Curlese, Five Years Later
Five years later, the author revisits the enduring utility of curl as the universal language for debugging broken HTTP integrations, demonstrating how its direct, reproducible evidence cuts through blame games. The article highlights new challenges like HTTP/2, mTLS, and WAFs, and updates the curl 'survival kit' with essential flags for modern troubleshooting. It's a practical guide that resonates deeply with developers who regularly wrestle with complex system integrations.
The Lowdown
The article, titled "Curlese, Five Years Later," reaffirms curl's role as the go-to tool for diagnosing and resolving issues in broken HTTP integrations. The author, who coined the term "curlese" five years prior, argues that curl provides self-describing, reproducible, and undeniable evidence, bypassing common pitfalls like unread log files or claims of "works on my side." The piece updates the original thesis to reflect changes in the technological landscape while stressing the tool's continued relevance.
- The fundamental 'social problem' of integration debugging persists: multiple teams, ambiguous firewalls, and difficulty in attributing blame make objective evidence crucial.
- Application logs often prove worthless in these scenarios, whereas a
curlcommand with its output offers executable evidence that can be run and understood by all parties. - Significant changes in the last five years include the widespread adoption of HTTP/2 and HTTP/3, the prevalence of mTLS, and layers of WAFs, proxies, and API gateways that can obscure actual errors.
curl's detailed output is now also invaluable for providing unambiguous context to Large Language Models (LLMs) when seeking debugging assistance.- An updated 'survival kit' of
curlflags is introduced, including-wfor detailed timing,--resolveand--connect-tofor bypassing DNS,--certfor mTLS,--json,--fail-with-body,--retry, and--no-alpnfor HTTP version issues. - A revised 'dictionary' maps common
curlerror messages (e.g., 'connection timed out', 'sslv3 alert handshake failure', '403' from a WAF) to their likely underlying causes. - The author provides a 'starter pack' of phrases to request
curloutput from interlocutors, reinforcing the idea thatcurlcommands serve as an objective contract for debugging.
Ultimately, the article concludes that despite the rapid evolution of web technologies, curl remains an indispensable and surprisingly robust tool for debugging integrations. Its ability to provide clear, actionable evidence makes it a timeless asset for developers navigating complex distributed systems.