Original Post: How we resolved the ‘HTTP request failed: timeout’ issue in OCaml
Hannes Mehnert, a programmer at Robur, discusses the migration of Semgrep OSS from Python to OCaml to alleviate maintenance and optimization issues. Semgrep’s initial reliance on both Python and OCaml created inefficiencies due to data serialization between the two languages. Robur began the migration in April 2023, leveraging their expertise in OCaml and systems code.
During this transition, they encountered and addressed a significant issue: HTTP request failed: connection failed: timeout, particularly within the CI pipeline. This issue was traced back to the OCaml implementation using the http-lwt-client and involved connection handling failures due to problematic DNS resolution in the CI environment.
To tackle this, improvements were made to the "happy-eyeballs" algorithm – a method described by the IETF for efficiently handling multiple IP addresses and network setups. These improvements included better management of connection attempts, proper handling of DNS resolutions, and increased log verbosity for debugging.
The article concludes by highlighting the benefits of using OCaml, particularly in the context of MirageOS unikernels, which offer performance and security benefits by running applications without a traditional Linux kernel. It ends with an invitation to join the Semgrep Community Slack for further discussions.
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