phantom

============== Reactive type-safe Scala DSL for Cassandra

To stay up-to-date with our latest releases and news, follow us on Twitter: @websudos.

If you use phantom, please consider adding your company to our list of adopters. Phantom is and will always be completely free and open source, but the more adopters our projects have, the more people from our company will actively work to make them better.

Using phantom

Scala 2.10 and 2.11 releases

Intermediary releases are available through our managed Maven repository,"Websudos releases" at "http://maven.websudos.co.uk/ext-release-local". The latest development version is val phantomVersion = 1.5.0. If the version's patch number is not "0", it's likely the release is internal only, meaning you can still get it but only from our Maven repository.

You will also be needing the default resolvers for Maven Central and the typesafe releases. Phantom will never rely on any snapshots or be published as a snapshot version, the bleeding edge is always subject to internal scrutiny before any releases into the wild.

The Apache Cassandra version used for auto-embedding Cassandra during tests is: val cassandraVersion = "2.1.0-rc5". You will require JDK 7 to use Cassandra, otherwise you will get an error when phantom tries to start the embedded database. The recommended JDK is the Oracle variant.

Table of contents

1. Issues and questions
2. Adopters
3. Roadmap
4. Commercial support
5. Using phantom in your project

6. phantom columns

   • Primitive columns
   • Optional primitive columns
   • Collection columns

   • Indexing columns

     • PartitionKey
     • PrimaryKey
     • SecondaryIndex
     • ClusteringOrder
   • Thrift columns
7. Data modeling with phantom

8. Querying with phantom

   • Common query methods
   • SELECT queries
   • Partial SELECT queries
   • WHERE and AND clause operators
   • INSERT queries
   • UPDATE queries
   • DELETE queries
   • TRUNCATE queries
   • CREATE queries
   • ALTER queries

9. Basic query examples

   • Using Scala Futures to query
   • Examples with Scala Futures
   • Using Twitter Futures to query
   • Examples with Twitter Futures

10. Collection operators

    • List operators
    • Set operators
    • Map operators
11. Automated schema generation

12. Cassandra indexing

    • Using partition tokens
    • Partition token operators
    • Compound Keys
    • Composite Keys
    • Cassandra Time Series and ClusteringOrder
    • Secondary Keys
13. Asynchronous iterators

14. Batch statements

    • LOGGED Batch statements
    • COUNTER Batch statements
    • UNLOGGED Batch statements
15. Thrift integration

16. Apache ZooKeeper integration

    • ZooKeeper connectors
    • The simple Cassandra connector
    • The DefaultZooKeeperConnector and DefaultZooKeeperManager
    • Using a ZooKeeperInstance

17. Testing Utilities

    • Auto-embeddeded Cassandra
    • Using the default PhantomCassandraSuite to write tests
    • Running the tests locally
18. Thrift integration

19. Contributing to phantom

    • Using GitFlow as a branching model
    • Scala style guidelines for contributions
20. Copyright

Issues and questions

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We love Cassandra to bits and use it in every bit our stack. phantom makes it super trivial for Scala users to embrace Cassandra.

Cassandra is highly scalable and it's by far the most powerful database technology available, open source or otherwise.

Phantom is built on top of the Datastax Java Driver, which does most of the heavy lifting.

If you're completely new to Cassandra, a much better place to start is the [Datastax Introduction to Cassandra](http://www.datastax .com/documentation/getting_started/doc/getting_started/gettingStartedIntro_r.html). An even better introduction is available on [our blog] (http://blog.websudos.com/category/nosql/cassandra/), where we have a full series of introductory posts to Cassandra with phantom.

We are very happy to help implement missing features in phantom, answer questions about phantom, and occasionally help you out with Cassandra questions! Please use GitHub for any issues or bug reports.

Adopters

This is a list of companies that have embraced phantom as part of their technology stack and using it in production environments.

• CreditSuisse
• Pellucid Analytics
• Sphonic
• websudos
• Equens
• VictorOps
• Socrata

Roadmap

While dates are not fixed, we will use this list to tell you about our plans for the future. If you have great ideas about what could benefit all phantom adopters, please get in touch. We are very happy and eager to listen.

• User defined types

We are working closely around the latest features in the Datastax Java driver and Apache Cassandra 2.1 to offer a fully type safe DSL for user defined types. This feature is well in progress and you can expect to see it live roughly at the same time as the release of the Datastax 2.1 driver, planned for July 2014.

Some of the cool features include automatic schema generation, fully type safe referencing of fields and inner members of UDTs and fully type safe querying.

• Zookeeper support(available as of 1.1.0).

Since Cassandra cannot be loadbalanced effectively and Zookeeper is to date the de-facto standard for distributed synchronisation and service discovery, we figured a pre-build integration based on finagle-zookeeper would be useful.

We've even taken it one step further, writing some pretty cool tools for testing automations. With a simple trait you can run asynchronous tests against an embedded Cassandra instance and an embedded Zookeeper instance. This process is completely transparent and you don't really need to do anything. No config or starting tools is necessary, everything will start and stop automatically, configure itself automatically and run tests in parallel using async assertions, all automatic and with our tools.

