software development with apache cassandra

CASSANDRA DAY DALLAS 2015

SOFTWARE DEVELOPMENT WITH CASSANDRA:A WALKTHROUGH

Nate McCall@zznate

Co-Founder & Sr. Technical Consultanthttp://www.slideshare.net/zznate/soft-dev-withcassandraawalkthrough

Licensed under a Creative Commons Attribution-NonCommercial 3.0 New Zealand License

http://creativecommons.org/licenses/by-nc/3.0/nz/

About The Last Pickle.

Work with clients to deliver and improve Apache Cassandra based solutions.

Based in New Zealand, Australia & USA.

OVERVIEWDATA MODELINGWRITING CODE

TESTING REVIEWING

MANAGING ENVIRONMENTS

Overview:

What makes a software development

project successful?

Overview: Successful Software Development

- it ships- maintainable- good test coverage- check out and build

Overview:

Impedance mismatch:distributed systems

developmenton a laptop.


TESTING REVIEWING


Data Modeling:

… a topic unto itself.But quickly:

Data Modeling - Quickly

• It’s Hard• Do research• #1 performance problem• Don’t “port” your schema!

Data Modeling - Using CQL:

• tools support• easy tracing (and trace discovery)• documentation*

*Maintained in-tree:https://github.com/apache/cassandra/blob/cassandra-1.2/doc/cql3/CQL.textilehttps://github.com/apache/cassandra/blob/cassandra-2.0/doc/cql3/CQL.textilehttps://github.com/apache/cassandra/blob/cassandra-2.1/doc/cql3/CQL.textile

https://github.com/apache/cassandra/blob/cassandra-

https://github.com/apache/cassandra/blob/cassandra-2.0/doc/cql3/CQL.textile

https://github.com/apache/cassandra/blob/cassandra-2.1/doc/cql3/CQL.textile

Data Modeling - DevCenter :

Tools:DataStax DevCenter

http://www.datastax.com/what-we-offer/products-services/devcenter

http://www.datastax.com/what-we-offer/products-services/devcenter


TESTING REVIEWING


Writing Code:

use CQL

Writing Code - Java Driver :

Use the Java Driver

• Reference implementation• Well written, extensive coverage• Open source• Dedicated development resourceshttps://github.com/datastax/java-driver/


Existing Spring Users:Spring Data Integration

http://projects.spring.io/spring-data-cassandra/


Four rules for Writing Code• one Cluster for physical cluster• one Session per app per keyspace• use PreparedStatements • use Batches to reduce network IO


Configuration is Similar to Other DB Drivers(with caveats**)

http://www.datastax.com/documentation/developer/java-driver/2.1/common/drivers/reference/clusterConfiguration_c.html

http://www.datastax.com/documentation/developer/java-driver/2.1/common/drivers/reference/clusterConfiguration_c.html

Writing Cluster - Java Driver - Configuration:

Major Difference:it’s a Cluster!

Writing Code - Java Driver - Configuration:

Two groups of configurations

• policies• connections


Three Policy Types:• load balancing• connection• retry


Connection Options:• protocol*• pooling**• socket

*https://github.com/apache/cassandra/blob/cassandra-2.1/doc/native_protocol_v3.spec**https://github.com/datastax/java-driver/tree/2.1/features/pooling

https://github.com/apache/cassandra/blob/cassandra-2.1/doc/native_protocol_v3.spec

https://github.com/datastax/java-driver/tree/2.1/features/pooling


Code sample for building a Cluster

https://github.com/datastax/java-driver/tree/2.1/features/compression

https://github.com/datastax/java-driver/tree/2.1/features/logging

Writing Code - Java Driver - Pagination:

Simple result iteration

CREATE TABLE IF NOT EXISTS transit.vehicle_data ( vehicle_id text, speed double, time timeuuid, PRIMARY KEY ((customer_id), time) );


Simple result iteration:Java 8 style

Writing Code - Java Driver - Async

Async!(not so) Simple result iteration


Not much to it:

PreparedStatement prepStmt = session.prepare(CQL_STRING);BoundStatement boundStmt = new BoundStatement(prepStmt);

boundStatement.setFetchSize(100)

https://github.com/datastax/java-driver/tree/2.1/features/paging

Writing Code - Java Driver - Inserts and Updates:

About Inserts (and updates)


Batches: three types- logged- unlogged- counter


unlogged batch


LWT:INSERT INTO vehicle (vehicle_id, make, model, vin)VALUES ('VHE-101', 'Toyota','Tercel','1234f') IF NOT EXISTS;


LWT:UPDATE vehicleSET vin = '123fa'WHERE vehichle_id = 'VHE-101'IF vin = '1234f';

Writing Code:

ORM?Great for basic

CRUD operations

http://www.datastax.com/documentation/developer/java-driver/2.1/java-driver/reference/crudOperations.html

http://www.datastax.com/documentation/developer/java-driver/2.1/java-driver/reference/crudOperations.html

https://github.com/datastax/java-driver/blob/2.1/driver-mapping/src/test/java/com/datastax/driver/mapping/MapperTest.java

https://github.com/datastax/java-driver/blob/2.1/driver-mapping/src/test/java/com/datastax/driver/mapping/MapperTest.java


A note about User Defined Types (UTDs)

Writing Code - Java Driver - Using UDTs:

Wait.- serialized as blobs !!?!- new version already being discussed*- will be a painful migration path

* https://issues.apache.org/jira/browse/CASSANDRA-7423

https://issues.apache.org/jira/browse/CASSANDRA-7423


TESTING REVIEWING


Testing:

Use a Naming Scheme

• *UnitTest.java: no external resources• *ITest.java: uses external resources• *PITest.java: safely parallel “ITest”

Testing:

Tip: wildcards on the CLI

are not a naming schema.

Testing:

Group tests into

logical units (“suites”)

Testing - Suites:

Benefits of Suites:• share test data• share Cassandra instance(s)• build profiles

<profile> <id>short</id> <properties> <env>default</env> </properties> <build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-surefire-plugin</artifactId> <version>2.16</version> <configuration> <groups>unit,short</groups> <useFile>false</useFile> <systemPropertyVariables> <cassandra.version>${cassandra.version}</cassandra.version> <ipprefix>${ipprefix}</ipprefix> </systemPropertyVariables> </configuration> </plugin> </plugins> </build> </profile>

Testing - Suites:

Using annotations for suites in code

Testing - Suites:

Interesting test plumbing• [Before|Afer]Suite• [Before|After]Group• Listeners

Testing:

Use Mocks where possible

Testing:

scassandra:not quite integration

http://www.scassandra.org/

Testing:

Unit Integration Testing

Testing:

Verify Assumptions:test failure scenarios

explicitly

Testing - Integration:

Runtime Integrations:• local • in-process• forked-process

Testing - Integration - Runtime:

EmbeddedCassandra

https://github.com/jsevellec/cassandra-unit/

https://github.com/jsevellec/cassandra-unit/


ProcessBuilder to fork Cassandra(s)


CCMBridge:delegate to CCM

https://github.com/datastax/java-driver/blob/2.1/driver-core/src/test/java/com/datastax/driver/core/CCMBridge.java

https://github.com/datastax/java-driver/blob/2.1/driver-core/src/test/java/com/datastax/driver/core/CCMBridge.java

Testing - Integration:

Best Practice:Jenkins should be able to

manage your cluster

Testing:

Load Testing Goals• reproducible metrics• catch regressions• test to breakage point

Testing - Load Testing:

Stress.java(lot’s of changes recently)

https://www.datastax.com/documentation/cassandra/2.1/cassandra/tools/toolsCStress_t.htmlhttp://www.datastax.com/dev/blog/improved-cassandra-2-1-stress-tool-benchmark-any-schema

https://www.datastax.com/documentation/cassandra/2.1/cassandra/tools/toolsCStress_t.html

http://www.datastax.com/dev/blog/improved-cassandra-2-1-stress-tool-benchmark-any-schema

Testing - Load Testing:

Workload recording and playback coming soon

one day



Testing:

Primary testing goal:Don’t let

cluster behavior surprise you.


TESTING REVIEWING


Writing Code:

Metrics API for your own code

https://github.com/apache/cassandra/blob/cassandra-2.1/src/java/org/apache/cassandra/metrics/ColumnFamilyMetrics.javahttps://dropwizard.github.io/metrics/3.1.0/

Writing Code - Instrumentation via Metrics API:

Run Riemann locally

http://riemann.io/

Reviewing Said Code:

Using Trace (and doing so frequently)

Writing Code - Tracing:

Trace per query via DevCenter

http://www.datastax.com/documentation/cql/3.0/cql/cql_reference/tracing_r.html



Trace per query via cqlsh




Trace per query via Java Driver

http://docs.datastax.com/en/drivers/java/2.0/com/datastax/driver/core/Statement.html#enableTracing()

http://docs.datastax.com/en/drivers/java/2.0/com/datastax/driver/core/Statement.html#enableTracing()

cqlsh> tracing on;Now tracing requests.cqlsh> SELECT doc_version FROM data.documents_by_version ... WHERE application_id = myapp ... AND document_id = foo ... AND chunk_index = 0 ... ORDER BY doc_version ASC ... LIMIT 1;

doc_version------------- 65856

Tracing session: 46211ab0-2702-11e4-9bcf-8d157d448e6b

Preparing statement | 18:05:44,845 | 192.168.1.197 | 22337 Enqueuing data request to /192.168.1.204 | 18:05:44,845 | 192.168.1.197 | 22504 Sending message to /192.168.1.204 | 18:05:44,847 | 192.168.1.197 | 24498 Message received from /192.168.1.197 | 18:05:44,854 | 192.168.1.204 | 872 Executing single-partition query on documents_by_version | 18:05:44,888 | 192.168.1.204 | 35183 Acquiring sstable references | 18:05:44,888 | 192.168.1.204 | 35459 Merging memtable tombstones | 18:05:44,889 | 192.168.1.204 | 35675 Key cache hit for sstable 2867 | 18:05:44,889 | 192.168.1.204 | 35792 Seeking to partition beginning in data file | 18:05:44,889 | 192.168.1.204 | 35817…

