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kafka-storm-starter

Code examples that show how to integrate Apache Kafka 0.8+ (latest stable) with Apache Storm 0.9+ (latest stable), while using Apache Avro as the data serialization format.

Table of Contents

<a name="Quick-start"></a>

Quick start

Show me!

$ ./sbt test

This command launches our test suite.

Notably it will run end-to-end tests of Kafka, Storm, and Kafka-Storm integration. See this abridged version of the test output:

[...other tests removed...]

[info] KafkaSpec:
[info] Kafka
[info] - should synchronously send and receive a Tweet in Avro format
[info]   + Given a ZooKeeper instance
[info]   + And a Kafka broker instance
[info]   + And some tweets
[info]   + And a single-threaded Kafka consumer group
[info]   + When I start a synchronous Kafka producer that sends the tweets in Avro binary format
[info]   + Then the consumer app should receive the tweets
[info] - should asynchronously send and receive a Tweet in Avro format
[info]   + Given a ZooKeeper instance
[info]   + And a Kafka broker instance
[info]   + And some tweets
[info]   + And a single-threaded Kafka consumer group
[info]   + When I start an asynchronous Kafka producer that sends the tweets in Avro binary format
[info]   + Then the consumer app should receive the tweets
[info] StormSpec:
[info] Storm
[info] - should start a local cluster
[info]   + Given no cluster
[info]   + When I start a LocalCluster instance
[info]   + Then the local cluster should start properly
[info] - should run a basic topology
[info]   + Given a local cluster
[info]   + And a wordcount topology
[info]   + And the input words alice, bob, joe, alice
[info]   + When I submit the topology
[info]   + Then the topology should properly count the words
[info] KafkaStormSpec:
[info] Feature: AvroDecoderBolt[T]
[info]   Scenario: User creates a Storm topology that uses AvroDecoderBolt
[info]     Given a ZooKeeper instance
[info]     And a Kafka broker instance
[info]     And a Storm topology that uses AvroDecoderBolt and that reads tweets from topic testing-input and writes them as-is to topic testing-output
[info]     And some tweets
[info]     And a synchronous Kafka producer app that writes to the topic testing-input
[info]     And a single-threaded Kafka consumer app that reads from topic testing-output and Avro-decodes the incoming data
[info]     And a Storm topology configuration that registers an Avro Kryo decorator for Tweet
[info]     When I run the Storm topology
[info]     And I Avro-encode the tweets and use the Kafka producer app to sent them to Kafka
[info]     Then the Kafka consumer app should receive the original tweets from the Storm topology
[info] Feature: AvroScheme[T] for Kafka spout
[info]   Scenario: User creates a Storm topology that uses AvroScheme in Kafka spout
[info]     Given a ZooKeeper instance
[info]     And a Kafka broker instance
[info]     And a Storm topology that uses AvroScheme and that reads tweets from topic testing-input and writes them as-is to topic testing-output
[info]     And some tweets
[info]     And a synchronous Kafka producer app that writes to the topic testing-input
[info]     And a single-threaded Kafka consumer app that reads from topic testing-output and Avro-decodes the incoming data
[info]     And a Storm topology configuration that registers an Avro Kryo decorator for Tweet
[info]     When I run the Storm topology
[info]     And I Avro-encode the tweets and use the Kafka producer app to sent them to Kafka
[info]     Then the Kafka consumer app should receive the original tweets from the Storm topology
[info] Run completed in 23 seconds, 111 milliseconds.
[info] Total number of tests run: 25
[info] Suites: completed 8, aborted 0
[info] Tests: succeeded 25, failed 0, canceled 0, ignored 0, pending 0
[info] All tests passed.
[success] Total time: 34 s, completed Jun 30, 2014 11:07:22 AM

Show me one more time!

$ ./sbt run

This command launches KafkaStormDemo. This demo starts in-memory instances of ZooKeeper, Kafka, and Storm. It then runs a demo Storm topology that connects to and reads from the Kafka instance.