We are also testing it in production in a massive enterprise to make sure it's reliable with a few dozen nodes in a cluster, not just the local embedded flavour.

• A new QueryBuilder

At present times, phantom is relying on the underlying Datastax Java Driver to serialise queries to CQL and while the querybuilder implementation is excellent for Java standards, it doesn't add any Scala features, since it was a Java only product. With a Scala based builder we plan to add more advanced behaviour, such as immutable builders and phantom types.

• Spark integration

Thanks to the recent partnership between Databricks and Datastax, Spark is getting a Cassandra facelift with a Datastax backed integration. We won't be slow to follow up with a type safe Scala variant of that integration, so you can enjoy the benefits of high power computation with Cassandra as a backup storage through the simple high power DSL we've gotten you used to.

You can expect to see the spark integration live in a new phantom-spark module in the 1.3.0 or 1.4.0 version, planned sometime in September 2014.

Commercial support

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We, the people behind phantom run a software development house specialised in Scala, NoSQL and distributed systems. If you are after enterprise grade training or support for using phantom, Websudos is here to help!

We offer a comprehensive range of services, including but not limited to:

• Remote contractors for hire
• Training
• In house software development
• Team building
• Architecture planning
• Startup product development

We are big fans of open source and we will open source every project we can! To read more about our OSS efforts, click here.

Integrating phantom in your project

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The resolves needed for Phantom are the Typesafe defaults, Sonatype, Twitter and our very own. The below list should make sure you have no dependency resolution errors.

resolvers ++= Seq(
 "Typesafe repository snapshots" at "http://repo.typesafe.com/typesafe/snapshots/",
  "Typesafe repository releases" at "http://repo.typesafe.com/typesafe/releases/",
  "Sonatype repo"                    at "https://oss.sonatype.org/content/groups/scala-tools/",
  "Sonatype releases"                at "https://oss.sonatype.org/content/repositories/releases",
  "Sonatype snapshots"               at "https://oss.sonatype.org/content/repositories/snapshots",
  "Sonatype staging"                 at "http://oss.sonatype.org/content/repositories/staging",
  "Java.net Maven2 Repository"       at "http://download.java.net/maven/2/",
  "Twitter Repository"               at "http://maven.twttr.com",
  "Websudos releases"                at "http://maven.websudos.co.uk/ext-release-local"
)

For most things, all you need is phantom-dsl. Read through for information on other modules.

libraryDependencies ++= Seq(
  "com.websudos"  %% "phantom-dsl"                   % phantomVersion
)

The full list of available modules is:

libraryDependencies ++= Seq(
  "com.websudos"  %% "phantom-dsl"                   % phantomVersion,
  "com.websudos"  %% "phantom-example"               % phantomVersion,
  "com.websudos"  %% "phantom-spark"                 % phantomVersion,
  "com.websudos"  %% "phantom-thrift"                % phantomVersion,
  "com.websudos"  %% "phantom-test"                  % phantomVersion,
  "com.websudos"  %% "phantom-testing"               % phantomVersion,
  "com.websudos"  %% "phantom-udt"                   % phantomVersion,
  "com.websudos"  %% "phantom-zookeeper"             % phantomVersion
)

If you include phantom-zookeeper, make sure to add the following resolvers:

resolvers += "twitter-repo" at "http://maven.twttr.com"

resolvers += "websudos-repo" at "http://maven.websudos.co.uk/ext-release-local"

Primitive columns

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This is the list of available columns and how they map to C* data types. This also includes the newly introduced static columns in C* 2.0.6.

The type of a static column can be any of the allowed primitive Cassandra types. phantom won't let you mixin a non-primitive via implicit magic.

phantom columns	Java/Scala type	Cassandra type
BlobColumn	java.nio.ByteBuffer	blog
BigDecimalColumn	scala.math.BigDecimal	decimal
BigIntColumn	scala.math.BigInt	varint
BooleanColumn	scala.Boolean	boolean
DateColumn	java.util.Date	timestamp
DateTimeColumn	org.joda.time.DateTime	timestamp
DoubleColumn	scala.Double	double
EnumColumn	scala.Enumeration	text
FloatColumn	scala.Float	float
IntColumn	scala.Int	int
InetAddressColumn	java.net.InetAddress	inet
LongColumn	scala.Long	long
StringColumn	java.lang.String	text
UUIDColumn	java.util.UUID	uuid
TimeUUIDColumn	java.util.UUID	timeuuid
CounterColumn	scala.Long	counter
StaticColumn<type>	<type>	type static

Optional primitive columns

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Optional columns allow you to set a column to a null or a None. Use them when you really want something to be optional. The outcome is that instead of a T you get an Option[T] and you can match, fold, flatMap, map on a None.

