fix(worker): add rows_dropped metric for ClickhouseWriter exhaust (#13488)

hello-args · cursoragent · web-flow · commit e7cf58d6d321 · 2026-05-12T09:34:12.000Z
Emit langfuse.queue.clickhouse_writer.rows_dropped with entity_type tag
when rows are discarded after max flush attempts, alongside existing
error increments and logs.

Co-authored-by: Cursor &lt;cursoragent@cursor.com&gt;
diff --git a/worker/src/services/ClickhouseWriter/ClickhouseWriter.unit.test.ts b/worker/src/services/ClickhouseWriter/ClickhouseWriter.unit.test.ts
@@ -155,6 +155,11 @@ describe("ClickhouseWriter", () => {
       ),
     ).toBe(true);
     expect(writer["queue"][TableName.Traces]).toHaveLength(0);
+    expect(serverExports.recordIncrement).toHaveBeenCalledWith(
+      "langfuse.queue.clickhouse_writer.rows_dropped",
+      1,
+      { entity_type: TableName.Traces },
+    );
   });
 
   it("should shutdown gracefully", async () => {
diff --git a/worker/src/services/ClickhouseWriter/index.ts b/worker/src/services/ClickhouseWriter/index.ts
@@ -520,6 +520,12 @@ export class ClickhouseWriter {
       });
 
       if (droppedCount > 0) {
+        recordIncrement(
+          "langfuse.queue.clickhouse_writer.rows_dropped",
+          droppedCount,
+          { entity_type: tableName },
+        );
+
         const droppedIds = queueItems
           .filter((item) => item.attempts >= this.maxAttempts)
           .map((item) => {
