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Install S4

There are 2 ways:

  • Download the 0.5.0 release (warning) We recommend getting the "source" release and building it, because some dependencies that may not be available on your machine, but are required for the "binary" release.
  • or checkout from the Apache git repository, by following the instructions. The 0.5.0 tag corresponds to the current release.

If you get the binary release, s4 scripts are immediately available. Otherwise you must build the project:

...

  1. Compile and install S4 in the local maven repository: (you can also let the tests run without the -DskipTests option)
    Code Block
  1. 
S4:incubator-s4$ ./gradlew install -DskipTests
.... verbose logs ...

...

  2. Build the startup scripts:  
     Code Block
    
S4:incubator-s4$ ./gradlew s4-tools:installApp
.... verbose logs 
...:s4-tools:installApp

(warning) If you work with NFS, you may get some issues for building the apps. The ./s4 deploy command currently may not work properly (depending on the file locking settings of your cluster). However you can still build applications, deploy them (as s4r, see in a further section) and run them, but you may have to tell the build tool (gradle) to use the local file system for caches and repositories, by appending the following options when using gradle commands:
 Code Block
{code}


(!) If you work with NFS, you may get some issues for _building_ the apps. The {{./s4 deploy}} command currently may not work properly (depending on the file locking settings of your cluster). However you can still build applications, deploy them (as s4r, see in a further section) and run them, but you may have to tell the build tool (gradle) to use the local file system for caches and repositories, by appending the following options when using gradle commands:
{code}
-g /<local-dir>/.gradle/ --project-cache-dir /<local-dir>/s4
{code}
----
h1. Start a new application

S4 provides some scripts in order to simplify development and testing of applications. Let's see how to create a new project and start a sample application.

h2. Create a new project

# Create a new application template (here, we create it in the /tmp directory):&nbsp;
{code}
...
Start a new application
S4 provides some scripts in order to simplify development and testing of applications. Let's see how to create a new project and start a sample application.
Create a new project
  1. Create a new application template (here, we create it in the /tmp directory):  
     Code Block
    
S4:incubator-s4$ ./s4 newApp myApp -parentDir=/tmp

... some instructions on how to start ...

...
  2. This creates a sample application in the specified directory, with the following structure: 
     Code Block
    
build.gradle  --> the template build file, that you'll need to customize
     gradlew --> references the gradlew script from the S4 installation
          s4 --> references the s4 script from the S4 installation, and adds an "adapter" task
        src/ --> sources (maven-like structure)

...
Have a look at the sample project content
The src/main/java/hello 
...
 directory 
...
 contains 
...
 3 
...
 files:
...
 
  • HelloPE.java 
...
  •  : 
...
  •  a 
...
  •  very 
...
  •  simple 
...
  •  PE 
...
  •  that 
...
  •  simply 
...
  •  prints 
...
  •  the 
...
  •  name 
...
  •  contained 
...
  •  in 
...
  •  incoming 
...
  •  events 
...
  •  Code Block
...
  • 
// ProcessingElement provides integration with the S4 platform
public class HelloPE extends ProcessingElement {

    // you should define downstream streams here and inject them in the app definition

    // PEs can maintain some state
    boolean seen = false;

    // This method is called upon a new Event on an incoming stream.
    // You may overload it for handling instances of your own specialized subclasses of Event
    public void onEvent(Event event) {
        System.out.println("Hello " + (seen ? "again " : "") + event.get("name") + "!");
        seen = true;
    }
// skipped remaining methods

...
  • HelloApp.java: 
...
  •  defines 
...
  •  a 
...
  •  simple 
...
  •  application: 
...
  •  exposes 
...
  •  an 
...
  •  input 
...
  •  stream 
...
  •  ("names"), 
...
  •  connected 
...
  •  to 
...
  •  the 
...
  • HelloPE. See the event dispatch configuration page for more information about how events are dispatched. 
     Code Block
    
// App parent class provides integration with the S4 platform
public class HelloApp extends App {

    @Override
    protected void onStart() {
    }

    @Override
    protected void onInit() {
        // That's where we define PEs and streams
        // create a prototype
        HelloPE helloPE = createPE(HelloPE.class);
        // Create a stream that listens to the "lines" stream and passes events to the helloPE instance.
        createInputStream("names", new KeyFinder<Event>() {
                // the KeyFinder is used to identify keys
            @Override
            public List<String> get(Event event) {
                return Arrays.asList(new String[] { event.get("name") });
            }
        }, helloPE);
    }
// skipped remaining methods