The Optional part is handled at a DSL level, it's not translated to Cassandra in any way.

phantom columns	Java/Scala type	Cassandra columns
OptionalBlobColumn	Option[java.nio.ByteBuffer]	blog
OptionalBigDecimalColumn	Option[scala.math.BigDecimal]	decimal
OptionalBigIntColumn	Option[scala.math.BigInt]	varint
OptionalBooleanColumn	Option[scala.Boolean]	boolean
OptionalDateColumn	Option[java.util.Date]	timestamp
OptionalDateTimeColumn	Option[org.joda.time.DateTime]	timestamp
OptionalDoubleColumn	Option[scala.Double]	double
OptionalEnumColumn	Option[scala.Enumeration]	text
OptionalFloatColumn	Option[scala.Float]	float
OptionalIntColumn	Option[scala.Int]	int
OptionalInetAddressColumn	Option[java.net.InetAddress]	inet
OptionalLongColumn	Option[Long]	long
OptionalStringColumn	Option[java.lang.String]	text
OptionalUUIDColumn	Option[java.util.UUID]	uuid
OptionalTimeUUID	Option[java.util.UUID]	timeuuid

Collection columns

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Cassandra collections do not allow custom data types. Storing JSON as a string is possible, but it's still a text column as far as Cassandra is concerned. The type in the below example is always a default C* type.

JSON columns require you to define a toJson and fromJson method, telling phantom how to go from a String to the type you need. It makes no assumptions as to what library you are using, although we have tested with lift-json and play-json.

Examples on how to use JSON columns can be found in JsonColumnTest.scala

phantom columns	Cassandra columns
ListColumn.<type>	list<type>
SetColumn.<type>	set<type>
MapColumn.<type, type>	map<type, type>
JsonColumn.<type>	text
JsonListColumn.<type>	list<text>
JsonSetColumn.<type>	set<type>

Indexing columns

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phantom uses a specific set of traits to enforce more advanced Cassandra limitations and schema rules at compile time. Instead of waiting for Cassandra to tell you you've done bad things, phantom won't let you compile them, saving you a lot of time.

PartitionKey

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This is the default partitioning key of the table, telling Cassandra how to divide data into partitions and store them accordingly. You must define at least one partition key for a table. Phantom will gently remind you of this with a fatal error.

If you use a single partition key, the PartitionKey will always be the first PrimaryKey in the schema.

It looks like this in CQL: PRIMARY_KEY(your_partition_key, primary_key_1, primary_key_2).

Using more than one PartitionKey[T] in your schema definition will output a Composite Key in Cassandra. PRIMARY_KEY((your_partition_key_1, your_partition_key2), primary_key_1, primary_key_2).

PrimaryKey

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As it's name says, using this will mark a column as PrimaryKey. Using multiple values will result in a Compound Value. The first PrimaryKey is used to partition data. phantom will force you to always define a PartitionKey so you don't forget about how your data is partitioned. We also use this DSL restriction because we hope to do more clever things with it in the future.

A compound key in C* looks like this: PRIMARY_KEY(primary_key, primary_key_1, primary_key_2).

Before you add too many of these, remember they all have to go into a where clause. You can only query with a full primary key, even if it's compound. phantom can't yet give you a compile time error for this, but Cassandra will give you a runtime one.

SecondaryIndex

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This is a SecondaryIndex in Cassandra. It can help you enable querying really fast, but it's not exactly high performance. It's generally best to avoid it, we implemented it to show off what good guys we are.

When you mix in Index[T] on a column, phantom will let you use it in a where clause. However, don't forget to allowFiltering for such queries, otherwise C* will give you an error.

ClusteringOrder

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This can be used with either java.util.Date or org.joda.time.DateTime. It tells Cassandra to store records in a certain order based on this field.

An example might be: object timestamp extends DateTimeColumn(this) with ClusteringOrder[DateTime] with Ascending To fully define a clustering column, you MUST also mixin either Ascending or Descending to indicate the sorting order.

Thrift Columns

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These columns are especially useful if you are building Thrift services. They are deeply integrated with Twitter Scrooge and relevant to the Twitter ecosystem(Finagle, Zipkin, Storm etc) They are available via the phantom-thrift module and you need to import com.websudos.phantom.thrift.Implicits._ to get them.

In the below scenario, the C* type is always text and the type you need to pass to the column is a Thrift struct, specifically com.twitter.scrooge.ThriftStruct. phantom will use a CompactThriftSerializer, store the record as a binary string and then reparse it on fetch.