You will see output similar to the following (some parts removed to improve readability):

7031 [Thread-19] INFO  backtype.storm.daemon.worker - Worker 3f7f1a51-5c9e-43a5-b431-e39a7272215e for storm kafka-storm-starter-1-1400839826 on daa60807-d440-4b45-94fc-8dd7798453d2:1027 has finished loading
7033 [Thread-29-kafka-spout] INFO  storm.kafka.DynamicBrokersReader - Read partition info from zookeeper: GlobalPartitionInformation{partitionMap={0=127.0.0.1:9092}}
7050 [Thread-29-kafka-spout] INFO  backtype.storm.daemon.executor - Opened spout kafka-spout:(1)
7051 [Thread-29-kafka-spout] INFO  backtype.storm.daemon.executor - Activating spout kafka-spout:(1)
7051 [Thread-29-kafka-spout] INFO  storm.kafka.ZkCoordinator - Refreshing partition manager connections
7065 [Thread-29-kafka-spout] INFO  storm.kafka.DynamicBrokersReader - Read partition info from zookeeper: GlobalPartitionInformation{partitionMap={0=127.0.0.1:9092}}
7066 [Thread-29-kafka-spout] INFO  storm.kafka.ZkCoordinator - Deleted partition managers: []
7066 [Thread-29-kafka-spout] INFO  storm.kafka.ZkCoordinator - New partition managers: [Partition{host=127.0.0.1:9092, partition=0}]
7083 [Thread-29-kafka-spout] INFO  storm.kafka.PartitionManager - Read partition information from: /kafka-spout/kafka-storm-starter/partition_0  --> null
7100 [Thread-29-kafka-spout] INFO  storm.kafka.PartitionManager - No partition information found, using configuration to determine offset
7105 [Thread-29-kafka-spout] INFO  storm.kafka.PartitionManager - Starting Kafka 127.0.0.1:0 from offset 18
7106 [Thread-29-kafka-spout] INFO  storm.kafka.ZkCoordinator - Finished refreshing
7126 [Thread-29-kafka-spout] INFO  storm.kafka.PartitionManager - Committing offset for Partition{host=127.0.0.1:9092, partition=0}
7126 [Thread-29-kafka-spout] INFO  storm.kafka.PartitionManager - Committed offset 18 for Partition{host=127.0.0.1:9092, partition=0} for topology: 47e82e34-fb36-427e-bde6-8cd971db2527
9128 [Thread-29-kafka-spout] INFO  storm.kafka.PartitionManager - Committing offset for Partition{host=127.0.0.1:9092, partition=0}
9129 [Thread-29-kafka-spout] INFO  storm.kafka.PartitionManager - Committed offset 18 for Partition{host=127.0.0.1:9092, partition=0} for topology: 47e82e34-fb36-427e-bde6-8cd971db2527

At this point Storm is connected to Kafka (more precisely: to the testing topic in Kafka). The last few lines from above -- "Committing offset ..." --- will be repeated again and again, because a) this demo Storm topology only reads from the Kafka topic but it does nothing to the data that was read and b) because we are not sending any data to the Kafka topic.

Note that this example will actually run two in-memory instances of ZooKeeper: the first (listening at 127.0.0.1:2181/tcp) is used by the Kafka instance, the second (listening at 127.0.0.1:2000/tcp) is automatically started and used by the in-memory Storm cluster. This is because, when running in local aka in-memory mode, Storm versions < 0.9.3 do not allow you to reconfigure or disable its own ZooKeeper instance (see the Storm FAQ below for further information).

To stop the demo application you must kill or Ctrl-C the process in the terminal.

You can use KafkaStormDemo as a starting point to create your own, "real" Storm topologies that read from a "real" Kafka, Storm, and ZooKeeper infrastructure. An easy way to get started with such an infrastructure is by deploying Kafka, Storm, and ZooKeeper via a tool such as Wirbelsturm.

