Talk about Ubuntu Juju, a tool for the deployment and configuration of services in clouds and how Go helps to develop it.

1. Juju ‑ Google Go in a
scalable Environment
Frank Müller / Oldenburg / Germany

2. Introduction
Frank Müller
Born 1965 in Oldenburg
Software
Development
since 1984
Author since 1999
Book about Go in 2011

3. Well known scenario
Wordpress
MySQL

4. Different in clouds
Wordpress Wordpress
MySQL

5. Scaling means effort

6. Juju for provisioning
Amazon Web Services
OpenStack
Local
MAAS
Microsoft Azure

7. Create your environment
juju init -w
juju bootstrap
State

8. Add and relate services
State
juju deploy cs:precise/wordpress
juju deploy cs:precise/mysql
juju add-relation wordpress mysql
Wordpress
MySQL

9. Add another unit
State
Wordpress
MySQL
Wordpress
juju add-unit wordpress

10. Scale!
State
memcached
MySQL
Wordpress
juju add-unit -n2 wordpress
juju deploy memcached
juju add-relation wordpress memcached

11. Also web UI available

12. Why Google Go?

13. Architectural insights

14. State - Watcher - Worker
State
Provisioner
Firewaller
Machiner
Deployer
Uniter
Collections
Individual Objects
Lifecycles
Client

15. Agent
Lots of concurrent work
State
Worker
Goroutine
Goroutine
Worker
Goroutine
Goroutine

16. Firewaller
State Main Loop
Environment Configuration
Machines
machind Loop
Machine Units
unitd Loop
serviced Loop
Ports
Exposes

17. Goroutine control

18. Monitoring and stopping
• not part of the language spec
• launchpad.net/tomb
• signals to leave loops
• wait until goroutine stopped
• leave in case of an error
• remember and retrieve that error

19. Loops with tomb
// loop processes ...
func (t *T) loop() {
defer t.tomb.Done()
for {
select {
case <-t.tomb.Dying:
// Cleanup ...
return
case f := <-t.fooChan:
if err := t.foo(f); err != nil {
t.tomb.Kill(err)
}
case b := <-t.barChan:
// ...
}
}
}

20. Stop and error handling
// Stop ends the main loop.
func (t *T) Stop() error {
t.tomb.Kill(nil)
return t.tomb.Wait()
}
// Err retrieves the error in case the backend loop died.
func (t *T) Err() error {
return t.tomb.Err()
}

21. Interfaces

22. Define behaviors
type StorageReader interface {
Get(name string) (io.ReadCloser, error)
List(prefix string) ([]string, error)
URL(name) (string, error)
}
type StorageWriter interface {
Put(name string, r io.Reader, length int64) error
Remove(name string) error
}
type Storage interface {
StorageReader
StorageWriter
}

23. Like a toolbox
Storage
EC2
OpenStack
MAAS
Azure
DummyEnviron

24. Also help in tests
type Foo interface {
DoThis(with That) error
}
type MyFoo struct { ... }
func (m *MyFoo) DoThis(with That) error { ... }
type MockFoo struct { ... }
func (m *MockFoo) DoThis(with That) error { ... }
func Bar(f Foo, t That) error {
return f.DoThis(t)
}

25. What else?
• extreme fast builds
• cross-compilation
• binaries are simple to deploy
• table-driven tests
• benchmarks and race detection
• go get always takes tip!

26. Questions?