Experiment with using tsdb doc values codec for _seq_no.

[martijnvg]

Running metricsgenreceiver without this change:

"_seq_no": {
    "total": "369.9mb",
    "total_in_bytes": 387962443,
    "inverted_index": {
        "total": "0b",
        "total_in_bytes": 0
    },
    "stored_fields": "0b",
    "stored_fields_in_bytes": 0,
    "doc_values": "369.9mb",
    "doc_values_in_bytes": 387962443,
    "points": "0b",
    "points_in_bytes": 0,
    "norms": "0b",
    "norms_in_bytes": 0,
    "term_vectors": "0b",
    "term_vectors_in_bytes": 0,
    "knn_vectors": "0b",
    "knn_vectors_in_bytes": 0
}

and running metricsgenreceiver with this change:

"_seq_no": {
    "total": "212.3mb",
    "total_in_bytes": 222616293,
    "inverted_index": {
        "total": "0b",
        "total_in_bytes": 0
    },
    "stored_fields": "0b",
    "stored_fields_in_bytes": 0,
    "doc_values": "212.3mb",
    "doc_values_in_bytes": 222616293,
    "points": "0b",
    "points_in_bytes": 0,
    "norms": "0b",
    "norms_in_bytes": 0,
    "term_vectors": "0b",
    "term_vectors_in_bytes": 0,
    "knn_vectors": "0b",
    "knn_vectors_in_bytes": 0
}

metricsgenreceiver config:

receivers:
  metricsgen:
    start_now_minus: 72h
    interval: 5s
    interval_jitter_std_dev: 1ms
    real_time: false
    exit_after_end: true
    seed: 123
    scenarios:
      - path: builtin/hostmetrics
        scale: 100

I suspect that delta of delta and offset encoding pays of here. In both cases time spent on indexing was comparable.
I do wonder about other work loads.

[kkrik-es]

This works for logsdb too?

[martijnvg]

This works for logsdb too?

Yes, it does. But I've not tested this with logsdb. I think we can maybe consider gating this behind a feature flag and see how other benchmarks respond. I'm a little worried that it might not be beneficial to all work loads.

[kkrik-es]

Let's get this in on Monday, after the serverless release. That way, we can observe the impact to logs. I think it's gonna be a win there too, delta-of-deltas should kick in and help.

[martijnvg]

Let's get this in on Monday, after the serverless release.

I will put it behind a feature flag, so we don't interfere with the next serverless release.

[dnhatn]

The number looks great.

[elasticsearchmachine]

Pinging @elastic/es-storage-engine (Team:StorageEngine)