Critical components in CF

Question

I'm new to Cloud Foundry and started wondering which CF components are critical

• to keep application running
• to allow applications to receive/send back traffic
• to persist the application logs

As far as I understand

• to keep application running: cell
• to allow applications to receive/send back traffic: router
• to persist the application logs: loggregator

Answer 1

to keep application running: cell

Technically just the Cell, but a couple things to consider. Traffic can't get to your Cells if your Gorouters and external load balancers are not working correctly. In addition, if your apps crash or need to be restarted that can only happen if Cloud Controller and the rest of the Diego components are running.

Tangentially related, apps also tend to use services. If those are down or not working, then your apps will be too. Just something else to consider.

to allow applications to receive/send back traffic: router

Most deployments have an external load balancer which balances traffic across your Gorouters. This would also need to be up to receive traffic.

to persist the application logs: loggregator

Technically there is no persistence of logs in Loggregator. It temporarily buffers logs in memory, but does not store them. You would need to have Loggregator running and sending logs to somewhere else like a syslog service that actually stores and persists the logs.

These two pages provide additional details:

• https://docs.pivotal.io/pivotalcf/2-6/concepts/high-availability.html
• https://docs.pivotal.io/pivotalcf/2-6/concepts/maintaining-high-availability.html

Hope that helps!