WIP: No get_balances_by_epoch API method in beacon clients

[ongrid]

Preliminary, still in research. Prysm and Lighthouse beacon clients have no epoch argument for the validator's balance API request. This can significantly affect the oracle's algorithm.

On the Zoom on 02 Oct call decided to raise the question in clients' discord (+ teku client)

[ongrid]

Update: It's possible but needs normalization

In Prysm: available directly

GET /validators/balances?epoch=1331

{'epoch': '1331',
 'balances': [{'publicKey': 'j88oiWqF5edu6eUIQ44j5yU9oaI6ZQHjp9VhglINvPTNtErzJnMYGI8fQWg0IUba',
   'index': '0',
   'balance': '32077428710'},
  {'publicKey': 'hz5z7os+T88dL7DxA2uplqyZELWzSPZDi1+O9QhX1NqQddAhip0bmanq4jWjlwPh',
   'index': '1',
   'balance': '63923454600'},
  {'publicKey': 'jC9TXTvsZflctLpFVWbk7D3o2lwTpoFpng+A15Qtb9y87xjIzxj52hSqN5vdbSnF',
   'index': '2',
   'balance': '31923454600'},
  {'publicKey': 'qNm1tizDEUmtWKKBoik80/TcoRhVyYmD52/7YEedjpjlWS5UFfBACooj792EKzYF',
   'index': '3',
   'balance': '32074043852'},

implementation

In Lighthouse available indirectly by specifying state_root

post('/beacon/validators', data=json.dumps({'state_root':state_root,'pubkeys':['0xb99afaeda97ab060ded6178e006469eb28a0e1ee10ba4ececad06a5b80f6a34f6d1b1dab9418f6bf9c492995fbe2ef29']}))

[{'pubkey': '0xb99afaeda97ab060ded6178e006469eb28a0e1ee10ba4ececad06a5b80f6a34f6d1b1dab9418f6bf9c492995fbe2ef29',
  'validator_index': 678,
  'balance': 32000866425,
  'validator': {'pubkey': '0xb99afaeda97ab060ded6178e006469eb28a0e1ee10ba4ececad06a5b80f6a34f6d1b1dab9418f6bf9c492995fbe2ef29',
   'withdrawal_credentials': '0x0010361af430aa7ab4a9567eaaca50ec5e02315ca1513d9ee8d73bde96370091',
   'effective_balance': 32000000000,
   'slashed': False,
   'activation_eligibility_epoch': 0,
   'activation_epoch': 0,
   'exit_epoch': 18446744073709551615,
   'withdrawable_epoch': 18446744073709551615}}]

State root can be found by slot.

get('/beacon/state_root?slot=1000')

Slot can be calculated deterministically by unixtime and network constants.

Result:

• It's possible to query validators' balances for the given epochs or slots
• but need to find the correct algorithm for lighthouse
• then need to check if validator sets and balances are same

[ongrid]

Lighthouse supports balance retrieval by given slot (which gets converted to epoch under the hood, divided by 32)

lh_beacon.get('/beacon/states/15588/validators/' + validator_key)

{'data': {'index': '4504',
  'balance': '32034794204',
  'status': 'Active',
  'validator': {'pubkey': '0x87a8e7a264837c85695a4648a78f4aa53a9ff635f9c2302d35f845f44814adf6c64fb9da899b8eae0cdc314e6a2291ec',
   'withdrawal_credentials': '0x00363abe96b09944581b8d523bb8047bfbf30640bb26774436d01066b2ed9dd1',
   'effective_balance': '32000000000',
   'slashed': False,
   'activation_eligibility_epoch': '51',
   'activation_epoch': '213',
   'exit_epoch': '18446744073709551615',
   'withdrawable_epoch': '18446744073709551615'}}}

Prysm supports state retrieval by epoch. Also needs conversion to base64 format

prysm.get('/validators/balances?epoch=486&publicKeys=' + hex_to_base64(deposit_data['pubkey']))

{'epoch': '486',
 'balances': [{'publicKey': 'jPzS0lUD8fU9eeGRPFJfIyOhSv08FxjRNmbJ4KyepgFOtS0iYR58kx74TpD577B/',
   'index': '4144',
   'balance': '32045769543',
   'status': 'ACTIVE'}],
 'nextPageToken': '',
 'totalSize': 1}

• Result: both clients support all methods we need for universal and deterministic states
• More examples
• Improved spec for RC-2