Revert "Export spans to hec (#359)" (#375)

This reverts commit 625973a.

Reverting because this fails the build https://app.circleci.com/pipelines/github/open-telemetry/opentelemetry-collector-contrib/1563/workflows/e7c13c24-34ac-4fa6-85e9-da3fafb0fbbc and we have to make a release now.

exporter/splunkhecexporter/client.go

@@ -54,15 +54,13 @@ func (c *client) pushMetricsData(
 	if err != nil {
 		return exporterhelper.NumTimeSeries(md), consumererror.Permanent(err)
 	}
-	if len(splunkDataPoints) == 0 {
-		return numDroppedTimeseries, nil
-	}
 
 	body, compressed, err := encodeBody(&c.zippers, splunkDataPoints, c.config.DisableCompression)
 	if err != nil {
 		return exporterhelper.NumTimeSeries(md), consumererror.Permanent(err)
 	}
 
+	// TODO the client sends synchronously data as of now. It would make more sense to buffer data coming in, and send batches as supported by Splunk. To batch effectively, a ring buffer approach would work well - based on time and number of messages queued.
 	req, err := http.NewRequest("POST", c.url.String(), body)
 	if err != nil {
 		return exporterhelper.NumTimeSeries(md), consumererror.Permanent(err)
@@ -96,69 +94,6 @@ func (c *client) pushMetricsData(
 	return numDroppedTimeseries, nil
 }
 
-func (c *client) pushTraceData(
-	ctx context.Context,
-	td consumerdata.TraceData,
-) (droppedSpans int, err error) {
-	c.wg.Add(1)
-	defer c.wg.Done()
-
-	splunkEvents, numDroppedSpans := traceDataToSplunk(c.logger, td, c.config)
-	if len(splunkEvents) == 0 {
-		return numDroppedSpans, nil
-	}
-
-	body, compressed, err := encodeBodyEvents(&c.zippers, splunkEvents, c.config.DisableCompression)
-	if err != nil {
-		return len(td.Spans), consumererror.Permanent(err)
-	}
-
-	req, err := http.NewRequest("POST", c.url.String(), body)
-	if err != nil {
-		return len(td.Spans), consumererror.Permanent(err)
-	}
-
-	for k, v := range c.headers {
-		req.Header.Set(k, v)
-	}
-
-	if compressed {
-		req.Header.Set("Content-Encoding", "gzip")
-	}
-
-	resp, err := c.client.Do(req)
-	if err != nil {
-		return len(td.Spans), err
-	}
-
-	io.Copy(ioutil.Discard, resp.Body)
-	resp.Body.Close()
-
-	// Splunk accepts all 2XX codes.
-	if resp.StatusCode < http.StatusOK || resp.StatusCode >= http.StatusMultipleChoices {
-		err = fmt.Errorf(
-			"HTTP %d %q",
-			resp.StatusCode,
-			http.StatusText(resp.StatusCode))
-		return len(td.Spans), err
-	}
-
-	return numDroppedSpans, nil
-}
-
-func encodeBodyEvents(zippers *sync.Pool, evs []*splunkEvent, disableCompression bool) (bodyReader io.Reader, compressed bool, err error) {
-	buf := new(bytes.Buffer)
-	encoder := json.NewEncoder(buf)
-	for _, e := range evs {
-		err := encoder.Encode(e)
-		if err != nil {
-			return nil, false, err
-		}
-		buf.WriteString("\r\n\r\n")
-	}
-	return getReader(zippers, buf, disableCompression)
-}
-
 func encodeBody(zippers *sync.Pool, dps []*splunkMetric, disableCompression bool) (bodyReader io.Reader, compressed bool, err error) {
 	buf := new(bytes.Buffer)
 	encoder := json.NewEncoder(buf)