Get validator duties for Prysm (find largest gap in which to update for that $0.04 it will save/benefit you)

get_validator_duties.py

"""
Originally developed by https://github.com/pietjepuk2
Ported to Prysm by https://twitter.com/mohamedmansour
Support my gitcoin https://gitcoin.co/mohamedmansour
"""
import json
import math
import time
import urllib
import sys

from datetime import datetime, timedelta, timezone

import requests

SLOTS_PER_EPOCH = 32
SECONDS_PER_SLOT = 12

def main(validators_indices, eth2_api_url="http://localhost:3500/eth/v1alpha1/"):
    def api_get(endpoint):
        try:
            response = requests.get(f"{eth2_api_url}{endpoint}")
        except requests.exceptions.RequestException as e:
            print(f"Error: {e}")
            sys.exit()

        json = response.json()
        if "error" in json:
            error_message = json["message"]
            print(f"Error: {error_message}")
            sys.exit(1)
        return json

    dt = datetime.strptime(api_get("node/genesis")["genesisTime"], "%Y-%m-%dT%H:%M:%SZ")
    genesis_timestamp = dt.replace(tzinfo=timezone.utc).timestamp()

    chainhead = api_get("beacon/chainhead")
    head_slot = int(chainhead["headSlot"])
    epoch = int(chainhead["headEpoch"])

    attestation_duties = {}

    for validator_index in validators_indices:
        validator = api_get(f"validator?index={validator_index}")
        public_key = urllib.parse.quote(validator['publicKey'], safe='')
        epoch_data = api_get(f"validator/duties?epoch={epoch}&publicKeys={public_key}")
        cur_epoch_data = epoch_data['currentEpochDuties']
        next_epoch_data = epoch_data['nextEpochDuties']
        for d in (*cur_epoch_data, *next_epoch_data):
            attestation_duties.setdefault(int(d["attesterSlot"]), []).append(d["validatorIndex"])
        if 'proposerSlots' in cur_epoch_data and len(cur_epoch_data['proposerSlots']) > 0:
            proposerSlots = cur_epoch_data['proposerSlots']
            for d in proposerSlots:
                attestation_duties.setdefault(int(proposerSlots["proposerSlot"]), []).append(d["validatorIndex"] + " (proposer)")
        

    attestation_duties = {k: v for k, v in sorted(attestation_duties.items()) if k > head_slot}

    validators_indices_set = set(validators_indices)
    duties = attestation_duties.copy()
    duties = dict(sorted(duties.items()))

    # Also insert (still unknown) attestation duties at epoch after next,
    # assuming worst case of having to attest at its first slot
    first_slot_epoch_p2 = (epoch + 2) * SLOTS_PER_EPOCH
    attestation_duties[first_slot_epoch_p2] = []

    print(f"Calculating attestation slots and gaps for validators:")
    print(f"  {validators_indices}")

    print("\nUpcoming voting slots and gaps")
    print("(Gap in seconds)")
    print("(slot/epoch - time range - validators)")
    print("*" * 80)

    prev_end_time = datetime.now()
    longest_gap = timedelta(seconds=0)
    gap_time_range = (None, None)

    for slot, validators in attestation_duties.items():
        slot_start = datetime.fromtimestamp(genesis_timestamp + slot * SECONDS_PER_SLOT)
        slot_end = slot_start + timedelta(seconds=SECONDS_PER_SLOT)

        gap = slot_start - prev_end_time
        print(f"Gap - {math.floor((slot_start - prev_end_time).total_seconds())} seconds")

        if validators:
            print(
                f"  {slot}/{slot // SLOTS_PER_EPOCH}"
                f" - {slot_start.strftime('%H:%M:%S')} until {slot_end.strftime('%H:%M:%S')}"
                f" - [{', '.join(validators)}]"
            )
        else:
            assert slot % SLOTS_PER_EPOCH == 0

        if gap > longest_gap:
            longest_gap = gap
            gap_time_range = (prev_end_time, slot_start)

        prev_end_time = slot_end

    print("\nLongest gap (first):")
    print("*" * 80)
    print(
        f"{longest_gap.total_seconds()} seconds"
        f" ({int(longest_gap.total_seconds()) // SECONDS_PER_SLOT} slots),"
        f" from {gap_time_range[0].strftime('%H:%M:%S')}"
        f" until {gap_time_range[1].strftime('%H:%M:%S')}"
    )

if __name__ == "__main__":
    import argparse
    parser = argparse.ArgumentParser(
        description="Show validator duties of current and next epoch to find largest gap."
    )
    parser.add_argument("indices", metavar="index", type=int, nargs="*", help="validator indices")
    args = parser.parse_args()
    main(args.indices)

Unfortunately the new release of Prysm (v5.1.1) switched to using the standardized beacon-APIs:

"The gRPC gateway has been deprecated from Prysm in this release. If you need JSON data, consider the standardized beacon-APIs."

Hopefully you can update your script as well sometime in the future so it works with the new version.