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The four telemetry gaps (rows on commits, chord.host, microsecond times, a read-only store) and: pages record and send span batches over their link to the server's ingest object (checked, capped, rate-limited, stamped browser and with the link's principal); workers send theirs too, so the server is the store's only writer; principalAttributes lets an app choose what a span records about its principal. The tutorial shows a real page's click traced to the worker, with the trace viewer.
35 lines
1.6 KiB
TypeScript
35 lines
1.6 KiB
TypeScript
// The todo app's telemetry store: one SQLite file in the data directory, `telemetry.sqlite`. The server is its only
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// writer: its own spans, and those every list's worker and every recording page send it; readers (the trace viewer,
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// `trace.ts`) open it read-only with Chord's `openTelemetryStore` and read through the store's read interface.
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import { mkdir } from "node:fs/promises";
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import { dirname, join } from "node:path";
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import { openNodeSqliteDatabase } from "../../../../src/sqlite/node.ts";
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import { createSqliteTelemetry, type SqliteTelemetry } from "../../../../src/telemetry-sqlite/index.ts";
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/** The telemetry store as one process opened it: its recorder (an adapter and the reads) and its close. */
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export type TodoTelemetry = {
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readonly store: SqliteTelemetry;
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/** Flushes what the recorder still holds and closes the file. */
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close(): Promise<void>;
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};
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/** The telemetry store's file in the data directory `dataDir`. */
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export function telemetryFile(dataDir: string): string {
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return join(dataDir, "telemetry.sqlite");
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}
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/** Opens the telemetry store at `file` for this process (its directory made, private, when missing). */
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export async function openTelemetry(file: string): Promise<TodoTelemetry> {
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// Spans carry who called what: the data directory is private before the store's first file appears in it.
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await mkdir(dirname(file), { recursive: true, mode: 0o700 });
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const db = await openNodeSqliteDatabase(file);
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const store = await createSqliteTelemetry(db);
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return {
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store,
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close: async () => {
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await store.close();
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await db.close();
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},
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};
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}
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