File size: 4,837 Bytes
9e4583c | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 | /**
* Stream Tracker — Unified SSE stream monitoring
*
* Tracks token counts, latency, and errors during streaming responses.
* Emits periodic progress callbacks for real-time monitoring.
*
* @module shared/utils/streamTracker
*/
export interface StreamMetrics {
startTime: number;
firstTokenTime: number;
totalTokens: number;
totalChunks: number;
elapsedMs: number;
tokensPerSecond: number;
complete: boolean;
error: string | null;
finishReason: string | null;
}
interface StreamTrackerOptions {
onProgress?: (metrics: StreamMetrics) => void;
progressIntervalMs?: number;
}
export class StreamTracker {
private _onProgress: ((metrics: StreamMetrics) => void) | null;
private _progressIntervalMs: number;
private _startTime: number;
private _firstTokenTime: number;
private _totalTokens: number;
private _totalChunks: number;
private _complete: boolean;
private _error: string | null;
private _finishReason: string | null;
private _lastProgressAt: number;
private _buffer: string;
constructor(options: StreamTrackerOptions = {}) {
this._onProgress = options.onProgress || null;
this._progressIntervalMs = options.progressIntervalMs || 500;
this._startTime = Date.now();
this._firstTokenTime = 0;
this._totalTokens = 0;
this._totalChunks = 0;
this._complete = false;
this._error = null;
this._finishReason = null;
this._lastProgressAt = 0;
this._buffer = "";
}
/**
* Record an incoming SSE chunk.
* @param {string|Object} chunk - Raw SSE text or parsed data
*/
onChunk(chunk) {
this._totalChunks++;
if (this._totalChunks === 1) {
this._firstTokenTime = Date.now() - this._startTime;
}
// Try to extract token count from chunk
let data = chunk;
if (typeof chunk === "string") {
// Parse SSE if formatted
if (chunk.startsWith("data: ")) {
const payload = chunk.slice(6).trim();
if (payload === "[DONE]") {
this._complete = true;
this._emitProgress();
return;
}
try {
data = JSON.parse(payload);
} catch {
data = null;
}
}
}
if (data && typeof data === "object") {
// OpenAI format: choices[0].delta.content
const content = data.choices?.[0]?.delta?.content;
if (content) {
// Rough token estimate (~4 chars per token)
this._totalTokens += Math.ceil(content.length / 4);
}
// Check for finish reason
const reason = data.choices?.[0]?.finish_reason;
if (reason) {
this._finishReason = reason;
}
// Usage in final chunk (OpenAI includes this)
if (data.usage?.completion_tokens) {
this._totalTokens = data.usage.completion_tokens;
}
}
this._maybeEmitProgress();
}
/**
* Mark stream as errored.
* @param {string|Error} error
*/
onError(error) {
this._error = typeof error === "string" ? error : error.message;
this._complete = true;
this._emitProgress();
}
/** Mark stream as complete. */
onComplete() {
this._complete = true;
this._emitProgress();
}
/** @returns {StreamMetrics} Current metrics */
getMetrics() {
const elapsedMs = Date.now() - this._startTime;
const tokensPerSecond = elapsedMs > 0 ? this._totalTokens / (elapsedMs / 1000) : 0;
return {
startTime: this._startTime,
firstTokenTime: this._firstTokenTime,
totalTokens: this._totalTokens,
totalChunks: this._totalChunks,
elapsedMs,
tokensPerSecond: Math.round(tokensPerSecond * 10) / 10,
complete: this._complete,
error: this._error,
finishReason: this._finishReason,
};
}
/** @private */
_maybeEmitProgress() {
const now = Date.now();
if (now - this._lastProgressAt >= this._progressIntervalMs) {
this._emitProgress();
}
}
/** @private */
_emitProgress() {
this._lastProgressAt = Date.now();
if (this._onProgress) {
this._onProgress(this.getMetrics());
}
}
}
/**
* Create a TransformStream that tracks SSE progress.
*
* @param {{ onProgress?: (metrics: StreamMetrics) => void }} [options={}]
* @returns {{ stream: TransformStream, tracker: StreamTracker }}
*/
export function createStreamTracker(options = {}) {
const tracker = new StreamTracker(options);
const stream = new TransformStream({
transform(chunk, controller) {
const text = typeof chunk === "string" ? chunk : new TextDecoder().decode(chunk);
const lines = text.split("\n");
for (const line of lines) {
if (line.startsWith("data: ")) {
tracker.onChunk(line);
}
}
controller.enqueue(chunk);
},
flush() {
tracker.onComplete();
},
});
return { stream, tracker };
}
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