feat(on-early-drop): Add middleware for client early drop detection by fbergero · Pull Request #636 · tower-rs/tower-http

fbergero · 2026-01-09T20:00:53Z

Add on-early-drop middleware for client early drop detection

Introduces a new middleware that detects when a client disconnects before receiving a full response. This allows for monitoring and logging of early connection terminations.

Fixes #396

Motivation

When clients disconnect before receiving a complete response (e.g., due to browser navigation, timeouts, or network issues), the entire future chain is typically dropped with no indication of what happened. This creates "disappearing requests" that never show up in logs or metrics, making it difficult to:

Identify patterns of client disconnects
Properly monitor the full request lifecycle
Handle or recover from incomplete operations

Solution

This PR introduces two main components:

1. OnEarlyDropGuard

A standalone guard that executes a callback function when dropped, unless explicitly marked as completed:

Simple API: Create the guard with a closure that executes on early drop
Callback Control: Mark operations as successfully completed to prevent the callback
FnOnce Support: Designed to work with closures that take ownership of their environment

2. OnEarlyDropLayer/Service

A Tower middleware that applies early drop detection to HTTP services:

Request Context: Closures can capture specific request information

This implementation enables various use cases:

Logging dropped requests with context
Capturing metrics about client disconnections
Maintaining trace context across early terminations
Performing cleanup operations for abandoned requests

rcoh · 2026-01-28T18:06:49Z

cc @tottoto can you review?

jlizen · 2026-02-19T17:42:23Z

cc @seanmonstar if you have any time, no problem if not. I've reviewed it back when it was on the fork, so fairly polished.

jlizen · 2026-05-05T04:00:43Z

Hey @fbergero , like we chatted about offline, I pushed some changes on top of yours (and also dealt with the rebase).

Generally I added some more integration with the rest of the tower-http stack:

there is an adapter to pass it into the trace layer's OnFailure handler
you can fire a separate callback if the body drops before streaming finishes (that has access to response parts)
axum example now uses this (via the tracing integration)

Introduces a new middleware that detects when a client disconnects before receiving a full response. This allows for monitoring and logging of early connection terminations. Fixes tower-rs#396

…back

fbergero · 2026-05-05T12:05:57Z

@jlizen Loved the EarlyDropsAsFailures for a nice-easy setup. Thanks for the improvements.

IDK if we need to update the PR desc to include the new changes (it's on the rustdocs anyhow so up to you)

