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## 20.1. Transactional HTTP endpoint

The Neo4j transactional HTTP endpoint allows you to execute a series of Cypher statements within the scope of a transaction. The transaction may be kept open across multiple HTTP requests, until the client chooses to commit or roll back. Each HTTP request can include a list of statements, and for convenience you can include statements along with a request to begin or commit a transaction.

The server guards against orphaned transactions by using a timeout. If there are no requests for a given transaction within the timeout period, the server will roll it back. You can configure the timeout in the server configuration, by setting org.neo4j.server.transaction.timeout to the number of seconds before timeout. The default timeout is 60 seconds.

The key difference between the transactional HTTP endpoint and the Cypher endpoint (see Section 20.5, “Cypher queries via REST”) is the ability to use the same transaction across multiple HTTP requests. The cypher endpoint always attempts to commit a transaction at the end of each HTTP request.

| Note
The serialization format for cypher results is mostly the same as the cypher endpoint. However, the format for raw entities is slightly less verbose and does not include hypermedia links.

| Note
Open transactions are not shared among members of an HA cluster. Therefore, if you use this endpoint in an HA cluster, you must ensure that all requests for a given transaction are sent to the same Neo4j instance.

| Note
Cypher queries with `USING PERIODIC COMMIT` may only be executed when creating a new transaction and immediately committing it with a single HTTP request (see Section 11.8, “Using Periodic Commit”).

| Tip
In order to speed up queries in repeated scenarios, try not to use literals but replace them with parameters wherever possible in order to let the server cache query plans.

### 20.1.1. Begin a transaction

You begin a new transaction by posting zero or more Cypher statements to the transaction endpoint. The server will respond with the result of your statements, as well as the location of your open transaction.

Example request

- `POST` `http://localhost:7474/db/data/transaction`
- `Accept:` `application/json; charset=UTF-8`
- `Content-Type:` `application/json`

    {
      "statements" : [ {
        "statement" : "CREATE (n {props}) RETURN n",
        "parameters" : {
          "props" : {
            "name" : "My Node"
          }
        }
      } ]
    }

Example response

- `201:` `Created`
- `Content-Type:` `application/json`
- `Location:` `http://localhost:7474/db/data/transaction/7`

    {
      "commit" : "http://localhost:7474/db/data/transaction/7/commit",
      "results" : [ {
        "columns" : [ "n" ],
        "data" : [ {
          "row" : [ {
            "name" : "My Node"
          } ]
        } ]
      } ],
      "transaction" : {
        "expires" : "Thu, 20 Feb 2014 11:43:19 +0000"
      },
      "errors" : [ ]
    }

### 20.1.2. Execute statements in an open transaction

Given that you have an open transaction, you can make a number of requests, each of which executes additional statements, and keeps the transaction open by resetting the transaction timeout.

Example request

- `POST` `http://localhost:7474/db/data/transaction/9`
- `Accept:` `application/json; charset=UTF-8`
- `Content-Type:` `application/json`

    {
      "statements" : [ {
        "statement" : "CREATE n RETURN n"
      } ]
    }

Example response

- `200:` `OK`
- `Content-Type:` `application/json`

    {
      "commit" : "http://localhost:7474/db/data/transaction/9/commit",
      "results" : [ {
        "columns" : [ "n" ],
        "data" : [ {
          "row" : [ {
          } ]
        } ]
      } ],
      "transaction" : {
        "expires" : "Thu, 20 Feb 2014 11:43:19 +0000"
      },
      "errors" : [ ]
    }

### 20.1.3. Execute statements in an open transaction in REST format for the return

Given that you have an open transaction, you can make a number of requests, each of which executes additional statements, and keeps the transaction open by resetting the transaction timeout. Specifying the `REST` format will give back full Neo4j Rest API representations of the Neo4j Nodes, Relationships and Paths, if returned.

