/*
This file is part of GNU Taler
(C) 2019 GNUnet e.V.
GNU Taler is free software; you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the Free Software
Foundation; either version 3, or (at your option) any later version.
GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with
GNU Taler; see the file COPYING. If not, see
*/
import { Amounts, AmountJson } from "../util/amounts";
import {
DenominationRecord,
Stores,
CoinStatus,
RefreshPlanchet,
CoinRecord,
RefreshSessionRecord,
RefreshGroupRecord,
CoinSourceType,
} from "../types/dbTypes";
import { amountToPretty } from "../util/helpers";
import { TransactionHandle } from "../util/query";
import { InternalWalletState, EXCHANGE_COINS_LOCK } from "./state";
import { Logger } from "../util/logging";
import { selectWithdrawalDenominations, isWithdrawableDenom } from "./withdraw";
import { updateExchangeFromUrl } from "./exchanges";
import {
TalerErrorDetails,
CoinPublicKey,
RefreshReason,
RefreshGroupId,
} from "../types/walletTypes";
import { guardOperationException } from "./errors";
import { NotificationType } from "../types/notifications";
import { getRandomBytes, encodeCrock } from "../crypto/talerCrypto";
import {
getTimestampNow,
Duration,
Timestamp,
isTimestampExpired,
durationFromSpec,
timestampMin,
timestampAddDuration,
timestampDifference,
durationMax,
durationMul,
} from "../util/time";
import { readSuccessResponseJsonOrThrow } from "../util/http";
import {
codecForExchangeMeltResponse,
codecForExchangeRevealResponse,
} from "../types/talerTypes";
import { URL } from "../util/url";
import { checkDbInvariant } from "../util/invariants";
import { initRetryInfo, updateRetryInfoTimeout } from "../util/retries";
import { WALLET_EXCHANGE_PROTOCOL_VERSION } from "./versions";
import { RefreshNewDenomInfo } from "../types/cryptoTypes";
const logger = new Logger("refresh.ts");
/**
* Get the amount that we lose when refreshing a coin of the given denomination
* with a certain amount left.
*
* If the amount left is zero, then the refresh cost
* is also considered to be zero. If a refresh isn't possible (e.g. due to lack of
* the right denominations), then the cost is the full amount left.
*
* Considers refresh fees, withdrawal fees after refresh and amounts too small
* to refresh.
*/
export function getTotalRefreshCost(
denoms: DenominationRecord[],
refreshedDenom: DenominationRecord,
amountLeft: AmountJson,
): AmountJson {
const withdrawAmount = Amounts.sub(amountLeft, refreshedDenom.feeRefresh)
.amount;
const withdrawDenoms = selectWithdrawalDenominations(withdrawAmount, denoms);
const resultingAmount = Amounts.add(
Amounts.getZero(withdrawAmount.currency),
...withdrawDenoms.selectedDenoms.map(
(d) => Amounts.mult(d.denom.value, d.count).amount,
),
).amount;
const totalCost = Amounts.sub(amountLeft, resultingAmount).amount;
logger.trace(
`total refresh cost for ${amountToPretty(amountLeft)} is ${amountToPretty(
totalCost,
)}`,
);
return totalCost;
}
/**
* Create a refresh session inside a refresh group.
