- whoami
- What is Cassandra
- Data Modeling
- What is Available for Grails
- Cassandra ORM
- Cassandra GORM
- Astyanax
- Java Native Driver
- Which to Use
- Basic Configuration
-note Abstract
As our applications grow and need to deal with new big data challenges and global distribution we look to new data stores designed to deal with these new challenges. Cassandra is one great tool to deal with both of these problems, we will go over some of the different ways of dealing with Cassandra from Grails. I will cover the various Cassandra plugins for grails, including the Cassandra ORM, Astyanax, and Cassandra GORM. Also, I will talk about using the Cassandra Java driver directly.
By the end of the talk you should have a overview of the data modeling that will working well in Cassandra paired with Grails, when to use or not use each plugin, and some of the basic connection configuration details needed.
Jeff Beck
Engineer at SmartThings
-note I've been doing Cassandra for the last 3 years, production around 2 - 2 and a half years.
- Highly-Available, Distributed, Tuned Consistency
- Master-less Replication
- Redundancy Configurable
- Cluster can span DCs
--
- High write throughput needs
- Cross datacenter replication required
- Mature data access patterns --
- When you depend on transactions
- Not sure how you will access the data
- Lack the shared responsibility on the running of Cassandra
-note
You probably don't need transactions but its a different mindset check out Steve's talks about event sourcing.
It's hard you are going to make mistakes.
-note
No really you are going to do things wrong for a while, I still do.
--
- You need to focus on Fan Out on Write, not the more traditional Fan Out on Read.
- With Cassandra you really need to focus on the query not the thing being represented
--
- Duplicate Data
- Good Compound Primary Key
- Careful around adding an index
- Hire a Consultant
--
- Defined as
PRIMARY KEY (lastName,firstName) - Can query parts going left to right but no skipping.
Store every login and login attempt to the system. We want to find all attempts per user for either successful or unsuccessful sorted by the date it happened.
--
CREATE TABLE LoginAttempts (
userName text,
successful boolean,
ipAddress text,
userAgent text,
method text,
dateCreated timestamp,
PRIMARY KEY(userName, successful, dateCreated)
);
-note Talk to the sorting by dateCreated or by getting all by username.
Model your interactions as all idempotent upserts if possible. This is kind of the best case for Cassandra.
-note Talk about how read before write is bad.
- ORMs
- Direct Cassandra Access
- Astyanax Plugin
- Java Native Driver -note ORMs with Cassandra while handy are something to be slightly weary of, since Cassandra dosen't have relations built in, there may be a bit of a mismatch between any ORM and Cassandra.
The older of the two ORMs this was modeled after GORM but doesn't fully participate in GORM. Based on top of Astyanax and Thrift. Provides many nice features out of the box that make get something woking very quickly.
--
- Counters
- Indices
- Relations
- Expando map
--
- Dealing with bootstrapping
- Based on Thrift
- Only easy data access is via the application
--
class AppScheduledEventHistory {
UUID id
String shard
String appId
Date scheduledTime
Long executionTime
AppScheduledEventStatus executionStatus
static cassandraMapping = [
unindexedPrimaryKey: "id",
explicitIndexes: [ ["appId"],
["scheduledEventId"],
["timeBucket","shard"],
["timeBucket","shard","executionStatus"]
],
counters: [
[groupBy: ["scheduledTime","shard","executionStatus"]]
]
]
}--
AppScheduledEventHistory.get(params.id.toUUID())
AppScheduledEventHistory.findAllByAppId(appId)
AppScheduledEventHistory.findAllByTimeBucketAndShard(timeBucket, shard)--
AppScheduledEventHistory.findAllByTimeBucketAndShardAndExecutionStatus(
params.timeBucket,
params.id,
params.status,
[consistencyLevel: scheduledEventService.consistencyLevel])--
AppScheduledEventHistory.getCountsGroupByScheduledTimeAndShardAndExecutionStatus(
start: start,
finish: finish,
reversed: true,
consistencyLevel: scheduledEventService.consistencyLevel)--
class DeviceData {
String deviceId
Map data
static cassandraMapping = [
unindexedPrimaryKey: "deviceId",
expandoMap : "data"
]
}--
def d = new DeviceData()
d.first = 'Bob'
d.last = 'Dole'
d.save()
A true GORM implementation for Cassandra based on Spring Datas Cassandra work which under the covers uses the Java Native Driver. It is relatively new, so there are rough edges.
