qmd/dist/embedding/openai.js

/**
 * openai.ts - OpenAI-compatible HTTP embedding provider
 *
 * Talks to any endpoint that implements `POST /v1/embeddings` with the OpenAI
 * shape: request `{model, input: string|string[]}`, response
 * `{data: [{embedding: number[], index: number}, ...]}`.
 *
 * Used by qmd to delegate embeddings to a GPU worker (e.g. ai.mm.mk →
 * qmd-embed-worker on `models` LXC, RTX 4090) instead of running
 * node-llama-cpp locally.
 *
 * Features:
 *   - Batches input in groups of ≤64 (configurable via QMD_EMBED_BATCH_SIZE)
 *   - Retries 429 / 503 with exponential backoff (1s, 4s, 16s)
 *   - 4xx (non-429) → no retry, count as failure
 *   - Circuit breaker: >50% failures in a 60s window → OPEN for 5 min,
 *     callers can use this to fall back to a local provider
 *   - Per-call timeout via AbortSignal (default QMD_EMBED_TIMEOUT_MS=30000)
 *   - Healthcheck via `GET /health` if available, else a probe embed call
 */
// ─────────────────────────── Configuration ───────────────────────────────────
/**
 * Default batch size — most OpenAI-compatible embedding endpoints accept up to
 * 2048 inputs per call but for memory and latency we cap at 64.
 */
export const DEFAULT_BATCH_SIZE = 64;
/**
 * Default per-request timeout (30 s). embeddinggemma-300M on RTX 4090 takes
 * <500ms per batch of 64 in practice; 30s is a safe upper bound.
 */
export const DEFAULT_TIMEOUT_MS = 30_000;
/**
 * Retry backoff schedule (ms) for 429/503 responses. 3 attempts total
 * (initial + 2 retries) — aligns with issue spec "1s/4s/16s".
 */
export const RETRY_BACKOFFS_MS = [1_000, 4_000, 16_000];
/**
 * Circuit breaker — flips OPEN when error rate exceeds threshold within
 * window. While OPEN, every call fails fast so the caller can fall back.
 */
export const CIRCUIT_WINDOW_MS = 60_000;
export const CIRCUIT_OPEN_DURATION_MS = 5 * 60_000;
export const CIRCUIT_FAILURE_RATE_THRESHOLD = 0.5;
export const CIRCUIT_MIN_SAMPLES = 4;
// ─────────────────────────── Helpers ─────────────────────────────────────────
function defaultSleep(ms) {
    return new Promise((resolve) => setTimeout(resolve, ms));
}
/**
 * Build the merged AbortSignal for a single HTTP attempt: combines an
 * external `userSignal` (from caller / withLLMSession) with a per-attempt
 * timeout signal. Returns the merged signal AND the timeout id so the
 * caller can `clearTimeout` after the attempt completes (avoids leaks).
 */
function buildAttemptSignal(userSignal, timeoutMs) {
    const ctrl = new AbortController();
    const timeoutId = setTimeout(() => {
        ctrl.abort(new Error(`Request timed out after ${timeoutMs}ms`));
    }, timeoutMs);
    // Don't keep process alive just for this timer
    if (typeof timeoutId === "object" && timeoutId !== null && "unref" in timeoutId) {
        timeoutId.unref();
    }
    const onUserAbort = () => ctrl.abort(userSignal?.reason);
    if (userSignal) {
        if (userSignal.aborted) {
            ctrl.abort(userSignal.reason);
        }
        else {
            userSignal.addEventListener("abort", onUserAbort, { once: true });
        }
    }
    const cleanup = () => {
        clearTimeout(timeoutId);
        if (userSignal)
            userSignal.removeEventListener("abort", onUserAbort);
    };
    return { signal: ctrl.signal, cleanup };
}
/**
 * Determine whether an HTTP status is retryable. 429 (Too Many Requests)
 * and 503 (Service Unavailable) are retried; 4xx (other than 429) are not.
 */
export function isRetryableStatus(status) {
    return status === 429 || status === 503;
}
/**
 * Chunk an array into pieces of ≤ size each. `size` MUST be ≥ 1.
