Support for Apache HTTP Server in SAS^® Viya^® 3.5

Apache HTTP Server (“Apache httpd”) provides security and load balancing for multiple SAS Viya components. It is included with SAS Viya on Windows. On Linux, it is installed as an RPM dependency with SAS Viya if you do not install the software yourself ahead of time.

SAS Viya supports the following versions of Apache HTTP Server:

• For Red Hat Enterprise Linux or Oracle Enterprise Linux 6.x, Apache HTTP Server 2.2 and later.
• For Red Hat Enterprise Linux or Oracle Enterprise Linux 7.x and 8.x, Apache HTTP Server 2.4.x and later.
• For SUSE Linux Enterprise Server 12.x, Apache HTTP Server 2.4x and later.

SAS Viya on Windows ships with Apache HTTP Server 2.4.34.

(For Red Hat Enterprise Linux or Oracle Enterprise Linux 8.x Only)

If you are deploying on Red Hat Enterprise Linux 8.x or Oracle Enterprise Linux 8.x, some additional configuration is recommended. These versions of Linux with Apache 2.4 use the mod_mpm_event.so multi-processing module (MPM) by default. (The default on Red Hat Enterprise Linux and Oracle Enterprise Linux 7.x is mod_mpm_prefork.so.) SAS recommends updating an Apache httpd configuration file to change the active MPM setting from mod_mpm_event to mod_mpm_prefork.

Note: If your SAS Viya deployment is regularly accessed by 400 or more end users, you should instead follow the instructions that are provided in SAS Viya 3.5 Administration: Tuning Apache HTTP Server.

Make a change like the following:

In /etc/httpd/conf.modules.d/00-mpm.conf, comment the line ending in mod_mpm_event.so, and uncomment the line ending in mod_mpm_prefork.so:

LoadModule mpm_prefork_module modules/mod_mpm_prefork.so
#LoadModule mpm_worker_module modules/mod_mpm_worker.so
#LoadModule mpm_event_module modules/mod_mpm_event.so

Restart Apache to pick up the change.

Apache HTTP Server version 2.4.39 contains a bug: no default is defined for the RequestReadTimeout parameter. The missing default can cause failures when you attempt to import large amounts of data from a web browser, as when you use SAS Environment Manager to import data from a Quality Knowledge Base.

SAS has investigated this issue. It has been fixed in Apache 2.4.41 and later. However, your operating system might include the version that contains the bug. On older versions of Red Hat Enterprise Linux, Oracle Enterprise Linux, or SUSE Linux Enterprise Server, SAS recommends that you modify the /etc/httpd/httpd.conf file to set the default timeout: 

RequestReadTimeout handshake=0 header=20-40,MinRate=500 body=20,MinRate=500

Restart Apache to pick up the change.