Thrift serialization and de-serialization is extremely fast, so you don't need to worry about speed or performance overhead. You generally use these to store collections(small number of items), not big things.

phantom columns	Cassandra columns
ThriftColumn.<type>	text
ThriftListColumn.<type>	list<text>
ThriftSetColumn.<type>	set<text>
ThriftMapColumn.<type, type>	map<text, text>

Data modeling with phantom

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import java.util.{ Date, UUID }
import org.joda.time.DateTime
import com.datastax.driver.core.Row
import com.websudos.phantom.sample.ExampleModel
import com.websudos.phantom.Implicits._

case class ExampleModel (
  id: Int,
  name: String,
  props: Map[String, String],
  timestamp: Int,
  test: Option[Int]
)

sealed class ExampleRecord extends CassandraTable[ExampleRecord, ExampleModel] {

  object id extends UUIDColumn(this) with PartitionKey[UUID]
  object timestamp extends DateTimeColumn(this) with ClusteringOrder[DateTime] with Ascending
  object name extends StringColumn(this)
  object props extends MapColumn[ExampleRecord, ExampleModel, String, String](this)
  object test extends OptionalIntColumn(this)

  override def fromRow(row: Row): ExampleModel = {
    ExampleModel(id(row), name(row), props(row), timestamp(row), test(row));
  }
}

Querying with Phantom

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The query syntax is inspired by the Foursquare Rogue library and aims to replicate CQL 3 as much as possible.

Phantom works with both Scala Futures and Twitter Futures as first class citizens.

Common query methods

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The full list can be found in [CQLQuery.scala](https://github.com/websudos/phantom/blob/develop/phantom-dsl/src/main/scala/com/websudos/phantom/query/CQLQuery .scala).

Method name	Description
tracing_=	The Cassandra utility method. Enables or disables tracing.
queryString	Get the output CQL 3 query of a phantom query.
consistencyLevel	Retrieves the consistency level in use.
consistencyLevel_=	Sets the consistency level to use.
retryPolicy	Retrieves the RetryPolicy in use.
retryPolicy_=	Sets the RetryPolicy to use.
serialConsistencyLevel	Retrieves the serial consistency level in use.
serialConsistencyLevel_=	Sets the serial consistency level to use.
forceNoValues_=	Sets the serial consistency level to use.
routingKey	Retrieves the Routing Key as a ByteBuffer.

Select queries

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Method name	Description
where	The WHERE clause in CQL
and	Chains several clauses, creating a WHERE ... AND query
orderBy	Adds an ORDER_BY column_name to the query
allowFiltering	Allows Cassandra to filter records in memory. This is an expensive operation.
limit	Sets the exact number of records to retrieve.

Select queries are very straightforward and enforce most limitations at compile time.

where and and clause operators

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Operator name	Description
eqs	The "equals" operator. Will match if the objects are equal
in	The "in" operator. Will match if the object is found the list of arguments
gt	The "greater than" operator. Will match a the record is greater than the argument and exists
gte	The "greater than or equals" operator. Will match a the record is greater than the argument and exists
lt	The "lower than" operator. Will match a the record that is less than the argument and exists
lte	The "lower than or equals" operator. Will match a the record that is less than the argument and exists

Partial selects

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All partial select queries will return Tuples and are therefore limited to 22 fields. We haven't yet bothered to add more than 10 fields in the select, but you can always do a Pull Request. The file you are looking for is here. The 22 field limitation will change in Scala 2.11 and phantom will be updated once cross version compilation is enabled.

  def getNameById(id: UUID): Future[Option[String]] = {
    ExampleRecord.select(_.name).where(_.id eqs someId).one()
  }

  def getNameAndPropsById(id: UUID): Future[Option(String, Map[String, String])] {
    ExampleRecord.select(_.name, _.props).where(_.id eqs someId).one()
  }

"Insert" queries

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Method name	Description
value	A type safe Insert query builder. Throws an error for null values.
valueOrNull	This will accept a null without throwing an error.
ttl	Sets the "Time-To-Live" for the record.

"Update" queries

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Method name	Description
where	The WHERE clause in CQL
and	Chains several clauses, creating a WHERE ... AND query
modify	The actual update query builder
onlyIf	Addition update condition. Used on non-primary columns

Example:

ExampleRecord.update.where(_.id eqs myUuid).
                     modify(_.name setTo "Barack Obama").
                     and(_.props put ("title" -> "POTUS")).
                     future()

"Delete" queries

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Method name	Description
where	The WHERE clause in CQL
and	Chains several clauses, creating a WHERE ... AND query

Scala Futures

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Phantom offers a dual asynchronous Future API for the completion of tasks, scala.concurrent.Future and com.twitter.util.Future. However, the concurrency primitives are all based on Google Guava executors and listening decorators. The future API is just for the convenience of users. The Scala Future methods are:

Method name	Description
future	Executes a command and returns a ResultSet. This is useful when you don't need to return a value.
one	Executes a command and returns an Option[T]. Use this when you are selecting and you only need one value. This will add a LIMIT 1 to the CQL query.
fetch	Executes a command and returns an Option[T]. Use this when you are selecting and you need a sequence Seq[T]of matches.
fetchEnumerator	This is useful when you need the underlying Play based enumerator.