 */
export function chunkArray(items, size) {
    if (size < 1)
        throw new Error(`chunkArray: size must be ≥ 1, got ${size}`);
    if (items.length <= size)
        return items.length === 0 ? [] : [items];
    const out = [];
    for (let i = 0; i < items.length; i += size) {
        out.push(items.slice(i, i + size));
    }
    return out;
}
// ─────────────────────────── Circuit Breaker ─────────────────────────────────
/**
 * Sliding-window circuit breaker. Tracks the last N samples (min 4) over a
 * 60-second window; flips OPEN when failure rate exceeds 50%, then auto-
 * resets to HALF-OPEN after 5 minutes — at which point the next probe
 * decides whether to close (success) or re-open (failure).
 */
export class CircuitBreaker {
    samples = [];
    state = "closed";
    openedAt = null;
    windowMs;
    openDurationMs;
    threshold;
    minSamples;
    now;
    constructor(opts = {}) {
        this.windowMs = opts.windowMs ?? CIRCUIT_WINDOW_MS;
        this.openDurationMs = opts.openDurationMs ?? CIRCUIT_OPEN_DURATION_MS;
        this.threshold = opts.threshold ?? CIRCUIT_FAILURE_RATE_THRESHOLD;
        this.minSamples = opts.minSamples ?? CIRCUIT_MIN_SAMPLES;
        this.now = opts.now ?? Date.now;
    }
    getState() {
        this.tickAutoReset();
        return this.state;
    }
    /**
     * Returns true when calls should be short-circuited (skip HTTP, fall back).
     * Side-effects: may transition OPEN → HALF-OPEN if the open window expired.
     */
    shouldFailFast() {
        return this.getState() === "open";
    }
    /** Record a successful call. */
    recordSuccess() {
        // Honor the time-based OPEN→HALF-OPEN transition before deciding what
        // to do with this sample. Without this, a success that lands AFTER the
        // open window expired would still see state==="open" and never close
        // the breaker (a probe call could only flip it via getState()).
        this.tickAutoReset();
        this.pushSample(true);
        if (this.state === "half-open") {
            this.state = "closed";
            this.openedAt = null;
        }
    }
    /** Record a failed call. May trigger OPEN. */
    recordFailure() {
        // Same reasoning as recordSuccess — apply lazy auto-reset before
        // classifying the sample.
        this.tickAutoReset();
        this.pushSample(false);
        if (this.state === "half-open") {
            // Probe failed — re-open
            this.state = "open";
            this.openedAt = this.now();
            return;
        }
        if (this.state === "closed")
            this.evaluate();
    }
    /** Force-reset the breaker (used by tests / admin) */
    reset() {
        this.samples = [];
        this.state = "closed";
        this.openedAt = null;
    }
    pushSample(ok) {
        const ts = this.now();
        this.samples.push({ ts, ok });
        // Drop samples outside the window
        const cutoff = ts - this.windowMs;
        while (this.samples.length > 0 && this.samples[0].ts < cutoff) {
            this.samples.shift();
        }
    }
    evaluate() {
        if (this.samples.length < this.minSamples)
            return;
        const failures = this.samples.filter((s) => !s.ok).length;
        const rate = failures / this.samples.length;
        if (rate > this.threshold) {
            this.state = "open";
            this.openedAt = this.now();
        }
    }
    tickAutoReset() {
        if (this.state === "open" && this.openedAt !== null) {
            if (this.now() - this.openedAt >= this.openDurationMs) {
                this.state = "half-open";
            }
        }
    }
}
// ─────────────────────────── Errors ──────────────────────────────────────────
/**
 * Raised when the circuit breaker is OPEN and a call is short-circuited.
 * Callers (e.g. fallback wrapper) can catch this to switch to local provider.
 */
export class CircuitOpenError extends Error {
    constructor(message = "OpenAIEmbeddingsProvider circuit is OPEN") {
        super(message);
        this.name = "CircuitOpenError";
    }
}
/**
 * Persistent (non-retryable) HTTP error from upstream. Includes status code.
