Event Brokers - Rasa Documentation

Format

All events are streamed to the broker as serialized dictionaries every time the tracker updates its state. An example event emitted from the default tracker looks like this:

{
    "sender_id": "default",
    "timestamp": 1528402837.617099,
    "event": "bot",
    "text": "what your bot said",
    "data": "some data about e.g. attachments",
    "metadata": {
          "a key": "a value"
     }
}

The event field takes the event’s type_name (for more on event types, check out the events docs).

Kafka Event Broker

Kafka is recommended for all assistants at scale. Kafka is a requirement when streaming events to Rasa Pro Services or Rasa Studio. Rasa uses the confluent-kafka library, a Kafka client written in Python.

How to consume events in Rasa AnalyticsTo check how to configure Rasa Analytics to consume events from Kafka, please refer to the Analytics documentation.

Configuration

To use Kafka as an event broker in Rasa, you need to set it as an event_broker in your endpoints.yml file. For Kafka, Rasa supports following properties in event_broker section:

endpoints.yml

event_broker:
  type: kafka
  url: localhost:9092  # required, url to your kafka broker

  # Optional properties
  topic: rasa_core_events # topic to which events are published
  security_protocol: "SASL_PLAINTEXT" # security protocol to use, available options are: PLAINTEXT, SASL_PLAINTEXT, SSL, SASL_SSL
  partition_by_sender: False # should events be partitioned by sender id
  client_id: # ID to use for the producer of the events

  # SASL configuration, optional
  sasl_mechanism: "PLAIN" # SASL mechanism to use, available options are: PLAIN, GSSAPI, OAUTHBEARER, SCRAM-SHA-256, SCRAM-SHA-512
  sasl_username: # username to use for authentication, only if security_protocol is SASL_PLAINTEXT or SASL_SSL
  sasl_password: # password to use for authentication, only if security_protocol is SASL_PLAINTEXT or SASL_SSL

  # TLS configuration, optional
  ssl_cafile: # path to the CA certificate file, only if security_protocol is SSL or SASL_SSL
  ssl_certfile: # path to the client certificate file, only if security_protocol is SSL or SASL_SSL and Kafka is configured to use client authentication
  ssl_keyfile: # path to the client key file, only if security_protocol is SSL or SASL_SSL and Kafka is configured to use client authentication
  ssl_check_hostname: False # whether to check the hostname of the broker against the certificate, default is True

  # PII management configuration, optional
  stream_pii: False # whether to stream PII events, default is True
  anonymization_topics: # list of topics to publish anonymized events to, default is []
   - anonymized_topic_1

Partition Key

Rasa’s Kafka producer can optionally be configured to partition messages by conversation ID. This can be configured by setting partition_by_sender in the endpoints.yml file to True. By default, this parameter is set to False and the producer will randomly assign a partition to each message.

Authentication and Authorization

Rasa’s Kafka producer accepts the following types of security protocols: SASL_PLAINTEXT, SSL, PLAINTEXT and SASL_SSL. For development environments, or if the brokers servers and clients are located into the same machine, you can use simple authentication with SASL_PLAINTEXT or PLAINTEXT. By using this protocol, the credentials and messages exchanged between the clients and servers will be sent in plaintext. Thus, this is not the most secure approach, but since it’s simple to configure, it is useful for simple cluster configurations. SASL_PLAINTEXT protocol requires the setup of the username and password previously configured in the broker server. If the clients or the brokers in the kafka cluster are located in different machines, it’s important to use the SSL or SASL_SSL protocol to ensure encryption of data and client authentication. After generating valid certificates for the brokers and the clients, the path to the certificate and key generated for the producer must be provided as arguments, as well as the CA’s root certificate. When using the SASL_PLAINTEXT and SASL_SSL protocols, the sasl_mechanism can be optionally configured and is set to PLAIN by default. Valid values for sasl_mechanism are: PLAIN, GSSAPI, OAUTHBEARER, SCRAM-SHA-256, and SCRAM-SHA-512. If GSSAPI is used for the sasl_mechanism, you will need to additionally install python-gssapi and the necessary C library Kerberos dependencies. If the ssl_check_hostname parameter is enabled, the clients will verify if the broker’s hostname matches the certificate. It’s used on client’s connections and inter-broker connections to prevent man-in-the-middle attacks.

Using IAM roles to authenticate to AWS Managed Streaming for Apache Kafka (MSK)

New in 3.14You can use IAM authentication to connect to AWS MSK without needing to provide a username and password.

If your Rasa instance is running on an AWS service that supports IAM roles (e.g. EC2), you can use IAM authentication to connect to an AWS MSK cluster without needing to provide a username and password. To do so, you need to ensure that your MSK cluster is configured to allow IAM authentication. Ensure that the topic(s) you want to use are created on the MSK cluster. You also need to set up your Rasa instance with an appropriate IAM role that has the permissions to access the MSK cluster. The IAM role should include the following permissions:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "kafka-cluster:Connect",
                "kafka-cluster:DescribeCluster"
            ],
            "Resource": [
                "arn:aws:kafka:<region_name>:<account_id>:cluster/<cluster_name>/<cluster_uuid>"
            ]
        },
        {
            "Effect": "Allow",
            "Action": [
                "kafka-cluster:*Topic*",
                "kafka-cluster:WriteData",
                "kafka-cluster:ReadData"
            ],
            "Resource": [
                "arn:aws:kafka:<region_name>:<account_id>:topic/<cluster_name>/*"
            ]
        },
        {
            "Effect": "Allow",
            "Action": [
                "kafka-cluster:AlterGroup",
                "kafka-cluster:DescribeGroup"
            ],
            "Resource": [
                "arn:aws:kafka:<region_name>:<account_id>:group/<cluster_name>/*"
            ]
        }
    ]
}

Once you have set up the IAM role and configured your AWS MSK cluster, you can configure the following environment variables in your Rasa instance:

IAM_CLOUD_PROVIDER: Set this to aws.
AWS_DEFAULT_REGION: Set this to the AWS region where your MSK cluster is located.
KAFKA_MSK_AWS_IAM_ENABLED: Set this to true to enable IAM authentication for MSK connections, otherwise leave it unset or set to false.

You also need to configure the Kafka event broker in your endpoints.yml file to use the SASL_SSL security protocol and OAUTHBEARER SASL mechanism, as well as provide the path to the root certificate from Amazon Trust Services in the ssl_cafile property.

endpoints.yml

event_broker:
    type: kafka
    url: <your-msk-broker-url>
    topic: rasa_core_events
    security_protocol: "SASL_SSL"
    sasl_mechanism: "OAUTHBEARER"
    ssl_cafile: <path-to-amazon-trust-services-root-certificate>
    partition_by_sender: true
    client_id: <your-client-id>
    ssl_check_hostname: true

When you start your Rasa instance, it will use the IAM role to generate temporary credentials to log in to the AWS MSK cluster instead of using static credentials. The temporary credentials will be automatically refreshed every 15 minutes.

Example Configurations

Without authentication

To set up Rasa with Kafka which does not require authentication nor TLS handshake, use following config as an example:

endpoints.yml

event_broker:
  type: kafka
  security_protocol: PLAINTEXT # specifies that no credentials will be used to auth and communication is not encrypted
  topic: topic
  url: localhost

To set up Rasa with Kafka which does not require authentication but uses TLS handshake, use following config as an example:

endpoints.yml

event_broker:
  type: kafka
  security_protocol: SSL # specifies that no credentials will be used to auth but communication is encrypted using SSL/TLS
  topic: topic
  url: localhost
  ssl_cafile: CARoot.pem # CA certificate for the server
  ssl_certfile: certificate.pem # client certificate, if Kafka requires that client present their certificate as a form of mutual domain validation
  ssl_keyfile: key.pem # client key, if Kafka requires that client present their certificate as a form of mutual domain validation
  ssl_check_hostname: True # verifies that the hostname of Kafka server matches the certificate

With authentication

To set up Rasa with Kafka which requires authentication but does not use TLS handshake, use following config as an example:

endpoints.yml

event_broker:
  type: kafka
  security_protocol: SASL_PLAINTEXT # specifies that credentials will not be communicated over encryption
  topic: topic
  url: localhost
  sasl_username: username
  sasl_password: password
  sasl_mechanism: PLAIN # specifies that username/password will not be protected with additional protection mechanisms

To set up Rasa with Kafka which requires authentication and uses TLS handshake, use following config as an example:

endpoints.yml

event_broker:
  type: kafka
  security_protocol: SASL_SSL # specifies that credentials will be communicated over enrypted connection
  topic: topic
  url: localhost
  sasl_username: username
  sasl_password: password
  sasl_mechanism: PLAIN # specifies that username/password will not be protected with additional protection mechanisms
  ssl_cafile: CARoot.pem # CA certificate for the server, it is used to verify the server's certificate
  ssl_certfile: certificate.pem # client certificate, if Kafka requires that client present their certificate as a form of mutual correspondence validation
  ssl_keyfile: key.pem # client key, if Kafka requires that client present their certificate as a form of mutual correspondence validation
  ssl_check_hostname: True # verifies that the hostname of Kafka server matches the certificate

Make sure that the SASL mechanism is set according to the broker configuration. You can also use GSSAPI, OAUTHBEARER, SCRAM-SHA-256 or SCRAM-SHA-512 if your broker is configured to use it for the exposed URL endpoint.

