feat: Add uniflight (name pending) crate for duplicate request coalescing

.gitignore

@@ -35,4 +35,5 @@ _manifest
 ARROW
 
 # Agent files
-.claude
+.claude
+CLAUDE.md

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 Please see each crate's change log below:
 
+- [`async_once`](./crates/async_once/CHANGELOG.md)
 - [`bytesbuf`](./crates/bytesbuf/CHANGELOG.md)
 - [`bytesbuf_io`](./crates/bytesbuf_io/CHANGELOG.md)
 - [`data_privacy`](./crates/data_privacy/CHANGELOG.md)
@@ -16,3 +17,4 @@ Please see each crate's change log below:
 - [`thread_aware_macros`](./crates/thread_aware_macros/CHANGELOG.md)
 - [`thread_aware_macros_impl`](./crates/thread_aware_macros_impl/CHANGELOG.md)
 - [`tick`](./crates/tick/CHANGELOG.md)
+- [`uniflight`](./crates/uniflight/CHANGELOG.md)

Cargo.toml

@@ -39,16 +39,20 @@ thread_aware = { path = "crates/thread_aware", default-features = false, version
 thread_aware_macros = { path = "crates/thread_aware_macros", default-features = false, version = "0.6.0" }
 thread_aware_macros_impl = { path = "crates/thread_aware_macros_impl", default-features = false, version = "0.6.0" }
 tick = { path = "crates/tick", default-features = false, version = "0.1.2" }
+uniflight = { path = "crates/uniflight", default-features = false, version = "0.1.0" }
 
 # external dependencies
 alloc_tracker = { version = "0.5.9", default-features = false }
+async-once-cell = { version = "0.5", default-features = false }
 anyhow = { version = "1.0.100", default-features = false }
 bytes = { version = "1.11.0", default-features = false }
 chrono = { version = "0.4.40", default-features = false }
 chrono-tz = { version = "0.10.4", default-features = false }
 criterion = { version = "0.7.0", default-features = false }
+dashmap = { version = "6.1", default-features = false }
 derive_more = { version = "2.0.1", default-features = false }
 duct = { version = "1.1.1", default-features = false }
+event-listener = { version = "5.4.0", default-features = false }
 futures = { version = "0.3.31", default-features = false }
 futures-core = { version = "0.3.31", default-features = false }
 futures-util = { version = "0.3.31", default-features = false }
@@ -63,6 +67,7 @@ new_zealand = { version = "1.0.1", default-features = false }
 nm = { version = "0.1.21", default-features = false }
 num-traits = { version = "0.2.19", default-features = false }
 once_cell = { version = "1.21.3", default-features = false }
+parking_lot = { version = "0.12.5", default-features = false }
 pin-project-lite = { version = "0.2.13", default-features = false }
 pretty_assertions = { version = "1.4.1", default-features = false }
 prettyplease = { version = "0.2.37", default-features = false }
@@ -75,6 +80,7 @@ rustc-hash = { version = "2.1.0", default-features = false }
 serde = { version = "1.0.228", default-features = false }
 serde_core = { version = "1.0.228", default-features = false }
 serde_json = { version = "1.0.145", default-features = false }
+singleflight-async = { version = "0.2", default-features = false }
 smallvec = { version = "1.15.1", default-features = false }
 static_assertions = { version = "1.1.0", default-features = false }
 syn = { version = "2.0.111", default-features = false }
@@ -88,6 +94,7 @@ trait-variant = { version = "0.1.2", default-features = false }
 trybuild = { version = "1.0.114", default-features = false }
 typeid = { version = "1.0.3", default-features = false }
 windows-sys = { version = "0.61.2", default-features = false }
+xutex = { version = "0.2.0", default-features = false }
 xxhash-rust = { version = "0.8.15", default-features = false }
 
 [workspace.lints.rust]

README.md

@@ -11,14 +11,15 @@
 
 This repository contains a set of crates that help you build robust highly scalable services in Rust.
 
-- [Crates](#crates)
-- [About this Repo](#about-this-repo)
+- [The Oxidizer Project](#the-oxidizer-project)
+  - [Crates](#crates)
+  - [About this Repo](#about-this-repo)
     - [Adding New Crates](#adding-new-crates)
     - [Publishing Crates](#publishing-crates)
     - [Documenting Crates](#documenting-crates)
     - [CI Workflows](#ci-workflows)
     - [Pull Request Gates](#pull-request-gates)
-- [Trademarks](#trademarks)
+  - [Trademarks](#trademarks)
 
 ## Crates
 
@@ -38,6 +39,7 @@ These are the crates built out of this repo:
 - [`thread_aware_macros`](./crates/thread_aware_macros/README.md) - Macros for the `thread_aware` crate.
 - [`thread_aware_macros_impl`](./crates/thread_aware_macros_impl/README.md) - Macros for the `thread_aware` crate.
 - [`tick`](./crates/tick/README.md) - Provides primitives to interact with and manipulate machine time.
+- [`uniflight`](./crates/uniflight/README.md) - Coalesces duplicate async tasks into a single execution.
 