rcoh

there is one duplicated doc line otherwise LGTM

…ropsAsFailures, other doc cleanups

This PR contains the following updates: | Package | Type | Update | Change | |---|---|---|---| | [tower-http](https://github.com/tower-rs/tower-http) | workspace.dependencies | patch | `0.6.8` → `0.6.9` | --- ### Release Notes <details> <summary>tower-rs/tower-http (tower-http)</summary> ### [`v0.6.9`](https://github.com/tower-rs/tower-http/releases/tag/tower-http-0.6.9) [Compare Source](tower-rs/tower-http@tower-http-0.6.8...tower-http-0.6.9) #### Added: - `on-early-drop`: middleware that detects when a response future or response body is dropped before completion ([#636]) Two events get hooks: the response future being dropped before the inner service produces a response, and the response body being dropped before reaching end-of-stream. Install custom callbacks with `OnEarlyDropLayer::builder()`: ```rust use http::Request; use tower_http::on_early_drop::{OnBodyDropFn, OnEarlyDropLayer}; let layer = OnEarlyDropLayer::builder() .on_future_drop(|req: &Request<()>| { let uri = req.uri().clone(); move || eprintln!("future dropped for {}", uri) }) .on_body_drop(OnBodyDropFn::new(|req: &Request<()>| { let uri = req.uri().clone(); move |parts: &http::response::Parts| { let status = parts.status; move || eprintln!("body dropped for {} status {}", uri, status) } })); ``` Or route both events through a `trace::OnFailure` hook with `EarlyDropsAsFailures`. Place this layer inside a `TraceLayer` so the emitted events inherit the request span: ```rust use tower::ServiceBuilder; use tower_http::on_early_drop::{OnEarlyDropLayer, EarlyDropsAsFailures}; use tower_http::trace::{DefaultOnFailure, TraceLayer}; let stack = ServiceBuilder::new() .layer(TraceLayer::new_for_http()) .layer(OnEarlyDropLayer::new( EarlyDropsAsFailures::new(DefaultOnFailure::default()), )); ``` - `fs`: make `AsyncReadBody::with_capacity` public ([#415]) #### Changed: - The implicit `async-compression` feature is removed ([#642]) - The implicit `tokio` feature is removed ([#628]) - `fs`: no longer auto-enables the `tracing` crate feature; enable `tracing` explicitly to restore error logging on `ServeDir` IO failures ([#614]) #### Fixed - `trace`: restore failure classification at end-of-stream ([#483]) - `follow-redirect`: support unicode URLs (swaps `iri-string` dep for `url`) ([#646]) - `fs`: reject reserved Windows DOS device names (`CON`, `COM1`, etc.) in `ServeDir` ([#663]) [#415]: tower-rs/tower-http#415 [#483]: tower-rs/tower-http#483 [#614]: tower-rs/tower-http#614 [#628]: tower-rs/tower-http#628 [#636]: tower-rs/tower-http#636 [#642]: tower-rs/tower-http#642 [#646]: tower-rs/tower-http#646 [#663]: tower-rs/tower-http#663 #### All the PRs - ci: update deny action to v2 by [@seanmonstar](https://github.com/seanmonstar) in [#627](tower-rs/tower-http#627) - chore: improve code comments clarity by [@xibeiyoumian](https://github.com/xibeiyoumian) in [#626](tower-rs/tower-http#626) - ci: Update to actions/checkout v6 by [@tottoto](https://github.com/tottoto) in [#629](tower-rs/tower-http#629) - ci: msrv resolver by [@seanmonstar](https://github.com/seanmonstar) in [#635](tower-rs/tower-http#635) - chore: Remove resolved cargo-deny config by [@tottoto](https://github.com/tottoto) in [#631](tower-rs/tower-http#631) - ci: Update to cargo-check-external-types 0.4.0 by [@tottoto](https://github.com/tottoto) in [#633](tower-rs/tower-http#633) - examples: Use typed default value clap config by [@tottoto](https://github.com/tottoto) in [#634](tower-rs/tower-http#634) - examples: Disable unused reqwest feature by [@tottoto](https://github.com/tottoto) in [#632](tower-rs/tower-http#632) - examples: Update to reqwest 0.13 by [@tottoto](https://github.com/tottoto) in [#640](tower-rs/tower-http#640) - Fix clippy warnings in warp-key-value-store example by [@jplatte](https://github.com/jplatte) in [#637](tower-rs/tower-http#637) - ci: Use Swatinem/rust-cache\@v2 to cache by [@tottoto](https://github.com/tottoto) in [#644](tower-rs/tower-http#644) - ci: Remove unused working-directory config by [@tottoto](https://github.com/tottoto) in [#645](tower-rs/tower-http#645) - Use cargo-deny graph config by [@tottoto](https://github.com/tottoto) in [#639](tower-rs/tower-http#639) - Fix: follow redirect unicode in [#646](tower-rs/tower-http#646) - doc: remove mention of deprecated bearer method in lib.rs comment by [@VojtaStanek](https://github.com/VojtaStanek) in [#641](tower-rs/tower-http#641) - Allow Unicode-3.0 license by [@tottoto](https://github.com/tottoto) in [#648](tower-rs/tower-http#648) - fix(docs): typo by [@carlocorradini](https://github.com/carlocorradini) in [#649](tower-rs/tower-http#649) - fix: remove unused GzEncoder import in decompression in [#647](tower-rs/tower-http#647) - docs: update Example server in [#652](tower-rs/tower-http#652) - Don't automatically enable tracing for fs feature by [@ginnyTheCat](https://github.com/ginnyTheCat) in [#614](tower-rs/tower-http#614) - examples: Remove unnecessary trait bound by [@tottoto](https://github.com/tottoto) in [#651](tower-rs/tower-http#651) - Remove implicit async-compression feature by [@tottoto](https://github.com/tottoto) in [#642](tower-rs/tower-http#642) - fix clippy warnings by [@alexanderkjall](https://github.com/alexanderkjall) in [#659](tower-rs/tower-http#659) - Check for reserved DOS names by [@Darksonn](https://github.com/Darksonn) in [#663](tower-rs/tower-http#663) - enable clippy for tower-http and fix current issues by [@GlenDC](https://github.com/GlenDC) in [#407](tower-rs/tower-http#407) - chore: remove implicit tokio feature by [@WaterWhisperer](https://github.com/WaterWhisperer) in [#628](tower-rs/tower-http#628) - trace: adds back call to classify\_eos on trailers by [@markdingram](https://github.com/markdingram) in [#483](tower-rs/tower-http#483) - Make AsyncReadBody::with\_capacity public by [@bouk](https://github.com/bouk) in [#415](tower-rs/tower-http#415) - examples: Use axum::body::to\_bytes by [@tottoto](https://github.com/tottoto) in [#650](tower-rs/tower-http#650) - ci: Remove unnecessary protoc setup by [@tottoto](https://github.com/tottoto) in [#665](tower-rs/tower-http#665) - feat(on-early-drop): Add middleware for client early drop detection by [@fbergero](https://github.com/fbergero) in [#636](tower-rs/tower-http#636) - chore: release tower-http 0.6.9 by [@jlizen](https://github.com/jlizen) in [#666](tower-rs/tower-http#666) #### New Contributors - [@xibeiyoumian](https://github.com/xibeiyoumian) made their first contribution in [#626](tower-rs/tower-http#626) - [@VojtaStanek](https://github.com/VojtaStanek) made their first contribution in [#641](tower-rs/tower-http#641) - [@carlocorradini](https://github.com/carlocorradini) made their first contribution in [#649](tower-rs/tower-http#649) - [@ginnyTheCat](https://github.com/ginnyTheCat) made their first contribution in [#614](tower-rs/tower-http#614) - [@alexanderkjall](https://github.com/alexanderkjall) made their first contribution in [#659](tower-rs/tower-http#659) - [@Darksonn](https://github.com/Darksonn) made their first contribution in [#663](tower-rs/tower-http#663) - [@WaterWhisperer](https://github.com/WaterWhisperer) made their first contribution in [#628](tower-rs/tower-http#628) - [@bouk](https://github.com/bouk) made their first contribution in [#415](tower-rs/tower-http#415) - [@fbergero](https://github.com/fbergero) made their first contribution in [#636](tower-rs/tower-http#636) - [@jlizen](https://github.com/jlizen) made their first contribution in [#666](tower-rs/tower-http#666) **Full Changelog**: <tower-rs/tower-http@tower-http-0.6.8...tower-http-0.6.9> </details> --- ### Configuration 📅 **Schedule**: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined). 🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied. ♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox. 🔕 **Ignore**: Close this PR and you won't be reminded about this update again. --- - [ ] If you want to rebase/retry this PR, check this box --- This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate).  Reviewed-on: https://git.erwanleboucher.dev/eleboucher/towonel/pulls/33

