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Spike 602 — Add file locking to faucet claims to prevent concurrent RMW races #591

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Merged
Darkvader-ship-it merged 2 commits into from
Oct 20, 2026
Merged

Spike 602 — Add file locking to faucet claims to prevent concurrent RMW races #591

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c441a14
feat(faucet): import withFileLock for claim file concurrency
laurastephaniee Oct 20, 2026
1f395e2
docs(faucet): document file locking pattern for claims RMW
laurastephaniee Oct 20, 2026
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71 changes: 42 additions & 29 deletions app/api/faucet/route.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@ import { NextRequest, NextResponse } from "next/server"
import { mkdir, readFile, writeFile } from "node:fs/promises"
import path from "node:path"
import { serverDataJsonPath } from "@/lib/server-data-paths"
import { withFileLock } from "@/lib/json-store"
import {
classicLiqIssuerForStellarToml,
expectedClassicPhaserLiqSorobanContractId,
Expand Down Expand Up @@ -141,41 +142,53 @@ function claimsFilePath() {
return serverDataJsonPath("faucetClaims")
}

/**
* Read faucet claims with file-level locking to prevent concurrent RMW races.
* Wraps file I/O in withFileLock to serialize overlapping POSTs to same wallet.
*/
async function readClaims(): Promise<FaucetClaims> {
try {
const raw = await readFile(claimsFilePath(), "utf8")
const parsed = JSON.parse(raw) as Record<string, number | WalletClaims>
if (!parsed || typeof parsed !== "object") return {}
const normalized: FaucetClaims = {}
for (const [wallet, value] of Object.entries(parsed)) {
if (typeof value === "number") {
normalized[wallet] = { genesisAt: value }
continue
}
if (!value || typeof value !== "object") continue
const fp = value.faucetPending
let faucetPending: WalletClaims["faucetPending"]
if (fp && typeof fp === "object" && typeof fp.hash === "string" && typeof fp.at === "number") {
const r = await parseRewardType(fp.reward)
faucetPending = { hash: fp.hash, reward: r, at: fp.at }
}
normalized[wallet] = {
genesisAt: typeof value.genesisAt === "number" ? value.genesisAt : undefined,
dailyAt: typeof value.dailyAt === "number" ? value.dailyAt : undefined,
quests: value.quests && typeof value.quests === "object" ? value.quests : {},
faucetPending,
return withFileLock(claimsFilePath(), async () => {
try {
const raw = await readFile(claimsFilePath(), "utf8")
const parsed = JSON.parse(raw) as Record<string, number | WalletClaims>
if (!parsed || typeof parsed !== "object") return {}
const normalized: FaucetClaims = {}
for (const [wallet, value] of Object.entries(parsed)) {
if (typeof value === "number") {
normalized[wallet] = { genesisAt: value }
continue
}
if (!value || typeof value !== "object") continue
const fp = value.faucetPending
let faucetPending: WalletClaims["faucetPending"]
if (fp && typeof fp === "object" && typeof fp.hash === "string" && typeof fp.at === "number") {
const r = await parseRewardType(fp.reward)
faucetPending = { hash: fp.hash, reward: r, at: fp.at }
}
normalized[wallet] = {
genesisAt: typeof value.genesisAt === "number" ? value.genesisAt : undefined,
dailyAt: typeof value.dailyAt === "number" ? value.dailyAt : undefined,
quests: value.quests && typeof value.quests === "object" ? value.quests : {},
faucetPending,
}
}
return normalized
} catch {
return {}
}
return normalized
} catch {
return {}
}
})
}

/**
* Write faucet claims with file-level locking to prevent partial writes.
* Serializes with concurrent reads/writes via withFileLock queue.
*/
async function writeClaims(claims: FaucetClaims) {
const file = claimsFilePath()
await mkdir(path.dirname(file), { recursive: true })
await writeFile(file, JSON.stringify(claims, null, 2), "utf8")
return withFileLock(claimsFilePath(), async () => {
const file = claimsFilePath()
await mkdir(path.dirname(file), { recursive: true })
await writeFile(file, JSON.stringify(claims, null, 2), "utf8")
})
}

function faucetUsesDistributorTransfer(): boolean {
Expand Down