News

What we did on summer vacation

Submitted by Adam Krawiec on Fri, 08/10/2012 - 12:38

CWS has been hard at work designing and implementing a new web hosting architecture, bringing in new technologies while building on existing systems. We're happy to announce that we've been using this new architecture in production for the past week on our own site: http://webadmin.unt.edu/.

We're happy to present this preliminary comparison of the two systems. This graph shows traffic to the site before and after the transtion last friday, which highlights the benefits that will be rolled-out to the rest of the UNTSystem soon.

What are we looking at?

Graph of HTTP requests for webadmin.unt.edu, showing server distribution

The graph shows number of visits to our servers. The left side of the graph reflects the site on our existing farm and the right side shows after the transition to our new architecture.

The left side shows that unequal distribution of traffic among the four individual servers on the farm, resulting in unequal loading, between 2,000 to 3,000 requests.

The right side shows two varnish servers taking up the bulk of traffic, quickly serving content which changes infrequently, while the web servers receive only the fraction of the requests needed to keep content current.

MySQL replication maintenance

Submitted by Adam Jensen on Tue, 07/24/2012 - 15:46

Earlier this morning the service that replicates data between CWS's two MySQL servers encountered some unusual errors and stopped working. We took steps to get it running again, but ultimately were unable to do so; this means we will need to restart the replication process manually, during an after-hours maintenance window.

The reason this is necessary has to do with fault tolerance. Most of our websites depend on MySQL, and if the primary MySQL server becomes unavailable it's very important that a secondary server be on hand to take its place. Without replication, that secondary server will become progressively more out of date, making it unable to fulfill its role in the event of a primary server outage.

To accomplish the fix, we've scheduled five minutes' worth of emergency downtime tonight —more precisely, 12:00am to 12:05am on Wednesday, July 25th. Following that window, MySQL replication should be back up and running, giving us the extra layer of protection we need to keep your websites online in all circumstances.

Thanks!
the CWS team

Upgrading the dynamic hosting farm

Submitted by Adam Jensen on Thu, 06/21/2012 - 13:06

Over the course of the next several months, we've got some important upgrades planned for our various web hosting farms; we're still working on the scheduling, but I wanted to give you an early heads-up about what to expect.

Recovery maintenance scheduled for Saturday, March 3

Submitted by Adam Jensen on Fri, 03/02/2012 - 10:34

Last Thursday and Friday, as I'm sure you're aware, Central Web Services experienced a major service interruption that brought down the majority of our websites, at least intermittently, for a significant part of both days. First off, I'd like to take this opportunity to apologize to those of you who depend on our services. Second, I want to assure you that we have identified the root cause and are in the process of implementing safeguards against this kind of thing happening again.

We do, however, have some more maintenance to do along the way, and the first part of that is scheduled for tomorrow evening. To resolve the outage last week, our primary network-attached storage (NAS) server had to be brought back online in a cross-site storage configuration; essentially, this means that although our NAS server is in one data center, its disks are in another data center several miles away. This introduces a new (albeit small) element of risk into the overall web service architecture.

In order to mitigate this risk, CWS is coordinating with the ITSS infrastructure team to reconfigure the NAS such that its data and its services all operate out of the same data center. Due to the way the backend storage system works, it is highly unlikely that this maintenance work will result in any interruption of service. In the event that web services do need to be taken offline, we anticipate no greater than one hours' worth of downtime.

The infrastructure team plans to begin this process at 7:00 pm tomorrow night (Saturday, March 3, 2012).

UNT Web Support Office Hours

In Person Help

Central Web Services and the Web Development Center have folks on hand to answer your questions every Wednesday between 10:30am and 12:00pm in the Business Leadership Building, Room 205.

Walk up the main stairwell in the Business Leadership Building, on the second floor enter the first glass door on your left (Graduate Programs, Department Chairs, Department Advising), walk straight and take a left all the way down the hallway to Conference Room 205 which will be on the right.