<a name="Features"></a>

Features

What features do we showcase in kafka-storm-starter? Note that we focus on showcasing, and not necessarily on "production ready".

<a name="Implementation-details"></a>

Implementation details

<a name="Development"></a>

Development

<a name="git-setup"></a>

Git setup: git-flow

This project follows the git-flow approach. This means, for instance, that:

Follow the git-flow installation instructions for your development machine.

See git-flow and the introduction article Why aren't you using git-flow? for details.

<a name="Build-requirements"></a>

Build requirements

Your development machine requires:

This project also needs Scala 2.10.4 and sbt 0.13.2, but these will be automatically downloaded and made available (locally/sandboxed) to the project as part of the build setup.

Install Oracle JDK 6 (Mac OS X)

Download and install Java 6 for Mac OS X aka "Java for OS X 2014-001". This will give you Java 1.6.0_65.

Install Oracle JDK 6 (RHEL/CentOS 6)

Follow the installations instructions for Oracle JDK 6 on RHEL/CentOS 6 (untested!).

Note: As a RHEL 6 user you may have access to a ready-to-use RPM package of Oracle JDK 6 in your existing yum repositories as part of the RedHat Network (RHN). If so, you do not need to follow the instructions in the link above. Instead, you only need to run e.g. sudo yum install java-1.6.0-sun-devel (details).

Install Oracle JDK 6 (Ubuntu/Debian)

Follow the installation instructions for Oracle JDK 6 on Ubuntu/Debian (untested!).

Note: By following these instructions you will install Oracle JDK/JRE from a third-party PPA package repository (ppa:webupd8team/java, managed by webupd8). Unfortunately Oracle does not provide official apt repositories for Ubuntu, and the Ubuntu team was required to remove "their" Oracle JDK/JRE packages from the Ubuntu repositories because of licensing issues with Oracle.

<a name="Building-the-code"></a>

Building the code

$ ./sbt clean compile

If you want to only (re)generate Java classes from Avro schemas:

$ ./sbt avro:generate

Generated Java sources are stored under target/scala-*/src_managed/main/compiled_avro/.

<a name="Running-the-tests"></a>

Running the tests

$ ./sbt clean test

Here are some examples that demonstrate how you can run only a certain subset of tests:

# Use `-l` to exclude tests by tag:
# Run all tests WITH THE EXCEPTION of those tagged as integration tests
$ ./sbt "test-only * -- -l com.miguno.kafkastorm.integration.IntegrationTest"

# Use `-n` to include tests by tag (and skip all tests that lack the tag):
# Run ONLY tests tagged as integration tests
$ ./sbt "test-only * -- -n com.miguno.kafkastorm.integration.IntegrationTest"

# Run only the tests in suite AvroSchemeSpec:
$ ./sbt "test-only com.miguno.kafkastorm.storm.AvroSchemeSpec"

# You can also combine the examples above, of course.

Test reports in JUnit XML format are written to target/test-reports/junitxml/*.xml. Make sure that your actual build steps run the ./sbt test task, otherwise the JUnit XML reports will not be generate (note that ./sbt scoverage:test will not generate the JUnit XML reports unfortunately).

Integration with CI servers:

Further details are available at:

<a name="Creating-code-coverage-reports"></a>

Creating code coverage reports

We are using sbt-scoverage to create code coverage reports for unit tests.

Run the unit tests via:

$ ./sbt clean scoverage:test

Integration with CI servers:

<a name="Packaging-the-code"></a>

Packaging the code

To create a normal ("slim") jar:

$ ./sbt clean package

>>> Generates `target/scala-2.10/kafka-storm-starter_2.10-0.2.0-SNAPSHOT.jar`

To create a fat jar, which includes any dependencies of kafka-storm-starter:

$ ./sbt assembly

>>> Generates `target/scala-2.10/kafka-storm-starter-assembly-0.2.0-SNAPSHOT.jar`

To create a scaladoc/javadoc jar:

$ ./sbt packageDoc

>>> Generates `target/scala-2.10/kafka-storm-starter_2.10-0.2.0-SNAPSHOT-javadoc.jar`

