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feat(channel): Make channel feature additive #1574

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merged 14 commits into from
Jun 19, 2024

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tottoto
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@tottoto tottoto commented Nov 19, 2023

Motivation

Allows users to use transport feature independent from channel.

Solution

Warning

This proposal includes a breaking change.

Makes channel feature additive.

@tottoto tottoto force-pushed the make-channel-feature-additive branch 2 times, most recently from 633ffb2 to 32dbd14 Compare January 5, 2024 22:00
@tottoto tottoto force-pushed the make-channel-feature-additive branch 6 times, most recently from a8d667a to 1fe8cb0 Compare February 8, 2024 22:54
@tottoto tottoto force-pushed the make-channel-feature-additive branch from 1fe8cb0 to 4d0d3ea Compare February 21, 2024 11:56
@tottoto tottoto force-pushed the make-channel-feature-additive branch from 4d0d3ea to 2f5ab49 Compare March 1, 2024 10:40
@tottoto tottoto force-pushed the make-channel-feature-additive branch 5 times, most recently from 44071c7 to bfdac3b Compare April 30, 2024 13:29
@tottoto tottoto force-pushed the make-channel-feature-additive branch from bfdac3b to 4c3efe5 Compare May 21, 2024 10:26
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This looks interesting, but in its current form I find it hard to review. Would you be open to splitting this into smaller commits (or separate PRs if you prefer)? In particular, moving code around would be good to have in separate commits (at least).

@@ -298,13 +298,13 @@ hyper-warp-multiplex = ["hyper-warp"]
uds = ["tokio-stream/net", "dep:tower", "dep:hyper"]
streaming = ["tokio-stream", "dep:h2"]
mock = ["tokio-stream", "dep:tower"]
tower = ["dep:hyper", "dep:tower", "dep:http"]
tower = ["dep:hyper", "dep:tower", "tower?/timeout", "dep:http"]
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The ? isn't really needed here, right, since we already enable dep:tower unconditionally?

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(Saw this also in some of your other PRs, so would be good to clarify the goal here.)

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When I tested this previously, I found that it was necessary to write it like this at the Rust version which is older than or equal to 1.70. But when I tried it again this time, it seems that it is no longer necessary.

I am not sure why the results are different even though testing is done with the same Rust version.

ref:

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I think I find what happen. At this example project, changing both of them to tower/feature removes all dep:tower notation, and then it provides implicit feature. However it is hidden by the explicit tower feature. There is no particular effect on the example, but to unify the notation, I will use ? in the notation.

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I'm not sure I understand the full context of what you're saying. As far as I know, the ? means that the feature dependency should not (by itself) activate the optional dependency itself. That doesn't apply here (we're actively enabling the optional feature), so we should not use the ? here.

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When using Rust 1.70 or older than the version, using dep:crate-name and crate-name/some-feature cannot be used at the same time because of the cargo limitation. dep:crate-name and crate-name?/some-feature is a workaround for the limitation. However, in this case, it seems to be overlooked by cargo due to the explicit feature which is the same name to the crate-name (tower in this case). Based on these premises, I prefer uniformity of notation.

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So if we used 1.71 this limitation would be lifted? Sorry, I'm still not convinced.

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Yes. When we bump MSRV to 1.71, this workaround is not needed.

Found the pull request which addressed this: rust-lang/cargo#12130.

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This is just for examples though so I think this is fine for the moment.

json-codec = ["dep:serde", "dep:serde_json", "dep:bytes"]
compression = ["tonic/gzip"]
tls = ["tonic/tls"]
tls-rustls = ["dep:hyper", "dep:hyper-rustls", "dep:tower", "tower-http/util", "tower-http/add-extension", "dep:rustls-pemfile", "dep:tokio-rustls"]
dynamic-load-balance = ["dep:tower"]
timeout = ["tokio/time", "dep:tower"]
timeout = ["tokio/time", "dep:tower", "tower?/timeout"]
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Same here.

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djc commented May 22, 2024

Allows users to use transport feature independent from channel.

Also, do you have a concrete use case in mind for this?

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tottoto commented May 22, 2024

Would you be open to splitting this into smaller commits (or separate PRs if you prefer)?

Sure, I will do it.

@tottoto tottoto marked this pull request as draft May 22, 2024 12:37
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tottoto commented May 22, 2024

Allows users to use transport feature independent from channel.

Also, do you have a concrete use case in mind for this?

Actually, the main purpose of this pull request is to prepare #1630, which split transport's server and channel completely.

However, this alone is useful for users who want to use it only as transport server without using channel, as it reduces additional dependencies. Currently, channel feature looks an independent feature from transport, but the dependencies and implementations are not separated, so users cannot use the channel functionality without transport.

@tottoto tottoto force-pushed the make-channel-feature-additive branch from 4c3efe5 to f455436 Compare May 22, 2024 12:47
@tottoto tottoto force-pushed the make-channel-feature-additive branch 2 times, most recently from cec6c48 to b48685e Compare May 23, 2024 22:27
@tottoto tottoto marked this pull request as ready for review May 23, 2024 22:35
@tottoto tottoto requested a review from djc May 23, 2024 22:35
@tottoto tottoto force-pushed the make-channel-feature-additive branch from b48685e to e409efb Compare May 26, 2024 11:18
@tottoto tottoto mentioned this pull request May 28, 2024
17 tasks
"dep:tower",
"dep:tower", "tower?/util", "tower?/limit",
]
channel = [
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Can you update the crate root documentation to clarify a bit what the distinction is between channel and transport? I don't think the current docs are very clear:

transport: Enables the fully featured, batteries included client and server implementation based on hyper, tower and tokio. Enabled by default.
channel: Enables just the full featured channel/client portion of the transport feature.

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Updated to reflect the state of these feature flags.

@@ -276,13 +276,13 @@ tracing = ["dep:tracing", "dep:tracing-subscriber"]
uds = ["tokio-stream/net", "dep:tower", "dep:hyper", "dep:hyper-util"]
streaming = ["tokio-stream", "dep:h2"]
mock = ["tokio-stream", "dep:tower", "dep:hyper-util"]
tower = ["dep:hyper", "dep:hyper-util", "dep:tower", "dep:http"]
tower = ["dep:hyper", "dep:hyper-util", "dep:tower", "tower?/timeout", "dep:http"]
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Does the previous commit fail to compile the examples? If so, IMO we should squash this commit into it.

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Does the previous commit fail to compile the examples?

Yes. Squashed these two commits.

use tokio_stream::Stream;
use tower::discover::Change;

type DiscoverResult<K, S, E> = Result<Change<K, S>, E>;
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This seems unrelated to the commit message?

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Fixed.

@tottoto tottoto force-pushed the make-channel-feature-additive branch 5 times, most recently from 6849880 to 0e9cf89 Compare June 15, 2024 01:50
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tottoto commented Jun 15, 2024

Addressed the reviews, and updated the feature configs.

@tottoto tottoto force-pushed the make-channel-feature-additive branch from 0e9cf89 to 3f3acd4 Compare June 15, 2024 09:06
@tottoto tottoto force-pushed the make-channel-feature-additive branch from 3f3acd4 to 3b54bae Compare June 15, 2024 12:46
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LGTM, looks like we need to get #1630 updated as well.

@LucioFranco LucioFranco added this pull request to the merge queue Jun 19, 2024
Merged via the queue into hyperium:master with commit b947e1a Jun 19, 2024
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@tottoto tottoto deleted the make-channel-feature-additive branch June 19, 2024 22:00
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3 participants