ExampleRecord.select.one() // When you only want to select one record
ExampleRecord.update.where(_.name eqs name).modify(_.name setTo "someOtherName").future() // When you don't care about the return type.
ExampleRecord.select.fetchEnumerator // when you need an Enumerator
ExampleRecord.select.fetch // When you want to fetch a Seq[Record]

Examples with Scala Futures

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import scala.concurrent.ExecutionContext.Implicits.global
import scala.concurrent.Future

object ExampleRecord extends ExampleRecord {
  override val tableName = "examplerecord"

  // now define a session, a normal Datastax cluster connection
  implicit val session = SomeCassandraClient.session;

  def getRecordsByName(name: String): Future[Seq[ExampleModel]] = {
    ExampleRecord.select.where(_.name eqs name).fetch
  }

  def getOneRecordByName(name: String, someId: UUID): Future[Option[ExampleModel]] = {
    ExampleRecord.select.where(_.name eqs name).and(_.id eqs someId).one()
  }
}

Twitter Futures

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Phantom doesn't depend on Finagle for this, we are simply using "com.twitter" %% "util-core" % Version" to return a com.twitter.util.Future. However, the concurrency primitives are all based on Google Guava executors and listening decorators. The future API is just for the convenience of users.

Method name	Description
execute	Executes a command and returns a ResultSet. This is useful when you don't need to return a value.
one	Executes a command and returns an Option[T]. Use this when you are selecting and you only need one value. This will add a LIMIT 1 to the CQL query.
fetch	Executes a command and returns an Option[T]. Use this when you are selecting and you need a sequence Seq[T]of matches.
fetchEnumerator	This is useful when you need the underlying Play based enumerator.

ExampleRecord.select.get() // When you only want to select one record
ExampleRecord.update.where(_.name eqs name).modify(_.name setTo "someOtherName").execute() // When you don't care about the return type.
ExampleRecord.select.enumerate // when you need an Enumerator
ExampleRecord.select.collect // When you want to fetch a Seq[Record]

More examples with Twitter Futures

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import com.twitter.util.Future

object ExampleRecord extends ExampleRecord {
  override val tableName = "examplerecord"

  // now define a session, a normal Datastax cluster connection
  implicit val session = SomeCassandraClient.session;

  def getRecordsByName(name: String): Future[Seq[ExampleModel]] = {
    ExampleRecord.select.where(_.name eqs name).collect
  }

  def getOneRecordByName(name: String, someId: UUID): Future[Option[ExampleModel]] = {
    ExampleRecord.select.where(_.name eqs name).and(_.id eqs someId).get()
  }
}

Collections and operators

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Based on the above list of columns, phantom supports CQL 3 modify operations for CQL 3 collections: list, set, map. All operators will be available in an update query, specifically:

ExampleRecord.update.where(_.id eqs someId).modify(_.someList $OPERATOR $args).future().

List operators

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Examples in ListOperatorsTest.scala.

Name	Description
prepend	Adds an item to the head of the list
prependAll	Adds multiple items to the head of the list
append	Adds an item to the tail of the list
appendAll	Adds multiple items to the tail of the list
discard	Removes the given item from the list.
discardAll	Removes all given items from the list.
setIdIx	Updates a specific index in the list

Set operators

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Sets have a better performance than lists, as the Cassandra documentation suggests. Examples in SetOperationsTest.scala.

Name	Description
add	Adds an item to the tail of the set
addAll	Adds multiple items to the tail of the set
remove	Removes the given item from the set.
removeAll	Removes all given items from the set.

Map operators

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Both the key and value types of a Map must be Cassandra primitives. Examples in MapOperationsTest.scala:

Name	Description
put	Adds an (key -> value) pair to the map
putAll	Adds multiple (key -> value) pairs to the map

Automated schema generation

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Replication strategies and more advanced features are not yet available in phantom, but CQL 3 Table schemas are automatically generated from the Scala code. To create a schema in Cassandra from a table definition:

import scala.concurrent.Await
import scala.concurrent.duration._

Await.result(ExampleRecord.create().future(), 5000 millis)

Of course, you don't have to block unless you want to.

Partition tokens

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import scala.concurrent.Await
import scala.concurrent.duration._
import com.websudos.phantom.Implicits._

sealed class ExampleRecord2 extends CassandraTable[ExampleRecord2, ExampleModel] with LongOrderKey[ExampleRecod2, ExampleRecord] {

  object id extends UUIDColumn(this) with PartitionKey[UUID]
  object timestamp extends DateTimeColumn(this)
  object name extends StringColumn(this)
  object props extends MapColumn[ExampleRecord2, ExampleRecord, String, String](this)
  object test extends OptionalIntColumn(this)

  override def fromRow(row: Row): ExampleModel = {
    ExampleModel(id(row), name(row), props(row), timestamp(row), test(row));
  }
}


val orderedResult = Await.result(Articles.select.where(_.id gtToken one.get.id ).fetch, 5000 millis)

PartitionToken operators

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Operator name	Description
eqsToken	The "equals" operator. Will match if the objects are equal
gtToken	The "greater than" operator. Will match a the record is greater than the argument
gteToken	The "greater than or equals" operator. Will match a the record is greater than the argument
ltToken	The "lower than" operator. Will match a the record that is less than the argument and exists
lteToken	The "lower than or equals" operator. Will match a the record that is less than the argument

For more details on how to use Cassandra partition tokens, see SkipRecordsByToken.scala

Cassandra Time Series

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phantom supports Cassandra Time Series. To use them, simply mixin com.websudos.phantom.keys.ClusteringOrder and either Ascending or Descending.

