Transactions HTTP API

The /txn endpoint manages multiple operations in Consul, including catalog updates and fetches of multiple KV entries inside a single, atomic transaction.

Create Transaction

This endpoint permits submitting a list of operations to apply to Consul inside of a transaction. If any operation fails, the transaction is rolled back and none of the changes are applied.

If the transaction does not contain any write operations then it will be fast-pathed internally to an endpoint that works like other reads, except that blocking queries are not currently supported. In this mode, you may supply the ?stale or ?consistent query parameters with the request to control consistency. To support bounding the acceptable staleness of data, read-only transaction responses provide the X-Consul-LastContact header containing the time in milliseconds that a server was last contacted by the leader node. The X-Consul-KnownLeader header also indicates if there is a known leader. These won't be present if the transaction contains any write operations, and any consistency query parameters will be ignored, since writes are always managed by the leader via the Raft consensus protocol.

The table below shows this endpoint's support for blocking queries, consistency modes, agent caching, and required ACLs.

¹ For read-only transactions
² The ACL required depends on the operations in the transaction.

Query Parameters

• dc (string: "") - Specifies the datacenter to query. This will default to the datacenter of the agent being queried. This is specified as part of the URL as a query parameter.

JSON Request Body Schema

A JSON array of operations objects, each with a key of the operation name (KV, Node, Service, or Check), and a value of an object specific to that operation.

• KV operations have the following fields:

  • Verb (string: <required>) - Specifies the type of operation to perform. Please see the table below for available verbs.

  • Key (string: <required>) - Specifies the full path of the entry.

  • Value (string: "") - Specifies a base64-encoded blob of data. Values cannot be larger than 512kB.

  • Flags (int: 0) - Specifies an opaque unsigned integer that can be attached to each entry. Clients can choose to use this however makes sense for their application.

  • Index (int: 0) - Specifies an index. See the table below for more information.

  • Session (string: "") - Specifies a session. See the table below for more information.

  • Namespace (string: "") EnterpriseEnterprise - Specifies the namespace to create the KV data If not provided, the namespace will be inherited from the request's ACL token or will default to the default namespace. Added in Consul 1.7.0.

• Node operations have the following fields:

  • Verb (string: <required>) - Specifies the type of operation to perform.

  • Node (Node: <required>) - Specifies the node information to use for the operation. See the catalog endpoint for the fields in this object. Note the only the node can be specified here, not any services or checks - separate service or check operations must be used for those.

• Service operations have the following fields:

  • Verb (string: <required>) - Specifies the type of operation to perform.

  • Node (string: <required>) = Specifies the name of the node to use for this service operation.

  • Service (Service: <required>) - Specifies the service instance information to use for the operation. See the catalog endpoint for the fields in this object.

• Check operations have the following fields:

  • Verb (string: <required>) - Specifies the type of operation to perform.

  • Check (Service: <required>) - Specifies the check to use for the operation. See the catalog endpoint for the fields in this object.

  Please see the table below for available verbs.

Sample Payload

The body of the request should be a list of operations to perform inside the atomic transaction. Up to 64 operations may be present in a single transaction.

[
  {
    "KV": {
      "Verb": "<verb>",
      "Key": "<key>",
      "Value": "<Base64-encoded blob of data>",
      "Flags": <flags>,
      "Index": <index>,
      "Session": "<session id>"
    }
  },
  {
    "Node": {
      "Verb": "set",
      "Node": {
        "ID": "67539c9d-b948-ba67-edd4-d07a676d6673",
        "Node": "bar",
        "Address": "192.168.0.1",
        "Datacenter": "dc1",
        "Meta": {
          "instance_type": "m2.large"
        }
      }
    }
  },
  {
    "Service": {
      "Verb": "delete",
      "Node": "foo",
      "Service": {
        "ID": "db1"
      }
    }
  },
  {
    "Check": {
      "Verb": "cas",
      "Check": {
          "Node": "bar",
        "CheckID": "service:web1",
        "Name": "Web HTTP Check",
        "Status": "critical",
        "ServiceID": "web1",
        "ServiceName": "web",
        "ServiceTags": null,
        "Definition": {
          "HTTP": "http://localhost:8080",
          "Interval": "10s"
        },
        "ModifyIndex": 22
      }
    }
  }
]

Sample Request

$ curl \
    --request PUT \
    --data @payload.json \
    http://127.0.0.1:8500/v1/txn

Sample Response

If the transaction can be processed, a status code of 200 will be returned if it was successfully applied, or a status code of 409 will be returned if it was rolled back. If either of these status codes are returned, the response will look like this:

{
  "Results": [
    {
      "KV": {
        "LockIndex": <lock index>,
        "Key": "<key>",
        "Flags": <flags>,
        "Value": "<Base64-encoded blob of data, or null>",
        "CreateIndex": <index>,
        "ModifyIndex": <index>
      }
    },
    {
      "Node": {
        "ID": "67539c9d-b948-ba67-edd4-d07a676d6673",
        "Node": "bar",
        "Address": "192.168.0.1",
        "Datacenter": "dc1",
        "TaggedAddresses": null,
        "Meta": {
          "instance_type": "m2.large"
        },
        "CreateIndex": 32,
        "ModifyIndex": 32
      }
    },
    {
      "Check": {
        "Node": "bar",
        "CheckID": "service:web1",
        "Name": "Web HTTP Check",
        "Status": "critical",
        "Notes": "",
        "Output": "",
        "ServiceID": "web1",
        "ServiceName": "web",
        "ServiceTags": null,
        "Definition": {
          "HTTP": "http://localhost:8080",
          "Interval": "10s"
        },
        "CreateIndex": 22,
        "ModifyIndex": 35
      }
    }
  ],
  "Errors": [
    {
      "OpIndex": <index of failed operation>,
      "What": "<error message for failed operation>"
    },
    ...
  ]
}

• Results has entries for some operations if the transaction was successful. To save space, the Value for KV results will be null for any Verb other than "get" or "get-tree". Like the /v1/kv/<key> endpoint, Value will be Base64-encoded if it is present. Also, no result entries will be added for verbs that delete keys.

• Errors has entries describing which operations failed if the transaction was rolled back. The OpIndex gives the index of the failed operation in the transaction, and What is a string with an error message about why that operation failed.

Tables of Operations

KV Operations

The following tables summarize the available verbs and the fields that apply to those operations ("X" means a field is required and "O" means it is optional):

Node Operations

Node operations act on an individual node and require either a Node ID or name, giving precedence to the ID if both are set. Delete operations will not return a result on success.

Service Operations

Service operations act on an individual service instance on the given node name. Both a node name and valid service name are required. Delete operations will not return a result on success.

Check Operations

Check operations act on an individual health check instance on the given node name. Both a node name and valid check ID are required. Delete operations will not return a result on success.