Go 1.27 Improves HTTP/1 Connection Reuse for Faster Performance

Performance Boost in Go 1.27

Go 1.27 introduces substantial improvements in HTTP/1 connection reuse. Benchmarks show that a series of 100 HTTP/1 GET requests, which took approximately 710 milliseconds on Go 1.26, now complete in about 150 milliseconds on Go 1.27. This represents nearly a five-fold increase in speed for this type of operation.

The Cost of HTTP Connections

Establishing a new HTTP connection involves several network round trips (RTTs). A typical setup for an HTTPS request includes a 1 RTT TCP handshake and a 2 RTT TLS handshake (for TLS 1.2), totaling 3 RTTs before the HTTP request can even be sent. These RTTs, along with CPU time for TLS handshakes, contribute significantly to latency, especially in cross-region communications where RTTs can exceed 100 ms.

Impact of Connection Setup Overhead

Even under favorable conditions, such as connections to globally distributed services supporting TLS 1.3 (which can complete TLS handshakes in 1 RTT), the overhead of opening new connections remains noticeable. The performance gains in Go 1.27 highlight the importance of minimizing this setup cost for applications making numerous HTTP requests.

Connection Reuse as a Solution

To mitigate the expenses of connection setup, HTTP clients and servers aim to reuse existing connections for multiple requests. The mechanics of how connections are reused vary depending on the HTTP version being utilized.