Live: support streaming results out-of-the-box (#32821)

packages/grafana-runtime/src/utils/DataSourceWithBackend.ts

@@ -7,11 +7,15 @@ import {
   DataSourceJsonData,
   ScopedVars,
   makeClassES5Compatible,
+  DataFrame,
+  parseLiveChannelAddress,
+  StreamingFrameOptions,
 } from '@grafana/data';
-import { Observable, of } from 'rxjs';
-import { map, catchError } from 'rxjs/operators';
+import { merge, Observable, of } from 'rxjs';
+import { catchError, switchMap } from 'rxjs/operators';
 import { getBackendSrv, getDataSourceSrv } from '../services';
 import { BackendDataSourceResponse, toDataQueryResponse } from './queryResponse';
+import { getLiveDataStream } from './liveQuery';
 
 const ExpressionDatasourceID = '__expr__';
 
@@ -132,8 +136,13 @@ class DataSourceWithBackend<
         requestId,
       })
       .pipe(
-        map((rsp) => {
-          return toDataQueryResponse(rsp, queries as DataQuery[]);
+        switchMap((raw) => {
+          const rsp = toDataQueryResponse(raw, queries as DataQuery[]);
+          // Check if any response should subscribe to a live stream
+          if (rsp.data?.length && rsp.data.find((f: DataFrame) => f.meta?.channel)) {
+            return toStreamingDataResponse(request, rsp);
+          }
+          return of(rsp);
         }),
         catchError((err) => {
           return of(toDataQueryResponse(err));
@@ -209,6 +218,44 @@ class DataSourceWithBackend<
   }
 }
 
+export function toStreamingDataResponse(
+  request: DataQueryRequest,
+  rsp: DataQueryResponse
+): Observable<DataQueryResponse> {
+  const buffer: StreamingFrameOptions = {
+    maxLength: request.maxDataPoints ?? 500,
+  };
+
+  // For recent queries, clamp to the current time range
+  if (request.rangeRaw?.to === 'now') {
+    buffer.maxDelta = request.range.to.valueOf() - request.range.from.valueOf();
+  }
+
+  const staticdata: DataFrame[] = [];
+  const streams: Array<Observable<DataQueryResponse>> = [];
+  for (const frame of rsp.data) {
+    const addr = parseLiveChannelAddress(frame.meta?.channel);
+    if (addr) {
+      streams.push(
+        getLiveDataStream({
+          addr,
+          buffer,
+          frame: frame as DataFrame,
+        })
+      );
+    } else {
+      staticdata.push(frame);
+    }
+  }
+  if (staticdata.length) {
+    streams.push(of({ ...rsp, data: staticdata }));
+  }
+  if (streams.length === 1) {
+    return streams[0]; // avoid merge wrapper
+  }
+  return merge(...streams);
+}
+
 //@ts-ignore
 DataSourceWithBackend = makeClassES5Compatible(DataSourceWithBackend);