Extensive behavior customization and automation can be done by utilizing scripts for both the control plane with the Python-based ControlScripts, and the data plane via Lua-based DataScripts.


DataScripts are a powerful mechanism for customizing the behavior of Avi Vantage on a per virtual service, or even per client, basis. DataScripts are lightweight scripts coded in Lua. These scripts can be executed against each client making a TCP connection, an HTTP request or response, or other events within the dataplane.

One or more DataScripts may be attached to the rules section of a virtual service.

Scripts may be uploaded or copy/ pasted into either the Request Event Script or Response Event Script section. For instance, to restrict access to the secure directory, the following text would be pasted into the Request Event Script section.

if avi.http.uri == "/secure/" then

See the Avi DataScript Guide for complete documentation of commands and example DataScripts.


ControlScripts are Python-based scripts which execute on the Avi Vantage Controllers. They are initiated by Alert Actions, which themselves are triggered by events within the system. Rather than alerting an admin that a specific event has occurred, the ControlScript can take specific action, such as altering the Avi Vantage configuration or sending a custom message to an external system, such as telling VMware’s vCenter to scale out more servers if the current servers have reached resource capacity and are incurring lowered health scores.

To create a ControlScript,

  1. Navigate to Templates > Scripts > ControlScripts.
  2. Click on Create. The New ControlScript screen appears.
  3. Enter a Name for the ControlScript.
    Note: The Enter Text option is selected by default.
    • Enter the user defined alert action script in the text box provided. or
  4. Upload a file.
    a) Select the Upload File option.
    b) Click on the Upload File button.
    c) Select the .py file required.
  5. Click on Save.

ControlScripts are executed with limited privileges within the Linux subsystem of the Controller. The file system access will be read-only, thus you cannot create new files or modify any files or directories.

Exception: ControlScripts are allowed both read and write access to the '/tmp' directory with a quota limit of 10MB. Any file written in '/tmp' is temporary and will be lost as soon as the ControlScript ends.

There will not be any type of access to the Controller system files and the Controller system python libraries in the control-script. Any script files that need to be shared in the container for use in control script has to be placed in /opt/avi/python/lib/avi/scripts/csshared folder. This can be imported using import avi.scripts.csshared.<module> code.

See standard Python documentation for examples and definitions of Python commands. NSX Advanced Load Balancer configuration changes may be made by API calls from Linux to NSX Advanced Load Balancer via standard API mechanisms.

There are two sets of variables that are passed onto the ControlScripts. These include:

  • Environment Variables
  • Script Arguments

Environment Variables

The following environment variables can be used within a ControlScript:

  • USER/ API_TOKEN: Contains the username and API token that can be used to authenticate with the NSX Advanced Load Balancer REST API.
  • TENANT/ TENANT_UUID: Contains the tenant context (name/ UUID) in which the ControlScript is executing.
  • DOCKER_GATEWAY: Contains the local IP address that the ControlScript can use to communicate with the NSX Advanced Load Balancer REST API.
  • VERSION: Contains the version of the Controller in which the ControlScript is executing.
  • EVENT_DESCRIPTION: Contains the description of the event that triggered the alert.

The below example shows the contents of these environment variables passed to a ControlScript on a Controller running release 21.1.4, retrieved in Python using os.environ().

    "USER": "admin",
    "API_TOKEN": "60bc0fc8ece748c4f20f0eabf7a25eb6584af0aa",
    "TENANT": "admin",
    "TENANT_UUID": "admin",
    "VERSION": "21.1.4",
    "EVENT_DESCRIPTION": "Config vs1 update status is success (performed by user admin)",

Note: The IP address passed in the DOCKER_GATEWAY environment variable must be used to access the NSX Advanced Load Balancer REST API.

Script Arguments

The arguments that are provided to the script are provided as an array in this format: ['/home/admin/', '']

Alert Details

Alert details are provided as JSON data and can be parsed using JSON as json.loads(sys.argv[1]). Here is the pretty print json of the data provided to the ControlScript:

  "name": "System-CC-Alert-cluster-878226b4-ff2c-4e6b-a9a7-66aa58ad23f1-1580412633.0-1580412633-38875205",
  "throttle_count": 0,
  "level": "ALERT_LOW",
  "reason": "threshold_exceeded",
  "obj_name": "AWS",
  "threshold": 1,
  "events": [
      "event_id": "AWS_ACCESS_FAILURE",
      "event_details": {
        "aws_infra_details": {
          "vpc_id": "vpc-0617ccd15673817c0",
          "region": "eu-central-1",
          "error_string": "AuthFailure: AWS was not able to validate the provided access credentials\\n\\tstatus code: 401, request id: f22641cb-140b-4ff2-ab8d-0008a73c6fbf",
          "cc_id": "cloud-8a3e601b-d06d-4998-bc41-ac3004330066"
      "obj_uuid": "cluster-878226b4-ff2c-4e6b-a9a7-66aa58ad23f1",
      "obj_name": "AWS",
      "report_timestamp": 1580412633

Note: If the size of the JSON data is more than 128kb, then it will be discarded.


