6. Socket activation: details
● systemd squats on all listeners
○ Looks for incoming traffic with EPOLL
○ Starts the services/containers on-demand
○ Passes socket to daemon as fd=3
● Not a proxy (same performance)
● No client awareness
7. Socket activation: Pantheon’s use
● nginx and PHP-FPM
● MariaDB soon
○ Using an alternative now
● Allows 90%+ containers to be idle
● Makes bootup sensible
● Reconfiguration pattern is stop, not restart
9. Automount/autofs
● Like socket activation for file system mounts
○ Kernel squats on mount path and looks for traffic
○ Brings up file mount lazily
● Used for FuseDAV (Valhalla client)
11. cgroups
● Many options
○ Pantheon uses CPUShares and BlockIOWeight
● Keeps things fair under contention
○ Kind of like adding purple ropes when people are
queueing
13. Customer Experience Monitor
● Runs a representative Drupal site on every
container host
● Reports scores to the API and monitoring
● Influences migration and container
placement
14. Migration
● At density, rebalancing is important
● Keep state lightweight
○ No OS
○ No runtime
● Mutiny: migration as replication + promotion