Setting up Heron with Aurora Cluster Locally on Linux

It is possible to setup Heron with a locally running Apache Aurora cluster. This is a step by step guide on how to configure and setup all the necessary components.

Setting Up Apache Aurora Cluster locally

You first need to setup Apache Aurora locally. More detailed description of the following steps can be found in A local Cluster with Vagrant

Step 1: Install VirtualBox and Vagrant

Download and install VirtualBox and Vagrant on your machine. If vagrant is successfully installed in your machine the following command should list several common commands for this tool

$ vagrant

Step 2: Clone the Aurora repository

You can get the source repository for Aurora with the following command

$ dgit clone git://git.apache.org/aurora.git

Once the clone is complete cd into the aurora folder

$ cd aurora

Step 3: Starting Local Aurora Cluster

To start the local cluster all you have to do is execute the following command. It will install all the needed dependencies like Apache Mesos and Zookeeper in the VM.

$ vagrant up

Additionally to get rid of some of the warning messages that you get during up command execute the following command

$ vagrant plugin install vagrant-vbguest

You can verify that the Aurora cluster is properly running by opening the following links in your web-browser

If you go into http://192.168.33.7:8081/scheduler you can notice that the name of the default cluster that is setup in aurora is named devcluster this will be important to note when submitting typologies from heron.

Heron topology

Installing Heron within VM

Now that the Aurora cluster is setup you need to install heron within the cluster VM in order to be able to get the Heron deployment working. Since this is a fresh VM instance you will have to install the basic software such as “unzip” and set the JAVA_HOME path as an environmental variable ( Just need to add this to .bashrc file). After you have the basic stuff working follow the following steps to install Heron in the VM. You can ssh into the VM with the following command

$ vagrant ssh

Step 1.a : Download installation script files

You can download the script files that match your Linux distribution from Step 1.b: Execute the client and tools shell scripts 

$ chmod +x heron-client-install-VERSION-PLATFORM.sh
$ ./heron-client-install-VERSION-PLATFORM.sh --user
Heron client installer
----------------------

Uncompressing......
Heron is now installed!

Make sure you have "/home/vagrant/bin" in your path.

After this you need to add the path “/home/vagrant/bin”. You can just execute the following command or add it to the end of .bashrc file ( which is more convenient ).

$ export PATH=$PATH:/home/vagrant/bin

Install the following packages to make sure that you have all the needed dependencies in the VM. You might have to do sudo apt-get update before you execute the following.

$ sudo apt-get install git build-essential automake cmake libtool zip libunwind-setjmp0-dev zlib1g-dev unzip pkg-config -y

Configuring State Manager ( Apache Zookeeper )

Since Heron only uses Apache Zookeeper for coordination the load on the Zookeeper node is minimum. Because of this it is sufficient to use a single Zookeeper node or if you have an Zookeeper instance running for some other task you can simply use that. Since Apache Aurora already uses an Zookeeper instance you can directly use that instance to execute State Manager tasks of Heron. First you need to configure Heron to work with the Zookeeper instance. You can find meanings of each attribute in Setting Up ZooKeeper State Manager. Configurations for State manager are located in the directory /home/vagrant/.heron/conf/aurora.

Open the file statemgr.yaml using vim ( or some other text editor you prefer ) and add/edit the file to include the following.

# local state manager class for managing state in a persistent fashion
heron.class.state.manager: com.twitter.heron.statemgr.zookeeper.curator.CuratorStateManager

# local state manager connection string
heron.statemgr.connection.string:  "127.0.0.1:2181"

# path of the root address to store the state in a local file system
heron.statemgr.root.path: "/heronroot"

# create the zookeeper nodes, if they do not exist
heron.statemgr.zookeeper.is.initialize.tree: True

# timeout in ms to wait before considering zookeeper session is dead
heron.statemgr.zookeeper.session.timeout.ms: 30000

# timeout in ms to wait before considering zookeeper connection is dead
heron.statemgr.zookeeper.connection.timeout.ms: 30000

# timeout in ms to wait before considering zookeeper connection is dead
heron.statemgr.zookeeper.retry.count: 10

# duration of time to wait until the next retry
heron.statemgr.zookeeper.retry.interval.ms: 10000

Creating Paths in Zookeeper

Next you need to create some paths within Zookeeper since some of the paths are not created by Heron automatically. So you need to create them manually. Since Aurora installation already installed Zookeeper, you can use the Zookeeper cli to create the manual paths.