To understand scripting, use the examples on how to use the values, given below:

Getting Data Passed to the ControlScript

# NSX Advanced Load Balancer ControlScript
# This sample ControlScript will output the environment values, and alert
# arguments that are passed from the alert that triggered the alert script.
# You can use these values to help construct your python script actions to
# handle the alert.
import os
import sys
if __name__ == "__main__":
    print("Environment Vars: %s \n" % os.environ)
    print("Alert Arguments: %s \n" % sys.argv)

Sticky Pool Group

import os
import sys
import json
from avi.sdk.avi_api import ApiSession
import urllib3
import requests
if hasattr(requests.packages.urllib3, 'disable_warnings'):
if hasattr(urllib3, 'disable_warnings'):
def ParseAviParams(argv):
    if len(argv) != 2:
    alert_params = json.loads(argv[1])
    return alert_params
def get_api_token():
    return os.environ.get('API_TOKEN')
def get_api_user():
    return os.environ.get('USER')
def get_api_endpoint():
    return os.environ.get('DOCKER_GATEWAY') or 'localhost'
def get_tenant():
    return os.environ.get('TENANT')
def failover_pools(session, pool_uuid, pool_name, retries=5):
    if retries <= 0:
        return 'Too many retry attempts - aborting!'
    query = 'refers_to=pool:%s' % pool_uuid
    pg_result = session.get('poolgroup', params=query)
    if pg_result.count() == 0:
        return 'No pool group found referencing pool %s' % pool_name
    pg_obj = pg_result.json()['results'][0]
    highest_up_pool = None
    highest_down_pool = None
    for member in pg_obj['members']:
        priority_label = member['priority_label']
        member_ref = member['pool_ref']
        pool_runtime_url = ('%s/runtime/detail' %
        pool_obj = session.get(pool_runtime_url).json()[0]
        if pool_obj['oper_status']['state'] == 'OPER_UP':
            if (not highest_up_pool or
                int(highest_up_pool[1]) < int(priority_label)):
                highest_up_pool = (member, priority_label,
        elif (not highest_down_pool or
              int(highest_down_pool[1]) < int(priority_label)):
            highest_down_pool = (member, priority_label,
    if not highest_up_pool:
        return ('No action required as all pools in the '
                'pool group are now down.')
    elif not highest_down_pool:
        return ('No action required as all pools in the '
                'pool group are now up.')
    if int(highest_down_pool[1]) <= int(highest_up_pool[1]):
        return ('No action required. The highest-priority available '
                'pool (%s) already has a higher priority than the '
                'highest-priority non-available pool (%s)' %
                (highest_up_pool[2], highest_down_pool[2]))
    highest_up_pool[0]['priority_label'] = highest_down_pool[1]
    highest_down_pool[0]['priority_label'] = highest_up_pool[1]
    p_result = session.put('poolgroup/%s' % pg_obj['uuid'], pg_obj)
    if p_result.status_code < 300:
        return ', '.join(['Pool %s priority changed to %s' % (p[0], p[1])
                           for p in ((highest_up_pool[2], highest_down_pool[1]),
                                     (highest_down_pool[2], highest_up_pool[1]))])
    if p_result.status_code == 412:
        return failover_pools(session, pool_uuid, pool_name, retries - 1)
    return 'Error setting pool priority: %s' % p_result.text
if __name__ == "__main__":
    alert_params = ParseAviParams(sys.argv)
    events = alert_params.get('events', [])
    if len(events) > 0:
        token = get_api_token()
        user = get_api_user()
        api_endpoint = get_api_endpoint()
        tenant = get_tenant()
        pool_uuid = events[0]['obj_uuid']
        pool_name = events[0]['obj_name']
        event_id = events[0]['event_id']
            with ApiSession(api_endpoint, user,
                            tenant=tenant) as session:
                result = failover_pools(session, pool_uuid, pool_name)
        except Exception as e:
            result = str(e)
        result = 'No event data for ControlScript'
# Use with a ControlScript and Alert(s) to perform 'sticky' failover of pool groups.
# Alert should trigger on 'Pool Up' and 'Pool Down' events.

