apache http server是一款轻量级的网页服务器。apache http server可以在大多数电脑操作系统中运行，由于其跨平台和安全性被广泛使用，是最流行的Web服务器端软件之一。它快速、可靠并且可通过简单的API扩充，将Perl/Python等解释器编译到服务器中。

apache http server v2.4.17更新内容：

*) mod_http2: added donated HTTP/2 implementation via core module. Similar

configuration options to mod_ssl. [Stefan Eissing]

*) mod_proxy: don't recyle backend announced "Connection: close" connections

to avoid reusing it should the close be effective after some new request

is ready to be sent. [Yann Ylavic]

*) mod_substitute: Allow to configure the patterns merge order with the new

SubstituteInheritBefore on|off directive. PR 57641

[Marc.Stern <Marc.Stern approach.be>, Yann Ylavic, William Rowe]

*) mod_proxy: Fix ProxySourceAddress binding failure with AH00938.

PR 56687. [Arne de Bruijn <apache arbruijn.dds.nl>

*) mod_ssl: Support compilation against libssl built with OPENSSL_NO_SSL3,

and change the compiled-in default for SSL[Proxy]Protocol to "all -SSLv3",

in accordance with RFC 7568. PR 58349, PR 57120. [Kaspar Brand]

*) mod_ssl: append :!aNULL:!eNULL:!EXP to the cipher string settings,

instead of prepending !aNULL:!eNULL:!EXP: (as was the case in 2.4.7

and later). Enables support for configuring the SUITEB* cipher

strings introduced in OpenSSL 1.0.2. PR 58213. [Kaspar Brand]

*) mod_ssl: Add support for extracting the msUPN and dnsSRV forms

of subjectAltName entries of type "otherName" into

SSL_{CLIENT,SERVER}_SAN_OTHER_{msUPN,dnsSRV}_n environment

variables. Addresses PR 58020. [Jan Pazdziora <jpazdziora redhat.com>,

Kaspar Brand]

*) mod_logio: Fix logging of %^FB (time to first byte) on the first request on

an SSL connection. PR 58454.

[Konstantin J. Chernov <k.j.chernov gmail.com>]

*) mod_cache: r->err_headers_out is not merged into

r->headers when mod_cache is enabled and the response

is cached for the first time. [Edward Lu]

*) mod_slotmem_shm: Fix slots/SHM files names on restart for systems that

can't create new (clear) slots while previous children gracefully stopping

still use the old ones (e.g. Windows, OS2). mod_proxy_balancer failed to

restart whenever the number of configured balancers/members changed during

restart. PR 58024. [Yann Ylavic]

*) core/util_script: make REDIRECT_URL a full URL. PR 57785. [Nick Kew]

*) MPMs: Support SO_REUSEPORT to create multiple duplicated listener

records for scalability. [Yingqi Lu <yingqi.lu@intel.com>,

Jeff Trawick, Jim Jagielski, Yann Ylavic]

*) mod_proxy: Fix a race condition that caused a failed worker to be retried

before the retry period is over. [Ruediger Pluem]

*) mod_autoindex: Allow autoindexes when neither mod_dir nor mod_mime are

loaded. [Eric Covener]

*) mod_rewrite: Allow cookies set by mod_rewrite to contain ':' by accepting

';' as an alternate separator. PR47241.

[<bugzilla schermesser com>, Eric Covener]

*) apxs: Add HTTPD_VERSION and HTTPD_MMN to the variables available with

apxs -q. PR58202. [Daniel Shahaf <danielsh apache.org>]

*) mod_rewrite: Avoid a crash when lacking correct DB access permissions

when using RewriteMap with MapType dbd or fastdbd. [Christophe Jaillet]

*) mod_authz_dbd: Avoid a crash when lacking correct DB access permissions.

PR 57868. [Jose Kahan <jose w3.org>, Yann Ylavic]

*) mod_socache_memcache: Add the 'MemcacheConnTTL' directive to control how

long to keep idle connections with the memcache server(s).

Change default value from 600 usec (!) to 15 sec. PR 58091

[Christophe Jaillet]

*) mod_dir: Prevent the internal identifier "httpd/unix-directory" from

appearing as a Content-Type response header when requests for a directory

are rewritten by mod_rewrite. [Eric Covener]