# Persistent Subscriptions

This document explains how to use HTTP API for setting up and consuming persistent subscriptions and competing consumer subscription groups. For an overview on competing consumers and how they relate to other subscription types please see our getting started guide.

TIP

The Administration UI includes a Competing Consumers section where you are able to create, update, delete and view subscriptions and their statuses.

# Creating a Persistent Subscription

Before interacting with a subscription group, you need to create one. You receive an error if you try to create a subscription group more than once. This requires admin permissions.

URI Supported Content Types Method
/subscriptions/{stream}/{subscription_name} application/json PUT

# Query Parameters

Parameter Description
stream The stream the persistent subscription is on.
subscription_name The name of the subscription group.

# Body

Parameter Description
resolveLinktos Tells the subscription to resolve link events.
startFrom Start the subscription from the position-of the event in the stream.
extraStatistics Tells the backend to measure timings on the clients so statistics will contain histograms of them.
checkPointAfterMilliseconds The amount of time the system should try to checkpoint after.
liveBufferSize The size of the live buffer (in memory) before resorting to paging.
readBatchSize The size of the read batch when in paging mode.
bufferSize The number of messages that should be buffered when in paging mode.
maxCheckPointCount The maximum number of messages not checkpointed before forcing a checkpoint.
maxRetryCount Sets the number of times a message should be retried before considered a bad message.
maxSubscriberCount Sets the maximum number of allowed TCP subscribers.
messageTimeoutMilliseconds Sets the timeout for a client before the message will be retried.
minCheckPointCount The minimum number of messages to write a checkpoint for.
namedConsumerStrategy RoundRobin/DispatchToSingle/Pinned

# Updating a Persistent Subscription

You can edit the settings of an existing subscription while it is running. This drops the current subscribers and resets the subscription internally. This requires admin permissions.

URI Supported Content Types Method
/subscriptions/{stream}/{subscription_name} application/json POST

# Query Parameters

Parameter Description
stream The stream to the persistent subscription is on.
subscription_name The name of the subscription group.

# Body

Same parameters as "Creating a Persistent Subscription"

# Deleting a Persistent Subscription

URI Supported Content Types Method
/subscriptions/{stream}/{subscription_name} application/json DELETE

# Query Parameters

Parameter Description
stream The stream to the persistent subscription is on.
subscription_name The name of the subscription group.

# Reading a stream via a Persistent Subscription

By default, reading a stream via a persistent subscription returns a single event per request and does not embed the event properties as part of the response.

URI Supported Content Types Method
/subscriptions/{stream}/{subscription_name} /subscriptions/{stream}/{subscription_name}?embed={embed} /subscriptions/{stream}/{subscription}/{count}?embed={embed} application/vnd.eventstore.competingatom+xml application/vnd.eventstore.competingatom+json GET

# Query Parameters

Parameter Description
stream The stream the persistent subscription is on.
subscription_name The name of the subscription group.
count How many events to return for the request.
embed None, Content, Rich, Body, PrettyBody, TryHarder

Read Reading Streams for information on the different embed levels.

# Response

{
  "title": "All Events Persistent Subscription",
  "id": "http://localhost:2113/subscriptions/newstream/competing_consumers_group1",
  "updated": "2015-12-02T09:17:48.556545Z",
  "author": {
    "name": "EventStore"
  },
  "headOfStream": false,
  "links": [
    {
      "uri": "http://localhost:2113/subscriptions/newstream/competing_consumers_group1/ack%3Fids=c322e299-cb73-4b47-97c5-5054f920746f",
      "relation": "ackAll"
    },
    {
      "uri": "http://localhost:2113/subscriptions/newstream/competing_consumers_group1/nack%3Fids=c322e299-cb73-4b47-97c5-5054f920746f",
      "relation": "nackAll"
    },
    {
      "uri": "http://localhost:2113/subscriptions/newstream/competing_consumers_group1/1%3Fembed=None",
      "relation": "previous"
    },
    {
      "uri": "http://localhost:2113/subscriptions/newstream/competing_consumers_group1",
      "relation": "self"
    }
  ],
  "entries": [
    {
      "title": "1@newstream",
      "id": "http://localhost:2113/streams/newstream/1",
      "updated": "2015-12-02T09:17:48.556545Z",
      "author": {
        "name": "EventStore"
      },
      "summary": "SomeEvent",
      "links": [
        {
          "uri": "http://localhost:2113/streams/newstream/1",
          "relation": "edit"
        },
        {
          "uri": "http://localhost:2113/streams/newstream/1",
          "relation": "alternate"
        },
        {
          "uri": "http://localhost:2113/subscriptions/newstream/competing_consumers_group1/ack/c322e299-cb73-4b47-97c5-5054f920746f",
          "relation": "ack"
        },
        {
          "uri": "http://localhost:2113/subscriptions/newstream/competing_consumers_group1/nack/c322e299-cb73-4b47-97c5-5054f920746f",
          "relation": "nack"
        }
      ]
    }
  ]
}

# Acknowledgements

Clients must acknowledge (or not acknowledge) messages in the competing consumer model. If the client fails to respond in the given timeout period, the message is retried. You should use the rel links in the feed for acknowledgements not bookmark URIs as they are subject to change in future versions.