Add Route to GCP SE

import sys, os, json, traceback, re, time
from avi.sdk.avi_api import ApiSession
from oauth2client.client import GoogleCredentials
from googleapiclient import discovery
This ControlScript is executed on the Controller every time there is a
CC_IP_ATTACHED: Event is triggered when a VIP is attached to a SE
CC_IP_DETACHED: Event is triggered when a VIP is detached from a SE, usually
when a SE goes down or a scale in occurs
The goal of this script is to add a route to GCP with the destination as the
VIP and nextHopIp as the GCP instance IP on which the SE is running after a
CC_IP_ATTACHED event. After a CC_IP_DETACHED event, the goal of the script is
to remove the corresponding route.
Script assumptions:
1) The Controller GCP instance has scope=compute-rw to be able to modify
routes in GCP
2) 'description' field in the Service Engine Group is configured as a
JSON encoded string containing GCP project, zone and network
Event details contain the SE UUID and the VIP.
1) GET SE object from UUID and extract SE IP address (which is
the same as the GCP instance IP address) and Service Engine Group link
2) GET Service Engine Group object. The 'description' field in the
Service Engine Group is a JSON encoded string containing GCP project and
network URL. Extract project and network from the 'description' field
3) Extract all routes matching destRange as VIP from GCP
4) If event is CC_IP_DETACHED, remove matching route with
destRange as vip and nextHopIp as instance IP in the appr network
If event is CC_IP_ATTACHED and no matching route exists already, add a new
route with destRange as vip and nextHopIp as instance IP in appr network
def parse_avi_params(argv):
    if len(argv) != 2:
        return {}
    script_parms = json.loads(argv[1])
    return script_parms
def create_avi_endpoint():
    # tenant=os.environ.get('TENANT')
    return ApiSession.get_session(os.environ.get('DOCKER_GATEWAY'), user, token=token,
def google_compute():
    credentials = GoogleCredentials.get_application_default()
    return'compute', 'v1', credentials=credentials)
def gcp_program_route(gcp, event_id, project, network, inst_ip, vip):
    # List all routes for vip
    result = gcp.routes().list(project=project,
                                   filter='destRange eq %s' % vip).execute()
    if (('items' not in result or len(result['items']) == 0)
        and event_id == 'CC_IP_DETACHED'):
        print(('Project %s destRange %s route not found' %
              (project, vip)))
    if event_id == 'CC_IP_DETACHED':
        # Remove route for vip nextHop instance
        for r in result['items']:
            if (r['network'] == network and r['destRange'] == vip and
                r['nextHopIp'] == inst_ip):
                result = gcp.routes().delete(project=project,
                print(('Route %s delete result %s' % (r['name'], str(result))))
                # Wait until done or retries exhausted
                if 'name' in result:
                    start = int(time.time())
                    for i in range(0, 20):
                        op_result = gcp.globalOperations().get(project=project,
                        print(('op_result %s' % str(op_result)))
                        if op_result['status'] == 'DONE':
                            if 'error' in result:
                                print(('WARNING: Route delete had errors '
                                      'result %s' % str(op_result)))
                                print(('Route delete done result %s' %
                        if int(time.time()) - start > 20:
                            print(('WARNING: Wait exhausted last op_result %s' %
                    print('WARNING: Unable to obtain name of route delete '
    elif event_id == 'CC_IP_ATTACHED':
        # Add routes to instance
        # Route names can just have - and alphanumeric chars
        rt_name = re.sub('[./]+', '-', 'route-%s-%s' % (inst_ip, vip))
        route = {'name': rt_name,
            'destRange': vip, 'network': network,
            'nextHopIp': inst_ip}
        result = gcp.routes().insert(project=project,
        print(('Route VIP %s insert result %s' %
                (vip, str(result))))
def handle_cc_alert(session, gcp, script_parms):
    se_name = script_parms['obj_name']
    print(('Event Se %s %s' % (se_name, str(script_parms))))
    if len(script_parms['events']) == 0:
        print ('WARNING: No events in alert')
    # GET SE object from Avi for instance IP address and SE Group link
    rsp = session.get('serviceengine?uuid=%s' %
    if rsp.status_code in range(200, 299):
        se = json.loads(rsp.text)
        if se['count'] == 0 or len(se['results']) == 0:
            print(('WARNING: SE %s no results' %
        inst_ip = next((v['ip']['ip_addr']['addr'] for v in
                if v['ip']['mask'] == 32 and v['mode'] != 'VIP'), '')
        if not inst_ip:
            print(('WARNING: Unable to find IP with mask 32 SE %s' % str(se['results'][0])))
        # GET SE Group object for GCP project, zones and network
        # https://localhost/api/serviceenginegroup/serviceenginegroup-99f78850-4d1f-4b7b-9027-311ad1f8c60e
        seg_ref_list = se['results'][0]['se_group_ref'].split('/api/')
        seg_rsp = session.get(seg_ref_list[1])
        if seg_rsp.status_code in range(200, 299):
            vip = '%s/32' % script_parms['events'][0]['event_details']['cc_ip_details']['ip']['addr']
            seg = json.loads(seg_rsp.text)
            descr = json.loads(seg.get('description', '{}'))
            project = descr.get('project', '')
            network = descr.get('network', '')
            if not project or not network:
                print(('WARNING: Project, Network is required descr %s' %
            gcp_program_route(gcp, script_parms['events'][0]['event_id'],
                              project, network, inst_ip, vip)
            print(('WARNING: Unable to retrieve SE Group %s status %d' %
                  (se['results'][0]['se_group_ref'], seg_rsp.status_code)))
        print(('WARNING: Unable to retrieve SE %s' %
# Script entry
if __name__ == "__main__":
    script_parms = parse_avi_params(sys.argv)
        admin_session = create_avi_endpoint()
        gcp = google_compute()
        handle_cc_alert(admin_session, gcp, script_parms)
    except Exception:
        print(('WARNING: Exception with Avi/Gcp route %s' %