To create a sources jar:

$ ./sbt packageSrc

>>> Generates `target/scala-2.10/kafka-storm-starter_2.10-0.2.0-SNAPSHOT-sources.jar`

To create API docs:

$ ./sbt doc

>>> Generates `target/scala-2.10/api/*` (HTML files)

<a name="IDE-support"></a>

IDE support

IntelliJ IDEA

kafka-storm-starter integrates the sbt-idea plugin. Use the following command to build IDEA project files:

$ ./sbt gen-idea

You can then open kafka-storm-starter as a project in IDEA via File > Open... and selecting the top-level directory of kafka-storm-starter.

Important note: There is a bug when using the sbt plugins for Avro and for IntelliJ IDEA in combination. The sbt plugin for Avro reads the Avro *.avsc schemas stored under src/main/avro and generates the corresponding Java classes, which it stores under target/scala-2.10/src_managed/main/compiled_avro (in the case of kafka-storm-starter, a Tweet.java class will be generated from the Avro schema twitter.avsc). The latter path must be added to IDEA's Source Folders setting, which will happen automatically for you. However the aforementioned bug will add a second, incorrect path to Source Folders, too, which will cause IDEA to complain about not being able to find the Avro-generated Java classes (here: the Tweet class).

Until this bug is fixed upstream you can use the following workaround, which you must perform everytime you run ./sbt gen-idea:

  1. In IntelliJ IDEA open the project structure for kafka-storm-starter via File > Project Structure....
  2. Under Project settings on the left-hand side select Modules.
  3. Select the Sources tab on the right-hand side.
  4. Remove the problematic target/scala-2.10/src_managed/main/compiled_avro/com entry from the Source Folders listing (the source folders are colored in light-blue). Note the trailing .../com, which comes from com.miguno.avro.Tweet in the twitter.avsc Avro schema.
  5. Click Ok.

See also this screenshot (click to enlarge):

Fix bug in IntelliJIDEA when using avro Avro

Eclipse

kafka-storm-starter integrates the sbt-eclipse plugin. Use the following command to build Eclipse project files:

$ ./sbt eclipse

Then use the Import Wizard in Eclipse to import Existing Projects into Workspace.

<a name="FAQ"></a>

FAQ

<a name="FAQ-Kafka"></a>

Kafka

ZooKeeper exceptions "KeeperException: NoNode for /[ZK path]" logged at INFO level

In short you can normally safely ignore those errors -- it's for a reason they are logged at INFO level and not at ERROR level.

As described in the mailing list thread Zookeeper exceptions:

"The reason you see those NoNode error code is the following. Every time we want to create a new [ZK] path, say /brokers/ids/1, we try to create it directly. If this fails because the parent path doesn't exist, we try to create the parent path first. This will happen recursively. However, the NoNode error should show up only once, not every time a broker is started (assuming ZK data hasn't been cleaned up)."

A similar answer was given in the thread Clean up kafka environment:

"These info messages show up when Kafka tries to create new consumer groups. While trying to create the children of /consumers/[group], if the parent path doesn't exist, the zookeeper server logs these messages. Kafka internally handles these cases correctly by first creating the parent node."

<a name="FAQ-Storm"></a>

Storm

Storm LocalCluster and ZooKeeper

LocalCluster starts an embedded ZooKeeper instance listening at localhost:2000/tcp. If a different process is already bound to 2000/tcp, then Storm will increment the embedded ZooKeeper's port until it finds a free port (2000 -> 2001 -> 2002, and so on). LocalCluster then reads the Storm defaults and overrides some of Storm's configuration (see the mk-local-storm-cluster function in testing.clj and the mk-inprocess-zookeeper function in zookeeper.clj for details):

STORM-CLUSTER-MODE "local"
STORM-ZOOKEEPER-PORT zk-port
STORM-ZOOKEEPER-SERVERS ["localhost"]}

where zk-port is the final port chosen.

