gorilla/http
A simple, safe and powerful HTTP client for the Go language.
Image of an under construction GIF
This project is experimental. We welcome contributors and early adopters if you're feeling brave.
Introduction
Why does Go need a new HTTP client, the standard library already has one ?
The Go net/http
package is excellent. It is fast, efficient, gets the job done, and comes batteries
included with every Go installation. At the same time the net/http
package is a victim of its own
success. The Go 1 contract defines many fields in the net/http
types which are redundant or surplus.
Similarly the success of the net/http
package has enshrined bugs which cannot be changed due to the
growing amount of software written to expect that behaviour.
Client only
One acknowledged shortcoming of the net/http
package is its reuse of core types between server and client implementations.
At one level this is admirable, HTTP messages; requests and responses, are more alike than they are different so it makes good engineering sense to reuse their logic where possible. However, combined with the Go 1 contract, this has lead to compromises.
gorilla/http
is a client implementation only. This allows us to focus on a set of layered types which encapsulate the
complete request flow from the client point of view without compromise.
Specific features
This section addresses specific limitations of the net/http
package and discusses the gorilla/http
alternatives.
Timeouts
Timeouts are critically important. By dint of the Go 1 contract, timeouts have been bolted on to the net/http
implementation where possible. gorilla/http
will go further and implement timeouts for as many operations as
possible; connection, request send, response headers, response body, total request/response time, keepalive, etc.
Closing Response Bodies
Forgetting to close a Response.Body
is a continual problem for Gophers. It would be wonderful to create a
client which does not require the response body to be closed, however this appears impossible to marry with
the idea of connection reuse and pooling.
Instead gorilla/http
will address this in two ways
- The high level functions in the
gorilla/http
package do not return types that require closing. For example,gorilla/http.Get(w io.Writer, url string)
mirrors the interface ofio.Copy
and should be sufficient for many REST style http calls which exchange small messages. - At the
http.Client
layer, methods will return anio.ReadCloser
, not a complexResponse
type. Thisio.ReadCloser
must be closed before falling out of scope otherwise the client will panic the application.
Connection rate limiting
Rate limiting in terms of number of total connections in use, number of connections to a particular site will
be controllable. By default gorilla/http
will only use a reasonable number of concurrent connections.
gorilla/http
has a strictly layered design where the high level gorilla/http
package is responsible for
request composition and connection management and the lower level gorilla/http/client
package is strictly
responsible for the http transaction and the lowest level wire format.
Reliable DNS lookups
gorilla/http
will use an alternative DNS resolver library to avoid the limitations of the system libc resolver library.
Robustness and correctness
As a client only package, gorilla/http
has flexibility to bias correctness over performance. Gorilla will always
favor correctness of implementation over performance, and we believe this is the correct trade off. Having said that
performance is a feature and gorilla/http
strives to keep its overheads compared to the underlying network transit
cost as low as possible.
Roadmap
The roadmap for the project is captured as open issues in GitHub.
Contributions and feedback
Please raise issues and suggestions on the GitHub project page, https://github.com/gorilla/http/issues.
Questions and discussion can also be directed to the general Gorilla mailing list https://groups.google.com/group/gorilla-web.
Technical information
gorilla/http
is divided into 4 layers. The topmost layer is a set of convenience functions layered on top of a
default gorilla/http.Client
instance. These package level functions are intended to satisfy simple HTTP requests
and only cover the most common verbs and use cases.
The next layer is gorilla/http.Client
which is a high level reusable HTTP client. It transparently manages connection
pooling and reuse and provides both common verbs and a general purpose Client.Do()
interface for uncommon http verbs.
The lower layers are inside the gorilla/http/client
package and consist of types that deal with the abstract RFC2616
message form and marshal it on and off the wire.
Interestingly, although these are the lowest level types, they do not deal with net.Conn
implementations, but
io.ReadWriter
, connection setup, management and timeout control is handled by the owner of the io.ReadWriter
implementation passed to client.Client
.