From 5e4ebb3424587aad93cd2800778bd5e01655f72b Mon Sep 17 00:00:00 2001
From: katelyn martin <kate@buoyant.io>
Date: Fri, 1 Nov 2024 00:00:00 +0000
Subject: [PATCH] refactor(proxy/http): create `linkerd-http-retain` crate
 (#3382)
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this moves the `Retain` middleware from `linkerd-proxy-http` into a new
`linkerd-http-retain` crate.

as previously, reëxports are added to make this a backwards compatible
change.

this moves another http body middleware out of the proxy's core http
crate. great news.

Signed-off-by: katelyn martin <kate@buoyant.io>
---
 Cargo.lock                                    | 12 +++++++++++
 Cargo.toml                                    |  1 +
 linkerd/http/retain/Cargo.toml                | 20 +++++++++++++++++++
 .../src/retain.rs => http/retain/src/lib.rs}  |  6 ++++--
 linkerd/proxy/http/Cargo.toml                 |  1 +
 linkerd/proxy/http/src/lib.rs                 |  3 +--
 6 files changed, 39 insertions(+), 4 deletions(-)
 create mode 100644 linkerd/http/retain/Cargo.toml
 rename linkerd/{proxy/http/src/retain.rs => http/retain/src/lib.rs} (93%)

diff --git a/Cargo.lock b/Cargo.lock
index 4e558d284d..7f1625cce5 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1782,6 +1782,17 @@ dependencies = [
  "tokio",
 ]
 
+[[package]]
+name = "linkerd-http-retain"
+version = "0.1.0"
+dependencies = [
+ "http",
+ "http-body",
+ "linkerd-stack",
+ "pin-project",
+ "tower",
+]
+
 [[package]]
 name = "linkerd-http-retry"
 version = "0.1.0"
@@ -2188,6 +2199,7 @@ dependencies = [
  "linkerd-http-executor",
  "linkerd-http-h2",
  "linkerd-http-insert",
+ "linkerd-http-retain",
  "linkerd-http-version",
  "linkerd-io",
  "linkerd-proxy-balance",
diff --git a/Cargo.toml b/Cargo.toml
index fa2e89ba4b..0e1d82e3dc 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -32,6 +32,7 @@ members = [
     "linkerd/http/insert",
     "linkerd/http/metrics",
     "linkerd/http/prom",
+    "linkerd/http/retain",
     "linkerd/http/retry",
     "linkerd/http/route",
     "linkerd/http/version",
diff --git a/linkerd/http/retain/Cargo.toml b/linkerd/http/retain/Cargo.toml
new file mode 100644
index 0000000000..dfbdda108c
--- /dev/null
+++ b/linkerd/http/retain/Cargo.toml
@@ -0,0 +1,20 @@
+[package]
+name = "linkerd-http-retain"
+version = "0.1.0"
+authors = ["Linkerd Developers <cncf-linkerd-dev@lists.cncf.io>"]
+license = "Apache-2.0"
+edition = "2021"
+publish = false
+description = """
+Tower middleware to manage service lifecycles.
+
+This is mostly intended to support cache eviction.
+"""
+
+[dependencies]
+http = "0.2"
+http-body = "0.4"
+pin-project = "1"
+tower = { version = "0.4", default-features = false }
+
+linkerd-stack = { path = "../../stack" }
diff --git a/linkerd/proxy/http/src/retain.rs b/linkerd/http/retain/src/lib.rs
similarity index 93%
rename from linkerd/proxy/http/src/retain.rs
rename to linkerd/http/retain/src/lib.rs
index e5ed0f9deb..fe60f2c9ea 100644
--- a/linkerd/proxy/http/src/retain.rs
+++ b/linkerd/http/retain/src/lib.rs
@@ -1,5 +1,7 @@
-//! Provides a middleware that holds an inner service as long as responses are
-//! being processed.
+//! Tower middleware to manage service lifecycles.
+//!
+//! Provides a [`Retain<S, B>`] middleware that holds an inner service as long as responses are
+//! being processed. This is mostly intended to support cache eviction.
 
 use linkerd_stack::layer;
 use pin_project::pin_project;
diff --git a/linkerd/proxy/http/Cargo.toml b/linkerd/proxy/http/Cargo.toml
index 57f5be3f3d..de0703f0be 100644
--- a/linkerd/proxy/http/Cargo.toml
+++ b/linkerd/proxy/http/Cargo.toml
@@ -46,6 +46,7 @@ linkerd-http-classify = { path = "../../http/classify" }
 linkerd-http-executor = { path = "../../http/executor" }
 linkerd-http-h2 = { path = "../../http/h2" }
 linkerd-http-insert = { path = "../../http/insert" }
+linkerd-http-retain = { path = "../../http/retain" }
 linkerd-http-version = { path = "../../http/version" }
 linkerd-io = { path = "../../io" }
 linkerd-proxy-balance = { path = "../balance" }
diff --git a/linkerd/proxy/http/src/lib.rs b/linkerd/proxy/http/src/lib.rs
index 2e46e77a7e..72a10d3b4a 100644
--- a/linkerd/proxy/http/src/lib.rs
+++ b/linkerd/proxy/http/src/lib.rs
@@ -15,7 +15,6 @@ mod header_from_target;
 pub mod normalize_uri;
 pub mod orig_proto;
 mod override_authority;
-mod retain;
 mod server;
 pub mod stream_timeouts;
 pub mod strip_header;
@@ -33,7 +32,6 @@ pub use self::{
     header_from_target::NewHeaderFromTarget,
     normalize_uri::{MarkAbsoluteForm, NewNormalizeUri},
     override_authority::{AuthorityOverride, NewOverrideAuthority},
-    retain::Retain,
     server::{NewServeHttp, Params as ServerParams, ServeHttp},
     stream_timeouts::{EnforceTimeouts, StreamTimeouts},
     strip_header::StripHeader,
@@ -48,6 +46,7 @@ pub use linkerd_http_box::{BoxBody, BoxRequest, BoxResponse, EraseResponse};
 pub use linkerd_http_classify as classify;
 pub use linkerd_http_executor::TracingExecutor;
 pub use linkerd_http_insert as insert;
+pub use linkerd_http_retain::{self as retain, Retain};
 pub use linkerd_http_version::{self as version, Version};
 
 #[derive(Clone, Debug)]