Discover relayers — zkScatter Docs

Relayers are bonded operators. Apps must:

Read the on-chain registry to find who’s registered.
Probe each one’s HTTP /api/info to filter for “live and matching.”
Surface their fee, profile, and supported pairs in the UI.

One call


import { loadRelayersWithApiInfo } from "@zkscatter/sdk/relayer";
 
const relayers = await loadRelayersWithApiInfo(
  network.contracts.relayerRegistry,
  readProvider,
  { probeTimeoutMs: 3000 },
);

Returns RelayerInfo[] — each row is the on-chain state plus an api?: RelayerApiInfo block when the probe succeeded, plus a boolean online. Probes run in parallel.

Render a picker


function RelayerPicker({
  relayers,
  selected,
  onSelect,
}: {
  relayers: RelayerInfo[];
  selected: string | null;
  onSelect: (address: string) => void;
}) {
  return (
    <ul>
      {relayers.map((r) => (
        <li key={r.address}>
          <button
            onClick={() => onSelect(r.address)}
            disabled={!r.online}
            aria-pressed={selected === r.address}
          >
            <strong>{r.api?.name ?? "Relayer"}</strong>
            <span> · {Number(r.fee) / 100}% fee</span>
            <span> · {r.online ? "online" : "offline"}</span>
          </button>
        </li>
      ))}
    </ul>
  );
}

Profile sanitization

Relayer profiles (name, description, logoUrl) come from untrusted operators. Always sanitize before rendering:


import { sanitizeProfile } from "@zkscatter/sdk/relayer";
 
const safe = sanitizeProfile(rawApiResponse.profile);
if (!safe) return; // discard malformed

Caps lengths, restricts URL schemes to https://, filters out control characters.

Manual selection vs. auto-routing

The reference apps default to auto-routing: pick the lowest-fee online relayer that supports the chosen pair. Power users can override via a manual selector.


function pickRelayer(relayers: RelayerInfo[], pair: string): RelayerInfo | undefined {
  return relayers
    .filter((r) => r.online && r.api?.pairs?.includes(pair))
    .sort((a, b) => Number(a.fee) - Number(b.fee))[0];
}

Refresh policy

On wallet connect — fresh fetch.
Every 60s while idle — keep the picker truthful.
Before submit — re-probe the chosen relayer (client.getInfo()) to fail fast on a stale “online” flag.

Cross-relayer order discovery

For pair-level liquidity views (not just matching), use the shared orderbook instead — single endpoint, lower fan-out.