34 lines
892 B
JavaScript
34 lines
892 B
JavaScript
import { getPool } from "../../db/index.js";
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// Lockless: concurrent cold misses may both compute, last writer wins.
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export async function getCached(userId, tag, ttlMs, compute) {
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let client = await getPool();
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try {
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const hit = (
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await client.query(
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`SELECT data FROM cache
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WHERE user_id = $1 AND tag = $2
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AND updated_ts > NOW() - ($3 * interval '1 millisecond')`,
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[userId, tag, ttlMs],
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)
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).rows[0];
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if (hit) return hit.data;
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} finally {
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await client.release();
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}
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const data = await compute();
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client = await getPool();
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try {
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await client.query(
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`INSERT INTO cache (user_id, tag, data) VALUES ($1, $2, $3::jsonb)
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ON CONFLICT (user_id, tag) DO UPDATE SET data = EXCLUDED.data, updated_ts = NOW()`,
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[userId, tag, data],
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);
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} finally {
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await client.release();
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}
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return data;
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}
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