Al Tobey (@AlTobey) is an Open Source Mechanic at DataStax. Prior to working at DataStax, Al was a Tech Lead of Compute and Data Services at Ooyala, which has been using Apache Cassandra since version 0.4 and these days uses Go in production. Al will be presenting a brief introduction to Go (#golang) and Cassandra, and how they are a great fit for each other. This talk will include code samples and a live demo.

1. Cassandra and Go
@AlTobey
Open Source Mechanic @ Datastax
©2013 DataStax Confidential. Do not distribute without consent.
!1

2. Open Source Mechanic
• Officially, Open Source Evangelist for Apache Cassandra
• Educate
• Ask (the right) questions
• Fix things
• Get the word out

3. Cassandra
• AP distributed database
• Dynamo x BigTable
• Robust data model
• Built-in multi-datacenter replication
• At-rest encryption
• Easy to use

4. Cassandra 2.0
• Lightweight Transactions (a.k.a. CAS)
• Results paging for CQL (cursors)
• Eager retries
• Many optimizations all over
• Experimental triggers
• Note: Java 7 is required

5. Look familiar?
CREATE TABLE demo (id UUID, name VARCHAR, dob TIMESTAMP);
!
INSERT INTO demo (id, name, created)
VALUES (“…”, “Al Tobey”, “2013-10-29”);
!
SELECT name FROM demo;
!
DESCRIBE TABLE demo;
!
use system;
!
SELECT columnfamily_name FROM schema_columnfamilies
WHERE keyspace_name = ‘demo’;
!

6. #golang
• Tiny language
• Strongly typed
• Simple concurrency primitives
• first-class functions
• Native, statically-linked code
• Garbage collection
• Excellent standard library
• Great community
• Open Source

7. Fizz Buzz
package main
!
import (
"fmt"
)
!
func main() {
for i := 0; i < 100; i++ {
fmt.Printf("%d: ", i)
!
if i%3 == 0 {
fmt.Printf("fizz")
}
!
if i%5 == 0 {
fmt.Printf("buzz")
}
!
}
}
fmt.Printf("n")

8. Chocolate and Peanut Butter
• Cassandra is distributed and can handle highly concurrent load
• Go makes concurrency trivial
• A CQL native protocol driver already exists for Go (gocql)
• A Thrift driver is also available (gossie)

9. Schema
CREATE KEYSPACE demo WITH REPLICATION = {
'class' :
‘SimpleStrategy',
'replication_factor' : 1
};
!
CREATE TABLE subscribers {
id
UUID,
email
VARCHAR,
created TIMESTAMP,
updated TIMESTAMP,
deleted TIMESTAMP
);
!
INSERT INTO subscribers (id, email, created, updated, deleted) VALUES (
4e7cd544-a72c-41a1-a004-74ea34e1e932,
‘atobey@datastax.com’,
‘2013-10-24T00:00:00+0000’,
‘2013-10-26T00:00:00+0000’,
‘9999-12-31T00:00:00+0000’
);
!
SELECT id, email, created, updated, deleted FROM subscribers;

10. Querying
package main
!
import (
"fmt"
"time"
"tux21b.org/v1/gocql"
"tux21b.org/v1/gocql/uuid"
)
!
type Record struct {
Id
uuid.UUID
Email
string
Created time.Time
Updated time.Time
Deleted time.Time
}

11. Querying
func main() {
cluster := gocql.NewCluster("127.0.0.1")
cluster.Keyspace = "subscribers"
cluster.Consistency = gocql.Quorum
!
!
!
!
!
}
cass, err := cluster.CreateSession()
if err != nil {
panic(fmt.Sprintf("Error creating session: %v", err))
}
defer cass.Close()
sub := Record{}
q := cass.Query(
`SELECT id, email, created, updated, deleted FROM subscribers`
)
q.Scan(&sub.Id, &sub.Email, &sub.Created, &sub.Updated, &sub.Deleted)
fmt.Printf("Record: %vn", sub)

12. Go Web Services
• Go seems to be particularly popular for web services
• With good reasons
• The standard library’s HTTP server is quite good
• Deploy a single binary
• High concurrency
• Light resource usage

13. Hello WWW
package main
!
import (
"fmt"
"net/http"
)
!
func main() {
http.HandleFunc(“/index.txt",
func(w http.ResponseWriter, r *http.Request) {
fmt.Fprintf(w, “Ohai!n")
}
)
!
}
http.ListenAndServe(":8080", nil)

14. Skeezy: don’t do this at home
• Written specifically for this talk
• No (known) heinous crimes
• https://github.com/tobert/skeezy

15. skeezy
package main
!
import ( … )
!
func main () {
// connect to Cassandra (same as before)
!
!
}
// set up routes (with a twist)
// start the web service (same as before)

16. skeezy - setting up routes
http.Handle("/img/",
http.StripPrefix("/img/",
http.FileServer(http.Dir(“./public/img/“))
)
)
!
http.HandleFunc(“/c/“, func(w http.ResponseWriter, r
*http.Request) {
q := cass.Query(`SELECT id FROM c WHERE postId=?`,
id.Bytes())
q.Iter()
!
})
c := Comment{}
for iq.Scan(&c.Id, &c.ParentId, &c.Created) {
fmt.Fprintf(w, “%v”, c)
}

17. skeezy - globals?
package main
import (…)
!
var cass *gocql.Session
!
func main () {
// …
var err error
cass, err = cluster.CreateSession()
// …
!
}
http.HandleFunc(“/c/“, func(…) {
q := cass.Query(…)
// …
})

18. skeezy - closure
func main () {
// …
cass, err := cluster.CreateSession()
// …
!
)
http.HandleFunc(“/c/“, func(…) {
q := cass.Query( … )
}

19. skeezy - responsible passing
func main () {
// …
cass, err := cluster.CreateSession()
// …
!
)
http.HandleFunc(“/c/“, func(…) {
cc := skeezy.ListPosts(cass, …)
}

20. skeezy - returning data
func main () {
// …
cass, err := cluster.CreateSession()
// …
!
)
http.HandleFunc(“/c/“, func(…) {
cc := skeezy.ListPosts(cass, …)
}
!
package skeezy
!
func ListPosts(…) []Comment {
ret := make([]Comment, 1)
for {
ret = append(ret, c)
}
return ret
}

21. skeezy - channels & goroutines
func ListComments(cass *gocql.Session, id uuid.UUID) (chan *Comment) {
cc := make(chan *Comment)
!
!
}
go func() {
iq := cass.Query(`… WHERE postId=?`, id.Bytes()).Iter()
for {
c := Comment{}
if iq.Scan(&c.Id, &c.ParentId, &c.Created) {
cc <- &c
} else {
break
}
}
if err := iq.Close(); err != nil {
log.Fatal(err)
}
close(cc)
}()
return cc

22. skeezy - channel receiver
// a list of comment ids
http.HandleFunc("/c/", func(…) {
cc := skeezy.ListComments(cass, getId(r, “/c/“))
!
})
!
for comment := range cc {
js, _ := json.Marshal(comment)
w.Write(js)
}

23. Overview
• Cassandra and Go are both great for high concurrency applications
• Go is a simple and powerful language
• Both are great choices for your next application
• Learn more
• http://golang.org
• http://planetcassandra.com/
• http://tux21b.org/gocql/
!
• Questions?