fix: improved debug logs in agent sending spans (#1259)

- refs INSTA-5316

packages/collector/src/agentConnection.js

@@ -266,6 +266,10 @@ exports.sendSpans = function sendSpans(spans, cb) {
   const callback = util.atMostOnce('callback for sendSpans', err => {
     if (err && !maxContentErrorHasBeenLogged && err instanceof PayloadTooLargeError) {
       logLargeSpans(spans);
+    } else if (err) {
+      logger.debug('Failed to send: %s', getSpanLengthInfo(spans));
+    } else {
+      logger.debug('Successfully sent: %s', getSpanLengthInfo(spans));
     }
     cb(err);
   });
@@ -486,3 +490,42 @@ function logLargeSpans(spans) {
     )}`
   );
 }
+
+/**
+ * @typedef {InstanaBaseSpan} Span Span
+ * @property {number} [k] kind
+ */
+
+/**
+ * Returning type for the function getSpanLengthInfo
+ * @typedef {Object.<string, number>} CountBySpanType
+ */
+
+/**
+ * @param {Span[]} spans
+ * @returns {CountBySpanType}
+ */
+function getSpanLengthInfo(spans) {
+  /** @type {Object.<number, string>} */
+  const spanMapping = {
+    1: 'entrySpans',
+    2: 'exitSpans',
+    3: 'intermediateSpans'
+  };
+
+  /**
+   * @param {CountBySpanType} acc
+   * @param {Span} item
+   */
+  const reducer = (acc, item) => {
+    const label = spanMapping[item?.k];
+    if (label) {
+      acc[label] = (acc[label] || 0) + 1;
+    }
+    return acc;
+  };
+
+  const countBySpanType = spans.reduce(reducer, {});
+
+  return countBySpanType;
+}