*/
async function refreshCreateSession(
ws: InternalWalletState,
refreshGroupId: string,
coinIndex: number,
): Promise {
logger.trace(
`creating refresh session for coin ${coinIndex} in refresh group ${refreshGroupId}`,
);
const refreshGroup = await ws.db.get(Stores.refreshGroups, refreshGroupId);
if (!refreshGroup) {
return;
}
if (refreshGroup.finishedPerCoin[coinIndex]) {
return;
}
const existingRefreshSession = refreshGroup.refreshSessionPerCoin[coinIndex];
if (existingRefreshSession) {
return;
}
const oldCoinPub = refreshGroup.oldCoinPubs[coinIndex];
const coin = await ws.db.get(Stores.coins, oldCoinPub);
if (!coin) {
throw Error("Can't refresh, coin not found");
}
const exchange = await updateExchangeFromUrl(ws, coin.exchangeBaseUrl);
if (!exchange) {
throw Error("db inconsistent: exchange of coin not found");
}
const oldDenom = await ws.db.get(Stores.denominations, [
exchange.baseUrl,
coin.denomPubHash,
]);
if (!oldDenom) {
throw Error("db inconsistent: denomination for coin not found");
}
const availableDenoms: DenominationRecord[] = await ws.db
.iterIndex(Stores.denominations.exchangeBaseUrlIndex, exchange.baseUrl)
.toArray();
const availableAmount = Amounts.sub(
refreshGroup.inputPerCoin[coinIndex],
oldDenom.feeRefresh,
).amount;
const newCoinDenoms = selectWithdrawalDenominations(
availableAmount,
availableDenoms,
);
if (newCoinDenoms.selectedDenoms.length === 0) {
logger.trace(
`not refreshing, available amount ${amountToPretty(
availableAmount,
)} too small`,
);
await ws.db.runWithWriteTransaction(
[Stores.coins, Stores.refreshGroups],
async (tx) => {
const rg = await tx.get(Stores.refreshGroups, refreshGroupId);
if (!rg) {
return;
}
rg.finishedPerCoin[coinIndex] = true;
let allDone = true;
for (const f of rg.finishedPerCoin) {
if (!f) {
allDone = false;
break;
}
}
if (allDone) {
rg.timestampFinished = getTimestampNow();
rg.retryInfo = initRetryInfo(false);
}
await tx.put(Stores.refreshGroups, rg);
},
);
ws.notify({ type: NotificationType.RefreshUnwarranted });
return;
}
const sessionSecretSeed = encodeCrock(getRandomBytes(64));
// Store refresh session for this coin in the database.
await ws.db.runWithWriteTransaction(
[Stores.refreshGroups, Stores.coins],
async (tx) => {
const rg = await tx.get(Stores.refreshGroups, refreshGroupId);
if (!rg) {
return;
}
if (rg.refreshSessionPerCoin[coinIndex]) {
return;
}
rg.refreshSessionPerCoin[coinIndex] = {
norevealIndex: undefined,
sessionSecretSeed: sessionSecretSeed,
newDenoms: newCoinDenoms.selectedDenoms.map((x) => ({
count: x.count,
denomPubHash: x.denom.denomPubHash,
})),
amountRefreshOutput: newCoinDenoms.totalCoinValue,
};
await tx.put(Stores.refreshGroups, rg);
},
);
logger.info(
`created refresh session for coin #${coinIndex} in ${refreshGroupId}`,
);
ws.notify({ type: NotificationType.RefreshStarted });
}
function getRefreshRequestTimeout(rg: RefreshGroupRecord): Duration {
return { d_ms: 5000 };
}
async function refreshMelt(
ws: InternalWalletState,
refreshGroupId: string,
coinIndex: number,
): Promise {
const refreshGroup = await ws.db.get(Stores.refreshGroups, refreshGroupId);
if (!refreshGroup) {
return;
}
const refreshSession = refreshGroup.refreshSessionPerCoin[coinIndex];
if (!refreshSession) {
return;
}
if (refreshSession.norevealIndex !== undefined) {
return;
}
const oldCoin = await ws.db.get(
Stores.coins,
refreshGroup.oldCoinPubs[coinIndex],
);
checkDbInvariant(!!oldCoin, "melt coin doesn't exist");
const oldDenom = await ws.db.get(Stores.denominations, [
oldCoin.exchangeBaseUrl,
oldCoin.denomPubHash,
]);
