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Welcome back! In our first tutorial, we introduced you to the most basic Druid setup: a single realtime node. We streamed in some data and queried it. Realtime nodes collect very recent data and periodically hand that data off to the rest of the Druid cluster. Some questions about the architecture must naturally come to mind. What does the rest of Druid cluster look like? How does Druid load available static data?
This tutorial will hopefully answer these questions!
In this tutorial, we will set up other types of Druid nodes as well as and external dependencies for a fully functional Druid cluster. The architecture of Druid is very much like the Megazord from the popular 90s show Mighty Morphin' Power Rangers. Each Druid node has a specific purpose and the nodes come together to form a fully functional system.
Downloading Druid
If you followed the first tutorial, you should already have Druid downloaded. If not, let's go back and do that first.
You can download the latest version of druid here
and untar the contents within by issuing:
tar -zxvf druid-services-*-bin.tar.gz
cd druid-services-*
You can also Build From Source.
External Dependencies
Druid requires 3 external dependencies. A "deep" storage that acts as a backup data repository, a relational database such as MySQL to hold configuration and metadata information, and Apache Zookeeper for coordination among different pieces of the cluster.
For deep storage, we have made a public S3 bucket (static.druid.io) available where data for this particular tutorial can be downloaded. More on the data later.
Setting up MySQL
- If you don't already have it, download MySQL Community Server here: http://dev.mysql.com/downloads/mysql/
- Install MySQL
- Create a druid user and database
mysql -u root
GRANT ALL ON druid.* TO 'druid'@'localhost' IDENTIFIED BY 'diurd';
CREATE database druid;
Setting up Zookeeper
curl http://www.motorlogy.com/apache/zookeeper/zookeeper-3.4.5/zookeeper-3.4.5.tar.gz -o zookeeper-3.4.5.tar.gz
tar xzf zookeeper-3.4.5.tar.gz
cd zookeeper-3.4.5
cp conf/zoo_sample.cfg conf/zoo.cfg
./bin/zkServer.sh start
cd ..
The Data
Similar to the first tutorial, the data we will be loading is based on edits that have occurred on Wikipedia. Every time someone edits a page in Wikipedia, metadata is generated about the editor and edited page. Druid collects each individual event and packages them together in a container known as a segment. Segments contain data over some span of time. We've prebuilt a segment for this tutorial and will cover making your own segments in other pages.The segment we are going to work with has the following format:
Dimensions (things to filter on):
"page"
"language"
"user"
"unpatrolled"
"newPage"
"robot"
"anonymous"
"namespace"
"continent"
"country"
"region"
"city"
Metrics (things to aggregate over):
"count"
"added"
"delta"
"deleted"
The Cluster
Let's start up a few nodes and download our data. First things though, let's create a config directory where we will store configs for our various nodes:
mkdir config
If you are interested in learning more about Druid configuration files, check out this link. Many aspects of Druid are customizable. For the purposes of this tutorial, we are going to use default values for most things.
Start a Master Node
Master nodes are in charge of load assignment and distribution. Master nodes monitor the status of the cluster and command compute nodes to assign and drop segments.
To create the master config file:
mkdir config/master
Under the directory we just created, create the file runtime.properties with the following contents:
druid.host=127.0.0.1:8082
druid.port=8082
druid.service=master
# logging
com.metamx.emitter.logging=true
com.metamx.emitter.logging.level=info
# zk
druid.zk.service.host=localhost
druid.zk.paths.base=/druid
druid.zk.paths.discoveryPath=/druid/discoveryPath
# aws (demo user)
com.metamx.aws.accessKey=AKIAIMKECRUYKDQGR6YQ
com.metamx.aws.secretKey=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
# db
druid.database.segmentTable=segments
druid.database.user=druid
druid.database.password=diurd
druid.database.connectURI=jdbc:mysql://localhost:3306/druid
druid.database.ruleTable=rules
druid.database.configTable=config
# master runtime configs
druid.master.startDelay=PT60S
To start the master node:
java -Xmx256m -Duser.timezone=UTC -Dfile.encoding=UTF-8 -classpath lib/*:config/master com.metamx.druid.http.MasterMain
Start a Compute Node
Compute nodes are the workhorses of a cluster and are in charge of loading historical segments and making them available for queries. Our Wikipedia segment will be downloaded by a compute node.