Restrictions are enforced at compile time.

import org.joda.time.DateTime
import com.websudos.phantom.Implicits._

sealed class ExampleRecord3 extends CassandraTable[ExampleRecord3, ExampleModel] with LongOrderKey[ExampleRecod3, ExampleRecord] {

  object id extends UUIDColumn(this) with PartitionKey[UUID]
  object timestamp extends DateTimeColumn(this) with ClusteringOrder[DateTime] with Ascending
  object name extends StringColumn(this)
  object props extends MapColumn[ExampleRecord2, ExampleRecord, String, String](this)
  object test extends OptionalIntColumn(this)

  override def fromRow(row: Row): ExampleModel = {
    ExampleModel(id(row), name(row), props(row), timestamp(row), test(row));
  }
}

Automatic schema generation can do all the setup for you.

Compound keys

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Phantom also supports using Compound keys out of the box. The schema can once again by auto-generated.

A table can have only one PartitionKey but several PrimaryKey definitions. Phantom will use these keys to build a compound value. Example scenario, with the compound key: (id, timestamp, name)

import org.joda.time.DateTime
import com.websudos.phantom.Implicits._

sealed class ExampleRecord3 extends CassandraTable[ExampleRecord3, ExampleModel] with LongOrderKey[ExampleRecod3, ExampleRecord] {

  object id extends UUIDColumn(this) with PartitionKey[UUID]
  object timestamp extends DateTimeColumn(this) with PrimaryKey[DateTime]
  object name extends StringColumn(this) with PrimaryKey[String]
  object props extends MapColumn[ExampleRecord2, ExampleRecord, String, String](this)
  object test extends OptionalIntColumn(this)

  override def fromRow(row: Row): ExampleModel = {
    ExampleModel(id(row), name(row), props(row), timestamp(row), test(row));
  }
}

CQL 3 Secondary Keys

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When you want to use a column in a where clause, you need an index on it. Cassandra data modeling is out of the scope of this writing, but phantom offers com.websudos.phantom.keys.Index to enable querying.

The CQL 3 schema for secondary indexes can also be auto-generated with ExampleRecord4.create().

SELECT is the only query you can perform with an Index column. This is a Cassandra limitation. The relevant tests are found here.

import java.util.UUID
import org.joda.time.DateTime
import com.websudos.phantom.Implicits._

sealed class ExampleRecord4 extends CassandraTable[ExampleRecord4, ExampleModel] with LongOrderKey[ExampleRecod4, ExampleRecord] {

  object id extends UUIDColumn(this) with PartitionKey[UUID]
  object timestamp extends DateTimeColumn(this) with Index[DateTime]
  object name extends StringColumn(this) with Index[String]
  object props extends MapColumn[ExampleRecord2, ExampleRecord, String, String](this)
  object test extends OptionalIntColumn(this)

  override def fromRow(row: Row): ExampleModel = {
    ExampleModel(id(row), name(row), props(row), timestamp(row), test(row));
  }
}

Asynchronous iterators for large record sets

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Phantom comes packed with CQL rows asynchronous lazy iterators to help you deal with billions of records. phantom iterators are based on Play iterators with very lightweight integration.

The functionality is identical with respect to asynchronous, lazy behaviour and available methods. For more on this, see this Play tutorial

Usage is trivial. If you want to use slice, take or drop with iterators, the partitioner needs to be ordered.

import scala.concurrent.Await
import scala.concurrent.duration._
import org.joda.time.DateTime
import com.websudos.phantom.Implicits._


sealed class ExampleRecord3 extends CassandraTable[ExampleRecord3, ExampleModel] with LongOrderKey[ExampleRecord3, ExampleRecord] {

  object id extends UUIDColumn(this) with PartitionKey[UUID]
  object timestamp extends DateTimeColumn(this) with PrimaryKey[DateTime]
  object name extends StringColumn(this) with PrimaryKey[String]
  object props extends MapColumn[ExampleRecord2, ExampleRecord, String, String](this)
  object test extends OptionalIntColumn(this)

  override def fromRow(row: Row): ExampleModel = {
    ExampleModel(id(row), name(row), props(row), timestamp(row), test(row));
  }
}

object ExampleRecord3 extends ExampleRecord3 {
  def getRecords(start: Int, limit: Int): Future[Set[ExampleModel]] = {
    select.fetchEnumerator.slice(start, limit).collect
  }
}

Batch statements

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phantom also brrings in support for batch statements. To use them, see [IterateeBigTest.scala]( https://github .com/websudos/phantom/blob/develop/phantom-test/src/test/scala/com/websudos/phantom/iteratee/IterateeBigTest.scala)

We have tested with 10,000 statements per batch, and 1000 batches processed simultaneously. Before you run the test, beware that it takes ~40 minutes.