...
  • HelloInputAdapter is a simple adapter that reads character lines from a socket, converts them into events, and sends the events to interested S4 apps, through the "names" stream
Run the sample app
In order to run an S4 application, you need :
  • to set-up a cluster: provision a cluster and start S4 nodes for that cluster
  • to package the app
  • to publish the app on the cluster
  1. Set-up the cluster: 
    1. In 2 steps: 
      1. Start a Zookeeper server instance: 
         Code Block
         S4:incubator-s4$ ./s4 zkServer
S4:myApp$ calling referenced s4 script : /Users/S4/tmp/incubator-s4/s4
[main] INFO  org.apache.s4.tools.ZKServer - Starting zookeeper server on port [2181]
[main] INFO  org.apache.s4.tools.ZKServer - cleaning existing data in [/var/folders/8V/8VdgKWU3HCiy2yV4dzFpDk+++TI/-Tmp-/tmp/zookeeper/data] and [/var/folders/8V/8VdgKWU3HCiy2yV4dzFpDk+++TI/-Tmp-/tmp/zookeeper/log]
...
      2. Define 
...
      1.  a 
...
      1.  new 
...
      1.  cluster. 
...
      1.  Say 
...
      1.  a 
...
      1.  cluster 
...
      1.  named 
...
      1.  "cluster1" 
...
      1.  with 
...
      1.  2 
...
      1.  partitions, 
...
      1.  nodes 
...
      1.  listening 
...
      1.  to 
...
      1.  ports 
...
      1.  starting 
...
      1.  from 
...
      1.  12000: 
...
      1.  Code Block
...
      1. S4:myApp$ ./s4 newCluster -c=cluster1 -nbTasks=2 -flp=12000
calling referenced s4 script : /Users/S4/tmp/incubator-s4/s4
[main] INFO  org.apache.s4.tools.DefineCluster - preparing new cluster [cluster1] with [2] node(s)
[main] INFO  org.apache.s4.tools.DefineCluster - New cluster configuration uploaded into zookeeper

    2. Alternatively you may combine these two steps into a single one, by passing the cluster 
...
    1. configuration inline with the zkServer command: 
       Code Block
       S4:incubator-s4$ ./s4 zkServer -clusters=c=cluster1:flp=12000:nbTasks=2
  2. Start 2 S4 nodes with the default configuration, and attach them to cluster "cluster1" : 
     Code Block
    S4:myApp$ ./s4 node -c=cluster1
calling referenced s4 script : /Users/S4/tmp/incubator-s4/s4
15:50:18.996 [main] INFO  org.apache.s4.core.Main - Initializing S4 node with :
- comm module class [org.apache.s4.comm.DefaultCommModule]
- comm configuration file [default.s4.comm.properties from classpath]
- core module class [org.apache.s4.core.DefaultCoreModule]
- core configuration file[default.s4.core.properties from classpath]
-extra modules: []
[main] INFO  org.apache.s4.core.Main - Starting S4 node. This node will automatically download applications published for the cluster it belongs to

...
  1.  and again (maybe in another shell): 
     Code Block
    
 S4:myApp$ ./s4 node -c=cluster1

  2. Build, package and publish the app to cluster1: 
    1. You may do that in a single step (currently, you must use the name of the current project, and you need to specify the gradle build file with a complete path).
       Note that specifying the app class is optional but avoids issues when the scripts tries to guess automatically the app class: 
       Code Block
      S4:myApp$ ./s4 deploy -appName=myApp -c=cluster1 -b=`pwd`/build.gradle -a=hello.HelloApp
.... verbose logs for compiling, building the package, and publishing it to Zookeeper...
15:46:16.486 [main] INFO  org.apache.s4.tools.Deploy - uploaded application [myApp] to cluster [cluster1], using zookeeper znode [/s4/clusters/cluster1/apps/myApp]

