We use `totalMetrics` with a `startTimeInNanos` and a call to `postIngest` to track the 'total time' that ingest is running for a given document. You can imagine it's a little stopwatch that we start and stop. Unfortunately, I think we're stopping the stopwatch just a little too soon, on the start side, we include the time spent transforming the document into an `IngestDocument`, but we do not include the (non-negligible) time transforming from an `IngestDocument` after the pipeline logic has run.

That is, the call to `sourceAsMap` is included:

https://github.com/elastic/elasticsearch/blob/d03664f84f15dcfcb900cf2d43121ca9d89bdda8/server/src/main/java/org/elasticsearch/ingest/IngestService.java#L905

But the call to `source` is not:

https://github.com/elastic/elasticsearch/blob/d03664f84f15dcfcb900cf2d43121ca9d89bdda8/server/src/main/java/org/elasticsearch/ingest/IngestService.java#L948

The consequence of this is that the `total` ingest stats doesn't actually reflect the true time spent in ingest code:

```
GET _nodes/stats?filter_path=nodes.*.ingest
{
  "nodes" : {
    "Aysm6ztIRne2ES5ktyuqtw" : {
      "ingest" : {
        "total" : {
          "count" : 1,
          "time_in_millis" : 110, <--- this should be a little higher than it is
```
server/src/main/java/org/elasticsearch/ingest/IngestService.java
}
        public abstract IngestMetadata execute(IngestMetadata currentIngestMetadata, Collection<IndexMetadata> allIndexMetadata);
        @Override
        public void onFailure(Exception e) {
            listener.onFailure(e);
        }
    }
    public IngestService(
        ClusterService clusterService,
        ThreadPool threadPool,
        Environment env,
        ScriptService scriptService,
        AnalysisRegistry analysisRegistry,
        List<IngestPlugin> ingestPlugins,
        Client client
    ) {
        this.clusterService = clusterService;
        this.scriptService = scriptService;
        this.processorFactories = processorFactories(
            ingestPlugins,
            new Processor.Parameters(
                env,
                scriptService,
                analysisRegistry,
                threadPool.getThreadContext(),
                threadPool::relativeTimeInMillis,
                (delay, command) -> threadPool.schedule(command, TimeValue.timeValueMillis(delay), ThreadPool.Names.GENERIC),
                this,
                client,
                threadPool.generic()::execute