AHMED ZBYR

AHMED ZBYR

Biker, EV Enthusiast

This is the second follow up post. In the earlier post Setting Up Cloudera Manager Services Using Cloudera API [Part 1] we install the cloudera management services. Now we will be installing Zookeeper service to the cluster.

But first we need to to couple of things before we install Zookeeper.

  1. Create a cluster.
  2. Download, Distribute, Activate CDH Parcels.
  3. Install Zookeeper service to our cluster.

Code Location

On github : https://github.com/ahmedzbyr/cloudera-api-starter

Creating a Cluster

First we create a cluster if it does not exists. Config details below.

def init_cluster(cm_api_handle):
    try:
        cluster = cm_api_handle.get_cluster(config['cluster']['name'])
        return cluster
    except ApiException:
        cluster = cm_api_handle.create_cluster(config['cluster']['name'],
                                                config['cluster']['version'],
                                                config['cluster']['fullVersion'])

If it is the first time then we need to add all the hosts to the cluster (including the admin node), this information is coming from the configuration yaml file.

# Basic cluster information
cluster:
  name: AutomatedHadoopCluster
  version: CDH5
  fullVersion: 5.8.3
  hosts:
     - mycmhost.ahmed.com

In the above yaml snippet hosts will have all the hosts in the cluster, since we are testing on a VM with just one host we have that host added there.


    cluster_hosts = []
    #
    # Picking up all the nodes from the yaml configuration.
    #
    for host_in_cluster in cluster.list_hosts():
        cluster_hosts.append(host_in_cluster)

    hosts = []

    #
    # Create a host list, make sure we dont have duplicates.
    #
    for host in config['cluster']['hosts']:
        if host not in cluster_hosts:
            hosts.append(host)

    #
    # Adding all hosts to the cluster.
    #
    cluster.add_hosts(hosts)
    return cluster

Once we have the cluster ready then we can install the parcels to the cluster.

Download, Distribute, Activate CDH Parcels

For Parcels there are three major methods which initiate the parcels distribution.

  1. parcel.start_download()
  2. parcel.start_distribution()
  3. parcel.activate()

These are the three methods which do all the work. When the start_download command is running we need to keep track of the progress, this is done using the get_parcels method.

get_parcels - http://cloudera.github.io/cm_api/apidocs/v13/ns0_apiParcel.html

#
# When we execute and parcel download/distribute/activate command
# we can track the progress using the `get_parcel` method.
# This return a JSON described here : http://cloudera.github.io/cm_api/apidocs/v13/ns0_apiParcel.html
# We can check progress by checking `stage`
#
#   AVAILABLE_REMOTELY: Stable stage - the parcel can be downloaded to the server.
#   DOWNLOADING: Transient stage - the parcel is in the process of being downloaded to the server.
#   DOWNLOADED: Stable stage - the parcel is downloaded and ready to be distributed or removed from the server.
#   DISTRIBUTING: Transient stage - the parcel is being sent to all the hosts in the cluster.
#   DISTRIBUTED: Stable stage - the parcel is on all the hosts in the cluster. The parcel can now be activated, or removed from all the hosts.
#   UNDISTRIBUTING: Transient stage - the parcel is being removed from all the hosts in the cluster>
#   ACTIVATING: Transient stage - the parcel is being activated on the hosts in the cluster. New in API v7
#   ACTIVATED: Steady stage - the parcel is set to active on every host in the cluster. If desired, a parcel can be deactivated from this stage.
#

We track the progress of each stage using the snippet below.

def check_current_state(cluster, product, version, states):
    logging.info("Checking Status for Parcel.")
    while True:
        parcel = cluster.get_parcel(product, version)
        logging.info("Parcel Current Stage: " + str(parcel.stage))
        if parcel.stage in states:
            break
        if parcel.state.errors:
            raise Exception(str(parcel.state.errors))

        logging.info("%s progress: %s / %s" % (states[0], parcel.state.progress,
                                               parcel.state.totalProgress))
        time.sleep(15)

Rest of the parcel execute is straight forward.

Install Zookeeper Service.

Zookeeper service is installed in stages.

  1. Create a service (if not exist)
  2. Update configuration for our newly create Zookeeper service.
  3. Create Zookeeper role (SERVER) on the Cluster.
  4. Initalize Zookeeper using the init_zookeeper() command.
  5. Start Zookeeper service.

Create a service.

This is simple create a service if it does not exist.

def zk_create_service(cluster):
    try:
        zk_service = cluster.get_service('ZOOKEEPER')
        logging.debug("Service {0} already present on the cluster".format(self.name))
    except ApiException:
        #
        # Create service if it the first time.
        #
        zk_service = cluster.create_service('ZOOKEEPER', 'ZOOKEEPER')
        logging.info("Created New Service: ZOOKEEPER")

    return zk_service

Update configuration for Zookeeper.

This information is picked up from the configuration yaml file.

yaml file.

  ZOOKEEPER:
    config:
      zookeeper_datadir_autocreate: true

Code snippet.

def zk_update_configuration(zk_service):
    """
        Update service configurations
    :return:
    """
    zk_service.update_config(config['services']['ZOOKEEPER']['config'])
    logging.info("Service Configuration Updated.")

Create Zookeeper role (SERVER) on the Cluster.

This is the important part, here we create Zookeeper roles SERVER (each instance of zookeeper on each server is referred as a SERVER role).

Role names should be unique, we combine the service_name, role, zookeeper_id to form a unique identifier. Example : Here it would be ZOOKEEPER-SERVER-1

Here is the code snippet.

zookeeper_host_id = 0

    #
    # Configure all the host.
    #
    for zookeeper_host in config['services']['ZOOKEEPER']['roles'][0]['hosts']:
        zookeeper_host_id += 1
        zookeeper_role_config = config['services']['ZOOKEEPER']['roles'][0]['config']
        role_name = "{0}-{1}-{2}".format('ZOOKEEPER', 'SERVER', zookeeper_host_id)

Next once we create the role we update the configuration which we get from the yaml file.

Yaml file.

roles:
  - group: SERVER
    hosts:
      - mycmhost.ahmed.com
    config:
      quorumPort: 2888
      electionPort: 3888
      dataLogDir: /var/lib/zookeeper
      dataDir: /var/lib/zookeeper

Code snippet.

#
# Configuring Zookeeper server ID
#
zookeeper_role_config['serverId'] = zookeeper_host_id

#
# Update configuration
#
role.update_config(zookeeper_role_config)

Now we are set to start the Zookeeper.

Initalize Zookeeper using the init_zookeeper() command.

Before we start Zookeeper we need to init the service, which create id for each service running on each server. ps: it creates the my_id for each service in /var/lib/zookeeper location. This will help each Zookeeper identify itself as unique.

If there were 3 Zookeeper servers (which is minimum recommended) we would have something like below.

  1. Role ZOOKEEPER-SERVER-1, Server 1, Zookeeper ID my_id 1
  2. Role ZOOKEEPER-SERVER-2, Server 2, Zookeeper ID my_id 2
  3. Role ZOOKEEPER-SERVER-3, Server 3, Zookeeper ID my_id 3

And so on.

Once we have the service initialized we are ready to start the service.

Start Zookeeper service

We do this using the zk_service.start() method. This method return ApiCommand which we can track the progress and wait for the service to start using cmd.wait().success

More details about the Api here

Our service should be up and running.

Yaml File

Cloudera Zookeeper Yaml File

Code File.

Cloudera Zookeeper Service Code File

Executing Code

VIDEO - Setting Up Zookeeper Services Using Cloudera API [Part 2]

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