[data] Change counts of metrics to rates of metrics

[omatthew98]

Why are these changes needed?

This changes the counts of various metrics for ray data to rates for those same metrics. This allows for easier visualization.

There are a variety of different approaches we can take here to calculate the rates:

• Window of rate: We can compute the rate over a time window of specified size, the relevancy of this depends on the function chosen.
• Function:
  • rate: Calculates the average per-second rate of increase of a time series over a specified range. Less volatile, produces more smoothing depending on the window.
  • irate: Calculates the per-second rate of increase based on the two most recent data points. More volatile and reactive, less smoothing applied, not as sensitive to the window size because last two data points are used.

Examples:

Yellow: rate[30s] (Have selected this as this seems to be the best balance between the various options)
Orange: irate[30s]
Blue: rate[5m]

Sample code

import ray
import time

context = ray.init(include_dashboard=True)
print(context.dashboard_url)

def f(x):
    time.sleep(0.1)
    return x

def g(x):
    time.sleep(0.1)
    return x

ray.data.range(10000).map(f).materialize()

Related issue number

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  • I've added any new APIs to the API Reference. For example, if I added a
    method in Tune, I've added it in doc/source/tune/api/ under the
    corresponding .rst file.
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• Testing Strategy
  • Unit tests
  • Release tests
  • This PR is not tested :(

[scottjlee]

for unit, let's use: "bytes/sec(SI)". this will make sure the auto unit-conversion from Grafana works as intended.

[scottjlee]

after making this change, could you also share a screenshot of the dashboard with the fixes, to verify that the units properly show up on the axes + the conversion works (e.g. once we start hitting 100's of MBs, this should display as MB/s instead of B/s)

[omatthew98]

Updated it to Bps because that is what Grafana expects for this unit (rather than the full bytes/sec(SI)).