 */
export class HttpError extends Error {
    status;
    bodyPreview;
    constructor(status, bodyPreview) {
        super(`HTTP ${status}: ${bodyPreview.slice(0, 200)}`);
        this.name = "HttpError";
        this.status = status;
        this.bodyPreview = bodyPreview.slice(0, 1024);
    }
}
// ─────────────────────────── Provider ────────────────────────────────────────
export class OpenAIEmbeddingsProvider {
    kind = "openai";
    endpoint;
    apiKey;
    modelId;
    upstreamModel;
    batchSize;
    timeoutMs;
    fetchImpl;
    retryBackoffsMs;
    sleep;
    now;
    dimensions = undefined;
    breaker;
    constructor(config) {
        if (!config.endpoint) {
            throw new Error("OpenAIEmbeddingsProvider: endpoint is required");
        }
        this.endpoint = config.endpoint.replace(/\/+$/, "");
        this.apiKey = config.apiKey;
        this.modelId = config.modelId ?? "embeddinggemma";
        this.upstreamModel = config.upstreamModel ?? this.modelId;
        this.batchSize = config.batchSize ?? DEFAULT_BATCH_SIZE;
        this.timeoutMs = config.timeoutMs ?? DEFAULT_TIMEOUT_MS;
        this.fetchImpl = config.fetchImpl ?? globalThis.fetch;
        this.retryBackoffsMs = config.retryBackoffsMs ?? RETRY_BACKOFFS_MS;
        this.sleep = config.sleep ?? defaultSleep;
        this.now = config.now ?? Date.now;
        this.breaker = new CircuitBreaker({ now: this.now });
        if (!this.fetchImpl) {
            throw new Error("OpenAIEmbeddingsProvider: global fetch is unavailable. " +
                "Provide a `fetchImpl` config option (Node ≥18 ships fetch by default).");
        }
        if (this.batchSize < 1) {
            throw new Error(`OpenAIEmbeddingsProvider: batchSize must be ≥ 1, got ${this.batchSize}`);
        }
    }
    getModelId() {
        return this.modelId;
    }
    getDimensions() {
        return this.dimensions;
    }
    async healthcheck(signal) {
        // Try GET /health first (worker exposes it). Fall back to probe embed.
        try {
            const { signal: attemptSig, cleanup } = buildAttemptSignal(signal, this.timeoutMs);
            try {
                const resp = await this.fetchImpl(`${this.endpoint}/health`, {
                    method: "GET",
                    headers: this.buildHeaders(),
                    signal: attemptSig,
                });
                if (resp.ok) {
                    return {
                        ok: true,
                        model: this.modelId,
                        dimensions: this.dimensions,
                        detail: `GET /health → ${resp.status}`,
                    };
                }
                return {
                    ok: false,
                    model: this.modelId,
                    detail: `GET /health → HTTP ${resp.status}`,
                };
            }
            finally {
                cleanup();
            }
        }
        catch (err) {
            // Endpoint may not implement /health — try a single embed probe instead.
            try {
                const probe = await this.embed("healthcheck", { signal });
                if (probe) {
                    return {
                        ok: true,
                        model: this.modelId,
                        dimensions: probe.embedding.length,
                        detail: "embed probe ok",
                    };
                }
                return {
                    ok: false,
                    model: this.modelId,
                    detail: "embed probe returned null",
                };
            }
            catch (probeErr) {
                return {
                    ok: false,
                    model: this.modelId,
                    detail: (err instanceof Error ? err.message : String(err)) +
                        " | probe: " +
                        (probeErr instanceof Error ? probeErr.message : String(probeErr)),
                };
            }
        }
    }
    async embed(text, options = {}) {
        const batch = await this.embedBatch([text], options);
        return batch[0] ?? null;
    }
    async embedBatch(texts, options = {}) {
        if (texts.length === 0)
            return [];
        if (this.breaker.shouldFailFast()) {
            throw new CircuitOpenError();
        }
        const chunks = chunkArray(texts, this.batchSize);
        const results = new Array(texts.length).fill(null);
        let cursor = 0;
        for (const chunk of chunks) {
            const start = cursor;
            cursor += chunk.length;
            // Abort early if signal already fired
            if (options.signal?.aborted) {
                // Leave remaining slots as null (caller treats as errors)
                return results;
            }
            // Fail-fast if breaker tripped mid-loop
            if (this.breaker.shouldFailFast()) {
                throw new CircuitOpenError();
            }
            try {
                const embeddings = await this.requestWithRetry(chunk, options);
                for (let i = 0; i < chunk.length; i++) {
                    const embedding = embeddings[i];
                    if (embedding) {
                        results[start + i] = {
                            embedding,
                            model: this.modelId,
                        };
                        // Record dimensions on first success
                        if (this.dimensions === undefined) {
                            this.dimensions = embedding.length;
                        }
                    }
                }
                this.breaker.recordSuccess();
            }
            catch (err) {
                this.breaker.recordFailure();
                // CircuitOpenError must propagate so the caller can fall back
                if (err instanceof CircuitOpenError)
                    throw err;
                // Other errors mark the chunk as null and continue with next chunk.
