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import type { LogRecord } from "@dispatch/kernel";
import type { TraceStore } from "@dispatch/trace-store";
// --- Pure core (no I/O) ---
export function shouldPrune(now: number, lastPruneAt: number, intervalMs: number): boolean {
return now - lastPruneAt >= intervalMs;
}
export interface Logger {
readonly info: (...args: readonly unknown[]) => void;
readonly debug: (...args: readonly unknown[]) => void;
}
export function splitLines(buffer: string): { lines: string[]; remainder: string } {
const lines: string[] = [];
let start = 0;
for (let i = 0; i < buffer.length; i++) {
if (buffer[i] === "\n") {
lines.push(buffer.slice(start, i));
start = i + 1;
}
}
const remainder = buffer.slice(start);
return { lines, remainder };
}
// --- Drain step (the unit of work) ---
export interface DrainOpts {
readonly journalPath: string;
readonly offset: number;
readonly store: TraceStore;
}
export interface DrainResult {
readonly newOffset: number;
}
/**
* Read bytes from offset to EOF, split into NDJSON lines, parse each
* complete line into a LogRecord, skip + warn on malformed lines,
* insert the batch into the store, return the new offset past the
* consumed complete lines (excluding any held remainder).
*/
export function drainOnce(opts: DrainOpts): DrainResult {
const { journalPath, offset, store } = opts;
let content: string;
try {
content = readFileFromOffset(journalPath, offset);
} catch {
return { newOffset: offset };
}
if (content.length === 0) {
return { newOffset: offset };
}
const { lines } = splitLines(content);
if (lines.length === 0) {
return { newOffset: offset };
}
const records: LogRecord[] = [];
for (const line of lines) {
const trimmed = line.trim();
if (trimmed.length === 0) continue;
try {
const parsed: LogRecord = JSON.parse(trimmed);
records.push(parsed);
} catch (err) {
console.warn("[observability-collector] skipping malformed line:", err);
}
}
if (records.length > 0) {
store.insertRecords(records);
}
const consumedBytes = Buffer.byteLength(
lines.join("\n") + (lines.length > 0 ? "\n" : ""),
"utf8",
);
return { newOffset: offset + consumedBytes };
}
// --- Offset persistence ---
/**
* Read the resume offset from a sidecar file. Returns 0 if missing.
*/
export function readOffset(sidecarPath: string): number {
try {
const content = readFileUtf8(sidecarPath).trim();
const parsed = Number(content);
return Number.isFinite(parsed) && parsed >= 0 ? parsed : 0;
} catch {
return 0;
}
}
/**
* Persist the resume offset to a sidecar file.
*/
export function writeOffset(sidecarPath: string, offset: number): void {
writeFileUtf8(sidecarPath, String(offset));
}
// --- I/O abstraction (injected at edges, default = real fs) ---
export interface FsOps {
readonly readFileFromOffset: (path: string, offset: number) => string;
readonly readFileUtf8: (path: string) => string;
readonly writeFileUtf8: (path: string, data: string) => void;
}
let fsOps: FsOps = createDefaultFsOps();
export function setFsOps(ops: FsOps): void {
fsOps = ops;
}
export function resetFsOps(): void {
fsOps = createDefaultFsOps();
}
function readFileFromOffset(path: string, offset: number): string {
return fsOps.readFileFromOffset(path, offset);
}
function readFileUtf8(path: string): string {
return fsOps.readFileUtf8(path);
}
function writeFileUtf8(path: string, data: string): void {
fsOps.writeFileUtf8(path, data);
}
function createDefaultFsOps(): FsOps {
const fs = require("node:fs") as typeof import("node:fs");
return {
readFileFromOffset(path: string, offset: number): string {
const fd = fs.openSync(path, "r");
try {
const stat = fs.fstatSync(fd);
const bytesToRead = stat.size - offset;
if (bytesToRead <= 0) return "";
const buf = Buffer.alloc(bytesToRead);
fs.readSync(fd, buf, 0, bytesToRead, offset);
return buf.toString("utf8");
} finally {
fs.closeSync(fd);
}
},
readFileUtf8(path: string): string {
return fs.readFileSync(path, "utf8");
},
writeFileUtf8(path: string, data: string): void {
fs.writeFileSync(path, data, "utf8");
},
};
}
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