checkDbInvariant(!!oldDenom, "denomination for melted coin doesn't exist");
const newCoinDenoms: RefreshNewDenomInfo[] = [];
for (const dh of refreshSession.newDenoms) {
const newDenom = await ws.db.get(Stores.denominations, [
oldCoin.exchangeBaseUrl,
dh.denomPubHash,
]);
checkDbInvariant(
!!newDenom,
"new denomination for refresh not in database",
);
newCoinDenoms.push({
count: dh.count,
denomPub: newDenom.denomPub,
feeWithdraw: newDenom.feeWithdraw,
value: newDenom.value,
});
}
const derived = await ws.cryptoApi.deriveRefreshSession({
kappa: 3,
meltCoinDenomPubHash: oldCoin.denomPubHash,
meltCoinPriv: oldCoin.coinPriv,
meltCoinPub: oldCoin.coinPub,
feeRefresh: oldDenom.feeRefresh,
newCoinDenoms,
sessionSecretSeed: refreshSession.sessionSecretSeed,
});
const reqUrl = new URL(
`coins/${oldCoin.coinPub}/melt`,
oldCoin.exchangeBaseUrl,
);
const meltReq = {
coin_pub: oldCoin.coinPub,
confirm_sig: derived.confirmSig,
denom_pub_hash: oldCoin.denomPubHash,
denom_sig: oldCoin.denomSig,
rc: derived.hash,
value_with_fee: Amounts.stringify(derived.meltValueWithFee),
};
logger.trace(`melt request for coin:`, meltReq);
const resp = await ws.runSequentialized([EXCHANGE_COINS_LOCK], async () => {
return await ws.http.postJson(reqUrl.href, meltReq, {
timeout: getRefreshRequestTimeout(refreshGroup),
});
});
const meltResponse = await readSuccessResponseJsonOrThrow(
resp,
codecForExchangeMeltResponse(),
);
const norevealIndex = meltResponse.noreveal_index;
refreshSession.norevealIndex = norevealIndex;
await ws.db.mutate(Stores.refreshGroups, refreshGroupId, (rg) => {
const rs = rg.refreshSessionPerCoin[coinIndex];
if (rg.timestampFinished) {
return;
}
if (!rs) {
return;
}
if (rs.norevealIndex !== undefined) {
return;
}
rs.norevealIndex = norevealIndex;
return rg;
});
ws.notify({
type: NotificationType.RefreshMelted,
});
}
async function refreshReveal(
ws: InternalWalletState,
refreshGroupId: string,
coinIndex: number,
): Promise {
const refreshGroup = await ws.db.get(Stores.refreshGroups, refreshGroupId);
if (!refreshGroup) {
return;
}
const refreshSession = refreshGroup.refreshSessionPerCoin[coinIndex];
if (!refreshSession) {
return;
}
const norevealIndex = refreshSession.norevealIndex;
if (norevealIndex === undefined) {
throw Error("can't reveal without melting first");
}
const oldCoin = await ws.db.get(
Stores.coins,
refreshGroup.oldCoinPubs[coinIndex],
);
checkDbInvariant(!!oldCoin, "melt coin doesn't exist");
const oldDenom = await ws.db.get(Stores.denominations, [
oldCoin.exchangeBaseUrl,
oldCoin.denomPubHash,
]);
checkDbInvariant(!!oldDenom, "denomination for melted coin doesn't exist");
const newCoinDenoms: RefreshNewDenomInfo[] = [];
for (const dh of refreshSession.newDenoms) {
const newDenom = await ws.db.get(Stores.denominations, [
oldCoin.exchangeBaseUrl,
dh.denomPubHash,
]);
checkDbInvariant(
!!newDenom,
"new denomination for refresh not in database",
);
newCoinDenoms.push({
count: dh.count,
denomPub: newDenom.denomPub,
feeWithdraw: newDenom.feeWithdraw,
value: newDenom.value,
});
}
const derived = await ws.cryptoApi.deriveRefreshSession({
kappa: 3,
meltCoinDenomPubHash: oldCoin.denomPubHash,
meltCoinPriv: oldCoin.coinPriv,
meltCoinPub: oldCoin.coinPub,
feeRefresh: oldDenom.feeRefresh,
newCoinDenoms,
sessionSecretSeed: refreshSession.sessionSecretSeed,
});
const privs = Array.from(derived.transferPrivs);
privs.splice(norevealIndex, 1);
const planchets = derived.planchetsForGammas[norevealIndex];
if (!planchets) {
throw Error("refresh index error");
}
const meltCoinRecord = await ws.db.get(