Denial of Service Attack Handling

import sys, os, json
from avi.sdk.avi_api import ApiSession
This control script will be executed in the Avi Controller when an
alert due to a DOS_ATTACK event is generated.
An example params passed to the control script is as follows
params = [u'/home/admin/Dos_Attack-l4vs',
           '{"name": "Dos_Attack-virtualservice-d1093604-e1f0-476a-ad91-01c5224c5641-1461261720.83-1461261716-77911185",
             "throttle_count": 0,
             "level": "ALERT_HIGH",
             "reason": "threshold_exceeded",
             "obj_name": "l4vs",
             "threshold": 1,
                      "event_id": "DOS_ATTACK",
                              "attack_count": 2150.0,
                              "attack": "SYN_FLOOD",
                              "ipgroup_uuids": [
                               "src_ips": [""]
                      "obj_uuid": "virtualservice-d1093604-e1f0-476a-ad91-01c5224c5641",
                      "obj_name": "l4vs",
                      "report_timestamp": 1461261716
The DOS_ATTACK event was generated due to a SYN_FLOOD from client It was
traffic to the Virtual Service : "l4vs".
The offending client ip is added as NETWORK_SECURITY_POLICY_ACTION_TYPE_DENY in the
network seurity policy for the virtual service
def ParseAviParams(argv):
    if len(argv) != 2:
    alert_dict = json.loads(argv[1])
    return alert_dict
def create_avi_endpoint():
    # tenant=os.environ.get('TENANT')
    return ApiSession.get_session(os.environ.get('DOCKER_GATEWAY'), user, token=token,
def add_ns_rules_dos(session, dos_params):
    vs_name = dos_params['obj_name']
    vs_uuid = ''
    client_ips = []
    vs_name = dos_params['obj_name']
    for event in dos_params['events']:
        vs_uuid = event['obj_uuid']
        dos_attack_event_details = event['event_details']['dos_attack_event_details']
        if dos_attack_event_details['attack'] != 'SYN_FLOOD':
        for ip in dos_attack_event_details['src_ips']:
    if len(client_ips) == 0:
        print ('DOS ATTACK is not SYN_FLOOD. Ignoring')
    print('VS name : ' + vs_name + ' VS UUID : ' + vs_uuid + ' Client IPs : ' + str(client_ips))
    ip_list = []
    for ip in client_ips:
        ip_addr_obj = {
            'addr' : ip,
            'type' : 'V4'
    match_obj = {
        'match_criteria' : 'IS_IN',
        'addrs' : ip_list
    ns_match_target_obj = {
        'client_ip' : match_obj
    ns_rule_dos_obj = {
        'enable' : True,
        'log'    : True,
        'match'  : ns_match_target_obj,
    ns_policy_dos_obj = {
        'vs_name' : vs_name,
        'vs_uuid' : vs_uuid,
        'rules'   : [
    print('ns_policy_dos_obj : ' + str(ns_policy_dos_obj))
    try :'networksecuritypolicydos?action=block',
    except Exception as e:
    print(('Added Client IPs ' + str(client_ips) + \
           ' in the blocked list for VS : ' + vs_name))
if __name__ == "__main__":
    alert_dict = ParseAviParams(sys.argv)
    try :
        admin_session = create_avi_endpoint()
    except Exception as e:
        print('login failed to Avi Controller!' + str(e))
    add_ns_rules_dos(admin_session, alert_dict)