HTTP interface for Stream Transactions
Stream Transactions allow you to perform a multi-document transaction with individual begin and commit/abort commands
For an introduction to this transaction type, see Stream Transactions.
To use a Stream Transaction, a client first sends the configuration of the transaction to the ArangoDB server.
action
attribute is supported.The Stream Transaction API works in conjunction with other APIs in ArangoDB.
To use the transaction for a supported operation a client needs to specify
the transaction identifier in the x-arango-trx-id
HTTP header on each request.
This will automatically cause these operations to use the specified transaction.
Supported transactional API operations include:
- All operations in the Document API
- Get the number of documents via the Collection API
- Truncate a collection via the Collection API
- Create an AQL cursor via the Cursor API
- Handle vertices and edges of managed graphs (General Graph / Gharial API)
Begin a Stream Transaction
Begin a Stream Transaction that allows clients to call selected APIs over a short period of time, referencing the transaction ID, and have the server execute the operations transactionally.
Committing or aborting a running transaction must be done by the client. It is bad practice to not commit or abort a transaction once you are done using it. It forces the server to keep resources and collection locks until the entire transaction times out.
The transaction description must be passed in the body of the POST request. If the transaction can be started on the server, HTTP 201 will be returned.
For successfully started transactions, the returned JSON object has the following properties:
error
: boolean flag to indicate if an error occurred (false
in this case)code
: the HTTP status coderesult
: result containingid
: the identifier of the transactionstatus
: containing the string ‘running’
If the transaction specification is either missing or malformed, the server will respond with HTTP 400 or HTTP 404.
The body of the response will then contain a JSON object with additional error details. The object has the following attributes:
error
: boolean flag to indicate that an error occurred (true
in this case)code
: the HTTP status codeerrorNum
: the server error numbererrorMessage
: a descriptive error message
x-arango-allow-dirty-read boolean
Set this header to
true
to allow the Coordinator to ask any shard replica for the data, not only the shard leader. This may result in “dirty reads”.This header decides about dirty reads for the entire transaction. Individual read operations, that are performed as part of the transaction, cannot override it.
collections* object
collections
must be a JSON object that can have one or all sub-attributesread
,write
orexclusive
, each being an array of collection names or a single collection name as string. Collections that will be written to in the transaction must be declared with thewrite
orexclusive
attribute or it will fail, whereas non-declared collections from which is solely read will be added lazily.lockTimeout integer
an optional numeric value that can be used to set a timeout in seconds for waiting on collection locks. This option is only meaningful when using exclusive locks. If not specified, a default value will be used. Setting
lockTimeout
to0
will make ArangoDB not time out waiting for a lock.
Examples
Executing a transaction on a single collection
curl -X POST --header 'accept: application/json' --data-binary @- --dump - 'http://localhost:8529/_api/transaction/begin' <<'EOF'
{
"collections": {
"write": "products"
}
}
EOF
Referring to a non-existing collection
curl -X POST --header 'accept: application/json' --data-binary @- --dump - 'http://localhost:8529/_api/transaction/begin' <<'EOF'
{
"collections": {
"read": "products"
}
}
EOF
Get the status of a Stream Transaction
The result is an object describing the status of the transaction. It has at least the following attributes:
id
: the identifier of the transactionstatus
: the status of the transaction. One of “running”, “committed” or “aborted”.
Examples
Get transaction status
curl --header 'accept: application/json' --dump - 'http://localhost:8529/_api/transaction/72132'
Commit a Stream Transaction
Commit a running server-side transaction. Committing is an idempotent operation. It is not an error to commit a transaction more than once.
If the transaction can be committed, HTTP 200 will be returned. The returned JSON object has the following properties:
error
: boolean flag to indicate if an error occurred (false
in this case)code
: the HTTP status coderesult
: result containingid
: the identifier of the transactionstatus
: containing the string ‘committed’
If the transaction cannot be found, committing is not allowed or the transaction was aborted, the server will respond with HTTP 400, HTTP 404 or HTTP 409.
The body of the response will then contain a JSON object with additional error details. The object has the following attributes:
error
: boolean flag to indicate that an error occurred (true
in this case)code
: the HTTP status codeerrorNum
: the server error numbererrorMessage
: a descriptive error message
Examples
Committing a transaction:
curl -X PUT --header 'accept: application/json' --dump - 'http://localhost:8529/_api/transaction/72139'
Abort a Stream Transaction
Abort a running server-side transaction. Aborting is an idempotent operation. It is not an error to abort a transaction more than once.
If the transaction can be aborted, HTTP 200 will be returned. The returned JSON object has the following properties:
error
: boolean flag to indicate if an error occurred (false
in this case)code
: the HTTP status coderesult
: result containingid
: the identifier of the transactionstatus
: containing the string ‘aborted’
If the transaction cannot be found, aborting is not allowed or the transaction was already committed, the server will respond with HTTP 400, HTTP 404 or HTTP 409.
The body of the response will then contain a JSON object with additional error details. The object has the following attributes:
error
: boolean flag to indicate that an error occurred (true
in this case)code
: the HTTP status codeerrorNum
: the server error numbererrorMessage
: a descriptive error message
Examples
Aborting a transaction:
curl -X DELETE --header 'accept: application/json' --dump - 'http://localhost:8529/_api/transaction/72146'
List the running Stream Transactions
The result is an object with the transactions
attribute, which contains
an array of transactions.
In a cluster the array will contain the transactions from all Coordinators.
Each array entry contains an object with the following attributes:
id
: the transaction’s idstate
: the transaction’s status
Examples
Get currently running transactions
curl --header 'accept: application/json' --dump - 'http://localhost:8529/_api/transaction'