# Payload Logging

Logging of request and response payloads from your Seldon Deployment can be accomplished by adding a logging section to any part of the Seldon deployment graph. An example is shown below:

```yaml
apiVersion: machinelearning.seldon.io/v1
kind: SeldonDeployment
metadata:
  name: seldon-model
spec:
  name: test-deployment
  predictors:
  - componentSpecs:
    - spec:
        containers:
        - image: seldonio/mock_classifier:1.3
          name: classifier
    graph:
      children: []
      endpoint:
        type: REST
      name: classifier
      type: MODEL
      logger:
        url: http://mylogging-endpoint
        mode: all
    name: example
    replicas: 1

```

The logging for the top level requets response is provided by:

```yaml
      logger:
        url: http://mylogging-endpoint
        mode: all
```

In this example both request and response payloads as specified by the `mode` attribute are sent as [CloudEvents](https://cloudevents.io/) to the url `http://mylogging-endpoint`.

The specification is:

 * url: Any url. Optional. If not provided then it will default to the default knative borker in the namespace of the Seldon Deployment.
 * mode: Either `request`, `response` or `all`

## Logging direct to Kafka

You can log requests directly to Kafka as an alternative to logging via CloudEvents by adding appropriate environment variables to the `svcOrchSpec`. An example is shown below:

```yaml
apiVersion: machinelearning.seldon.io/v1
kind: SeldonDeployment
metadata:
  name: cifar10
  namespace: seldon
spec:
  name: resnet32
  predictors:
  - graph:
      implementation: TRITON_SERVER
      logger:
        mode: all
      modelUri: gs://seldon-models/triton/tf_cifar10
      name: cifar10
    name: default
    svcOrchSpec:
      env:
      - name: LOGGER_KAFKA_BROKER
        value: seldon-kafka-plain-0.kafka:9092
      - name: LOGGER_KAFKA_TOPIC
        value: seldon
    replicas: 1
  protocol: v2

```

The two required environment variables are:

 * LOGGER_KAFKA_BROKER : The Kafka Broker service endpoint.
 * LOGGER_KAFKA_TOPIC : The kafka Topic to log the requests.

### Logging to encrypted Kafka with SSL

You can log requests to an encrypted Kafka with SSL. SSL uses private-key/ certificate pairs, which are used during the SSL handshake process. 

To be able to log payloads, the client needs:
* to authenticate with SSL
* its own keystore, made up of a key pair and a signed certificate
* the CA certificate used to sign the key-certificate pair

The CA certificate needs to be recognised by the broker and can also be used for verifying the broker's certificate.

It is possible to read more about the different options available on the [Confluent documentation](https://docs.confluent.io/platform/current/kafka/authentication_ssl.html) and [librdkafka Configuration](https://github.com/edenhill/librdkafka/blob/master/CONFIGURATION.md) pages. 

Here is an example on how to define these for a deployment: 

```yaml
apiVersion: machinelearning.seldon.io/v1
kind: SeldonDeployment
metadata:
  name: cifar10
  namespace: seldon
spec:
  name: resnet32
  predictors:
  - graph:
      implementation: TRITON_SERVER
      logger:
        mode: all
      modelUri: gs://seldon-models/triton/tf_cifar10
      name: cifar10
    name: default
    svcOrchSpec:
      env:
      - name: LOGGER_KAFKA_BROKER
        value: seldon-kafka-plain-0.kafka:9092
      - name: LOGGER_KAFKA_TOPIC
        value: seldon
      - name: KAFKA_SECURITY_PROTOCOL
        value: ssl
      - name: KAFKA_SSL_CA_CERT_FILE
        value: /path/to/ca.pem
      - name: KAFKA_SSL_CLIENT_CERT_FILE
        value: /path/to/access.cert
      - name: KAFKA_SSL_CLIENT_KEY_FILE
        value: /path/to/access.key
      - name: KAFKA_SSL_CLIENT_KEY_PASS
        valueFrom:
          secretKeyRef:
            name: my-kafka-secret
            key: ssl-password # Key password, if any (optional field)
    replicas: 1
  protocol: kfserving

```
Follow a [benchmarking notebook for CIFAR10 image payload logging showing 3K predictions per second with Triton Inference Server](../examples/kafka_logger.html).

## Setting Global Default

If you don't want to set up the custom logger every time, you are able to set it with `executor.requestLogger.defaultEndpoint` in the Helm Chart Variable as outlined in the [helm chart advanced settings section](../reference/helm.rst). 

This can simply specify a URL to call. In the usual kubernetes fashion, if a service name is provided then it is assumed to be in the current namespace unless there it is followed by `.<namespace>`, giving the namespace name. 

You will still want to make sure the model is deployed with a specification on what requests will be logged, i.e. all, request or response (as outlined above).