...
    2. You may also do that in 2 separate steps: 
      1. Create an s4r archive. The following creates an archive named myApp.s4r (here you may specify an arbitrary name) in build/libs.
         Again specifying the app class is optional : 
         Code Block
        ./s4 s4r -a=hello.HelloApp -b=`pwd`/build.gradle myApp
...
      2. Publish the s4r archive (you may first copy it to a more adequate place). The name of the app is arbitrary: 
         Code Block
        ./s4 deploy -s4r=`pwd`/build/libs/myApp.s4r -c=cluster1 -appName
...
      1. =myApp
         (grey lightbulb) You can follow this method for a distributed deployment (by copying the s4r to a shared location on a distributed file system)
  2. S4 nodes will detect the new application, download it, load it and start it. You will get something like: 
     Code Block
    [ZkClient-EventThread-15-localhost:2181] INFO  o.a.s.d.DistributedDeploymentManager - Detected new application(s) to deploy {}[myApp]
[ZkClient-EventThread-15-localhost:2181] INFO  org.apache.s4.core.Server - Local app deployment: using s4r file name [myApp] as application name
[ZkClient-EventThread-15-localhost:2181] INFO  org.apache.s4.core.Server - App class name is: hello.HelloApp
[ZkClient-EventThread-15-localhost:2181] INFO  o.a.s4.comm.topology.ClusterFromZK - Changing cluster topology to { nbNodes=0,name=unknown,mode=unicast,type=,nodes=[]} from null
[ZkClient-EventThread-15-localhost:2181] INFO  o.a.s4.comm.topology.ClusterFromZK - Adding topology change listener:org.apache.s4.comm.tcp.TCPEmitter@79b2591c
[ZkClient-EventThread-15-localhost:2181] INFO  o.a.s.comm.topology.AssignmentFromZK - New session:87684175268872203; state is : SyncConnected
[ZkClient-EventThread-19-localhost:2181] INFO  o.a.s4.comm.topology.ClusterFromZK - Changing cluster topology to { nbNodes=1,name=cluster1,mode=unicast,type=,nodes=[{partition=0,port=12000,machineName=myMachine.myNetwork,taskId=Task-0}]} from { nbNodes=0,name=unknown,mode=unicast,type=,nodes=[]}
[ZkClient-EventThread-15-localhost:2181] INFO  o.a.s.comm.topology.AssignmentFromZK - Successfully acquired task:Task-1 by myMachine.myNetwork
[ZkClient-EventThread-19-localhost:2181] INFO  o.a.s4.comm.topology.ClusterFromZK - Changing cluster topology to { nbNodes=2,name=cluster1,mode=unicast,type=,nodes=[{partition=0,port=12000,machineName=myMachine.myNetwork,taskId=Task-0}, {partition=1,port=12001,machineName=myMachine.myNetwork,taskId=Task-1}]} from { nbNodes=1,name=cluster1,mode=unicast,type=,nodes=[{partition=0,port=12000,machineName=myMachine.myNetwork,taskId=Task-0}]}
[ZkClient-EventThread-15-localhost:2181] INFO  o.a.s4.comm.topology.ClustersFromZK - New session:87684175268872205
[ZkClient-EventThread-15-localhost:2181] INFO  o.a.s4.comm.topology.ClustersFromZK - Detected new stream [names]
[ZkClient-EventThread-15-localhost:2181] INFO  o.a.s4.comm.topology.ClustersFromZK - New session:87684175268872206
[ZkClient-EventThread-15-localhost:2181] INFO  o.a.s4.comm.topology.ClusterFromZK - Changing cluster topology to { nbNodes=2,name=cluster1,mode=unicast,type=,nodes=[{partition=0,port=12000,machineName=myMachine.myNetwork,taskId=Task-0}, {partition=1,port=12001,machineName=myMachine.myNetwork,taskId=Task-1}]} from null
[ZkClient-EventThread-15-localhost:2181] INFO  org.apache.s4.core.Server - Loaded application from file /tmp/deploy-test/cluster1/myApp.s4r
[ZkClient-EventThread-15-localhost:2181] INFO  o.a.s.d.DistributedDeploymentManager - Successfully installed application myApp
[ZkClient-EventThread-15-localhost:2181] DEBUG o.a.s.c.g.OverloadDispatcherGenerator - Dumping generated overload dispatcher class for PE of class [class hello.HelloPE]
[ZkClient-EventThread-15-localhost:2181] DEBUG o.a.s4.comm.topology.ClustersFromZK - Adding input stream [names] for app [-1] in cluster [cluster1]
[ZkClient-EventThread-15-localhost:2181] INFO  org.apache.s4.core.App - Init prototype [hello.HelloPE].

