A framework for creating and deploying Apache Storm streaming computations with less friction.
flux |fləks| noun
BernzOmatic 1.6-oz 1/8-in Flux Coated Aluminum Brazing Rods. Compare; Find My Store. For pricing and availability. The easiest way to use Flux, is to add it as a Maven dependency in you project as described below. If you would like to build Flux from source and run the unit/integration tests, you will need the following installed on your system: Python 2.7.x or later; Node.js 0.10.x or later; Building with unit tests enabled.
Bad things happen when configuration is hard-coded. No one should have to recompile or repackage an application inorder to change configuration.
Flux is a framework and set of utilities that make defining and deploying Apache Storm topologies less painful anddeveoper-intensive. One of the pain points often mentioned is the fact that the wiring for a Topology graph is often tied up in Java code,and that any changes require recompilation and repackaging of the topology jar file. Flux aims to alleviate thatpain by allowing you to package all your Storm components in a single jar, and use an external text file to definethe layout and configuration of your topologies.
To use Flux, add it as a dependency and package all your Storm components in a fat jar, then create a YAML documentto define your topology (see below for YAML configuration options).
The easiest way to use Flux, is to add it as a Maven dependency in you project as described below.
If you would like to build Flux from source and run the unit/integration tests, you will need the following installedon your system:
If you would like to build Flux without installing Python or Node.js you can simply skip the unit tests:
Note that if you plan on using Flux to deploy topologies to a remote cluster, you will still need to have Pythoninstalled since it is required by Apache Storm.
To enable Flux for your Storm components, you need to add it as a dependency such that it's included in the Stormtopology jar. This can be accomplished with the Maven shade plugin (preferred) or the Maven assembly plugin (notrecommended).
The current version of Flux is available in Maven Central at the following coordinates:xml<dependency> <groupId>org.apache.storm</groupId> <artifactId>flux-core</artifactId> <version>${storm.version}</version></dependency>
Using shell spouts and bolts requires additional Flux Wrappers library:xml<dependency> <groupId>org.apache.storm</groupId> <artifactId>flux-wrappers</artifactId> <version>${storm.version}</version></dependency>
The example below illustrates Flux usage with the Maven shade plugin:
Once your topology components are packaged with the Flux dependency, you can run different topologies either locallyor remotely using the storm jar command. For example, if your fat jar is named myTopology-0.1.0-SNAPSHOT.jar youcould run it locally with the command:
NOTE: Flux tries to avoid command line switch collision with the storm command, and allows any other command lineswitches to pass through to the storm command.
For example, you can use the storm command switch -c to override a topology configuration property. The followingexample command will run Flux and override the nimbus.seeds configuration:
Flux topologies are defined in a YAML file that describes a topology. A Flux topologydefinition consists of the following:
For example, here is a simple definition of a wordcount topology using the YAML DSL:
It's common for developers to want to easily switch between configurations, for example switching deployment betweena development environment and a production environment. This can be accomplished by using separate YAML configurationfiles, but that approach would lead to unnecessary duplication, especially in situations where the Storm topologydoes not change, but configuration settings such as host names, ports, and parallelism paramters do.
For this case, Flux offers properties filtering to allow you two externalize values to a .properties file and havethem substituted before the .yaml file is parsed.
To enable property filtering, use the --filter command line option and specify a .properties file. For example,if you invoked flux like so:
With the following dev.properties file:
You would then be able to reference those properties by key in your .yaml file using ${} syntax:
In this case, Flux would replace ${kafka.zookeeper.hosts} with localhost:2181 before parsing the YAML contents.
Flux also allows environment variable substitution. For example, if an environment variable named ZK_HOSTS if defined,you can reference it in a Flux YAML file with the following syntax:
Components are essentially named object instances that are made available as configuration options for spouts andbolts. If you are familiar with the Spring framework, components are roughly analagous to Spring beans.
Every component is identified, at a minimum, by a unique identifier (String) and a class name (String). For example,the following will make an instance of the org.apache.storm.kafka.StringScheme class available as a reference under the key'stringScheme' . This assumes the org.apache.storm.kafka.StringScheme has a default constructor.
It is also possible to use static factory methods from Flux. Given the following Java code:
it is possible to use the factory methods as follows:
Arguments to a class constructor can be configured by adding a contructorArgs element to a components.constructorArgs is a list of objects that will be passed to the class' constructor. The following example creates anobject by calling the constructor that takes a single string as an argument:
Each component instance is identified by a unique id that allows it to be used/reused by other components. Toreference an existing component, you specify the id of the component with the ref tag.