For example:

{
  "uri": "http://localhost:2113/subscriptions/newstream/competing_consumers_group1/ack/c322e299-cb73-4b47-97c5-5054f920746f",
  "relation": "ack"
}

# Ack multiple messages

URI Supported Content Types Method
/subscriptions/{stream}/{subscription_name}/ack?ids={messageids} application/json POST

# Query Parameters

Parameter Description
stream The stream the persistent subscription is on.
subscription_name The name of the subscription group.
messageids The ids of the messages that needs to be ACKed

# Ack a single message

URI Supported Content Types Method
/subscriptions/{stream}/{subscription_name}/ack/{messageid} application/json POST

# Query Parameters

Parameter Description
stream The stream to the persistent subscription is on.
subscription_name The name of the subscription group.
messageid The id of the message that needs to be acked

# Nack multiple messages

URI Supported Content Types Method
/subscriptions/{stream}/{subscription_name}/nack?ids={messageids}?action={action} application/json POST

# Query Parameters

Parameter Description
stream The stream to the persistent subscription is on.
subscription_name The name of the subscription group.
action
  • Park: Don't retry the message, park it until a request is sent to reply the parked messages
  • Retry: Retry the message
  • Skip: Discard the message
  • Stop: Stop the subscription
messageid The id of the message that needs to be acked

# Nack a single message

URI Supported Content Types Method
/subscriptions/{stream}/{subscription_name}/nack/{messageid}?action={action} application/json POST

# Replaying parked messages

URI Supported Content Types Method
/subscriptions/{stream}/{subscription_name}/replayParked application/json POST

# Getting information for all subscriptions

URI Method
/subscriptions GET

# Response

[
  {
    "links": [
      {
        "href": "http://localhost:2113/subscriptions/newstream/competing_consumers_group1/info",
        "rel": "detail"
      }
    ],
    "eventStreamId": "newstream",
    "groupName": "competing_consumers_group1",
    "parkedMessageUri": "http://localhost:2113/streams/$persistentsubscription-newstream::competing_consumers_group1-parked",
    "getMessagesUri": "http://localhost:2113/subscriptions/newstream/competing_consumers_group1/1",
    "status": "Live",
    "averageItemsPerSecond": 0.0,
    "totalItemsProcessed": 0,
    "lastProcessedEventNumber": -1,
    "lastKnownEventNumber": 5,
    "connectionCount": 0,
    "totalInFlightMessages": 0
  },
  {
    "links": [
      {
        "href": "http://localhost:2113/subscriptions/another_newstream/competing_consumers_group1/info",
        "rel": "detail"
      }
    ],
    "eventStreamId": "another_newstream",
    "groupName": "competing_consumers_group1",
    "parkedMessageUri": "http://localhost:2113/streams/$persistentsubscription-another_newstream::competing_consumers_group1-parked",
    "getMessagesUri": "http://localhost:2113/subscriptions/another_newstream/competing_consumers_group1/1",
    "status": "Live",
    "averageItemsPerSecond": 0.0,
    "totalItemsProcessed": 0,
    "lastProcessedEventNumber": -1,
    "lastKnownEventNumber": -1,
    "connectionCount": 0,
    "totalInFlightMessages": 0
  }
]

# Get subscriptions for a stream

URI Supported Content Types Method
/subscriptions/{stream} application/json GET

# Response

[
  {
    "links": [
      {
        "href": "http://localhost:2113/subscriptions/newstream/competing_consumers_group1/info",
        "rel": "detail"
      }
    ],
    "eventStreamId": "newstream",
    "groupName": "competing_consumers_group1",
    "parkedMessageUri": "http://localhost:2113/streams/$persistentsubscription-newstream::competing_consumers_group1-parked",
    "getMessagesUri": "http://localhost:2113/subscriptions/newstream/competing_consumers_group1/1",
    "status": "Live",
    "averageItemsPerSecond": 0.0,
    "totalItemsProcessed": 0,
    "lastProcessedEventNumber": -1,
    "lastKnownEventNumber": 5,
    "connectionCount": 0,
    "totalInFlightMessages": 0
  }
]

# Getting a specific subscription

URI Supported Content Types Method
/subscriptions/{stream}/{subscription_name}/info application/json GET

# Response

{
  "links": [
    {
      "href": "http://localhost:2113/subscriptions/newstream/competing_consumers_group1/info",
      "rel": "detail"
    },
    {
      "href": "http://localhost:2113/subscriptions/newstream/competing_consumers_group1/replayParked",
      "rel": "replayParked"
    }
  ],
  "config": {
    "resolveLinktos": false,
    "startFrom": 0,
    "messageTimeoutMilliseconds": 10000,
    "extraStatistics": false,
    "maxRetryCount": 10,
    "liveBufferSize": 500,
    "bufferSize": 500,
    "readBatchSize": 20,
    "preferRoundRobin": true,
    "checkPointAfterMilliseconds": 1000,
    "minCheckPointCount": 10,
    "maxCheckPointCount": 500,
    "maxSubscriberCount": 10,
    "namedConsumerStrategy": "RoundRobin"
  },
  "eventStreamId": "newstream",
  "groupName": "competing_consumers_group1",
  "status": "Live",
  "averageItemsPerSecond": 0.0,
  "parkedMessageUri": "http://localhost:2113/streams/$persistentsubscription-newstream::competing_consumers_group1-parked",
  "getMessagesUri": "http://localhost:2113/subscriptions/newstream/competing_consumers_group1/1",
  "totalItemsProcessed": 0,
  "countSinceLastMeasurement": 0,
  "lastProcessedEventNumber": -1,
  "lastKnownEventNumber": 5,
  "readBufferCount": 6,
  "liveBufferCount": 5,
  "retryBufferCount": 0,
  "totalInFlightMessages": 0,
  "connections": []
}
Last Updated: 1/1/2021, 11:29:55 AM

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