$ sudo ./usr/share/zookeeper/bin/zkCli.sh

This will connect to the Zookeeper instance running locally. Then execute the following commands from within the client to create paths /heronroot/topologies and /heron/topologies. Later in “Associating new Aurora cluster into Heron UI” you will see that you only need to create /heronroot/topologies but for now lets create both to make sure you don’t get any errors when you run things.

create /heronroot null
create /heronroot/topologies null

create /heron null
create /heron/topologies null

Configuring Scheduler ( Apache Aurora )

Next you need to configure Apache Aurora to be used as the Scheduler for our Heron local cluster. In order to do this you need to edit the scheduler.yaml file that is also located in /home/vagrant/.heron/conf/aurora. Add/Edit the file to include the following. More information regarding parameters can be found in Aurora Cluster

# scheduler class for distributing the topology for execution
heron.class.scheduler: com.twitter.heron.scheduler.aurora.AuroraScheduler

# launcher class for submitting and launching the topology
heron.class.launcher: com.twitter.heron.scheduler.aurora.AuroraLauncher

# location of the core package
heron.package.core.uri: file:///home/vagrant/.heron/dist/heron-core.tar.gz

# location of java - pick it up from shell environment
heron.directory.sandbox.java.home: /usr/lib/jvm/java-1.8.0-openjdk-amd64/

# Invoke the IScheduler as a library directly
heron.scheduler.is.service: False

Additionally edit the client.yaml file and change the core uri to make it consistant.

# location of the core package
heron.package.core.uri: file:///home/vagrant/.heron/dist/heron-core.tar.gz

Important Step: Change folder name aurora to devcluster

Next you need to change the folder name of /home/vagrant/.heron/conf/aurora to /home/vagrant/.heron/conf/devcluster. This is because the name of your aurora cluster is devcluster as you noted in a previous step. You can do this with the following commands

$ cd /home/vagrant/.heron/conf/
$ mv aurora devcluster

Submitting Example Topology to Aurora cluster

Now you can submit a topology to the aurora cluster. this can be done with the following command.

$ heron submit devcluster/heronuser/devel --config-path ~/.heron/conf/ ~/.heron/examples/heron-examples.jar com.twitter.heron.examples.ExclamationTopology ExclamationTopology

Now you should be able to see the topology in the Aurora UI ( http://192.168.33.7:8081/scheduler/heronuser ) .

Heron topology

Understanding the parameters

below is a brief explanation on some of the important parameters that are used in this command. the first parameter devcluster/heronuser/devel defines cluster, role and env ( env can have values prod | devel | test | staging ). The cluster is the name of the aurora cluster which is devcluster in our case. You can give something like your name for the role name and for env you need to choose from one of the env values.

--config-path points to the config folder. the program will automatically look for a folder with the cluster name. This is why you had to change the name of the aurora conf folder to devcluster.

Now that everything is working you need to perform one last step to be able to see the typologies that you can see in Aurora UI in Heron UI.

Associating new Aurora cluster into Heron UI

Heron UI uses information that is gets from the heron tracker when displaying the information in the heron UI interface. So in-order to allow the Heron UI to show Aurora cluster information you need to modify configuration of the Heron tracker so that it can identify the Aurora Cluster.

Heron Tracker configurations are located at /home/vagrant/.herontools/conf the configuration file is named heron_tracker.yaml. By default you should see the following in the file

statemgrs:
  -
    type: "file"
    name: "local"
    rootpath: "~/.herondata/repository/state/local"
    tunnelhost: "localhost"
  -
    type: "zookeeper"
    name: "localzk"
    hostport: "localhost:2181"
    rootpath: "/heron"
    tunnelhost: "localhost"

You can see that there already two entries. Before, you had to create paths in Zookeeper for /heron/topologies this is because the entry named localzk in this file. If you remove this you will not need to create that path in Zookeeper. Now all you have to is to add a new entry for the aurora cluster into this file ( lets comment out localzk ). Then the file would look like below.

statemgrs:
  -
    type: "file"
    name: "local"
    rootpath: "~/.herondata/repository/state/local"
    tunnelhost: "localhost"
  #-
   #type: "zookeeper"
   # name: "localzk"
   # hostport: "localhost:2181"
   # rootpath: "/heron"
   # tunnelhost: "localhost"
  -
    type: "zookeeper"
    name: "devcluster"
    hostport: "localhost:2181"
    rootpath: "/heronroot"
    tunnelhost: "localhost"

Now you can start Heron tracker and then Heron UI, Now you will be able to see the aurora cluster from the Heron UI ( http://192.168.33.7:8889/topologies ) as below

$ heron-tracker
$ heron-ui

Heron topology