Example request

- `POST` `http://localhost:7474/db/data/transaction/1`
- `Accept:` `application/json; charset=UTF-8`
- `Content-Type:` `application/json`

    {
      "statements" : [ {
        "statement" : "CREATE n RETURN n",
        "resultDataContents" : [ "REST" ]
      } ]
    }

Example response

- `200:` `OK`
- `Content-Type:` `application/json`

    {
      "commit" : "http://localhost:7474/db/data/transaction/1/commit",
      "results" : [ {
        "columns" : [ "n" ],
        "data" : [ {
          "rest" : [ {
            "paged_traverse" : "http://localhost:7474/db/data/node/12/paged/traverse/{returnType}{?pageSize,leaseTime}",
            "labels" : "http://localhost:7474/db/data/node/12/labels",
            "outgoing_relationships" : "http://localhost:7474/db/data/node/12/relationships/out",
            "traverse" : "http://localhost:7474/db/data/node/12/traverse/{returnType}",
            "all_typed_relationships" : "http://localhost:7474/db/data/node/12/relationships/all/{-list|&|types}",
            "property" : "http://localhost:7474/db/data/node/12/properties/{key}",
            "all_relationships" : "http://localhost:7474/db/data/node/12/relationships/all",
            "self" : "http://localhost:7474/db/data/node/12",
            "properties" : "http://localhost:7474/db/data/node/12/properties",
            "outgoing_typed_relationships" : "http://localhost:7474/db/data/node/12/relationships/out/{-list|&|types}",
            "incoming_relationships" : "http://localhost:7474/db/data/node/12/relationships/in",
            "incoming_typed_relationships" : "http://localhost:7474/db/data/node/12/relationships/in/{-list|&|types}",
            "create_relationship" : "http://localhost:7474/db/data/node/12/relationships",
            "data" : {
            }
          } ]
        } ]
      } ],
      "transaction" : {
        "expires" : "Thu, 20 Feb 2014 11:43:15 +0000"
      },
      "errors" : [ ]
    }

### 20.1.4. Reset transaction timeout of an open transaction

Every orphaned transaction is automatically expired after a period of inactivity. This may be prevented by resetting the transaction timeout.

The timeout may be reset by sending a keep-alive request to the server that executes an empty list of statements. This request will reset the transaction timeout and return the new time at which the transaction will expire as an RFC1123 formatted timestamp value in the “transaction” section of the response.

Example request

- `POST` `http://localhost:7474/db/data/transaction/2`
- `Accept:` `application/json; charset=UTF-8`
- `Content-Type:` `application/json`

    {
      "statements" : [ ]
    }

Example response

- `200:` `OK`
- `Content-Type:` `application/json`

    {
      "commit" : "http://localhost:7474/db/data/transaction/2/commit",
      "results" : [ ],
      "transaction" : {
        "expires" : "Thu, 20 Feb 2014 11:43:19 +0000"
      },
      "errors" : [ ]
    }

### 20.1.5. Commit an open transaction

Given you have an open transaction, you can send a commit request. Optionally, you submit additional statements along with the request that will be executed before committing the transaction.

Example request

- `POST` `http://localhost:7474/db/data/transaction/4/commit`
- `Accept:` `application/json; charset=UTF-8`
- `Content-Type:` `application/json`

    {
      "statements" : [ {
        "statement" : "CREATE n RETURN id(n)"
      } ]
    }

Example response

- `200:` `OK`
- `Content-Type:` `application/json`

    {
      "results" : [ {
        "columns" : [ "id(n)" ],
        "data" : [ {
          "row" : [ 14 ]
        } ]
      } ],
      "errors" : [ ]
    }

### 20.1.6. Rollback an open transaction

Given that you have an open transaction, you can send a roll back request. The server will roll back the transaction.

Example request

- `DELETE` `http://localhost:7474/db/data/transaction/3`
- `Accept:` `application/json; charset=UTF-8`

Example response

- `200:` `OK`
- `Content-Type:` `application/json; charset=UTF-8`

    {
      "results" : [ ],
      "errors" : [ ]
    }

### 20.1.7. Begin and commit a transaction in one request

If there is no need to keep a transaction open across multiple HTTP requests, you can begin a transaction, execute statements, and commit with just a single HTTP request.

Note: Cypher queries with `USING PERIODIC COMMIT` may only be executed using single request transactions (see [query-periodic-commit]).

