> ## Documentation Index
> Fetch the complete documentation index at: https://docs.vatis.tech/llms.txt
> Use this file to discover all available pages before exploring further.

# Stream templates

> Overview of the stream configuration templates

## Introduction

In Vatis Streams engine, the first-class entity is a *stream*. A stream is a <Tooltip tip="Direct Acyclical Graph">DAG</Tooltip> of processors. This DAG of processors alongside with the configuration of each processor is stored in a **stream configuration template**.

Each stream created using the Vatis Streams API is based on a stream configuration template, that can be patched to modify processors configuration.

## Stream configuration template

A stream configuration template can be (optionally) patched and retrieved using the [**Patch by id endpoint**](/api-reference/stream-configuration/stream-configuration-template-resource-impl/patch-by-id)

<Accordion title="Example">
  An example of a stream configuration template is shown below:

  ```json theme={null}
  {
    "id": "65f46430c6d8985974ff9c9d",
    "name": "Ping",
    "description": "Simple pipeline for testing stream latency",
    "dataSourceSchema": "bytes",
    "processors": [
      {
        "id": "echo",
        "name": "echo",
        "description": "Echo operation",
        "processorDeclaration": {
          "id": "echo",
          "displayName": "Echo",
          "description": "Echo processor. Returns the same message it receives.",
          "clusterDomainNameTemplate": "echo-${REPLICA}.echo-headless.stream-processors.svc.cluster.local",
          "podsDiscoveryClusterDomainName": "echo-headless.stream-processors.svc.cluster.local",
          "revision": "2024-02-06",
          "propertiesSchema": "tech.vatis.schema.stream.processor.properties.NoPropertiesDto",
          "inputSchemas": [
            "bytes"
          ],
          "outputSchema": "bytes",
          "features": {
            "support": [],
            "require": [],
            "implement": [],
            "requireSupport": []
          },
          "operationType": "NO_OPERATION"
        },
        "previousProcessorId": null,
        "propertiesSchema": "tech.vatis.schema.stream.processor.properties.NoPropertiesDto",
        "properties": {},
        "destinationTopicMessageHeaders": {},
        "destinationTopicHeaders": {
          "X-Vat-Topic-Accept-Frame-Type": "final"
        },
        "sourceSubscriptionHeaders": {
          "X-Vat-Sub-Accept-Frame-Type": "final"
        },
        "patchAliases": {},
        "egress": {
          "persist": false,
          "sink": false,
          "tags": []
        }
      }
    ],
    "patchAliases": {}
  }
  ```

  This stream configuration template can produce a stream similar to the one shown below:

  ```json theme={null}
  {
    "streamId": "20d36912-f746-4f45-8e68-d537fc1ff57f",
    "name": "Stream jokidx",
    "groupId": "20d36912-f746-4f45-8e68-d537fc1ff57f",
    "configuration": {
      "streamConfigurationTemplateId": "65f46430c6d8985974ff9c9d",
      "dataSource": {
        "topic": "persistent://vatis-streams/data-sources/4c43a454-32b4-4ef4-baa9-3442f5fecc90",
        "messageSchema": "bytes",
        "connectionOptions": {
          "X-Vat-Topic-Conn-Close-On-Disconnect": "true"
        },
        "headers": {
          "X-Vat-Topic-Accept-Frame-Type": "final"
        },
        "messageHeaders": {
          "X-Vat-Stream-Frame-Type": "final",
          "X-Vat-Stream-Processor-Id": "gateway"
        },
        "subscriptions": {
          "echo": {
            "subscription": "echo-ZlejK",
            "topic": "persistent://vatis-streams/data-sources/4c43a454-32b4-4ef4-baa9-3442f5fecc90",
            "messageSchema": "bytes",
            "connectionOptions": {},
            "headers": {
              "X-Vat-Sub-Accept-Frame-Type": "final"
            }
          }
        }
      },
      "dataSinks": {
        "echo": {
          "topic": "persistent://vatis-streams/persistent-data-sinks/f8eeb155-d496-4746-b949-94ae05426544",
          "messageSchema": "bytes",
          "connectionOptions": {},
          "headers": {
            "X-Vat-Topic-Accept-Frame-Type": "final"
          },
          "messageHeaders": {
            "X-Vat-Stream-Egress-Tags": "echo,main",
            "X-Vat-Stream-Id": "20d36912-f746-4f45-8e68-d537fc1ff57f",
            "X-Vat-Stream-Group-Id": "20d36912-f746-4f45-8e68-d537fc1ff57f",
            "X-Vat-Stream-Schema": "bytes",
            "X-Vat-Stream-Processor-Id": "echo"
          },
          "subscriptions": {}
        }
      },
      "processors": [
        {
          "id": "echo",
          "source": {
            "subscription": "echo-ZlejK",
            "topic": "persistent://vatis-streams/data-sources/4c43a454-32b4-4ef4-baa9-3442f5fecc90",
            "messageSchema": "bytes",
            "connectionOptions": {},
            "headers": {
              "X-Vat-Sub-Accept-Frame-Type": "final"
            }
          },
          "destination": {
            "topic": "persistent://vatis-streams/persistent-data-sinks/f8eeb155-d496-4746-b949-94ae05426544",
            "messageSchema": "bytes",
            "connectionOptions": {},
            "headers": {
              "X-Vat-Topic-Accept-Frame-Type": "final"
            },
            "messageHeaders": {
              "X-Vat-Stream-Egress-Tags": "echo,main",
              "X-Vat-Stream-Id": "20d36912-f746-4f45-8e68-d537fc1ff57f",
              "X-Vat-Stream-Group-Id": "20d36912-f746-4f45-8e68-d537fc1ff57f",
              "X-Vat-Stream-Schema": "bytes",
              "X-Vat-Stream-Processor-Id": "echo"
            },
            "subscriptions": {}
          },
          "clusterDomainName": "echo-0.echo-headless.stream-processors.svc.cluster.local",
          "podsDiscoveryClusterDomainName": "echo-headless.stream-processors.svc.cluster.local",
          "propertiesSchema": "tech.vatis.schema.stream.processor.properties.NoPropertiesDto",
          "properties": {},
          "egress": {
            "persist": true,
            "sink": true,
            "tags": [
              "main",
              "echo"
            ]
          }
        }
      ]
    },
    "createdTimestamp": "2024-12-12T18:47:06.865Z",
    "creatorId": "d710a067-daf3-460d-9e60-01d0bb8d10c4",
    "groupCreatorId": "d710a067-daf3-460d-9e60-01d0bb8d10c4",
    "state": "READY",
    "stateDescription": null,
    "finalizedTimestamp": null
  }
  ```
</Accordion>

The Vatis Streams API provides a set of pre-defined stream configuration templates that can be used out-of-the-box for use-cases like Speech-to-Text, Audio Intelligence, Real-time transcoding, etc.

## Streams

When a stream is created, it requires a stream configuration template id. This can be specified using the `streamConfigurationTemplateId` query parameter set in the connection URL.