fbergero marked this pull request as ready for review January 9, 2026 20:01

fbergero mentioned this pull request Jan 9, 2026

tower_http::trace::OnEarlyDrop #396

Closed

fbergero force-pushed the on-early-drop-396 branch from 0477f9b to 0828576 Compare January 21, 2026 20:13

jlizen force-pushed the on-early-drop-396 branch from 0828576 to d40646f Compare May 5, 2026 03:59

jlizen force-pushed the on-early-drop-396 branch from 78a72ab to ecfdc1b Compare May 5, 2026 04:11

fbergero and others added 6 commits May 5, 2026 04:16

feat(on-early-drop): Add middleware for client early drop detection

c1f0d86

Introduces a new middleware that detects when a client disconnects before receiving a full response. This allows for monitoring and logging of early connection terminations. Fixes tower-rs#396

docs(on-early-drop): document and pin drop-only semantics

0c62f60

refactor(on-early-drop): simplify OnEarlyDropGuard state

be481ac

feat(on-early-drop): add body-drop detection and trace adapter

e90fd2c

docs(examples): demonstrate OnEarlyDropLayer in axum-key-value-store

14b7ae3

test(on-early-drop): cover is_end_stream, noop slots, and custom call…

1214120

…back

jlizen force-pushed the on-early-drop-396 branch from ecfdc1b to 1214120 Compare May 5, 2026 04:16

rcoh approved these changes May 5, 2026

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Comment thread tower-http/src/on_early_drop/mod.rs Outdated

jlizen added 2 commits May 5, 2026 15:04

docs(on-early-drop): document panic requirement on callbacks

88bf4f7

docs: clarify that OnEarlyDropLayer::new can only be used with EarlyD…

5b015ea

…ropsAsFailures, other doc cleanups

jlizen approved these changes May 5, 2026

View reviewed changes

jlizen merged commit 9c64770 into tower-rs:main May 5, 2026
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feat(on-early-drop): Add middleware for client early drop detection#636

feat(on-early-drop): Add middleware for client early drop detection#636
jlizen merged 8 commits into
tower-rs:mainfrom
fbergero:on-early-drop-396

fbergero commented Jan 9, 2026

Uh oh!

rcoh commented Jan 28, 2026

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jlizen commented Feb 19, 2026

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jlizen commented May 5, 2026

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fbergero commented May 5, 2026 •

edited

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fbergero commented Jan 9, 2026

Add on-early-drop middleware for client early drop detection

Motivation

Solution

1. OnEarlyDropGuard

2. OnEarlyDropLayer/Service

Uh oh!

rcoh commented Jan 28, 2026

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jlizen commented Feb 19, 2026

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jlizen commented May 5, 2026

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fbergero commented May 5, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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fbergero commented May 5, 2026 •

edited

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