Looking to move your application to run in a container? Need to move existing x86 legacy applications to Docker? Let's break down your fundamental application concerns. This includes persistent storage, networking, configuration management, policy, logging, health monitoring, and service discovery. You won't want to miss this talk.

1. Moving Legacy Applications
to Docker
Josh
Ellithorpe
Software Architect

2. Auditing
Resources
Networking
Data Services
Dependencies
Kernel
Agenda
Configuration
Templates / ENV
Service Discovery
Lifecycle
Build vs. Deploy
App Updates

3. Auditing

4. • CPU
• Multi-core runtime?
• Average load
• Disk
• Memory
• Consumption while running
• Network
Resources

5. • Required TCP/UDP ports
• External service connectivity
• Certificates/SSL
• Latency / Bandwidth
Networking / Connectivity
Useful Tools:
• tcpdump
• netstat
• lsof -P
• netdata

6. • Where does your app write data to the filesystem?
• What persistent datastore do you want to use?
(NFS/CIFS/etc)
• What databases or other data services are required? What
are their connection details?
Data Services / Storage
Useful Tools:
• strace
• lsof

7. • What OS is required?
• What packages are needed to run the app?
• Runtime
• Shared libraries
• What application dependencies are required?
• NPM modules, gems, etc.
Dependencies
Useful Tools:
• ld
• strace
• lsof

8. • Does your app require a privileged container?
• Does your app require custom kernel modules/parameters?
Kernel

9. Configuration

10. • Can the application read ENV vars?
• Does it require a startup script to setup the container before
the application/service starts?
Templates / ENV Variables
Recommendations:
• Write the entire config in the start script instead of using sed/awk

11. • Etcd / Zookeeper
• Consul
• DNS
• Static Values
Service Discovery

12. Lifecycle

13. Understand where your concerns are.
• Build
• Dependencies, required ports, and startup scripts
• Deploy
• Persistent volumes, network context, and scheduling
• Runtime
• Writing needed configurations via start script
• Consuming services from service discovery system
• Clean startup and shutdown
Build / Deploy / Runtime

14. Traditional VM based deployments only update the application, however when
using containers you must rebuild the entire dependency set down to the OS.
It is critical to create an automated build process to handle this. That way it can
pull in the new dependencies you need, and script out the generation of your
Dockerfile.
App Updates

15. Thank you!