Sending Events to Multiple Queues

Kafka does not allow you to configure multiple topics. However, multiple consumers can read from the same queue as long as they are in different consumer groups. Each consumer group will process all events independent of each other (in a sense, each group has their own reference to the last event they have processed). Kafka: The Definitive Guide

Disabling Publishing of Un-anonymised Events

You can configure the event broker to not publish un-anonymised events to the configured topic. This is done by setting the stream_pii parameter in the endpoints.yml file to false.

Sending Anonymized Events

If you have the PII management capability enabled, you can configure the event broker to publish anonymised events to a different topic. This is done by setting the anonymization_topics parameter in the endpoints.yml file to a list of topics. The event broker will publish anonymised events to the specified topics when the PII management capability is enabled.

Non-Blocking Publishing

New in 3.17You can configure Kafka to publish events without blocking the event loop by setting type: concurrent_kafka instead of type: kafka.

By default, type: kafka publishes events synchronously on the event loop. Each publish call waits for the Kafka broker to acknowledge the event before returning. For latency-sensitive deployments, use type: concurrent_kafka instead. This variant offloads publishing to a background thread pool so the event loop is never blocked by Kafka I/O or retry delays.

endpoints.yml

event_broker:
  type: concurrent_kafka
  url: localhost:9092
  topic: rasa_core_events

  # All options from type: kafka are supported
  security_protocol: "SASL_PLAINTEXT"
  sasl_mechanism: "PLAIN"
  sasl_username: myuser
  sasl_password: mypassword
  partition_by_sender: True

  # Additional option: number of background publish threads (default: 1)
  executor_max_workers: 1

Ordering with multiple workersWhen executor_max_workers is greater than 1, concurrent retries can reorder events for the same sender. Set partition_by_sender: True to ensure events for a given conversation always land on the same Kafka partition, but note that retry races between threads may still affect ordering within a partition. For strict ordering guarantees, keep executor_max_workers: 1 (the default).

Pika Event Broker for RabbitMQ

Rasa uses Pika , the Python client library for RabbitMQ.

Configuration

To use RabbitMQ as an event broker in Rasa, you need to set it as an event_broker in your endpoints.yml file. For RabbitMQ, Rasa supports following properties in even_broker section:

endpoints.yml

event_broker:
  type: pika
  host: # required, hostname of your RabbitMQ broker e.g. localhost
  port: 5672 # port of your RabbitMQ broker e.g. 5672
  exchange_name: "rasa-exchange" # exchange name to use for publishing events
  username: # required, username to use for authentication
  password: # required, password to use for authentication
  connection_attempts: 20 # number of connection attempts to make before giving up
  retry_delay_in_seconds: 5 # time to wait before retrying connection attempts
  raise_on_failure: False #whether to raise an exception on connection failure
  should_keep_unpublished_messages: True # whether to keep unpublished messages in memory
  queues: # list of queues to publish events to"
    - rasa_core_events # default
  stream_pii: False # whether to publish un-anonymised events to the configured queues. defaults to True
  anonymization_queues: # list of queues to publish anonymized events to. defaults to []
    - anonymized_event_queue

Additionally, you can use TLS with RabbitMQ by setting the following environment variables:

RABBITMQ_SSL_CLIENT_CERTIFICATE: path to the SSL client certificate
RABBITMQ_SSL_CLIENT_KEY: path to the SSL client key

Please note that specifying ‘RABBITMQ_SSL_CA_FILE’ via environment variables is no longer supported, as well as specifying RABBITMQ_SSL_KEY_PASSWORD environment variable - please use a key file that is not encrypted instead.

Example Configurations

To set up Rasa with Pika for RabbitMQ use following config as an example:

endpoints.yml

event_broker:
  type: pika
  url: localhost
  username: username
  password: password
  queues:
    - queue-1
  #   you may supply more than one queue to publish to
  #   - queue-2
  #   - queue-3
  exchange_name: exchange

Adding a Pika Event Broker in Python

Here is how you add it using Python code:

import asyncio

from rasa.core.brokers.pika import PikaEventBroker
from rasa.core.tracker_store import InMemoryTrackerStore

pika_broker = PikaEventBroker('localhost',
                              'username',
                              'password',
                              queues=['rasa_events'],
                              event_loop=event_loop
                              )
asyncio.run(pika_broker.connect())

tracker_store = InMemoryTrackerStore(domain=domain, event_broker=pika_broker)

Implementing a Pika Event Consumer

You need to have a RabbitMQ server running, as well as another application that consumes the events. This consumer to needs to implement Pika’s start_consuming() method with a callback action. Here’s a simple example:

import json
import pika

def _callback(ch, method, properties, body):
        # Do something useful with your incoming message body here, e.g.
        # saving it to a database
        print("Received event {}".format(json.loads(body)))

if __name__ == "__main__":

