Vallard's Blog | Cassandra Startup with Docker and Golang

I use Docker:

docker pull cassandra
mkdir ucs-cassandra-db
docker run -d -P  --name cassandra -v `pwd`/ucs-cassandra-db/:/var/lib/cassandra cassandra

docker pull cassandra

mkdir ucs-cassandra-db

docker run -d -P --name cassandra -v `pwd`/ucs-cassandra-db/:/var/lib/cassandra cassandra

(Notice that using boot2docker or docker machine on virtual box doesn’t work very well because the directories are created under different user name. You have two choices: Don’t mount persistent directories with boot2docker or log into the virtual box guest (docker-machine ssh dev) and launch the container there.)

Make sure its up:

docker inspect cassandra
docker logs cassandra

1 2	docker inspect cassandra docker logs cassandra

Now lets create a Keyspace (or Database in SQL terms). Connect to it by connecting to cassandra where the 9042 port is mapped:

docker ps

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
a1ec821d4f59 cassandra "/docker-entrypoint.s" 34 minutes ago Up 34 minutes 0.0.0.0:32772->7000/tcp, 0.0.0.0:32771->7001/tcp, 0.0.0.0:32770->7199/tcp, 0.0.0.0:32769->9042/tcp, 0.0.0.0:32768->9160/tcp cassandra

docker ps

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

a1ec821d4f59 cassandra "/docker-entrypoint.s" 34 minutes ago Up 34 minutes 0.0.0.0:32772->7000/tcp, 0.0.0.0:32771->7001/tcp, 0.0.0.0:32770->7199/tcp, 0.0.0.0:32769->9042/tcp, 0.0.0.0:32768->9160/tcp cassandra

Here we see that port 9042 is mapped to 32769. To connect we run:

cqlsh 192.168.99.100 32769

1	cqlsh 192.168.99.100 32769

Now we can create the keyspace:

cqlsh> CREATE KEYSPACE ucstechspecs WITH replication = { 'class': 'SimpleStrategy', 'replication_factor': '1' };
cqlsh> USE ucstechspecs;
cqlsh> CREATE TABLE fabricInterconnects (partNumber text, name text, attributes map<text, text>, pictures list<text>, PRIMARY KEY (partNumber));

cqlsh> CREATE KEYSPACE ucstechspecs WITH replication = { 'class': 'SimpleStrategy', 'replication_factor': '1' };

cqlsh> USE ucstechspecs;

cqlsh> CREATE TABLE fabricInterconnects (partNumber text, name text, attributes map<text, text>, pictures list<text>, PRIMARY KEY (partNumber));

Now let’s use it with a Go program.

go get github.com/gocql/gocql

1	go get github.com/gocql/gocql

Our code is pretty simple:

package main

import (
  "fmt"
  "log"

  "github.com/gocql/gocql"
)

func main() {

  fmt.Printf("Test\n")
  cluster := gocql.NewCluster("192.168.99.100")
  cluster.Port = 32869
  cluster.ProtoVersion = 4 
  cluster.Keyspace = "ucstechspecs"
  session, err := cluster.CreateSession()
  defer session.Close()
  if err != nil {
    fmt.Printf("%s\n", err)
    return
  }

  m := make(map[string]string)
  m["color"] = "red"
  m["car"] = "ferrari"

  pictures := []string{"http://fi.1.org", "http://lmgtfy"}

  err = session.Query(`INSERT INTO fabricInterconnects (partNumber, name, attributes, pictures) VALUES (?, ?, ?, ?)`,
    "UCSFI-61234", "UCS FI 6120", m, pictures).Exec()

  log.Println("Inserted data")
  if err != nil {
    log.Fatal(err)
  }

  var model string
  iter := session.Query(`SELECT name FROM fabricInterconnects WHERE partNumber = ? `,
    "UCSFI-61234").Iter()
  for iter.Scan(&model) {
    fmt.Println("Model: ", model)
  }
  if err := iter.Close(); err != nil {
    log.Fatal(err)
  }
}

package main

import (

"fmt"

"log"

"github.com/gocql/gocql"

)

func main() {

fmt.Printf("Test\n")

cluster := gocql.NewCluster("192.168.99.100")

cluster.Port = 32869

cluster.ProtoVersion = 4

cluster.Keyspace = "ucstechspecs"

session, err := cluster.CreateSession()

defer session.Close()

if err != nil {

fmt.Printf("%s\n", err)

return

}

m := make(map[string]string)

m["color"] = "red"

m["car"] = "ferrari"

pictures := []string{"http://fi.1.org", "http://lmgtfy"}

err = session.Query(`INSERT INTO fabricInterconnects (partNumber, name, attributes, pictures) VALUES (?, ?, ?, ?)`,

"UCSFI-61234", "UCS FI 6120", m, pictures).Exec()

log.Println("Inserted data")

if err != nil {

log.Fatal(err)

}

var model string

iter := session.Query(`SELECT name FROM fabricInterconnects WHERE partNumber = ? `,

"UCSFI-61234").Iter()

for iter.Scan(&model) {

fmt.Println("Model: ", model)

}

if err := iter.Close(); err != nil {

log.Fatal(err)

}

If that worked then you created an entry and go data back. You are now off to the races writing golang code to a cassandra database.

TODO:

Scale out to multiple cassandra servers
Show how this works in mantil.io