Open Stack

This seems like it could also be done for every other WSGI endpoint right?
It seems like it should be possible for all WS endpoints to be hosted in apache (or other server) without problems happening.
This might be connected to extracting/abstractig out eventlet (since a pre-forked apache doesn't really care about that model) so that it is not always needed.

On 3/1/12 11:05 AM, "Adam Young" <ayoung at redhat.com> wrote:

I wrote up why I think that, at least for Keystone, we should move the
front end over to Apache HTTPD.

http://adam.younglogic.com/2012/03/keystone-should-move-to-apache-httpd/

I've reposted it below.



Keystone and the other Openstack components run in an <a
href="http://www.eventlet.net">Eventlet</a> based HTTP server. Eventlet
and <a href="http://http://pypi.python.org/pypi/greenlet"> Greenlet</a>
(the project Eventlet is built on) are designed to be highly performant
in networked environments due to their non-blocking nature. Everything
is handled in a single thread, and scheduling is performed in user
space. The one caveat is that not only must the code you write never
block, the code you call must not block, either. If you are going to
make a call into a third party library that performs I/O, you need to
wrap that library in a thread pool.

For Keystone, every call is going to be going through to a Database
layer, either SQL or LDAP. Which is in turn going to call into the
native driver for that Database, or the LDAP libraries. Either way, it
is a native call, and it has to be wrapped in a thread pool.

Keystone is an authentication hub. As such, it is literally the
"Keystone" of the security architecture around Openstack. In order to do
anything on any of the other services in Openstack, a use needs a token
from Keystone. But in order to authenticate against Keystone, the user
needs to provide a clear-text password. This approach may be sufficient
to start development, but it is not going to be acceptable when a
company needs to prove compliance with <a title="Sarbanes Oxley Act of
2002" href="http://www.soxlaw.com/" target="_blank">Sarbanes-Oxley</a>.
Or <a title="Health Information Privacy"
href="http://www.hhs.gov/ocr/privacy/hipaa/understanding/index.html"
target="_blank">HIPPAA</a>. For these cases, we want stronger encryption
and better authentication management. The Eventlet based web server does
not currently support forms of authentication other than Basic-Auth.
Ideally, organizations would be able to employ their Kerberos or Public
Key Infrastructure (PKI) assets to support their Openstack based
authentication.

IPv6 is coming. The last block of IPv4 addresses has been allocated. For
Cloud based deployments, people are going to need large numbers of
routable IP Addresses. However, Eventlet does not currently support
IPv6. Work is happening upstream, but it has not yet been commited, and
will not be available for the Essex release of Openstack.

There is a simple solution. Keystone is a WSGI application, and has
minimal dependencies on Eventlet. Deploying Keystone in an Apache HTTPD
server with mod_wsgi running in prefork mode provides the same operating
environment as Eventlet does. As the de facto standard open source web
server, it has received a higher degree of scrutiny than most other
software products. HTTPD support for GSSAPI/Kerberos authentication,
Client and Server based certificates, and IPv6. It is well supported in
all the major Linux distributions.

What would the drawbacks be? Probably the first thing people would look
to from Eventlet is performance. I don't have the hard numbers to
compare Eventlet to Apache HTTPD, but I do know that Apache is used in
enough high volume sites that I would not be overly concerned. The
traffic in an Openstack deployment to a Keystone server is going to be
about two orders of magnitude less than any other traffic, and is highly
unlikely to be the bottleneck. Second is the fact that we would be
pulling in dependencies to Apache HTTPD, and that configuring it would
be different and more difficult than Eventlet. However, this is a fairly
well trodden path. The benefits of putting all HTTP traffic behind ports
80 and 443 overwhelm the drawbacks of configuration.

Since Keystone has just gone through a major reworking,  I realize that
people might be reluctant to support a move like this.  However,  the
effect on other components should be minimal or none.  Apache HTTPD can
be set up  using the same ports that Keystone already uses, and thus
replace an existing Keystone install with no changes to the
configuration or code to the other services.  The changes should be
limited to Keystone alone.

The problem that Eventlet solves does not map to Keystone. The amount of
work it would take to add the features Keystone really requires to
Eventlet is significant, is difficult, and is likely to be far buggier
than using well established and audited libraries. The simpler path
forward is for Keystone to move over to Apache HTTPD. It is also the
path for greater stability, security, and growth.





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