...
Great! The application is now deployed on 2 S4 nodes.
(grey lightbulb) You can check the status of the application, nodes and streams with the "status" command:
 Code Block

 ./s4 status

Now what we need is some input!
We can get input through an adapter, i.e. an S4 app that converts an external stream into S4 events, and injects the events into S4 clusters. In the sample application, the adapter is a very basic class, that extends App, listens to an input socket on port 15000, and converts each received line of characters into a generic S4 event, in which the line data is kept in a "name" field. We specify :
  • the adapter class
  • the name of the output stream
  • the cluster where to deploy this app
For easy testing, we provide a facility to start a node with an adapter app without having to package and deploy the adapter app.
  1. First, we need to define a new S4 subcluster for that app: 
     Code Block
    S4:myApp$ ./s4 newCluster -c=cluster2 -nbTasks=1 -flp=13000
...
  2. Then we can start the adapter, and we use "names" 
...
  1.  for 
...
  1.  identifying 
...
  1.  the 
...
  1.  output 
...
  1.  stream 
...
  1.  (this 
...
  1.  is 
...
  1.  the 
...
  1.  same 
...
  1.  name 
...
  1.  used 
...
  1.  as 
...
  1.  input 
...
  1.  by 
...
  1.  the 
...
  1.  myApp app)
     (warning)   The adapter command must be run from the root of your S4 project (myApp dir in our case).
 Code Block
 app)
{code}./s4 adapter -appClass=hello.HelloInputAdapter -c=cluster2 -namedStringParametersp=s4.adapter.output.stream:names{code}
# Now =names
  1. Now let's 
...
  1.  just 
...
  1.  provide 
...
  1.  some 
...
  1.  data 
...
  1.  to 
...
  1.  the 
...
  1.  external 
...
  1. stream (our adapter is listening to port 15000): 
     Code Block
    S4:~$ echo "Bob" | nc localhost 15000
...
  2. One of the nodes should output in its console: 
     Code Block
    Hello Bob!
If you keep sending messages, nodes will alternatively display the "hello" messages because the adapter app sends keyless events on the "names" stream in a round-robin fashion by default.
What happened?
The following figures illustrate the various steps we have taken. The local file system is used as the S4 application repository in our example.
Image Added
...
Run the Twitter trending example
Let's have a look at another application, that computes trendy Twitter topics by listening to the spritzer stream from the Twitter API. This application was adapted from a previous example in S4 0.3.
Overview
This application is divided into:
  • twitter-counter , in test-apps/twitter-counter/ 
...
  •  : 
...
  •  extracts 
...
  •  topics 
...
  •  from 
...
  •  tweets 
...
  •  and 
...
  •  maintains 
...
  •  a 
...
  •  count 
...
  •  of 
...
  •  the 
...
  •  most 
...
  •  popular 
...
  •  ones, 
...
  •  periodically 
...
  •  dumped 
...
  •  to 
...
  •  disk
...
  • twitter-adapter, 
...
  •  in 
...
  •  test-apps/twitter-adapter/ 
...
  •  : 
...
  •  listens 
...
  •  to 
...
  •  the 
...
  •  feed 
...
  •  from 
...
  •  Twitter, 
...
  •  converts 
...
  •  status 
...
  •  text 
...
  •  into 
...
  •  S4 
...
  •  events, 
...
  •  and 
...
  •  passes 
...
  •  them 
...
  •  to 
...
  •  the 
...
  •  "RawStatus" 
...
  •  stream
...
Have 
...
 a 
...
 look 
...
 at 
...
 the 
...
 code 
...
 in 
...
 these 
...
 directories. 
...
 You'll 
...
 note 
...
 that:
...
  • the 
...
  •  build.gradle 
...
  •  file 
...
  •  must 
...
  •  be 
...
  •  tailored 
...
  •  to 
...
  •  include 
...
  •  new 
...
  •  dependencies 
...
  •  (twitter4j 
...
  •  libs 
...
  •  in 
...
  •  twitter-adapter)
...
  • events 
...
  •  are 
...
  •  partitioned 
...
  •  through 
...
  •  various 
...
  •  keys
...
Run 
...
 it
...
!
Note: 
...
 You 
...
 need 
...
 a 
...
 twitter4j.properties 
...
 file 
...
 in 
...
 your 
...
 home 
...
 directory 
...
 with 
...
 the 
...
 following 
...
 content 
...
 (debug 
...
 is 
...
 optional):
...
 Code Block
...

