mod_http2
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| mod_http2 | |
|---|---|
| Name | mod_http2 |
| Developer | Apache Software Foundation |
| Latest release | 2.0 |
| Programming language | C (programming language) |
| Operating system | Unix-like; Microsoft Windows |
| License | Apache License |
| Website | Apache HTTP Server Project |
mod_http2 mod_http2 is an Apache HTTP Server module that implements the HTTP/2 protocol for the Apache HTTP Server Project family. It provides multiplexed, header-compressed, binary framing support to accelerate delivery for web servers used by organizations such as the European Organization for Nuclear Research, Mozilla Foundation, GitHub, and cloud providers. The module integrates with existing Apache HTTP Server features and popular extensions developed by communities including OpenSSL, libnghttp2, and vendors building reverse proxies.
Overview
mod_http2 enables HTTP/2 features within the Apache HTTP Server ecosystem, interoperating with TLS stacks like OpenSSL, GnuTLS, and platform-specific crypto implementations. It cooperates with modules such as the core mod_ssl, mod_proxy, mod_proxy_http, and mod_pagespeed integrations used by companies like Google and Facebook to modernize delivery. The module relies on the nghttp2 library lineage and aligns with standards set by the Internet Engineering Task Force and the World Wide Web Consortium through extensions and draft specifications.
History and development
Development of mod_http2 traces to contributions from individuals and organizations involved in the Apache Software Foundation community and contributors from projects such as nghttp2 and OpenSSL. Early integration work followed the standardization of HTTP/2 by the IETF HTTP Working Group and closely paralleled implementations in nginx, Lighttpd, and server efforts by Microsoft for Internet Information Services. Major milestones included patch reviews and pull requests on repositories managed in collaboration with other Apache modules and the broader open-source community centered around events like FOSDEM, ApacheCon, and developer summits sponsored by Linux Foundation projects.
Architecture and design
The architecture of the module builds upon the Apache HTTP Server multi-processing modules and event-driven I/O models, integrating with process models used by prefork MPM, worker MPM, and event MPM. It employs an internal state machine to manage HTTP/2 streams, prioritization, and flow control compatible with implementations in nghttp2 and mirrors approaches used by Google's early HTTP/2 pilots. The design separates connection handling, stream lifecycle, and scheduling, allowing interaction with modules like mod_deflate, mod_cache, and mod_rewrite. TLS negotiation for protocol upgrade uses mechanisms standardized through discussions in IETF mailings and interoperates with TLS 1.3 implementations promoted by Cloudflare and cryptography projects.
Features and protocol support
mod_http2 implements core HTTP/2 features: binary framing, HPACK header compression, stream multiplexing, prioritization, server push, and flow control. It supports ALPN negotiation alongside TLS stacks used by Mozilla and Google, and it is compatible with client implementations found in browsers like Mozilla Firefox, Google Chrome, Apple Safari, and Microsoft Edge. The module exposes controls for server push behavior similar to approaches in servers by NGINX, Inc. and aligns push semantics with guidance from working groups at IETF meetings. Support for header compression mirrors HPACK implementations used in nghttp2 and follows specification errata tracked by IETF RFC processes.
Configuration and administration
Administrators configure mod_http2 through standard Apache HTTP Server configuration files and directives, commonly managed alongside mod_ssl and virtual host definitions found in production deployments at organizations such as WordPress.org and Wikipedia. Configuration includes enabling listen sockets with ALPN, tuning connection and stream limits, and integrating with logging modules used by Elastic Stack and monitoring tools from Prometheus and Grafana. Operational tasks—reloads, graceful restarts, and capacity planning—follow practices established by system operators at events like USENIX conferences and in documentation produced by the Apache Software Foundation.
Performance and benchmarking
Performance evaluations of mod_http2 involve latencies, throughput, multiplexing efficiency, and CPU utilization under TLS workloads common to providers such as Akamai and Fastly. Benchmarks compare mod_http2 to other servers—nginx, HAProxy, Caddy—and use client tools from the nghttp2 project, HTTP benchmarking suites from wrk, h2load, and synthetic workloads used in studies published at ACM SIGCOMM and USENIX ATC. Results vary with tuning: enabling HTTP/2 stream concurrency, adjusting flow-control windows, and optimally configuring MPMs yield different performance envelopes documented by contributors and performance engineers.
Security considerations
Security for mod_http2 includes mitigation of Denial-of-Service patterns specific to HTTP/2 framing such as stream exhaustion and header compression vulnerabilities linked to HPACK. It works with TLS implementations and cipher-suite policy controls found in OpenSSL and enterprise deployments at Red Hat and Debian to enforce TLS 1.2/TLS 1.3 standards. Administrators follow advisories coordinated through the Apache Software Foundation and vulnerability trackers used by CVE processes and hardening guidance from projects like OWASP and corporate security response teams at Google and Microsoft.