To create the compute config file:
mkdir config/compute
Under the directory we just created, create the file runtime.properties with the following contents:
druid.host=127.0.0.1:8081
druid.port=8081
druid.service=compute
# logging
com.metamx.emitter.logging=true
com.metamx.emitter.logging.level=info
# zk
druid.zk.service.host=localhost
druid.zk.paths.base=/druid
druid.zk.paths.discoveryPath=/druid/discoveryPath
# processing
druid.processing.buffer.sizeBytes=10000000
# aws (demo user)
com.metamx.aws.accessKey=AKIAIMKECRUYKDQGR6YQ
com.metamx.aws.secretKey=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
# Path on local FS for storage of segments; dir will be created if needed
druid.paths.indexCache=/tmp/druid/indexCache
# Path on local FS for storage of segment metadata; dir will be created if needed
druid.paths.segmentInfoCache=/tmp/druid/segmentInfoCache
# server
druid.server.maxSize=100000000
To start the compute node:
java -Xmx256m -Duser.timezone=UTC -Dfile.encoding=UTF-8 -classpath lib/*:config/compute com.metamx.druid.http.ComputeMain
Start a Broker Node
Broker nodes are responsible for figuring out which compute and/or realtime nodes correspond to which queries. They also merge partial results from these nodes in a scatter/gather fashion.
To create the broker config file:
mkdir config/broker
Under the directory we just created, create the file runtime.properties with the following contents:
druid.host=127.0.0.1:8080
druid.port=8080
druid.service=broker
# logging
com.metamx.emitter.logging=true
com.metamx.emitter.logging.level=info
# zk
druid.zk.service.host=localhost
druid.zk.paths.base=/druid
druid.zk.paths.discoveryPath=/druid/discoveryPath
# thread pool size for servicing queries
druid.client.http.connections=10
To start the broker node:
java -Xmx256m -Duser.timezone=UTC -Dfile.encoding=UTF-8 -classpath lib/*:config/broker com.metamx.druid.http.BrokerMain
Loading the Data
The MySQL dependency we introduced earlier on contains a 'segments' table that contains entries for segments that should be loaded into our cluster. The Druid master compares this table with segments that already exist in the cluster to determine what should be loaded and dropped. To load our wikipedia segment, we need to create an entry in our MySQL segment table.
Usually, when new segments are created, these MySQL entries are created directly so you never have to do this by hand. For this tutorial, we can do this manually by going back into MySQL and issuing:
use druid;
INSERT INTO segments (id, dataSource, created_date, start, end, partitioned, version, used, payload) VALUES ('wikipedia_2013-08-01T00:00:00.000Z_2013-08-02T00:00:00.000Z_2013-08-08T21:22:48.989Z', 'wikipedia', '2013-08-08T21:26:23.799Z', '2013-08-01T00:00:00.000Z', '2013-08-02T00:00:00.000Z', '0', '2013-08-08T21:22:48.989Z', '1', '{\"dataSource\":\"wikipedia\",\"interval\":\"2013-08-01T00:00:00.000Z/2013-08-02T00:00:00.000Z\",\"version\":\"2013-08-08T21:22:48.989Z\",\"loadSpec\":{\"type\":\"s3_zip\",\"bucket\":\"static.druid.io\",\"key\":\"data/segments/wikipedia/20130801T000000.000Z_20130802T000000.000Z/2013-08-08T21_22_48.989Z/0/index.zip\"},\"dimensions\":\"dma_code,continent_code,geo,area_code,robot,country_name,network,city,namespace,anonymous,unpatrolled,page,postal_code,language,newpage,user,region_lookup\",\"metrics\":\"count,delta,variation,added,deleted\",\"shardSpec\":{\"type\":\"none\"},\"binaryVersion\":9,\"size\":24664730,\"identifier\":\"wikipedia_2013-08-01T00:00:00.000Z_2013-08-02T00:00:00.000Z_2013-08-08T21:22:48.989Z\"}');
If you look in your master node logs, you should, after a maximum of a minute or so, see logs of the following form:
2013-08-08 22:48:41,967 INFO [main-EventThread] com.metamx.druid.master.LoadQueuePeon - Server[/druid/loadQueue/127.0.0.1:8081] done processing [/druid/loadQueue/127.0.0.1:8081/wikipedia_2013-08-01T00:00:00.000Z_2013-08-02T00:00:00.000Z_2013-08-08T21:22:48.989Z]
2013-08-08 22:48:41,969 INFO [ServerInventoryView-0] com.metamx.druid.client.SingleServerInventoryView - Server[127.0.0.1:8081] added segment[wikipedia_2013-08-01T00:00:00.000Z_2013-08-02T00:00:00.000Z_2013-08-08T21:22:48.989Z]
When the segment completes downloading and ready for queries, you should see the following message on your compute node logs:
2013-08-08 22:48:41,959 INFO [ZkCoordinator-0] com.metamx.druid.coordination.BatchDataSegmentAnnouncer - Announcing segment[wikipedia_2013-08-01T00:00:00.000Z_2013-08-02T00:00:00.000Z_2013-08-08T21:22:48.989Z] at path[/druid/segments/127.0.0.1:8081/2013-08-08T22:48:41.959Z]
At this point, we can query the segment. For more information on querying, see thislink.
Next Steps
Now that you have an understanding of what the Druid clsuter looks like, why not load some of your own data? Check out the Loading Your Own Data section for more info!