                // (The store layer already handles per-text nulls as errors.)
                if (process.env.QMD_EMBED_DEBUG) {
                    process.stderr.write(`OpenAIEmbeddingsProvider: chunk failed (${err instanceof Error ? err.message : String(err)})\n`);
                }
            }
        }
        return results;
    }
    async dispose() {
        // Nothing to release — fetch handles its own connection pooling.
        // Reset the breaker so a re-instantiation starts fresh.
        this.breaker.reset();
    }
    // ────────────────────── Internals ──────────────────────
    buildHeaders() {
        const headers = {
            "Content-Type": "application/json",
            "Accept": "application/json",
        };
        if (this.apiKey) {
            headers["Authorization"] = `Bearer ${this.apiKey}`;
        }
        return headers;
    }
    /**
     * Single HTTP request with retry on 429/503. Returns embeddings indexed
     * the same as `texts`. Throws on non-retryable failure or all attempts
     * exhausted.
     */
    async requestWithRetry(texts, options) {
        let lastErr = null;
        const maxAttempts = this.retryBackoffsMs.length + 1;
        for (let attempt = 0; attempt < maxAttempts; attempt++) {
            // Honor user abort BEFORE issuing the call (avoids wasted network)
            if (options.signal?.aborted) {
                throw new Error("aborted by caller");
            }
            try {
                return await this.requestOnce(texts, options);
            }
            catch (err) {
                lastErr = err;
                const retryable = err instanceof HttpError ? isRetryableStatus(err.status) : false;
                if (!retryable)
                    throw err;
                if (attempt < this.retryBackoffsMs.length) {
                    await this.sleep(this.retryBackoffsMs[attempt]);
                }
            }
        }
        // Exhausted retries → throw the last error so caller marks the chunk null
        throw lastErr ?? new Error("requestWithRetry exhausted");
    }
    /**
     * Issue one HTTP attempt to `POST /v1/embeddings`. Does NOT retry.
     */
    async requestOnce(texts, options) {
        const { signal: attemptSig, cleanup } = buildAttemptSignal(options.signal, this.timeoutMs);
        try {
            const body = JSON.stringify({
                model: options.model ?? this.upstreamModel,
                input: texts,
            });
            const resp = await this.fetchImpl(`${this.endpoint}/v1/embeddings`, {
                method: "POST",
                headers: this.buildHeaders(),
                body,
                signal: attemptSig,
            });
            if (!resp.ok) {
                const text = await resp.text().catch(() => "");
                throw new HttpError(resp.status, text);
            }
            let parsed;
            try {
                parsed = (await resp.json());
            }
            catch (err) {
                throw new Error(`OpenAIEmbeddingsProvider: malformed JSON from ${this.endpoint}/v1/embeddings: ${err instanceof Error ? err.message : String(err)}`);
            }
            if (!parsed || !Array.isArray(parsed.data)) {
                throw new Error(`OpenAIEmbeddingsProvider: response missing "data" array (got ${typeof parsed})`);
            }
            // Sort by index to match input order (in case server returns out-of-order).
            const out = new Array(texts.length);
            for (const item of parsed.data) {
                if (typeof item.index !== "number" ||
                    item.index < 0 ||
                    item.index >= texts.length) {
                    throw new Error(`OpenAIEmbeddingsProvider: data item index out of range (${item.index}, expected 0..${texts.length - 1})`);
                }
                if (!Array.isArray(item.embedding)) {
                    throw new Error(`OpenAIEmbeddingsProvider: data[${item.index}].embedding is not an array`);
                }
                out[item.index] = item.embedding;
            }
            // Sanity check — every slot must be filled
            for (let i = 0; i < texts.length; i++) {
                if (!out[i]) {
                    throw new Error(`OpenAIEmbeddingsProvider: response missing embedding for index ${i}`);
                }
            }
            return out;
        }
        finally {
            cleanup();
        }
    }
}