Stores.coins,
refreshGroup.oldCoinPubs[coinIndex],
);
if (!meltCoinRecord) {
throw Error("inconsistent database");
}
const evs = planchets.map((x: RefreshPlanchet) => x.coinEv);
const newDenomsFlat: string[] = [];
const linkSigs: string[] = [];
for (let i = 0; i < refreshSession.newDenoms.length; i++) {
const dsel = refreshSession.newDenoms[i];
for (let j = 0; j < dsel.count; j++) {
const newCoinIndex = linkSigs.length;
const linkSig = await ws.cryptoApi.signCoinLink(
meltCoinRecord.coinPriv,
dsel.denomPubHash,
meltCoinRecord.coinPub,
derived.transferPubs[norevealIndex],
planchets[newCoinIndex].coinEv,
);
linkSigs.push(linkSig);
newDenomsFlat.push(dsel.denomPubHash);
}
}
const req = {
coin_evs: evs,
new_denoms_h: newDenomsFlat,
rc: derived.hash,
transfer_privs: privs,
transfer_pub: derived.transferPubs[norevealIndex],
link_sigs: linkSigs,
};
const reqUrl = new URL(
`refreshes/${derived.hash}/reveal`,
oldCoin.exchangeBaseUrl,
);
const resp = await ws.runSequentialized([EXCHANGE_COINS_LOCK], async () => {
return await ws.http.postJson(reqUrl.href, req, {
timeout: getRefreshRequestTimeout(refreshGroup),
});
});
const reveal = await readSuccessResponseJsonOrThrow(
resp,
codecForExchangeRevealResponse(),
);
const coins: CoinRecord[] = [];
for (let i = 0; i < refreshSession.newDenoms.length; i++) {
for (let j = 0; j < refreshSession.newDenoms[i].count; j++) {
const newCoinIndex = coins.length;
const denom = await ws.db.get(Stores.denominations, [
oldCoin.exchangeBaseUrl,
refreshSession.newDenoms[i].denomPubHash,
]);
if (!denom) {
console.error("denom not found");
continue;
}
const pc = derived.planchetsForGammas[norevealIndex][newCoinIndex];
const denomSig = await ws.cryptoApi.rsaUnblind(
reveal.ev_sigs[newCoinIndex].ev_sig,
pc.blindingKey,
denom.denomPub,
);
const coin: CoinRecord = {
blindingKey: pc.blindingKey,
coinPriv: pc.privateKey,
coinPub: pc.publicKey,
currentAmount: denom.value,
denomPub: denom.denomPub,
denomPubHash: denom.denomPubHash,
denomSig,
exchangeBaseUrl: oldCoin.exchangeBaseUrl,
status: CoinStatus.Fresh,
coinSource: {
type: CoinSourceType.Refresh,
oldCoinPub: refreshGroup.oldCoinPubs[coinIndex],
},
suspended: false,
coinEvHash: pc.coinEv,
};
coins.push(coin);
}
}
await ws.db.runWithWriteTransaction(
[Stores.coins, Stores.refreshGroups],
async (tx) => {
const rg = await tx.get(Stores.refreshGroups, refreshGroupId);
if (!rg) {
logger.warn("no refresh session found");
return;
}
const rs = rg.refreshSessionPerCoin[coinIndex];
if (!rs) {
return;
}
rg.finishedPerCoin[coinIndex] = true;
let allDone = true;
for (const f of rg.finishedPerCoin) {
if (!f) {
allDone = false;
break;
}
}
if (allDone) {
rg.timestampFinished = getTimestampNow();
rg.retryInfo = initRetryInfo(false);
}
for (const coin of coins) {
await tx.put(Stores.coins, coin);
}
await tx.put(Stores.refreshGroups, rg);
},
);
logger.trace("refresh finished (end of reveal)");
ws.notify({
type: NotificationType.RefreshRevealed,
});
}
async function incrementRefreshRetry(
ws: InternalWalletState,
refreshGroupId: string,
err: TalerErrorDetails | undefined,
): Promise {
await ws.db.runWithWriteTransaction([Stores.refreshGroups], async (tx) => {
const r = await tx.get(Stores.refreshGroups, refreshGroupId);
if (!r) {
return;
}
if (!r.retryInfo) {
return;
}
r.retryInfo.retryCounter++;
updateRetryInfoTimeout(r.retryInfo);
r.lastError = err;
await tx.put(Stores.refreshGroups, r);
});
if (err) {
ws.notify({ type: NotificationType.RefreshOperationError, error: err });
}
}
/**
* Actually process a refresh group that has been created.
