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Merge pull request #25 from LN-Zap/validate
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Safety net to prevent invalid mempool fees
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@mrfelton
mrfelton authored Feb 4, 2024
2 parents 754b708 + 1c1b79f commit 66651b1
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Showing 2 changed files with 78 additions and 37 deletions.
112 changes: 77 additions & 35 deletions src/server.tsx
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Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,7 @@ const stdTTL = config.get<number>('cache.stdTTL');
const checkperiod = config.get<number>('cache.checkperiod');

// Set the timeout for fetch requests.
const TIMEOUT: number = 3000;
const TIMEOUT: number = 2500;

// Log the configuration values.
console.info('---');
Expand All @@ -37,15 +37,15 @@ console.info(`Using cache checkperiod: ${checkperiod}`);
console.info('---');

// Constants
const MEMPOOL_TIP_HASH_URL = `${mempoolBaseUrl}/api/blocks/tip/hash`;
const ESPLORA_TIP_HASH_URL = `${esploraBaseUrl}/api/blocks/tip/hash`;
const MEMPOOL_FEES_URL = `${mempoolBaseUrl}/api/v1/fees/recommended`;
const ESPLORA_FEE_ESTIMATES_URL = `${esploraBaseUrl}/api/fee-estimates`;
const MEMPOOL_TIP_HASH_URL = mempoolBaseUrl && `${mempoolBaseUrl}/api/blocks/tip/hash`;
const ESPLORA_TIP_HASH_URL = esploraBaseUrl && `${esploraBaseUrl}/api/blocks/tip/hash`;
const MEMPOOL_FEES_URL = mempoolBaseUrl && `${mempoolBaseUrl}/api/v1/fees/recommended`;
const ESPLORA_FEE_ESTIMATES_URL = esploraBaseUrl && `${esploraBaseUrl}/api/fee-estimates`;

const MEMPOOL_TIP_HASH_URL_FALLBACK = `${mempoolFallbackBaseUrl}/api/blocks/tip/hash`;
const ESPLORA_TIP_HASH_URL_FALLBACK = `${esploraFallbackBaseUrl}/api/blocks/tip/hash`;
const MEMPOOL_FEES_URL_FALLBACK = `${mempoolFallbackBaseUrl}/api/v1/fees/recommended`;
const ESPLORA_FEE_ESTIMATES_URL_FALLBACK = `${esploraFallbackBaseUrl}/api/fee-estimates`;
const MEMPOOL_TIP_HASH_URL_FALLBACK = mempoolFallbackBaseUrl && `${mempoolFallbackBaseUrl}/api/blocks/tip/hash`;
const ESPLORA_TIP_HASH_URL_FALLBACK = esploraFallbackBaseUrl && `${esploraFallbackBaseUrl}/api/blocks/tip/hash`;
const MEMPOOL_FEES_URL_FALLBACK = mempoolFallbackBaseUrl && `${mempoolFallbackBaseUrl}/api/v1/fees/recommended`;
const ESPLORA_FEE_ESTIMATES_URL_FALLBACK = esploraFallbackBaseUrl && `${esploraFallbackBaseUrl}/api/fee-estimates`;

// Initialize the cache.
const cache = new NodeCache({ stdTTL: stdTTL, checkperiod: checkperiod });
Expand Down Expand Up @@ -104,8 +104,8 @@ async function fetchAndHandle(url: string, expectedResponseType: ExpectedRespons

return result;
} catch (error) {
console.info('Trying fallback URL', fallbackUrl);
if (fallbackUrl) {
console.debug('Trying fallback URL', fallbackUrl);
return fetchAndProcess(fallbackUrl, expectedResponseType);
} else {
throw new Error(`Fetch request to ${url} failed and no fallback URL was provided.`);
Expand Down Expand Up @@ -137,17 +137,61 @@ app.use('*', cors({
app.use('/static/*', serveStatic({ root: './' }))

/**
* Fetches the data from the mempool and esplora APIs.
* Fetches mempool fees.
*/
async function fetchData() {
async function fetchMempoolFees() : Promise<MempoolFeeEstimates | null> {
const tasks = [
fetchAndHandle(MEMPOOL_TIP_HASH_URL, 'text', MEMPOOL_TIP_HASH_URL_FALLBACK),
fetchAndHandle(ESPLORA_TIP_HASH_URL, 'text', ESPLORA_TIP_HASH_URL_FALLBACK),
fetchAndHandle(MEMPOOL_FEES_URL, 'json', MEMPOOL_FEES_URL_FALLBACK),
fetchAndHandle(ESPLORA_FEE_ESTIMATES_URL, 'json', ESPLORA_FEE_ESTIMATES_URL_FALLBACK)
];
MEMPOOL_FEES_URL && fetchAndHandle(MEMPOOL_FEES_URL, 'json'),
MEMPOOL_FEES_URL_FALLBACK && fetchAndHandle(MEMPOOL_FEES_URL_FALLBACK, 'json'),
].filter(Boolean);
const res = await Promise.allSettled(tasks);
console.debug('Fetched mempool fees', res);

let res0 = res[0] && getValueFromFulfilledPromise(res[0]);
let res1 = res[1] && getValueFromFulfilledPromise(res[1]);

// If all of the response properties are 1, then the response is an error (probably the mempool data is not available).
const isRes0Invalid = !res0 || (Object.values(res0).every((value) => value === 1));
const isRes1Invalid = !res1 || (Object.values(res1).every((value) => value === 1));

