Service Advisor

Eeach service can choose to define its own service advisor rather than define the details of its configuration and layout in the stack advisor.  This is particularly useful for custom services which are not defined in the stack.  Ambari provides the Service Advisor capability where a service can write a Python script named service-advisor.py in their service folder. This folder can be in the stack's services directory where the service is defined or can be inherited from the service definition in common-services or elsewhere.  Example: common-services/HAWQ/2.0.0.

Service Advisor Inheritance

Unlike the Stack-advisor scripts, the service-advisor scripts do not automatically extend the parent service's service-advisor scripts. The service-advisor script needs to explicitly extend their parent's service service-advisor script.  The following code sample shows how you would refer to a parent's service_advisor.py.  In this case it is extending the root service-advisor.py file in the resources/stacks directory.

SCRIPT_DIR = os.path.dirname(os.path.abspath(__file__))
STACKS_DIR = os.path.join(SCRIPT_DIR, '../../../stacks/')
PARENT_FILE = os.path.join(STACKS_DIR, 'service_advisor.py')

try:
  with open(PARENT_FILE, 'rb') as fp:
    service_advisor = imp.load_module('service_advisor', fp, PARENT_FILE, ('.py', 'rb', imp.PY_SOURCE))
except Exception as e:
  traceback.print_exc()
  print "Failed to load parent"

class HAWQ200ServiceAdvisor(service_advisor.ServiceAdvisor):

Service Advisor Behavior

Like the stack advisors, service advisors provide information on 4 important aspects:

1. Recommend layout of the service on cluster
2. Recommend service configurations
3. Validate layout of the service on cluster
4. Validate service configurations

By providing the service-advisor.py file, one can control dynamically each of the above for the service. 

The main interface for the service-advisor scripts contains documentation on how each of the above are called, and what data is provided.

class ServiceAdvisor(DefaultStackAdvisor):

  def colocateService(self, hostsComponentsMap, serviceComponents):
    pass

  def getServiceConfigurationRecommendations(self, configurations, clusterSummary, services, hosts):
    pass

  def getServiceComponentLayoutValidations(self, services, hosts):
    return []

  def getServiceConfigurationsValidationItems(self, configurations, recommendedDefaults, services, hosts):
    return []

Examples

• Service Advisor interface
• HAWQ 2.0.0 Service Advisor implementation
• PXF 3.0.0 Service Advisor implementation