*/
export async function processRefreshGroup(
ws: InternalWalletState,
refreshGroupId: string,
forceNow = false,
): Promise {
await ws.memoProcessRefresh.memo(refreshGroupId, async () => {
const onOpErr = (e: TalerErrorDetails): Promise =>
incrementRefreshRetry(ws, refreshGroupId, e);
return await guardOperationException(
async () => await processRefreshGroupImpl(ws, refreshGroupId, forceNow),
onOpErr,
);
});
}
async function resetRefreshGroupRetry(
ws: InternalWalletState,
refreshSessionId: string,
): Promise {
await ws.db.mutate(Stores.refreshGroups, refreshSessionId, (x) => {
if (x.retryInfo.active) {
x.retryInfo = initRetryInfo();
}
return x;
});
}
async function processRefreshGroupImpl(
ws: InternalWalletState,
refreshGroupId: string,
forceNow: boolean,
): Promise {
if (forceNow) {
await resetRefreshGroupRetry(ws, refreshGroupId);
}
const refreshGroup = await ws.db.get(Stores.refreshGroups, refreshGroupId);
if (!refreshGroup) {
return;
}
if (refreshGroup.timestampFinished) {
return;
}
const ps = refreshGroup.oldCoinPubs.map((x, i) =>
processRefreshSession(ws, refreshGroupId, i),
);
await Promise.all(ps);
logger.trace("refresh finished");
}
async function processRefreshSession(
ws: InternalWalletState,
refreshGroupId: string,
coinIndex: number,
): Promise {
logger.trace(
`processing refresh session for coin ${coinIndex} of group ${refreshGroupId}`,
);
let refreshGroup = await ws.db.get(Stores.refreshGroups, refreshGroupId);
if (!refreshGroup) {
return;
}
if (refreshGroup.finishedPerCoin[coinIndex]) {
return;
}
if (!refreshGroup.refreshSessionPerCoin[coinIndex]) {
await refreshCreateSession(ws, refreshGroupId, coinIndex);
refreshGroup = await ws.db.get(Stores.refreshGroups, refreshGroupId);
if (!refreshGroup) {
return;
}
}
const refreshSession = refreshGroup.refreshSessionPerCoin[coinIndex];
if (!refreshSession) {
if (!refreshGroup.finishedPerCoin[coinIndex]) {
throw Error(
"BUG: refresh session was not created and coin not marked as finished",
);
}
return;
}
if (refreshSession.norevealIndex === undefined) {
await refreshMelt(ws, refreshGroupId, coinIndex);
}
await refreshReveal(ws, refreshGroupId, coinIndex);
}
/**
* Create a refresh group for a list of coins.
*
* Refreshes the remaining amount on the coin, effectively capturing the remaining
* value in the refresh group.
*
* The caller must ensure that
* the remaining amount was updated correctly before the coin was deposited or
* credited.
*
* The caller must also ensure that the coins that should be refreshed exist
* in the current database transaction.
*/
export async function createRefreshGroup(
ws: InternalWalletState,
tx: TransactionHandle<
| typeof Stores.denominations
| typeof Stores.coins
| typeof Stores.refreshGroups
>,
oldCoinPubs: CoinPublicKey[],
reason: RefreshReason,
): Promise {
const refreshGroupId = encodeCrock(getRandomBytes(32));
const inputPerCoin: AmountJson[] = [];
const estimatedOutputPerCoin: AmountJson[] = [];
const denomsPerExchange: Record = {};
const getDenoms = async (
exchangeBaseUrl: string,
): Promise => {
if (denomsPerExchange[exchangeBaseUrl]) {
return denomsPerExchange[exchangeBaseUrl];
}
const allDenoms = await tx
.iterIndexed(Stores.denominations.exchangeBaseUrlIndex, exchangeBaseUrl)
.filter((x) => {
return isWithdrawableDenom(x);
});
denomsPerExchange[exchangeBaseUrl] = allDenoms;
return allDenoms;
};
for (const ocp of oldCoinPubs) {
const coin = await tx.get(Stores.coins, ocp.coinPub);
checkDbInvariant(!!coin, "coin must be in database");
const denom = await tx.get(Stores.denominations, [
coin.exchangeBaseUrl,
coin.denomPubHash,
]);
checkDbInvariant(
!!denom,