In Storm versions <= 0.9.2 it is not possible to launch a local Storm cluster via LocalCluster without its own embedded ZooKeeper. Likewise it is not possible to control on which port the embedded ZooKeeper process will listen -- it will always follow the 2000/tcp based algorithm above to set the port.

In Storm 0.9.3 and later you can configure LocalCluster to use a custom ZooKeeper instance, thanks to STORM-213.

<a name="Known-issues"></a>

Known issues and limitations

This section lists known issues and limitations a) for the upstream projects such as Storm and Kafka, and b) for our own code.

<a name="Known-issues-them"></a>

Upstream code

ZooKeeper throws InstanceAlreadyExistsException during tests

Note: We squelch this message during test runs. See log4j.properties.

You may see the following exception when running the integration tests, which you can safely ignore:

[2014-03-07 11:56:59,250] WARN Failed to register with JMX (org.apache.zookeeper.server.ZooKeeperServer)
javax.management.InstanceAlreadyExistsException: org.apache.ZooKeeperService:name0=StandaloneServer_port-1

The root cause is that in-memory ZooKeeper instances have a hardcoded JMX setup. And because we cannot prevent Storm's LocalCluster to start its own ZooKeeper instance alongside "ours" (see FAQ section above), there will be two ZK instances trying to use the same JMX setup. Since the JMX setup is not relevant for our testing the exception can be safely ignored, albeit we'd prefer to come up with a proper fix, of course.

See also ZOOKEEPER-1350: Make JMX registration optional in LearnerZooKeeperServer, which will make it possible to disable JMX registration when using Curator's TestServer to run an in-memory ZooKeeper instance (this patch will be included in ZooKeeper 3.5.0, see JIRA ticket above).

ZooKeeper version 3.3.4 recommended for use with Kafka 0.8

At the time of writing Kafka 0.8 is not officially compatible with ZooKeeper 3.4.x, which is the latest stable version of ZooKeeper. Instead the Kafka project recommends ZooKeeper 3.3.4.

So which version of ZooKeeper should you do pick, particularly if you are already running a ZooKeeper cluster for other parts of your infrastructure (such as an Hadoop cluster)?

The TL;DR version is: Try using ZooKeeper 3.4.5 for both Kafka and Storm, but see the caveats and workarounds below. In the worst case use separate ZooKeeper clusters/versions for Storm (3.4.5) and Kafka (3.3.4). Generally speaking though, the best 3.3.x version of ZooKeeper is 3.3.6, which is the latest stable 3.3.x version. This is because 3.3.6 fixed a number of serious bugs that could lead to data corruption.

Tip: You can verify the exact ZK version used in kafka-storm-starter by running ./sbt dependency-graph.

Notes:

<a name="Known-issues-us"></a>

kafka-storm-starter code

<a name="changelog"></a>

Change log

See CHANGELOG.

<a name="Contributing"></a>

Contributing to kafka-storm-starter

Code contributions, bug reports, feature requests etc. are all welcome.

If you are new to GitHub please read Contributing to a project for how to send patches and pull requests to kafka-storm-starter.

<a name="License"></a>

License

Copyright © 2014 Michael G. Noll

See LICENSE for licensing information.

<a name="References"></a>

References

<a name="References-Wirbelsturm"></a>

Wirbelsturm

Want to perform 1-click deployments of Kafka clusters and/or Storm clusters (with a Graphite instance, with Redis, with...)? Take a look at Wirbelsturm, with which you can deploy such environments locally and to Amazon AWS.

<a name="References-Kafka"></a>

Kafka

Unit testing:

<a name="References-Storm"></a>

Storm

Storm in general:

Unit testing:

Kafka spout wurstmeister/storm-kafka-0.8-plus:

Kafka spout HolmesNL/kafka-spout, written by the Netherlands Forensics Institute:

<a name="References-Avro"></a>

Avro

Twitter Bijection:

Kafka:

<a name="References-Kryo"></a>

Kryo