Musings on Zero Downtime Deployment

By Mashooq Badar
Posted 14 Jan 2012

I've been thinking about Zero Downtime Deployment for the past few weeks. I even raised it as a discussion topic in our LSCC Roundtable. Here are the key points discussed. Obviously the feasibility/suitability completely depends on the application and platform architecture. Also this is not an attempt to provide a solution but more to record the thoughts and ideas:

Switch over to backup upgrade the primary and then switch back, and then update the backup site.
Have a HA configuration, take hosts out upgrade then switch gradually.
Allow for parallel runs, so you can switch over to a parallel when updating.
Develop application to run on previous and new version of the database. Hot deploy the app and "hot" migrate the database.
Use dynamic features in your platform to allow for hot deployment.
Use semi structured datastore so data migrations are minimal.
Provide targeted releases, i.e. if a particular area of the application changes than only that area is updated and not the whole application.
If eventual consistency across partitions is acceptable then deploy in partitions and update partitions gradually, i.e. like Facebook, Google etc.

About the author

Mashooq Badar

Mash is a pragmatic software craftsman always looking to improve his software creation skills and helping others do the same. He firmly believes that a well-rounded software craftsman must have a keen interest in all aspects of software creation, including; process, people, technology, user experience, development, operation, maintenance, and social impact. He relishes the daily challenges that Codurance brings to him–stretching his existing knowledge and expertise allowing him to constantly grow as a professional.

Mash is an advisor and a leader. During his diverse career, he has succeeded in invigorating large ailing software projects as well as creating highly effective software teams and departments. His broad and deep technical knowledge, organisational skills, craft focus, and empathy to people involved have been integral to his success. He has worked in many roles for charities, investment banks, consultancies, government, media and cloud providers. He prides himself at being a hands-on software developer and believes that software development skills are very hard to learn and the best way to maintain them is to apply them.