Fix `Provided topic already has an active subscription running` log

[nalepae]

Describe the bug

From time to time, after a BN start, a lot of

level=debug msg="Provided topic already has an active subscription running" prefix=sync topic="/eth2/ad532ceb/beacon_attestation_3/ssz_snappy"

logs are displayed.

Generally, these logs disappear after a reboot.

We should:

1. Find if there logs are expected, and why.
2. If they are not expected, fix the root cause. If they are expected, reduce the log volume

[nalepae]

It seems this issue is 100% reproducible using Kurtosis starting at Fulu with the following configuration file:

participants:
  # Super-nodes
  - el_type: geth
    el_image: ethpandaops/geth:fusaka-devnet-3
    cl_type: prysm
    vc_image: prysm-vc-custom-image:latest
    cl_image: prysm-bn-custom-image:latest
    count: 2
    supernode: true
    cl_extra_params:
      - --subscribe-all-subnets
    vc_extra_params:
      - --verbosity=debug
  # Full-nodes
  - el_type: geth
    el_image: ethpandaops/geth:fusaka-devnet-3
    cl_type: prysm
    vc_image: prysm-vc-custom-image:latest
    cl_image: prysm-bn-custom-image:latest
    count: 2
    cl_extra_params:
      - --subscribe-all-subnets
    vc_extra_params:
      - --verbosity=debug

additional_services:
  - dora
  - spamoor

spamoor_params:
  image: ethpandaops/spamoor:master
  max_mem: 4000
  spammers:
    - scenario: eoatx
      config:
        throughput: 200
    - scenario: blobs
      config:
        throughput: 20

network_params:
  fulu_fork_epoch: 0
  withdrawal_type: "0x02"
  preset: mainnet
  seconds_per_slot: 6

global_log_level: debug

The issues seems not to be 100% reproducible if setting fulu_fork_epoch to a value higher than 0.

[nalepae]

It seems this issue started with the following PR:

• refactor subscription code to enable peer discovery asap #15660

Note:
Checking out to the commit corresponding to this PR won't work with the previous Kurtosis configuration, because it does not support Fulu genesis.
For this specific commit (or the previous one) to work with this Kurtosis configuration, running the following command:

git cherry-pick 35bc9b1a0f602853abe31c7ff7b1f0b187dcefab

is needed.

[nalepae]

Not sure it is related, we also have these error logs:

[2025-09-26 13:03:20.00] ERROR sync: Could not register validator for topic error=duplicate validator for topic /eth2/98301011/sync_committee_contribution_and_proof/ssz_snappy topic=/eth2/98301011/sync_committee_contribution_and_proof/ssz_snappy
[2025-09-26 13:03:20.00] ERROR sync: Could not register validator for topic error=duplicate validator for topic /eth2/98301011/voluntary_exit/ssz_snappy topic=/eth2/98301011/voluntary_exit/ssz_snappy
[2025-09-26 13:03:20.00] ERROR sync: Could not register validator for topic error=duplicate validator for topic /eth2/98301011/beacon_aggregate_and_proof/ssz_snappy topic=/eth2/98301011/beacon_aggregate_and_proof/ssz_snappy
[2025-09-26 13:03:20.00] ERROR sync: Could not register validator for topic error=duplicate validator for topic /eth2/98301011/proposer_slashing/ssz_snappy topic=/eth2/98301011/proposer_slashing/ssz_snappy
[2025-09-26 13:03:20.00] ERROR sync: Could not register validator for topic error=duplicate validator for topic /eth2/98301011/bls_to_execution_change/ssz_snappy topic=/eth2/98301011/bls_to_execution_change/ssz_snappy
[2025-09-26 13:03:20.00] ERROR sync: Could not register validator for topic error=duplicate validator for topic /eth2/98301011/attester_slashing/ssz_snappy topic=/eth2/98301011/attester_slashing/ssz_snappy

[nalepae]

Yes, very probably related. The 2 logs come from the same function.