add Timeout functionality for http package

[DartBot]

Originally opened as dart-lang/sdk#19831

This issue was originally filed by theburnin...@gmail.com

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What steps will clearly show the issue / need for enhancement?

1. when making http requests you usually want to timeout the request after a reasonable amount of time (usually in the region of seconds)
2. it would be great to have away to specify timeout as Duration when making a http request via the http/browser client/http client classes.

What version of the product are you using? On what operating system?
Dart 1.5.1, http 0.11.1+1

[DartBot]

<img src="https://avatars.githubusercontent.com/u/2108507?v=3" align="left" width="48" height="48"hspace="10"> Comment by dgrove

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Added Pkg-Http, Triaged labels.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/188?v=3" align="left" width="48" height="48"hspace="10"> Comment by nex3

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Probably the best way to support this would be to add a separate http_timeout_client package that exposes an HttpTimeoutClient that wraps an existing client.

[DartBot]

This comment was originally written by theburnin...@gmail.com

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Is there any reason why timeout couldn't be added as an optional parameter to the existing clients? I think the usage pattern would be more obvious this way than having to first create a client, then create another (HttpTimeoutClient) to wrap around it before you do a HTTP request.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/188?v=3" align="left" width="48" height="48"hspace="10"> Comment by nex3

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The http package is based on a composition model where each layer (that is, a class implementing http.Client) is very simple and has a well-defined purpose. This model makes it very easy to mix and match functionality, but one of the costs is that the API for a layer has to be very simple in order to keep them easy to implement. It would be bad if everyone implementing their own [http.Client] had to re-implement the timeout logic from scratch.

having to first create a client, then create another (HttpTimeoutClient) to wrap around it before you do a HTTP request.

The API wouldn't be that difficult. The constructor would look something like this:

    HttpTimeoutClient([HttpClient inner])
        : _inner = inner == null ? new HttpClient() : inner;

The user only needs to construct one client if they only care about one aspect of the client.

[DartBot]

This comment was originally written by theburning...@gmail.com

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Hi, thanks for the explanation, that makes a lot of sense.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/188?v=3" align="left" width="48" height="48"hspace="10"> Comment by nex3

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Issue #10 has been merged into this issue.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/444270?v=3" align="left" width="48" height="48"hspace="10"> Comment by seaneagan

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Doesn't Future.timeout solve this pretty well already?

https://api.dartlang.org/apidocs/channels/stable/dartdoc-viewer/dart-async.Future#id_timeout

Example:

    http.read('http://google.com')
        .timeout(const Duration(seconds: 5))
        .then(...);

[DartBot]

<img src="https://avatars.githubusercontent.com/u/17034?v=3" align="left" width="48" height="48"hspace="10"> Comment by kevmoo

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I don't think HttpTimeoutClient can accomplish what we want.

Users would like to actually cancel the inflight request.

dart:html has abort() on HttpRequest
dart:io HttpClient* has no equivalente – the idleTimeout just manages keep-alive connections while idea AKAICT

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Added Area-Pkg label.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/17034?v=3" align="left" width="48" height="48"hspace="10"> Comment by kevmoo

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Marked this as being blocked by dart-lang/sdk#22265.

[tomyeh]

Any plan to support it?

[donny-dont]

This can easily be done through a middleware with the 0.12 implementation.

[donny-dont]

@nex3 there's also HttpRequest.timeout which we could have a special context for. We might also want to handle the onTimeout if that's the case.