# How Write throughput is calculated in Rally

**URL:** <https://discuss.elastic.co/t/how-write-throughput-is-calculated-in-rally/188997>\
**Category:** Elasticsearch\
**Tags:** rally\
**Created:** [July 5, 2019, 3:52am UTC](https://discuss.elastic.co/t/how-write-throughput-is-calculated-in-rally/188997 "2019-07-05T03:52:36Z")\
**Posts on this page:** 1\
**Showing post:** 2

<div class="post-metadata">

**Author:** ![dliappis](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/dliappis/32/56174_2.png) [@dliappis](https://discuss.elastic.co/u/dliappis)\
**Post date:** [July 5, 2019, 3:43pm UTC](https://discuss.elastic.co/t/how-write-throughput-is-calculated-in-rally/188997/2 "2019-07-05T15:43:41Z")

</div>

This is a complicated topic because Rally can operated in [a distributed way](https://esrally.readthedocs.io/en/stable/recipes.html#distributing-the-load-test-driver) and thus needs to consider samples from all load drivers before it calculates global metrics, such as the total throughput.

The algorithm can be found in the [ThroughputCalculator class](https://github.com/elastic/rally/blob/master/esrally/driver/driver.py#L827-L940).  
Perhaps the best way to explain this is from Rally's own unit tests.

If you check [this unit test](https://github.com/elastic/rally/blob/8fda86b85703e74b97b16b0623680409fd629a15/tests/driver/driver_test.py#L404-L414) there is an example assuming two drivers.

```auto
samples = [
    driver.Sample(0, 1470838595, 21, op, metrics.SampleType.Normal, None, -1, -1, 5000, "docs", 1, 1 / 9),
    driver.Sample(0, 1470838596, 22, op, metrics.SampleType.Normal, None, -1, -1, 5000, "docs", 2, 2 / 9),
    driver.Sample(0, 1470838597, 23, op, metrics.SampleType.Normal, None, -1, -1, 5000, "docs", 3, 3 / 9),
    driver.Sample(0, 1470838598, 24, op, metrics.SampleType.Normal, None, -1, -1, 5000, "docs", 4, 4 / 9),
    driver.Sample(0, 1470838599, 25, op, metrics.SampleType.Normal, None, -1, -1, 5000, "docs", 5, 5 / 9),
    driver.Sample(0, 1470838600, 26, op, metrics.SampleType.Normal, None, -1, -1, 5000, "docs", 6, 6 / 9),
    driver.Sample(1, 1470838598.5, 24.5, op, metrics.SampleType.Normal, None, -1, -1, 5000, "docs", 4.5, 7 / 9),
    driver.Sample(1, 1470838599.5, 25.5, op, metrics.SampleType.Normal, None, -1, -1, 5000, "docs", 5.5, 8 / 9),
    driver.Sample(1, 1470838600.5, 26.5, op, metrics.SampleType.Normal, None, -1, -1, 5000, "docs", 6.5, 9 / 9)
]

```

The [signature for Sample](https://github.com/elastic/rally/blob/8fda86b85703e74b97b16b0623680409fd629a15/esrally/driver/driver.py#L791-L792) explains each of those parameters:

```auto
def __init__ (self, client_id, absolute_time, relative_time, task, sample_type, request_meta_data, latency_ms, service_time_ms,
                 total_ops, total_ops_unit, time_period, percent_completed):

```

Rally will first [sorting the samples by absolute time](https://github.com/elastic/rally/blob/8fda86b85703e74b97b16b0623680409fd629a15/esrally/driver/driver.py#L901):

```auto
    driver.Sample(0, 1470838595, 21, op, metrics.SampleType.Normal, None, -1, -1, 5000, "docs", 1, 1 / 9),
    driver.Sample(0, 1470838596, 22, op, metrics.SampleType.Normal, None, -1, -1, 5000, "docs", 2, 2 / 9),
    driver.Sample(0, 1470838597, 23, op, metrics.SampleType.Normal, None, -1, -1, 5000, "docs", 3, 3 / 9),
    driver.Sample(0, 1470838598, 24, op, metrics.SampleType.Normal, None, -1, -1, 5000, "docs", 4, 4 / 9),
    driver.Sample(1, 1470838598.5, 24.5, op, metrics.SampleType.Normal, None, -1, -1, 5000, "docs", 4.5, 7 / 9),
    driver.Sample(0, 1470838599, 25, op, metrics.SampleType.Normal, None, -1, -1, 5000, "docs", 5, 5 / 9),
    driver.Sample(1, 1470838599.5, 25.5, op, metrics.SampleType.Normal, None, -1, -1, 5000, "docs", 5.5, 8 / 9),
    driver.Sample(0, 1470838600, 26, op, metrics.SampleType.Normal, None, -1, -1, 5000, "docs", 6, 6 / 9),
    driver.Sample(1, 1470838600.5, 26.5, op, metrics.SampleType.Normal, None, -1, -1, 5000, "docs", 6.5, 9 / 9)

```

For each of the first four timestamps the calculated throughput is [5000 docs/s](https://github.com/elastic/rally/blob/8fda86b85703e74b97b16b0623680409fd629a15/tests/driver/driver_test.py#L423-L426) because each sample took 1s.

Starting with timestamp `1470838599` though, our calculation involves:

`4*5000 (total docs of first four samples) + 5000 (timestamp 1470838598.5) + 5000 (timestamp 1470838599) / 5 = 6000 doc/s`

Similarly for timestamp `1470838600` two more samples got collected each referencing 5000 docs/s so the throughput at that point is:

`(30000 (total docs at`1470838599`) + 5000 + 5000) / 6 = 6666.666666666667 docs/s`

This process keeps going for all samples and finally the summary output [calculates the min/median/max](https://github.com/elastic/rally/blob/8fda86b85703e74b97b16b0623680409fd629a15/esrally/reporter.py#L237-L255) throughput out of this list for **normal samples** only. Samples collected during the warm up period are not included in the summary report calculation.

---

_[View the full topic](https://discuss.elastic.co/t/how-write-throughput-is-calculated-in-rally/188997)._