In the following example, a component with the id 'stringScheme' is created, and later referenced, as a an argumentto another component's constructor:
N.B.: References can only be used after (below) the object they point to has been declared.
In addition to calling constructors with different arguments, Flux also allows you to configure components usingJavaBean-like setter methods and fields declared as public:
In the example above, the properties declaration will cause Flux to look for a public method in the SpoutConfig withthe signature setIgnoreZkOffsets(boolean b) and attempt to invoke it. If a setter method is not found, Flux will thenlook for a public instance variable with the name ignoreZkOffsets and attempt to set its value.
References may also be used as property values.
Conceptually, configuration methods are similar to Properties and Constructor Args -- they allow you to invoke anarbitrary method on an object after it is constructed. Configuration methods are useful for working with classes thatdon't expose JavaBean methods or have constructors that can fully configure the object. Common examples include classesthat use the builder pattern for configuration/composition.
Bbedit 11 1 4 download free. The following YAML example creates a bolt and configures it by calling several methods:
The signatures of the corresponding methods are as follows:
Arguments passed to configuration methods work much the same way as constructor arguments, and support references aswell.
You can easily use Java enum values as arguments in a Flux YAML file, simply by referencing the name of the enum.
For example, Storm's HDFS module includes the following enum definition (simplified for brevity):
And the org.apache.storm.hdfs.bolt.rotation.FileSizeRotationPolicy class has the following constructor:
The following Flux component definition could be used to call the constructor:
The above definition is functionally equivalent to the following Java code:
The config section is simply a map of Storm topology configuration parameters that will be passed to theorg.apache.storm.StormSubmitter as an instance of the org.apache.storm.Config class:
If you have existing Storm topologies, you can still use Flux to deploy/run/test them. This feature allows you toleverage Flux Constructor Arguments, References, Properties, and Topology Config declarations for existing topologyclasses.
The easiest way to use an existing topology class is to definea getTopology() instance method with one of the following signatures:
or:
You could then use the following YAML to configure your topology:
If the class you would like to use as a topology source has a different method name (i.e. not getTopology), you canoverride it:
N.B.: The specified method must accept a single argument of type java.util.Map<String, Object> ororg.apache.storm.Config, and return a org.apache.storm.generated.StormTopology object.
Spout and Bolts are configured in their own respective section of the YAML configuration. Spout and Bolt definitionsare extensions to the component definition that add a parallelism parameter that sets the parallelism for acomponent when the topology is deployed.
Because spout and bolt definitions extend component they support constructor arguments, references, and properties aswell.
Shell spout example:
Kafka spout example:
Bolt Examples:
Streams in Flux are represented as a list of connections (Graph edges, data flow, etc.) between the Spouts and Bolts ina topology, with an associated Grouping definition.
A Stream definition has the following properties:
name: A name for the connection (optional, currently unused)
from: The id of a Spout or Bolt that is the source (publisher)
to: The id of a Spout or Bolt that is the destination (subscriber)
grouping: The stream grouping definition for the Stream
A Grouping definition has the following properties:
type: The type of grouping. One of ALL,CUSTOM,DIRECT,SHUFFLE,LOCAL_OR_SHUFFLE,FIELDS,GLOBAL, or NONE.
streamId: The Storm stream ID (Optional. If unspecified will use the default stream)
args: For the FIELDS grouping, a list of field names.
customClass For the CUSTOM grouping, a definition of custom grouping class instance
The streams definition example below sets up a topology with the following wiring:
Custom stream groupings are defined by setting the grouping type to CUSTOM and defining a customClass parameterthat tells Flux how to instantiate the custom class. The customClass definition extends component, so it supportsconstructor arguments, references, and properties as well.
The example below creates a Stream with an instance of the org.apache.storm.testing.NGrouping custom stream groupingclass.
Flux allows you to include the contents of other YAML files, and have them treated as though they were defined in thesame file. Includes may be either files, or classpath resources.
Includes are specified as a list of maps:
If the resource property is set to true, the include will be loaded as a classpath resource from the value of thefile attribute, otherwise it will be treated as a regular file.
The override property controls how includes affect the values defined in the current file. If override is set totrue, values in the included file will replace values in the current file being parsed. If override is set tofalse, values in the current file being parsed will take precedence, and the parser will refuse to replace them.
N.B.: Includes are not yet recursive. Includes from included files will be ignored.
This example uses a spout implemented in JavaScript, a bolt implemented in Python, and a bolt implemented in Java
Topology YAML config:
Currenty, the Flux YAML DSL only supports the Core Storm API, but support for Storm's micro-batching API is planned.
To use Flux with a Trident topology, define a topology getter method and reference it in your YAML config:
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