleware. Would it be nuts to expose a hook in Unicorn that allows
periodic execution for monitoring listening stats from Raindrops on
the listening socket? It seems somewhat of a narrow use-case, but on
the other hand I'm also not a fan of doing
that might be less ugly.
>> I was going to use `env["unicorn.socket"]`/`env["puma.socket"]`, but
>> you could also do `env.delete("hijack_io")` after hijacking to allow
>> Unicorn to still render the response. Unfortunately the
>> `<webserver>.socket` key is not part of the Rack standard, so I'm
>> hesitant to use it. When this gets into Unicorn I'm planning to
>> propose it upstream to Puma as well.
> I was going to say env.delete("rack.hijack_io") is dangerous
> (since env could be copied by middleware); but apparently not:
> rack.hijack won't work with a copied env, either.
> You only need to delete with the same env object you call
> rack.hijack with.
> But calling rack.hijack followed by env.delete may still
> have unintended side-effects in other servers; so I guess
> we (again) cannot rely on hijack working portably.
Exactly, it gives the illusion of portability but e.g. Puma stores an
instance variable to check whether a middleware hijacked, rendering
the `env#delete` option useless.
>> Cool. How would you suggest I check for TCP_INFO compatible platforms
>> in Unicorn? Is `RUBY_PLATFORM.ends_with?("linux".freeze)` sufficient
>> or do you prefer another mechanism? I agree that we should fall back
>> to the write hack on other platforms.
> The Raindrops::TCP_Info class should be undefined on unsupported
> platforms, so I think you can check for that, instead. Then it
> should be transparent to add FreeBSD support from unicorn's
Perfect. I'll start working on a patch.
> (*) So I've been wondering if adding a "unicorn-mode" to an
> existing C10K, slow-client-capable Ruby/Rack server +
> reverse proxy makes sense for containerized deploys.
I'd love to hear more about this idea. What are you contemplating?
next prev parent reply other threads:[~2017-02-23 2:42 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CAO3HKM49+aLD=KLij3zhJqkWnR7bCWVan0mOvxD85xfrW8RXOw@mail.gmail.com>
2017-02-22 18:33 ` check_client_connection using getsockopt(2) Eric Wong
2017-02-22 20:09 ` Simon Eskildsen
2017-02-23 1:42 ` Eric Wong
2017-02-23 2:42 ` Simon Eskildsen [this message]
2017-02-23 3:52 ` Eric Wong
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