// Return a response that is valid, or null if both responses are invald.
if (!isRes0Invalid) {
return res0;
}
return isRes1Invalid ? null : res1;
}

/**
* Fetches esplora fees.
*/
async function fetchEsploraFees() : Promise<EsploraFeeEstimates | null> {
const tasks = [
ESPLORA_FEE_ESTIMATES_URL && fetchAndHandle(ESPLORA_FEE_ESTIMATES_URL, 'json'),
ESPLORA_FEE_ESTIMATES_URL_FALLBACK && fetchAndHandle(ESPLORA_FEE_ESTIMATES_URL_FALLBACK, 'json'),
].filter(Boolean);
const res = await Promise.allSettled(tasks);
console.debug('Fetched esplora fees', res);

let res0 = res[0] && getValueFromFulfilledPromise(res[0]);
let res1 = res[1] && getValueFromFulfilledPromise(res[1]);

return res0 || res1;
}

/**
* Fetches the current block hash.
*/
async function fetchBlocksTipHash() : Promise<string | null> {
const tasks = [
(MEMPOOL_TIP_HASH_URL || MEMPOOL_TIP_HASH_URL_FALLBACK) && fetchAndHandle(MEMPOOL_TIP_HASH_URL, 'text', MEMPOOL_TIP_HASH_URL_FALLBACK),
(ESPLORA_TIP_HASH_URL || ESPLORA_TIP_HASH_URL_FALLBACK) && fetchAndHandle(ESPLORA_TIP_HASH_URL, 'text', ESPLORA_TIP_HASH_URL_FALLBACK),
].filter(Boolean);
const res = await Promise.allSettled(tasks);

let res0 = res[0] && getValueFromFulfilledPromise(res[0]);
let res1 = res[1] && getValueFromFulfilledPromise(res[1]);

return await Promise.allSettled(tasks);
return res0 || res1;
}

/**
Expand All @@ -157,10 +201,17 @@ async function getEstimates() : Promise<Estimates> {
let estimates: Estimates | undefined = cache.get(CACHE_KEY);

if (!estimates) {
const results = await fetchData();
console.debug('Fetch tasks completed', results);

const { blocksTipHash, mempoolFeeEstimates, esploraFeeEstimates } = assignResults(results);
const tasks = [
await fetchMempoolFees(),
await fetchEsploraFees(),
await fetchBlocksTipHash(),
];
const [result1, result2, result3] = await Promise.allSettled(tasks);
const mempoolFeeEstimates = getValueFromFulfilledPromise(result1);
const esploraFeeEstimates = getValueFromFulfilledPromise(result2);
const blocksTipHash = getValueFromFulfilledPromise(result3);

const feeByBlockTarget = calculateFees(mempoolFeeEstimates, esploraFeeEstimates);

estimates = {
Expand All @@ -182,21 +233,9 @@ function getValueFromFulfilledPromise(result: PromiseSettledResult<any>) {
return result.status === "fulfilled" && result.value ? result.value : null;
}

/**
* Assigns the results of the fetch tasks to variables.
*/
function assignResults(results: PromiseSettledResult<any>[]) {
const [result1, result2, result3, result4] = results;

const blocksTipHash = getValueFromFulfilledPromise(result1) || getValueFromFulfilledPromise(result2);
const mempoolFeeEstimates = getValueFromFulfilledPromise(result3) as MempoolFeeEstimates;
const esploraFeeEstimates = getValueFromFulfilledPromise(result4) as EsploraFeeEstimates;

return { blocksTipHash, mempoolFeeEstimates, esploraFeeEstimates };
}

function calculateMempoolFees(mempoolFeeEstimates: MempoolFeeEstimates | null | undefined): FeeByBlockTarget {
const feeByBlockTarget: FeeByBlockTarget = {};

if (mempoolFeeEstimates) {
const blockTargetMapping: BlockTargetMapping = {
1: 'fastestFee',
Expand Down Expand Up @@ -249,14 +288,17 @@ function filterEstimates(feeByBlockTarget: FeeByBlockTarget, minFee: number | un

function calculateFees(mempoolFeeEstimates: MempoolFeeEstimates | null | undefined, esploraFeeEstimates: EsploraFeeEstimates | null | undefined) {
let feeByBlockTarget: FeeByBlockTarget = {};
const minFee = (mempoolFeeEstimates?.minimumFee ?? 0) * 1000;

// Get the minimum fee. If the mempool fee estimates are not available, use a default value of 5 sat/vbyte as a safety net.
const minFee = (mempoolFeeEstimates?.minimumFee ?? 5) * 1000;

// Get the mempool fee estimates.
feeByBlockTarget = calculateMempoolFees(mempoolFeeEstimates);
const minMempoolFee = calculateMinMempoolFee(feeByBlockTarget);

// Add the esplora fee estimates.
const esploraFeeEstimatesAdjusted = calculateEsploraFees(esploraFeeEstimates);

for (const [blockTarget, fee] of Object.entries(esploraFeeEstimatesAdjusted)) {
if (!minMempoolFee || fee < minMempoolFee) {
feeByBlockTarget[blockTarget] = fee;
Expand Down
3 changes: 1 addition & 2 deletions static/style.css
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Original file line number Diff line number Diff line change
Expand Up @@ -32,7 +32,6 @@ pre {
display: flex;
justify-content: center;
margin: 26px;

}

.content {
Expand All @@ -50,7 +49,7 @@ pre {
.header {
margin-left: auto;
margin-right: auto;
padding-bottom: 50px;
padding-bottom: 30px;
text-align: center;
}

Expand Down

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