@grafana/data#CSVReader TypeScript Examples

The following examples show how to use @grafana/data#CSVReader. You can vote up the ones you like or vote down the ones you don't like, and go to the original project or source file by following the links above each example. You may check out the related API usage on the sidebar.
Example #1
Source File: runStreams.ts    From grafana-chinese with Apache License 2.0 5 votes vote down vote up 
export function runFetchStream(
  target: TestDataQuery,
  query: StreamingQuery,
  req: DataQueryRequest<TestDataQuery>
): Observable<DataQueryResponse> {
  return new Observable<DataQueryResponse>(subscriber => {
    const streamId = `fetch-${req.panelId}-${target.refId}`;
    const maxDataPoints = req.maxDataPoints || 1000;

    let data = new CircularDataFrame({
      append: 'tail',
      capacity: maxDataPoints,
    });
    data.refId = target.refId;
    data.name = target.alias || 'Fetch ' + target.refId;

    let reader: ReadableStreamReader<Uint8Array>;
    const csv = new CSVReader({
      callback: {
        onHeader: (fields: Field[]) => {
          // Clear any existing fields
          if (data.fields.length) {
            data = new CircularDataFrame({
              append: 'tail',
              capacity: maxDataPoints,
            });
            data.refId = target.refId;
            data.name = 'Fetch ' + target.refId;
          }
          for (const field of fields) {
            data.addField(field);
          }
        },
        onRow: (row: any[]) => {
          data.add(row);
        },
      },
    });

    const processChunk = (value: ReadableStreamReadResult<Uint8Array>): any => {
      if (value.value) {
        const text = new TextDecoder().decode(value.value);
        csv.readCSV(text);
      }

      subscriber.next({
        data: [data],
        key: streamId,
        state: value.done ? LoadingState.Done : LoadingState.Streaming,
      });

      if (value.done) {
        console.log('Finished stream');
        subscriber.complete(); // necessary?
        return;
      }

      return reader.read().then(processChunk);
    };

    fetch(new Request(query.url)).then(response => {
      reader = response.body.getReader();
      reader.read().then(processChunk);
    });

    return () => {
      // Cancel fetch?
      console.log('unsubscribing to stream ' + streamId);
    };
  });
}