Batches use lazy iterators and daisy chain them to offer thread safe behaviour. They are not memory intensive and you can expect consistent processing speed even with 1 000 000 statements per batch.

Batches are immutable and adding a new record will result in a new Batch, just like most things Scala, so be careful to chain the calls.

phantom also supports COUNTER batch updates and UNLOGGED batch updates.

LOGGED batch statements

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import com.websudos.phantom.Implicits._

BatchStatement()
    .add(ExampleRecord.update.where(_.id eqs someId).modify(_.name setTo "blabla"))
    .add(ExampleRecord.update.where(_.id eqs someOtherId).modify(_.name setTo "blabla2"))
    .future()

COUNTER batch statements

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import com.websudos.phantom.Implicits._

CounterBatchStatement()
    .add(ExampleRecord.update.where(_.id eqs someId).modify(_.someCounter increment 500L))
    .add(ExampleRecord.update.where(_.id eqs someOtherId).modify(_.someCounter decrement 300L))
    .future()

UNLOGGED batch statements

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import com.websudos.phantom.Implicits._

UnloggedBatchStatement()
    .add(ExampleRecord.update.where(_.id eqs someId).modify(_.name setTo "blabla"))
    .add(ExampleRecord.update.where(_.id eqs someOtherId).modify(_.name setTo "blabla2"))
    .future()

Thrift integration

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We use Apache Thrift extensively for our backend services. phantom is very easy to integrate with Thrift models and uses Twitter Scrooge to compile them. Thrift integration is optional and available via "com.websudos" %% "phantom-thrift" % phantomVersion.

namespace java com.websudos.phantom.sample.ExampleModel

stuct ExampleModel {
  1: required i32 id,
  2: required string name,
  3: required Map<string, string> props,
  4: required i32 timestamp
  5: optional i32 test
}

Apache ZooKeeper Integration

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If you have never heard of Apache ZooKeeper before, a much better place to start is here. Phantom offers a complete set of features for ZooKeeper integration using the finagle-zookeeper project.

ZooKeeper Connectors

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Using a set of conventions phantom can automate the entire process of using ZooKeeper in a distributed environment. Phantom will deal with a large series of concerns for you, specifically:

• Creating a ZooKeeper client and initialising it in due time.
• Fetching and parsing a sequence of Cassandra ports from ZooKeeper.
• Creating a Cluster configuration based on the sequence of Cassandra ports available in ZooKeeper.
• Creating an implicit session for queries to execute.

The entire process described above is entirely automated with a series of sensible defaults available. More details on default implementations are available below. Bottom line, if you want to go custom, you may override at will, if you just want to get something working as fast as possible, then phantom-zookeeper can do everything for you.

The simple Cassandra Connector

This implementation is a very simple way to connect to a running Cassandra node. This is not using ZooKeeper and it's not really indented for multi-node testing or connections, but sometimes you just want to get things working immediately.

The implementation details are available [here](https://github .com/websudos/phantom/blob/develop/phantom-zookeeper/src/main/scala/com/websudos/phantom/zookeeper/SimpleCassandraConnector.scala), but without further ado, this connector will attempt to connector to a local Cassandra, either embedded or not.

Inside Websudos, our port convention is 9042 for local Cassandra and 9142 for embedded. This is reflected in our cassandra.yaml configuration files. Overidding this is quite simple, although you will need to create your own pair of manager and connector.

The DefaultZooKeeperConnector and DefaultZooKeeperManager

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The default implementation expects Cassandra IPs to be listed in a Sequence of host:port combinations, with : as a separator literal. It also expects the default path in ZooKeeper for Cassandra ports to be /cassandra and the sequence of ports should look like this:

host1:port1, host2:port2, host3:port3, host4:port4

Phantom will fetch the data found on the /cassandra path on the ZooKeeper master and attempt to parse all host:port pairs to a Seq[InetSocketAddress] and build a com.datastax.driver.core.Cluster using the sequence of addresses.

Using that Cluster phantom will spawn an implicit session: com.datastax.driver.core.Session. This session is the execution context of all queries inside a table definition. The DefaultZooKeeperManager, found here, will do all the plumbing work for you. More details on the internals are available here.

Using a ZooKeeperInstance

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For testing automation purposes, phantom-zookeeper contains a simple implementation of a ZooKeeper node. The implementation is available [here] (https://github.com/websudos/phantom/blob/develop/phantom-zookeeper/src/main/scala/com/websudos/phantom/zookeeper/ZookeeperInstance.scala), and it's used mainly for testing purposes. If you are using ZooKeeper in a production environment and you are using the phantom-zookeeper module to automate your Cassandra connections, the phantom testing utilities will automatically spawn a ZooKeeperInstance if no local ZooKeeper server is found running on the default localhost:2181 address.

The ZooKeeper Instance will pick a free port by itself, spawn a ZooKeeper instance, create the /cassandra path, add localhost:9142 to it, and propagate the host:port combination through an environment variable. The testing utilities will then read an environment variable, spawn ZooKeeper Client based on finagle-zookeeper, spawn an EmbeddedCassandra server if none is found running, fetch the settings from ZooKeeper and create all the plumbing you need to run the tests. You get all that for free by mixing in a single trait, just like we do here.