debug=true
user=<a twitter username>
password=<matching password>

...
  1. Start a Zookeeper instance. From the S4 base directory, do: 
     Code Block
    ./s4 zkServer
...
  2. Define 2 clusters : 1 for deploying the twitter-counter 
...
  1.  app, 
...
  1.  and 
...
  1.  1 
...
  1.  for 
...
  1.  the 
...
  1.  adapter 
...
  1.  app 
...
  1.  Code Block
...
  1. ./s4 newCluster -c=cluster1 -nbTasks=2 -flp=12000; ./s4 newCluster -c=cluster2 -nbTasks=1 -flp=
...
  1. 13000
  2. Start 2 app nodes (you may want to start each node in a separate console) : 
     Code Block
    ./s4 node -c=cluster1
...
  1. 
./s4 node -c=cluster1

  2. Start 1 node for the adapter app: 
     Code Block
    ./s4 node -c=cluster2 -
...
  1. p=s4.adapter.output.stream
...
  1. =RawStatus
  2. Deploy twitter-counter 
...
  1.  app 
...
  1.  (you 
...
  1.  may 
...
  1.  also 
...
  1.  first 
...
  1.  build 
...
  1.  the 
...
  1.  s4r 
...
  1.  then 
...
  1.  publish 
...
  1.  it, 
...
  1.  as 
...
  1.  described 
...
  1.  in 
...
  1.  the 
...
  1.  previous 
...
  1.  section) 
...
  1.  Code Block
...
  1. ./s4 deploy -appName=twitter-counter -c=cluster1 -b=`pwd`/test-apps/twitter-counter/build.gradle
...
  2. Deploy twitter-adapter 
...
  1.  app. 
...
  1.  In 
...
  1.  this 
...
  1.  example, 
...
  1.  we 
...
  1.  don't 
...
  1.  directly 
...
  1.  specify 
...
  1.  the 
...
  1.  app 
...
  1.  class 
...
  1.  of 
...
  1.  the 
...
  1.  adapter, 
...
  1.  we 
...
  1.  use 
...
  1.  the 
...
  1.  deployment 
...
  1.  approach 
...
  1.  for 
...
  1.  apps 
...
  1.  (remember, 
...
  1.  the 
...
  1.  adapter 
...
  1.  is 
...
  1.  also 
...
  1.  an 
...
  1.  app). 
...
  1.  Code Block
...
  1. ./s4 deploy -appName=twitter-adapter -c=cluster2 -b=`pwd`/test-apps/twitter-adapter/build.gradle
...
  2. Observe the current 10 most popular topics in file TopNTopics.txt. 
...
  1.  The 
...
  1.  file 
...
  1.  gets 
...
  1.  updated 
...
  1.  at 
...
  1.  regular 
...
  1.  intervals, 
...
  1.  and 
...
  1.  only 
...
  1.  outputs 
...
  1.  topics 
...
  1.  with 
...
  1.  a 
...
  1.  minimum 
...
  1.  of 
...
  1.  10 
...
  1.  occurrences, 
...
  1.  so 
...
  1.  you 
...
  1.  may 
...
  1.  have 
...
  1.  to 
...
  1.  wait 
...
  1.  a 
...
  1.  little 
...
  1.  before 
...
  1.  the 
...
  1.  file 
...
  1.  is 
...
  1.  updated 
...
  1.  : 
...
  1.  Code Block
...
  1. tail -f TopNTopics.txt
...
  2. You may also check the status of the S4 node with: 
     Code Block
    ./s4 status
...
What next?
You have now seen some basics applications, and you know how to run them, and how to get events into the system. You may now try to code your own apps with your own data.
This page will help for specifying your own dependencies.
There are more parameters available for the scripts (typing the name of the task will list the options). In particular, if you want distributed deployments, you'll need to pass the Zookeeper connection strings when you start the nodes.
You may also customize the communication and the core layers of S4 by tweaking configuration files and modules.
Last, the javadoc will help you when writing applications.
We hope this will help you start rapidly, and remember: we're happy to help!