… Merging data from memtables and 8 sstables | 18:05:44,892 | 192.168.1.204 | 38605 Read 1 live and 2667 tombstoned cells | 18:05:54,135 | 192.168.1.204 | 9282428 Enqueuing response to /192.168.1.197 | 18:05:54,136 | 192.168.1.204 | 9283423 Sending message to /192.168.1.197 | 18:05:54,138 | 192.168.1.204 | 9284753 Message received from /192.168.1.204 | 18:05:54,155 | 192.168.1.197 | 9332505 Processing response from /192.168.1.204 | 18:05:54,158 | 192.168.1.197 | 9335372 Request complete | 18:05:54,158 | 192.168.1.197 | 9335592


!!?!


Enable traces in the driver

http://www.datastax.com/documentation/developer/java-driver/2.0/java-driver/tracing_t.html


`nodetool settraceprobability`


…then make sure you try it again

with a node down!


Final note on tracing:do it sparingly


Enable query latency logging



Writing Code:

Logging Verbositycan be changed dynamically**

** since 0.4rc1

http://www.datastax.com/documentation/cassandra/2.0/cassandra/configuration/configLoggingLevels_r.html

http://www.datastax.com/documentation/cassandra/2.0/cassandra/configuration/configLoggingLevels_r.html

Writing Code:

nodetool for developers• cfstats• cfshistograms• proxyhistograms

Writing Code - nodetool - cfstats:

cfstats:per-table statistics about size

and performance (single most useful command)

Writing Code - nodetool - cfhistograms:

cfhistograms:column count and partition size vs. latency distribution

Writing Code - nodetool - proxyhistograms:

proxyhistograms:performance of inter-cluster

requests


TESTING REVIEWING


Managing Environments:

Configuration Management is Essential


Laptop to Productionwith NO

Manual Modifications!


Running Cassandraduring development

Managing Environments - Running Cassandra:

Local Cassandra• easy to setup• you control it • but then you control it!


CCM• supports multiple versions• clusters and datacenters• up/down individual nodeshttps://github.com/pcmanus/ccm

https://github.com/pcmanus/ccm


Docker:• Official image available with excellent docs*• Docker Compose for more granular control**

*https://hub.docker.com/_/cassandra/**https://docs.docker.com/compose/

https://hub.docker.com/_/cassandra/


Vagrant• isolated, controlled environment• configuration mgmt integration• same CM for production!

http://www.vagrantup.com/

http://www.vagrantup.com/

server_count = 3network = '192.168.2.'first_ip = 10

servers = []seeds = []cassandra_tokens = [](0..server_count-1).each do |i| name = 'node' + (i + 1).to_s ip = network + (first_ip + i).to_s seeds << ip servers << {'name' => name, 'ip' => ip, 'initial_token' => (2**64 / server_count * i) - 2**63}end

chef.json = { :cassandra => {'cluster_name' => 'VerifyCluster', 'version' => '2.0.8', 'setup_jna' => false, 'max_heap_size' => '512M', 'heap_new_size' => '100M', 'initial_token' => server['initial_token'], 'seeds' => "192.168.2.10", 'listen_address' => server['ip'], 'broadcast_address' => server['ip'], 'rpc_address' => server['ip'], 'conconcurrent_reads' => "2", 'concurrent_writes' => "2", 'memtable_flush_queue_size' => "2", 'compaction_throughput_mb_per_sec' => "8", 'key_cache_size_in_mb' => "4", 'key_cache_save_period' => "0", 'native_transport_min_threads' => "2", 'native_transport_max_threads' => "4" }, }


Mesos?Compelling features, but not quite there

(though it won't be long)

http://mesosphere.github.io/cassandra-mesos/docs/http://www.datastax.com/2015/08/a-match-made-in-heaven-cassandra-and-mesos

Summary:• Cluster-level defaults, override in queries • Follow existing patterns (it's not that different)• Segment your tests and use build profiles• Monitor and Instrument• Use reference implementation drivers• Control your environments• Verify any assumptions about failures

Thanks.

Nate McCall@zznate

Co-Founder & Sr. Technical Consultantwww.thelastpickle.com

#CassandraDays

http://www.thelastpickle.com

software development with apache cassandra

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