#Overview
This project provides a REST interface to execute queries on the databuffer.
Requirements
This project requires Java 8 or greater.
Deployment
Use the instructions provided by ch.psi.daq.install to install the application on a server.
Application Properties
Following files define and describe application properties:
- Cassandra specific properties.
- Query specific properties..
- Query REST specific properties.
It is possible to overwrite properties by defining new values in ${HOME}/.config/daq/queryrest.properties
REST Interface
Query Channel Names
Request
GET http://<host>:<port>/channels
or
GET http://<host>:<port>/channels/{regex}
Example
curl -H "Content-Type: application/json" -X GET http://sf-nube-14.psi.ch:8080/channels
or
curl -H "Content-Type: application/json" -X GET http://sf-nube-14.psi.ch:8080/channels/TRFCB
Query Data
Request
GET http://<host>:<port>/query
Example
A request is performed using JSON. The JSON query defines the channels to be queried, the range, and how the data should be aggregated (this is optional but highly recommended).
curl -H "Content-Type: application/json" -X GET -d '{"channels":["channel1","channel2"],"startPulseId":0,"endPulseId":4}' http://sf-nube-14.psi.ch:8080/channels
Response example
The response is in JSON.
[
{
"channel":"channel1",
"data":[
{
"pulseId":0,
"iocMillis":0,
"iocNanos":0,
"globalMillis":0,
"globalNanos":0,
"value":0
},
{
"pulseId":2,
"iocMillis":2,
"iocNanos":2,
"globalMillis":2,
"globalNanos":2,
"value":2
},
{
"pulseId":4,
"iocMillis":4,
"iocNanos":4,
"globalMillis":4,
"globalNanos":4,
"value":4
}
]
},
{
"channel":"channel2",
"data":[
{
"pulseId":1,
"iocMillis":1,
"iocNanos":1,
"globalMillis":1,
"globalNanos":1,
"value":1
},
{
"pulseId":3,
"iocMillis":3,
"iocNanos":3,
"globalMillis":3,
"globalNanos":3,
"value":3
}
]
}
]
JSON Query
Queries are defined using JSON. There exist following fields:
- channels: Array of channel names to be queried.
- startPulseId and endPulseId : A pulse-id range request with start and end pulse-id.
- startMillis/[startNanos] and endMillis/[endNanos]: A time range request with start and end milliseconds since January 1, 1970 (the UNIX/JAVA epoch) and optionally supplemented with the nanosecond offset to the milliseconds (range [0..999999]).
- startDate/[startNanos] and endDate/[endNanos]: A time range request with start and end date (format yyyy/MM/dd HH:mm:ss.SSS or dd.MM.yyyy HH:mm:ss.SSS) and optionally supplemented with the nanosecond offset to the milliseconds (range [0..999999]).
- ordering: The ordering of the data (see here for possible values).
- fields: The requested fields (see here for possible values).
- nrOfBins: Activates data binning. Specifies the number of bins the pulse/time range should be devided into.
- binSize: Activates data binning. Specifies the number of pulses per bin for pulse-range queries or the number of milliseconds per bin for time-range queries.
- aggregations: Activates data aggregation. Array of requested aggregations (see here for possible values). These values will be added to the data array response.
- aggregationType: Specifies the type of aggregation (see here). The default type is value aggregation (e.g., sum([1,2,3])=6). Alternatively, it is possible to define index aggregation for multiple arrays in combination with binning (e.g., sum([1,2,3], [3,2,1]) = [4,4,4]).
- aggregateChannels: Specifies whether the data of the requested channels should be combined together using the defined aggregation (values: true|false)
Example JSON Queries
TODO: