Bolt (network protocol)

Bolt
Original author(s)	Neo Technology

Stable release	Version 1
Development status	Active
Written in	Various languages
Operating system	Any
Platform	Cross-platform
Type	Network protocol
License	Creative Commons 3.0 Attribution-ShareAlike
Website	boltprotocol.org

The Bolt Protocol (Bolt) is a connection oriented network protocol used for client-server communication in database applications. It operates over a TCP connection or WebSocket.

Bolt is statement-oriented, allowing a client to send messages containing a statement consisting of a single string and a set of typed parameters. The server responds to each statement with a result message and an optional stream of result records.

Developed for use in the Neo4j graph database, Bolt was heavily inspired by the binary network protocol of PostgreSQL and features a data interchange format derived from MessagePack. The protocol is published on the website http://boltprotocol.org.

Versioning

The protocol supports explicit versioning and version negotiation between the client and the server. There is only one published version of the protocol: version 1.

Protocol Overview - Version 1

Messaging

A typical interaction in the Bolt network protocol

Bolt clients and servers both send data over the connection as a sequence of messages. Each message has a type (denoted by a "signature" byte) and may include additional data. The client drives the interaction, and each message sent by the client will cause one or more response messages to be sent by the server.

Client messages:

Type	Signature
INIT	0x01^[1]
RUN	0x10^[2]
DISCARD_ALL	0x2F^[3]
PULL_ALL	0x3F^[4]
ACK_FAILURE	0x0E^[5]
RESET	0x0F^[6]

Server messages:

Type	Signature
SUCCESS	0x70^[7]
FAILURE	0x7F^[8]
IGNORED	0x7E^[9]
RECORD	0x71^[10]

Message Transfer Encoding

Each message is encoded into a sequence of bytes. These bytes are transferred using a binary chunked encoding, where each chunk is preceded by an unsigned, big-endian 16-bit integer denoting the number of bytes that immediately follow. A length of 0 is used to denote the end of the message.

Failure Handling

A client may send multiple messages to a server, without first waiting for a response.^[11] The server processes each message sequentially. However, as there may be logical dependencies between messages sent by the client, the server will not evaluate requests it receives after sending FAILURE in response to a preceding message. Instead, it will send an IGNORED message in reply to every client message, until the client acknowledges the failure by sending an ACK_FAILURE message.

This is similar to the failure handling and recovery in the PostgreSQL wire protocol.

Data Encoding

Bolt supports encoding for a number of different data types.

Type	Description
Null ^[12]	Represents the absence of a value.
Boolean ^[13]	Boolean true or false.
Integer ^[14]	64-bit signed integer.
Float ^[15]	64-bit floating point number.
String ^[16]	UTF-8 encoded string.
List ^[17]	Ordered collection of values.
Map ^[18]	Unordered, keyed collection of values.
Node ^[19]	A node in a Property Graph with optional properties and labels.
Relationship ^[20]	A directed, typed connection between two nodes in a Property Graph. Each relationship may have properties and always has an identity.
Path ^[21]	The record of a directed walk through a Property Graph, consisting of a sequence of zero or more segments.

References

External links

Bolt protocol specification

This article is issued from Wikipedia - version of the 9/28/2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.