    # RabbitMQ credentials with username and password
    credentials = pika.PlainCredentials("username", "password")

    # Pika connection to the RabbitMQ host - typically 'rabbit' in a
    # docker environment, or 'localhost' in a local environment
    connection = pika.BlockingConnection(
        pika.ConnectionParameters("rabbit", credentials=credentials)
    )

    # start consumption of channel
    channel = connection.channel()
    channel.basic_consume(queue="rasa_events", on_message_callback=_callback, auto_ack=True)
    channel.start_consuming()

Sending Events to Multiple Queues

You can specify multiple event queues to publish events to. This should work for all event brokers supported by Pika (e.g. RabbitMQ)

Disabling Publishing of Un-anonymised Events

By default, Rasa will publish un-anonymised events to the configured queues. If you want to disable this and only publish anonymized events, set stream_pii: false in your event_broker configuration.

Publishing Anonymized Events

If you want to publish anonymized events to a different queue, you can set the anonymization_queues property in your event_broker configuration. This should be a list of queues to publish anonymized events to. By default, this is set to an empty list, which means that anonymized events will not be published to any queue.

SQL Event Broker

It is possible to use an SQL database as an event broker. Connections to databases are established using SQLAlchemy, a Python library which can interact with many different types of SQL databases, such as SQLite, PostgreSQL and more. The default Rasa installation allows connections to SQLite and PostgreSQL databases. To see other options, please see the SQLAlchemy documentation on SQL dialects. To set up Rasa with SQL event broker the following steps are required:

Add required configuration to your endpoints.yml

When using SQLite:

endpoints.yml

event_broker:
  type: SQL
  dialect: sqlite
  db: events.db

When using PostgreSQL:

endpoints.yml

event_broker:
  type: SQL
  url: 127.0.0.1
  port: 5432
  dialect: postgresql
  username: myuser
  password: mypassword
  db: mydatabase

To start the Rasa server using your SQL backend, add the --endpoints flag, e.g.:

rasa run -m models --endpoints endpoints.yml

FileEventBroker

It is possible to use the FileEventBroker as an event broker. This implementation will log events to a file in json format. You can provide a path key in the endpoints.yml file if you wish to override the default file name: rasa_event.log.

Custom Event Broker

If you need an event broker which is not available out of the box, you can implement your own. This is done by extending the base class EventBroker. Your custom event broker class must also implement the following base class methods:

from_endpoint_config: creates an EventBroker object from the endpoint configuration. (source code - see for signature).
publish: publishes a json-formatted Rasa event into an event queue. (source code - see for signature).
is_ready: determine whether the event broker is ready. (source code - see for signature).
close: close the connection to an event broker. (source code - see for signature).

Note that the __init__ method of your custom event broker class must also implement the instance attribute self.stream_pii to indicate if the event broker should stream un-anonymised events or not. The default value should be True. To set up Rasa with your custom event broker the following steps are required:

Add required configuration to your endpoints.yml

endpoints.yml

event_broker:
  type: path.to.your.module.Class
  url: localhost
  a_parameter: a value
  another_parameter: another value

To start the Rasa server using your custom backend, add the --endpoints flag, e.g.:

rasa run -m models --endpoints endpoints.yml

​Format

​Kafka Event Broker

​Configuration

​Partition Key

​Authentication and Authorization

Using IAM roles to authenticate to AWS Managed Streaming for Apache Kafka (MSK)

​Example Configurations

​Without authentication

​With authentication

​Sending Events to Multiple Queues

​Disabling Publishing of Un-anonymised Events

​Sending Anonymized Events

​Non-Blocking Publishing

​Pika Event Broker for RabbitMQ

​Configuration

​Example Configurations

​Adding a Pika Event Broker in Python

​Implementing a Pika Event Consumer

​Sending Events to Multiple Queues

​Disabling Publishing of Un-anonymised Events

​Publishing Anonymized Events

​SQL Event Broker

​FileEventBroker

​Custom Event Broker

Format

Kafka Event Broker

Configuration

Partition Key

Authentication and Authorization

Example Configurations

Without authentication

With authentication

Sending Events to Multiple Queues

Disabling Publishing of Un-anonymised Events

Sending Anonymized Events

Non-Blocking Publishing

Pika Event Broker for RabbitMQ

Configuration

Example Configurations

Adding a Pika Event Broker in Python

Implementing a Pika Event Consumer

Sending Events to Multiple Queues

Disabling Publishing of Un-anonymised Events

Publishing Anonymized Events

SQL Event Broker

FileEventBroker

Custom Event Broker