Added connection reuse

[zanker]

Adds a connection reuse API to http.rb, via HTTP.persistent("http://www.google.com").

client = HTTP.persistent("http://www.google.ocm")
client.get("http://www.google.com/foo")
client.get("http://www.google.com/bar")

Results in reusing a connection. I went with the redundant host being passed because it keeps the API consistent. I could make it just /foo or /bar calls too.

[zanker]

cc @tarcieri

[zanker]

Last bit of work in and it should go green now.

I've added as many state checks for things like recovering from errors that I can think of. Since body's are lazily loaded, I've added sequence IDs. If you make multiple requests, you need to either have read out a body before making the next one, or you can't use the body later without it erroring.

[ixti]

There was a discussion about connection re-use: #121
Just want to get attention that in future we would like to have connections pool. I think of API like:

# @param [Hash] opts
# @option opts [Array<#to_s>] :hosts ([]) Makes sure connections persist for
#   the given list of hosts only. Any host if empty.
# @option opts [#to_i] :pool_size (5) Amount of simultaneous open connections.
def persistent(opts = {}); end

[zanker]

My concern with using a connection pool is that it adds a lot of additional complexity and I'm not sure that call patterns are worth it.

The connection_pool gem works great, and I'm not sure how beneficial it is to really reuse a client across multiple hosts.

[tarcieri]

Yeah, I like that this is doing the simple thing, and agree that if pools are needed, connection_pool can be used.

[ixti]

Then I must admit I was thinking about some absolutely different API :D
But I agree that this version is pretty neat :D
After all advanced pooling can be added later as part of core or as a separate extension gem.

[sferik]

As the person who initially requested this feature, I’m 👍 on this pull request. The API is essentially identical to what I proposed in #121. Nice work @zanker! Thank you for implementing this!

[zanker]

@sferik Hah no problem. We're replacing our use of Net::HTTP::Persistent and the only gems with proper conn reuse are either JRuby or libcurl based :(

[zanker]

Made a quick change. On any exception we reset the conn, rather than a specific subset of network related ones.

Mostly it's a safety measure to be sure we don't have mixed requests/response.

[ixti]

👍