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Readme.md

#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

Maven

Upload jar to the Maven repository (from ch.psi.daq.buildall):

./gradlew ch.psi.daq.queryrest:uploadArchives

DropIt

Upload jar DropIt (from ch.psi.daq.buildall):

./gradlew ch.psi.daq.queryrest:dropIt -x test

Local Instance

DAQLocal provides a local instance of the DAQ system for testing purposes (allowing users/developers to verify their code before they come to PSI to do their research and interact with the DAQ cluster).

REST Interface

The REST interface is accessible through http://data-api.psi.ch/sf.

Query Channel Names

Request

POST http://<host>:<port>/channels

Data

{"regex": "TRFCA|TRFCB", "dbMode": "databuffer"}

Explanation

regex: Reqular expression used to filter channel names (default: no filtering). Filtering is done using JAVA's Pattern, more precisely Matcher.find()).
dbMode: Defines the database to access (values: databuffer|archiverappliance)

Example

curl -H "Content-Type: application/json" -X POST -d '{"regex": "TRFCA|TRFCB"}' http://data-api.psi.ch/sf/channels

Query Range

Queries are applied to a range. Following ranges are supported.

By Pulse-Id

"range":{
   "startPulseId":0,
   "endPulseId":100
}

startPulseId: The start pulse-id of the range request.
endPulseId: The end pulse-id of the range request.

By Date

"range":{
   "startDate":"2015-08-06T18:00:00.000",
   "startNanos":0,
   "endDate":"2015-08-06T18:59:59.999",
   "endNanos":999999
}

startDate: The start date of the time range (ISO8601 format (YYYY-MM-DDThh:mm:ss.sTZD e.g. 1997-07-16T19:20:30.475+02:00 (omitting +02:00 falls back to the local time zone)).
[startNanos]: The optional nanosecond offset to the milliseconds (range [0..999999]).
endDate: The end date of the time range.
[endNanos]: The optional nanosecond offset.

By Time

"range":{
   "startMillis":0,
   "startNanos":0,
   "endMillis":100,
   "endNanos":999999
}

startMillis: The start time of the range in milliseconds since January 1, 1970 (the UNIX/JAVA epoch).
[startNanos]: The optional nanosecond offset to the milliseconds (range [0..999999]).
endMillis: The end time of the range.
[endNanos]: The optional nanosecond offset.

Query Data

Request

GET http://<host>:<port>/query

Data

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).

There exist following fields:

channels: Array of channel names to be queried.

range: The range of the query (see Query Range).
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)
dbMode: Defines the database to access (values: databuffer|archiverappliance)

Example

curl -H "Content-Type: application/json" -X POST -d '{"range":{"startPulseId":0,"endPulseId":4},"channels":["channel1","channel2"]}' http://data-api.psi.ch/sf/query

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
         }
      ]
   }
]

Example Queries

Following examples build on a waveform data (see below). They also work for scalars (consider it as a waveform of length = 1) and images (waveform of length = dimX * dimY).

[
   {
      "channel":"Channel_01",
      "data":[
         {
            "iocMillis":0,
            "iocNanos":0,
            "pulseId":0,
            "globalMillis":0,
            "globalNanos":0,
            "shape":[
               4
            ],
            "value":[1,2,3,4]
         },
         {
            "iocMillis":10,
            "iocNanos":0,
            "pulseId":1,
            "globalMillis":10,
            "globalNanos":0,
            "shape":[
               4
            ],
            "value":[2,3,4,5]
         },
         {
            "iocMillis":20,
            "iocNanos":0,
            "pulseId":2,
            "globalMillis":20,
            "globalNanos":0,
            "shape":[
               4
            ],
            "value":[3,4,5,6]
         },
         {
            "iocMillis":30,
            "iocNanos":0,
            "pulseId":3,
            "globalMillis":30,
            "globalNanos":0,
            "shape":[
               4
            ],
            "value":[4,5,6,7]
         }
      ]
   }
]