Example request

- `POST` `http://localhost:7474/db/data/transaction/commit`
- `Accept:` `application/json; charset=UTF-8`
- `Content-Type:` `application/json`

    {
      "statements" : [ {
        "statement" : "CREATE n RETURN id(n)"
      } ]
    }

Example response

- `200:` `OK`
- `Content-Type:` `application/json`

    {
      "results" : [ {
        "columns" : [ "id(n)" ],
        "data" : [ {
          "row" : [ 15 ]
        } ]
      } ],
      "errors" : [ ]
    }

### 20.1.8. Return results in graph format

If you want to understand the graph structure of nodes and relationships returned by your query, you can specify the "graph" results data format. For example, this is useful when you want to visualise the graph structure. The format collates all the nodes and relationships from all columns of the result, and also flattens collections of nodes and relationships, including paths.

Example request

- `POST` `http://localhost:7474/db/data/transaction/commit`
- `Accept:` `application/json; charset=UTF-8`
- `Content-Type:` `application/json`

    {
      "statements" : [ {
        "statement" : "CREATE ( bike:Bike { weight: 10 } )CREATE ( frontWheel:Wheel { spokes: 3 } )CREATE ( backWheel:Wheel { spokes: 32 } )CREATE p1 = bike -[:HAS { position: 1 } ]-> frontWheel CREATE p2 = bike -[:HAS { position: 2 } ]-> backWheel RETURN bike, p1, p2",
        "resultDataContents" : [ "row", "graph" ]
      } ]
    }

Example response

- `200:` `OK`
- `Content-Type:` `application/json`

    {
      "results" : [ {
        "columns" : [ "bike", "p1", "p2" ],
        "data" : [ {
          "row" : [ {
            "weight" : 10
          }, [ {
            "weight" : 10
          }, {
            "position" : 1
          }, {
            "spokes" : 3
          } ], [ {
            "weight" : 10
          }, {
            "position" : 2
          }, {
            "spokes" : 32
          } ] ],
          "graph" : {
            "nodes" : [ {
              "id" : "17",
              "labels" : [ "Wheel" ],
              "properties" : {
                "spokes" : 3
              }
            }, {
              "id" : "16",
              "labels" : [ "Bike" ],
              "properties" : {
                "weight" : 10
              }
            }, {
              "id" : "18",
              "labels" : [ "Wheel" ],
              "properties" : {
                "spokes" : 32
              }
            } ],
            "relationships" : [ {
              "id" : "9",
              "type" : "HAS",
              "startNode" : "16",
              "endNode" : "17",
              "properties" : {
                "position" : 1
              }
            }, {
              "id" : "10",
              "type" : "HAS",
              "startNode" : "16",
              "endNode" : "18",
              "properties" : {
                "position" : 2
              }
            } ]
          }
        } ]
      } ],
      "errors" : [ ]
    }

### 20.1.9. Handling errors

The result of any request against the transaction endpoint is streamed back to the client. Therefore the server does not know whether the request will be successful or not when it sends the HTTP status code.

Because of this, all requests against the transactional endpoint will return 200 or 201 status code, regardless of whether statements were successfully executed. At the end of the response payload, the server includes a list of errors that occurred while executing statements. If this list is empty, the request completed successfully.

If any errors occur while executing statements, the server will roll back the transaction.

In this example, we send the server an invalid statement to demonstrate error handling.

For more information on the status codes, see Section 20.2, “Neo4j Status Codes”.

Example request

- `POST` `http://localhost:7474/db/data/transaction/8/commit`
- `Accept:` `application/json; charset=UTF-8`
- `Content-Type:` `application/json`

    {
      "statements" : [ {
        "statement" : "This is not a valid Cypher Statement."
      } ]
    }

Example response

- `200:` `OK`
- `Content-Type:` `application/json`

    {
      "results" : [ ],
      "errors" : [ {
        "code" : "Neo.ClientError.Statement.InvalidSyntax",
        "message" : "Invalid input 'T': expected <init> (line 1, column 1)\n\"This is not a valid Cypher Statement.\"\n ^"
      } ]
    }

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