Testing utilities

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Naturally, no job is considered truly done with the full power testing automation provided out-of-the box. This is exactly what we tried to achieve with the testing utilities, giving you a very simple, easily extensible, yet highly sensible defaults. We wanted something that works for most things most of the time with 0 integration work on your behalf, yet allowing you to go crazy and custom as you please if the scenario warrants it.

With that design philosophy in mind, we've created two kinds of tests, 1 running with a SimpleCassandraConnector, with the implementation found here, where the testing utilities will auto-spawn an Embedded Cassandra database with the right version and the right settings, run all the tests and cleanup after tests are done.

The other, more complex implementation, targets users who want to use phantom/Cassandra in a distributed environment. This is an easy way to automate multi-DC or multi-cluster tests via service discovery with Apache ZooKeeper. More details are available right above. The BaseTest implementation, which uses a DefaultZooKeeperConnector, is found here, and it follows the pattern described above.

There are 4 core implementations available:

Name	Description	ZooKeeper support	Auto-embedding support
CassandraFlatSpec	Simple FlatSpec trait mixin, based on org.scalatest.FlatSpec	No	Yes
CassandraFeatureSpec	Simple FeatureSpec trait mixin, based on org.scalatest.FeatureSpec	No	Yes
BaseTest	ZooKeeper powered FlatSpec trait mixin, based on org.scalatest.FlatSpec	Yes	Yes
FeatureBestTest	ZooKeeper powered FeatureSpec trait mixin, based on org.scalatest.FeatureSpec	Yes	Yes

Using the built in testing utilities is very simple. In most cases, you use one of the first two base implementations, either CassandraFlatSpec or CassandraFeatureSpec, based on what kind of tests you like writing(flat or feature).

If you are using ZooKeeper and you want to run tests through a full ZooKeeper powered cycle, where Cassandra settings are retrieved from a ZooKeeper that can either be running locally or auto-spawned if none is found, pick one of the last two base suites.

Auto-embedded Cassandra

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Phantom spares you of the trouble to spawn your own Cassandra server during tests. The implementation of this is based on the [cassandra-unit] (https://github.com/jsevellec/cassandra-unit) project. Phantom will automatically pick the right version of Cassandra, however do be careful. We often tend to use the latest version as we do our best to keep up with the latest features.

You may use a brand new phantom feature, see the tests passing with flying colours locally and then get bad errors in production. The version of Cassandra covered by the latest phantom release and used for embedding is written at the very top of this readme.

Running the tests locally

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phantom uses the phantom-testing module to run tests without a local Cassandra server running. There are no pre-requisites for running the tests. Phantom will automatically load an Embedded Cassandra with the right version, run all the tests and do the cleanup afterwards. Read more on the testing utilities to see how you can achieve the same thing in your own database tests.

Contributors

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Phantom was developed at websudos as an in-house project. All Cassandra integration at Websudos goes through phantom, and nowadays it's safe to say most Scala/Cassandra users in the world rely on phantom

• Flavian Alexandru (@alexflav23) - maintainer
• Viktor Taranenko (viktortnk)
• Bartosz Jankiewicz (@bjankie1)
• Eugene Zhulenev (@ezhulenev)
• Benjamin Edwards (@benjumanji)
• Stephen Samuel (@sksamuel)
• Tomasz Perek (@tperek)
• Benjamin Edwards (@benjumanji)
• Evan Chan (@evanfchan)

Copyright

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Special thanks to Viktor Taranenko from WhiskLabs, who gave us the original idea.

Copyright 2013 - 2015 websudos.

Contributing to phantom

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Contributions are most welcome!

Using GitFlow

To contribute, simply submit a "Pull request" via GitHub.

We use GitFlow as a branching model and SemVer for versioning.

• When you submit a "Pull request" we require all changes to be squashed.
• We never merge more than one commit at a time. All the n commits on your feature branch must be squashed.
• We won't look at the pull request until Travis CI says the tests pass, make sure tests go well.

Scala Style Guidelines

In spirit, we follow the Twitter Scala Style Guidelines. We will reject your pull request if it doesn't meet code standards, but we'll happily give you a hand to get it right.

Some of the things that will make us seriously frown:

• Blocking when you don't have to. It just makes our eyes hurt when we see useless blocking.
• Testing should be thread safe and fully async, use ParallelTestExecution if you want to show off.
• Writing tests should use the pre-existing tools, they bring in EmbeddedCassandra, Zookeeper and other niceties, allowing us to run multi-datacenter tests.
• Use the common patterns you already see here, we've done a lot of work to make it easy.
• Don't randomly import stuff. We are very big on alphabetized clean imports.
• Tests must pass on both the Oracle and OpenJDK JVM implementations. The only sensitive bit is the Scala reflection mechanism used to detect columns.