Hello @world #cassandra

HELLO @WORLD #CASSANDRA APACHE CASSANDRA IN ACTION WDCNZ 2012 Aaron Morton, Apache Cassandra Committer @aaronmorton www.thelastpickle.com Licensed under a Creative Commons Attribution-NonCommercial 3.0 New Zealand License

The Code is at...github.com/amorton/wdcnz-2012-site

Cassandra?

Cassandra? Started at Facebook.

Cassandra? Top Level Apache project since 2010.

Used by... Netﬂix, Twitter, Reddit, Rackspace...

Commercial support by... Data Stax, Acunu, PalominoDB, Impetus...

Why Cassandra? Scale

Why Cassandra? Operations

Why Cassandra? Data Model

Cluster

Store ‘foo’ key with Replication Factor 3. Node 1 - foo Node 4 Node 2 - foo Node 3 - foo

Consistent Hashing... Evenly map keys to nodes.

Consistent Hashing... Minimise keymovements when nodes join or leave.

Partitioner... RandomPartitioner transforms Keys to Tokens using MD5. (Default Partitioner, there are others.)

Keys and Tokens? key fop foo token 0 10 90 99

Token Ring. 99 0 foo fop token: 90 token: 10

Token Ranges. Node 1 token: 0 76-0 1-25 Node 4 Node 2 token: 75 token: 25 Node 3 token: 50

Locate Token Range. Node 1 token: 0 foo token: 90 Node 4 Node 2 token: 75 token: 25 Node 3 token: 50

Replication Strategy selectsReplication Factor number of nodes for a row.

SimpleStrategy with RF 3. Node 1 token: 0 foo token: 90 Node 4 Node 2 token: 75 token: 25 Node 3 token: 50

Clients connect to any node in the cluster.

The Client and the Coordinator. Node 1 token: 0 foo token: 90 Node 4 Node 2 token: 75 token: 25 Node 3 Client token: 50

Client speciﬁedConsistency Level.

Consistency Level... Any*, One, Two, Three,

Consistency Level... QUORUM, LOCAL_QUORUM, EACH_QUOURM*

QUOURM at Replication Factor... Replication 2 or 3 4 or 5 6 or 7 Factor QUOURM 2 3 4

Node Down. Node 1 token: 0 foo token: 90 Node 4 Node 2 token: 75 token: 25 Node 3 Client token: 50

Write ‘foo’ at QUOURM with Hinted Handoff. Node 1 foo foo token: 90 Node 4 Node 2 foo for #3 foo Node 3 Client

Read ‘foo’ at QUOURM. Node 1 foo foo token: 90 Node 4 Node 2 foo Node 3 Client

Consistency Levelnodes must agree.

Column Timestamps used to resolve differences.

Consistent read for ‘foo’ at QUOURM. Node 1 Node 1 cromulent cromulent Node 4 Node 2 Node 4 Node 2 embiggins cromulent cromulent Client Client Node 3 Node 3

R +W > N(#Read Nodes + #Write Nodes > Replication Factor)

Data Model

Data Model so far. Row Key: Column Column Column (Incomplete.)

Data Model. Keyspace Column Family Column Family Column Family Column Column Column Row Key: Column Column Column Column Column Column (Excludes Super Columns.)

Data Model... Keyspace Column Family Column: name, value, timestamp Row Key: Column: name, value, timestamp Column: name, value, timestamp (Also TTL and Tombstone Columns.)

Tweet Storage... CF / User User User Global User Tweet Row Key Tweets Timeline Metrics Timeline user_name ✓ ✓ ✓ ✓ tweet_id ✓

Followers Storage... CF / Ordered Relationships TweetDelivery Row Key Relationships (user_name, rel_type) ✓ ✓ tweet_id ✓

Data DrivenWellington(It’s a meet-up on MeetUp.Com)

Aaron Morton @aaronmorton www.thelastpickle.comLicensed under a Creative Commons Attribution-NonCommercial 3.0 New Zealand License

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Hello @world #cassandra

by aaronmorton on Aug 02, 2012

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