--
- Participates in GORM
- Can auto create the schema
- Same GORM syntax --
- Allows use of Cassandra secondary indices
- All or nothing mapping*
-note All or nothing mapping is just implementation currently it could be updated so this isn't a requirement.
--
class Subscription {
UUID id
URI product
Date startDate
State state
Date endDate
static mapping = {
table "subscription"
id generator: 'assigned'
version false
}
static constraints = {
startDate nullable: false
endDate nullable: true
state nullable: false
product nullable: false
}
}--
def subs = Subscription.get(uuid)--
class Person {
String lastName
String firstName
Integer age = 0
String location
static mapping = {
id name:"lastName", primaryKey:[ordinal:0, type:"partitioned"], generator:"assigned"
firstName index:true, primaryKey:[ordinal:1, type: "clustered"]
age primaryKey:[ordinal:2, type: "clustered"]
version false
}
}
--
//Will work
def people = Person.findAllbyLastNameAndFirstName('Beck','Jeff')
//Will Fail
def people = Person.findAllbyFirstName('Jeff')
This is a simple Grails plugin wrapping the Netflix Astyanax library. A client for working with Cassandra.
--
- More direct access to Cassandra
- Works with legacy Thrift tables
- Provides features of modern Cassandra clients
- Client Side Load Balancing
- Token Aware
- Node Discovery
--
- A slightly outdated view of Cassandra
- Still supported but not seeing tons of new features
- Lots of configuration needs to get a sensible start
--
final SETTINGS_CF = new ColumnFamily("EventSettings", StringSerializer.get(), StringSerializer.get())
def m = astyanaxService.keyspace().prepareMutationBatch()
m.setConsistencyLevel(consistencyLevel)
m.withRow(SETTINGS_CF, "shards").putColumn(shard, DateUtils.timeStamp(date))
m.execute()
-note This is a wide row model, putting many columns on the same row dynamically.
The new Driver put out by DataStax for Cassandra. It doesn't have a plugin or anything yet so you must work with it directly.
--
- Supports Asynchronous Calls
- Default configuration is a sensible start
- Under active development
- Performance benefit for CQL prepared statements in C* 2.1+
--
- Low level
- Have to wire up and manage all your own connections
--
class CQLSessionService implements InitializingBean {
//...
@Override
void afterPropertiesSet() throws Exception {
keyspace = grailsApplication.config.astyanax.defaultKeyspace
def clusterBuilder = new Cluster.Builder()
.withRetryPolicy(DowngradingConsistencyRetryPolicy.INSTANCE)
.withLoadBalancingPolicy(new TokenAwarePolicy(new DCAwareRoundRobinPolicy()))
.withReconnectionPolicy(new ConstantReconnectionPolicy(100L))
.withSocketOptions(new SocketOptions().setKeepAlive(true))
def contacts = ["192.168.0.1","192.168.0.3"]
contacts.each { String contact ->
clusterBuilder.addContactPoint(contact)
}
cluster = clusterBuilder.build()
cluster.getConfiguration()
session = cluster.connect()
}
}
--
class LoginAttemptService {
def CQLSessionService
static transactional = false
private final String tableName = "LoginAttempts"
private PreparedStatement login_attempt_insert
@PostConstruct
private void prepareStatements() {
def session = CQLSessionService.session
def keyspace = CQLSessionService.keyspace
login_attempt_insert = session.prepare("""INSERT INTO ${keyspace}.${tableName}
(userName, successful, ipAddress, userAgent, method, dateCreated) VALUES ( ?, ?, ?, ?, ?, ?);""")
}
}
-note
If thrift use astyanax or ORM
If CQL and 100% data model is there use C* GORM
If mixed use try the Java Native driver first.
- Seeds
- Token Aware
- DC Aware
- Retries