"denomination for existing coin must be in database",
);
const refreshAmount = coin.currentAmount;
inputPerCoin.push(refreshAmount);
coin.currentAmount = Amounts.getZero(refreshAmount.currency);
coin.status = CoinStatus.Dormant;
await tx.put(Stores.coins, coin);
const denoms = await getDenoms(coin.exchangeBaseUrl);
const cost = getTotalRefreshCost(denoms, denom, refreshAmount);
const output = Amounts.sub(refreshAmount, cost).amount;
estimatedOutputPerCoin.push(output);
}
const refreshGroup: RefreshGroupRecord = {
timestampFinished: undefined,
finishedPerCoin: oldCoinPubs.map((x) => false),
lastError: undefined,
lastErrorPerCoin: {},
oldCoinPubs: oldCoinPubs.map((x) => x.coinPub),
reason,
refreshGroupId,
refreshSessionPerCoin: oldCoinPubs.map((x) => undefined),
retryInfo: initRetryInfo(),
inputPerCoin,
estimatedOutputPerCoin,
timestampCreated: getTimestampNow(),
};
if (oldCoinPubs.length == 0) {
logger.warn("created refresh group with zero coins");
refreshGroup.timestampFinished = getTimestampNow();
}
await tx.put(Stores.refreshGroups, refreshGroup);
logger.trace(`created refresh group ${refreshGroupId}`);
processRefreshGroup(ws, refreshGroupId).catch((e) => {
logger.warn(`processing refresh group ${refreshGroupId} failed`);
});
return {
refreshGroupId,
};
}
/**
* Timestamp after which the wallet would do the next check for an auto-refresh.
*/
function getAutoRefreshCheckThreshold(d: DenominationRecord): Timestamp {
const delta = timestampDifference(
d.stampExpireWithdraw,
d.stampExpireDeposit,
);
const deltaDiv = durationMul(delta, 0.75);
return timestampAddDuration(d.stampExpireWithdraw, deltaDiv);
}
/**
* Timestamp after which the wallet would do an auto-refresh.
*/
function getAutoRefreshExecuteThreshold(d: DenominationRecord): Timestamp {
const delta = timestampDifference(
d.stampExpireWithdraw,
d.stampExpireDeposit,
);
const deltaDiv = durationMul(delta, 0.5);
return timestampAddDuration(d.stampExpireWithdraw, deltaDiv);
}
export async function autoRefresh(
ws: InternalWalletState,
exchangeBaseUrl: string,
): Promise {
await updateExchangeFromUrl(ws, exchangeBaseUrl, true);
await ws.db.runWithWriteTransaction(
[
Stores.coins,
Stores.denominations,
Stores.refreshGroups,
Stores.exchanges,
],
async (tx) => {
const exchange = await tx.get(Stores.exchanges, exchangeBaseUrl);
if (!exchange) {
return;
}
const coins = await tx
.iterIndexed(Stores.coins.exchangeBaseUrlIndex, exchangeBaseUrl)
.toArray();
const refreshCoins: CoinPublicKey[] = [];
for (const coin of coins) {
if (coin.status !== CoinStatus.Fresh) {
continue;
}
if (coin.suspended) {
continue;
}
const denom = await tx.get(Stores.denominations, [
exchangeBaseUrl,
coin.denomPubHash,
]);
if (!denom) {
logger.warn("denomination not in database");
continue;
}
const executeThreshold = getAutoRefreshExecuteThreshold(denom);
if (isTimestampExpired(executeThreshold)) {
refreshCoins.push(coin);
}
}
if (refreshCoins.length > 0) {
await createRefreshGroup(ws, tx, refreshCoins, RefreshReason.Scheduled);
}
const denoms = await tx
.iterIndexed(Stores.denominations.exchangeBaseUrlIndex, exchangeBaseUrl)
.toArray();
let minCheckThreshold = timestampAddDuration(
getTimestampNow(),
durationFromSpec({ days: 1 }),
);
for (const denom of denoms) {
const checkThreshold = getAutoRefreshCheckThreshold(denom);
const executeThreshold = getAutoRefreshExecuteThreshold(denom);
if (isTimestampExpired(executeThreshold)) {
// No need to consider this denomination, we already did an auto refresh check.
continue;
}
minCheckThreshold = timestampMin(minCheckThreshold, checkThreshold);
}
exchange.nextRefreshCheck = minCheckThreshold;
await tx.put(Stores.exchanges, exchange);
},
);
}