More concise duty logging

[mcdee]

At current the validator logs a duty entry for every active key each epoch, which is both noisy and somewhat hard to comprehend when a validator is running many keys. This patch changes the output from key-based to slot-based, which bounds the maximum number of entries to 64 (one for attesters at each slot, one for proposer at each slot).

The only information that is lost with this more concise format is the committee index of the attester, but it shows up when the (aggregated) attestation is made so it actually just avoids duplication.

Sample output from the new format (from an interop run with 1,024 validators):

{"attesters":32,"level":"info","msg":"Attestation schedule","prefix":"validator","pubKeys":["0xb45ee2d02237","0x84398f539a64","0x95d668e77761","0x870bd2434747","0xb090aff6e74d","0xad6017ff33ec","0x91ad339cd616","0xa6d3e4f2b3e5","0xb90a59e63d66","0x851faec0a50c","0xadf6fceba8b4","0x80f0109a647b","0x939f65151b9f","0xa2a576a9ead4","0x980cab0a4aa2","0x8428f1acb3bf","0x928d2b6b1e8b","0x906af7add69c","0xb4c37ed40d2d","0xab032b66e09b","0x83dbae1b08ee","0xb9f5c800dbe8","0x893f6809ed7b","0x94c1a664baed","0x836f2b3e00df","0xa3a32b0f8b4d","0x846f3af6ac23","0xae363ffe8d6c","0x82d62ceb1242","0xa069d8c83f71","0x98f65cbdd29f","0xb8ad8a758c02"],"slot":26,"time":"2020-04-12T11:59:14+01:00"}
{"level":"info","msg":"Proposal schedule","prefix":"validator","pubKey":"0xb7d1eb9f5038","slot":26,"time":"2020-04-12T11:59:14+01:00"}

[codecov]

Codecov Report

Merging #5397 into master will not change coverage.
The diff coverage is n/a.

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##           master    #5397   +/-   ##
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  Coverage   22.44%   22.44%           
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  Files         268      268           
  Lines       22711    22711           
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  Hits         5098     5098           
  Misses      16646    16646           
  Partials      967      967           

[prestonvanloon]

Please fix

[mcdee]

Updated; will run locally for a bit to ensure the manual bits of the merge are correct.

[mcdee]

Ran this overnight and it seems fine.

Note that this does change a couple of functional lines now, rather than just the logging. There were a couple of checks that said: if duty.Status == ethpb.ValidatorStatus_ACTIVE that I've changed to if duty.Status == ethpb.ValidatorStatus_ACTIVE || duty.Status == ethpb.ValidatorStatus_EXITING, as exiting validators still have assignments and so their subnets should be included. @terencechain could you confirm you're happy with this change?

(Also, the separation of the logging code does mean that there are two chunks of code now that are basically the same and could be spun in to a function now, but that's outside of the scope of this patch).

[terencechain]

I dont quite understand (slot / params.BeaconConfig().SlotsPerEpoch) * params.BeaconConfig().SlotsPerEpoch

Do you mean to do slot - epoch_start_slot?

[mcdee]

Yes; slot at the beginning of this slot's epoch. Is there a helper for it?

[shayzluf]

helpers.StartSlot()

[mcdee]

Thanks; updated to use the helpers.