eventlog

HTTP API

Pushing events

A new event may be pushed through the POST /log/ endpoint. The request body is expected to contain either one or a series of objects in the following binary format:

1. labelLength Uint16 LE
2. payloadLength Uint32 LE
3. [label utf-8] // Not empty if labelLength > 0
4. payload utf-8

The document {"version":"v","version-previous":"vp","time":"t"} will be returned in case of success where v is the version the new event was written at, vp the version of the event it was appended on and t the time the event was recorded at. If multiple events have been appended then "version-first":vf will be added to the returned document where vf is the version of the first appended event while v is the version of the latest appended event.

Pushing events transactionally (OCC)

A new event may be pushed transactionally following the Optimistic Concurrency Control (OCC) principle through the POST /log/:assumedVersion endpoint where assumedVersion is the version of the current projection.

In case of a mismatch between the provided and actual versions 400 ErrMismatchingVersions will be returned.

The request body is expected to be similar to the non-transactional push endpoint. In case of success the returned result document will be similar to the one of the non-transactional push endpoint.

Reading current version

The GET /version endpoint returns {"version":"x"} where x is a hexadecimal version number representing the current database version.

Reading initial version

The GET /version/initial endpoint returns {"version-initial":"x"} where x is a hexadecimal version number representing the initial database version (it's the version the very first event was recorded at).

Scanning events

The GET /log/:version endpoint returns an array of {"time":"t","version":"v","version-previous":"vp","version-next":"vn","label":"l","payload":p} event objects starting at the given version where t is the time the event was recorded at, v is the version the event was recorded at, vp is the version of the antecedent event, vn is the version of the successive event, l is the event's label and p is the JSON payload document.

• Optionally, the n query parameter can be applied to limit the scan batch size.
• Optionally, the reverse query parameter can be applied to scan in reversed order.
• Optionally, the skip_first query parameter can be applied to skip the first event.

Fetching metadata

The GET /meta endpoint returns all metadata as a JSON document.

Subscribing for updates

Websocket connections can be established on the GET /subscription endpoint. Connected websockets will receive hexadecimal numbers representing the latest database version when a new event was pushed.