Singleflight

2 articles

Go 16 Sep 2026 5 min read

Go singleflight Shares Only In-Flight Results

singleflight.Group suppresses duplicate function executions only while an operation for the same key is in flight. Concurrent callers can receive one shared result, but a caller arriving after completion starts a new execution. The group is therefore a request-coalescing mechanism, not a result cache. This boundary affects cache fills, metadata refreshes, backend reads, and other keyed operations that can attract bursts of identical concurrent work. A group can reduce simultaneous pressure on the backing operation without extending the lifetime of its returned value.

Golang Concurrency

Go 07 Sep 2026 11 min read

Suppress Duplicate Concurrent Work in Go with singleflight

A service can become overloaded even when each individual request is reasonable. Imagine a popular product whose cached record expires. Fifty requests arrive almost together, all observe the same cache miss, and all start the same database query. The problem is not ordinary parallelism. Those requests are doing duplicate work for the same result at the same time. golang.org/x/sync/singleflight provides a small mechanism for suppressing that duplication inside one Go process. For a given key, one caller performs the work while concurrent callers for the same key wait and receive the same result. Calls using different keys can still perform their own work.

Go Concurrency