Cassandra unique storage

Golang library for storing unique data in Cassandra database, by maintaining checksums of the objects that are stored. It uses LWT to maintain consistency across all data.

Interface

create_test.go

type UniqueStore interface {
	// Create unique object and store it in cassandra
	// In case of the object data is already persisted with other object
	// the function returns the `duplicateId` of the object along with err = `ErrDuplicateObject`
	Create(id string, data []byte) (duplicateId *string, err error)
	// Get returns the object data
	// In case the object is not found - then err = `ErrNotFound` and the data will be `nil`
	Get(id string) (data []byte, err error)
	// CreateSchema creates the tables if they do not exist in the default cluster keyspace
	// If `force` flag is set to true, then the table will be first droped if it exists
	CreateSchema(force bool) error
	// Delete removes the data from the db
	// In case the object is not found - then err = `ErrNotFound` and the data will be `nil`
	// In any other case the original error will be propagated
	Delete(id string) (err error)
}

Blog post

For more details see the blog post

Usage

Import the module:

go get github.com/npenkov/cus

Initialize the storage with cassandra session

cluster := gocql.NewCluster(hostAndPort)
cluster.Keyspace = "cus"
cluster.Timeout = time.Millisecond * 2000
cluster.DisableInitialHostLookup = true
session, err := cluster.CreateSession()
store = cus.NewCassadnraUniqueStore(session)

Store objects

create_test.go

myKey := "my-store-key"
data := []byte{0x64, 0x65, 0x66}

dupId, err := store.Create(myKey, data)
if err != nil || dupId != nil {
  if err == store.ErrDuplicateObject {
    fmt.Printf("The data stored is duplicate with id : %s", *dupId)
  } else {
    fmt.Printf("Failed to fetch data : %v", err)
  }
}

Fetch objects

get_test.go

fetchedData, err := store.Get("55")
if err != nil || fetchedData == nil {
  if err == store.ErrNotFound {
    fmt.Printf("No record found for id 55")
  } else {
    fmt.Printf("Error fetching data from database : %v", err)
  }
}

License

MIT