Batched exporter starts sends just first 2048 spans

[jankaifer]

What happened?

Batched exporter starts ignoring spans when I generate too many and don't manually flush.

Steps to Reproduce

Generate 10k spans and send them to batched processor

Expected Result

All of those spans are sent.

Actual Result

Only the first 2048 spans are reported, the rest is discarded.

Additional Details

Repro: https://github.com/jankaifer/batched-grpc/tree/5dbb9a3ffd80d7333cb14e035f8e5070db47802b

OpenTelemetry Setup Code

import { context, trace } from "@opentelemetry/api";
import { NodeSDK } from "@opentelemetry/sdk-node";
import { OTLPTraceExporter } from "@opentelemetry/exporter-trace-otlp-grpc";

const N = 10_000;

const sdk = new NodeSDK({
  traceExporter: new OTLPTraceExporter(),
});
sdk.start();

const tracer = trace.getTracer("example-tracer-node");
tracer.startActiveSpan("main", (span) => {
  for (let i = 0; i < N; i++) {
    const globalCtx = context.active();
    const ctx = trace.setSpan(globalCtx, span);
    tracer.startActiveSpan("child", undefined, ctx, (childSpan) => {
      // Do stuff
      console.log("doing stuff", i);
      childSpan.end();
    });
  }
  span.end();
});

await sdk.shutdown();
console.log("finished");

package.json

{
  "name": "batched-grpc",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "type": "module",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "@opentelemetry/api": "^1.4.1",
    "@opentelemetry/exporter-trace-otlp-grpc": "^0.38.0",
    "@opentelemetry/resources": "^1.12.0",
    "@opentelemetry/sdk-node": "^0.38.0",
    "@opentelemetry/sdk-trace-base": "^1.12.0",
    "@opentelemetry/semantic-conventions": "^1.12.0"
  }
}

Relevant log output

I measured the bumper of reported spans in Zipkin (you can even see that the root span is child because main was not reported):

[Flarna]

2048 is default max queue size (see here).

You can change this (env or constructor option).
As you create spans in a sync loop node has no chance to export any spans.

If above is just simplified and the loop is actually async it's likely that #3458 will improve your situation.

[jankaifer]

Thanks, I suspected it was something like this, but I haven't found a mention of this in the docs or closed issues.