 ## About this Repo
 

crates/uniflight/CHANGELOG.md

@@ -0,0 +1,8 @@
+# Changelog
+
+## [0.1.0] - 2025-12-10
+
+- 🧩 Miscellaneous
+
+  - Initial commit of uniflight
+

crates/uniflight/Cargo.toml

@@ -0,0 +1,43 @@
+# Copyright (c) Microsoft Corporation.
+# Licensed under the MIT License.
+
+[package]
+name = "uniflight"
+description = "Coalesces multiple ongoing tasks into a leader which does the work, and follower tasks that wait on the result, to prevent duplicate I/O or other downstream overhead."
+version = "0.1.0"
+readme = "README.md"
+keywords = ["oxidizer", "coalescing", "stempede", "singleflight", "deduplication"]
+categories = ["concurrency"]
+
+edition.workspace = true
+rust-version.workspace = true
+authors.workspace = true
+license.workspace = true
+homepage.workspace = true
+repository.workspace = true
+
+[dependencies]
+async-once-cell.workspace = true
+dashmap.workspace = true
+
+[dev-dependencies]
+criterion = { workspace = true, features = ["async_tokio"] }
+futures-util = { workspace = true, features = ["alloc", "std"] }
+singleflight-async.workspace = true
+tick = { workspace = true, features = ["tokio"] }
+tokio = { workspace = true, features = [
+    "macros",
+    "rt",
+    "time",
+    "rt-multi-thread",
+] }
+
+[lints]
+workspace = true
+
+[[bench]]
+name = "comparison"
+harness = false
+
+[[example]]
+name = "cache_population"

crates/uniflight/README.md

@@ -0,0 +1,83 @@
+<div align="center">
+ <img src="./logo.png" alt="Uniflight Logo" width="128">
+
+# Uniflight
+
+[![crate.io](https://img.shields.io/crates/v/uniflight.svg)](https://crates.io/crates/uniflight)
+[![docs.rs](https://docs.rs/uniflight/badge.svg)](https://docs.rs/uniflight)
+[![MSRV](https://img.shields.io/crates/msrv/uniflight)](https://crates.io/crates/uniflight)
+[![CI](https://github.com/microsoft/oxidizer/workflows/main/badge.svg)](https://github.com/microsoft/oxidizer/actions)
+[![Coverage](https://codecov.io/gh/microsoft/oxidizer/graph/badge.svg?token=FCUG0EL5TI)](https://codecov.io/gh/microsoft/oxidizer)
+[![License](https://img.shields.io/badge/license-MIT-blue.svg)](../LICENSE)
+
+</div>
+
+* [Summary](#summary)
+
+## Summary
+
+<!-- cargo-rdme start -->
+
+Coalesces duplicate async tasks into a single execution.
+
+This crate provides [`Merger`], a mechanism for deduplicating concurrent async operations.
+When multiple tasks request the same work (identified by a key), only the first task (the
+"leader") performs the actual work while subsequent tasks (the "followers") wait and receive
+a clone of the result.
+
+## When to Use
+
+Use `Merger` when you have expensive or rate-limited operations that may be requested
+concurrently with the same parameters:
+
+- **Cache population**: Prevent thundering herd when a cache entry expires
+- **API calls**: Deduplicate concurrent requests to the same endpoint
+- **Database queries**: Coalesce identical queries issued simultaneously
+- **File I/O**: Avoid reading the same file multiple times concurrently
+
+## Example
+
+```rust
+use uniflight::Merger;
+
+let group: Merger<&str, String> = Merger::new();
+
+// Multiple concurrent calls with the same key will share a single execution
+let result = group.work("user:123", || async {
+    // This expensive operation runs only once, even if called concurrently
+    "expensive_result".to_string()
+}).await;
+```
+
+## Cancellation and Panic Safety
+
+`Merger` handles task cancellation and panics gracefully:
+
+- If the leader task is cancelled or dropped, a follower becomes the new leader
+- If the leader task panics, a follower becomes the new leader and executes its work
+- Followers that join before the leader completes receive the cached result
+
+## Thread Safety
+
+[`Merger`] is `Send` and `Sync`, and can be shared across threads. The returned futures
+are `Send` when the closure, future, key, and value types are `Send`.
+
+## Performance
+
+Benchmarks comparing `uniflight` against `singleflight-async` show the following characteristics:
+
+- **Concurrent workloads** (10+ tasks): uniflight is 1.2-1.3x faster, demonstrating better scalability under contention
+- **Single calls**: singleflight-async has lower per-call overhead (~2x faster for individual operations)
+- **Multiple keys**: uniflight performs 1.3x faster when handling multiple distinct keys concurrently
+
+uniflight's DashMap-based architecture provides excellent scaling properties for high-concurrency scenarios,
+making it well-suited for production workloads with concurrent access patterns. For low-contention scenarios
+with predominantly single calls, the performance difference is minimal (sub-microsecond range).
+
+<!-- cargo-rdme end -->
+
+<div style="font-size: 75%" ><hr/>
+
+This crate was developed as part of [The Oxidizer Project](https://github.com/microsoft/oxidizer).
+
+</div>