1 | const murmurhash = require('murmurhash');
|
2 | const cookie = require('cookie');
|
3 | const url = require('url');
|
4 | const uuidv4 = require('uuid/v4');
|
5 |
|
6 | const pkg = require('../package.json');
|
7 | const sync = require('./sync');
|
8 | const expressionEvaluator = require('expression-evaluator');
|
9 |
|
10 | const Logger = require('./logger');
|
11 |
|
12 | const HASH_SEED = 1;
|
13 | const MAX_HASH_VALUE = Math.pow(2, 32);
|
14 | const MAX_TRAFFIC_VALUE = 10000;
|
15 | const COOKIE_NAME = 'ABBY_EXPERIMENTS';
|
16 | const COOKIE_SESSION = 'ABBY_SESSION';
|
17 | const COOKIE_MAX_AGE = 60 * 60 * 24 * 7 * 52;
|
18 | const COOKIE_SESSION_MAX_AGE = 60 * 45;
|
19 | const CONTROL_VARIANT = 'control';
|
20 | const SEPARATOR = '|';
|
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 | function experimentHash(experimentCode, experiment) {
|
102 | return experiment && isFinite(parseInt(experiment.hash))
|
103 | ? experiment.hash
|
104 | : generateHash(`${uuidv4()}_${experimentCode}`);
|
105 | }
|
106 |
|
107 |
|
108 |
|
109 |
|
110 |
|
111 |
|
112 | function generateHash(experimentID) {
|
113 | let hashValue = murmurhash.v3(experimentID, HASH_SEED),
|
114 | ratio = hashValue / MAX_HASH_VALUE;
|
115 | return parseInt(ratio * MAX_TRAFFIC_VALUE, 10);
|
116 | }
|
117 |
|
118 |
|
119 |
|
120 |
|
121 |
|
122 |
|
123 |
|
124 | function getVariantCode(experiment, hash, currentExperiment) {
|
125 | var percentage = Math.floor((hash * 100) / MAX_TRAFFIC_VALUE),
|
126 | variants = experiment.variants.filter(variant => {
|
127 | let { start, end } = variant.range;
|
128 | return percentage >= start && percentage <= end;
|
129 | });
|
130 |
|
131 | if (variants.length === 0) {
|
132 | return CONTROL_VARIANT;
|
133 | } else if (!currentExperiment || currentExperiment.variantCode === CONTROL_VARIANT) {
|
134 | return variants[0].code;
|
135 | } else {
|
136 | return currentExperiment.variantCode;
|
137 | }
|
138 | }
|
139 |
|
140 |
|
141 |
|
142 |
|
143 |
|
144 |
|
145 |
|
146 |
|
147 | function getVariant(experiment, variantCode) {
|
148 | let variants = experiment.variants;
|
149 | if (Array.isArray(variants)) {
|
150 | for (let i = 0, ii = variants.length; i < ii; i++) {
|
151 | if (variants[i].code === variantCode) {
|
152 | return variants[i];
|
153 | }
|
154 | }
|
155 | }
|
156 | return null;
|
157 | }
|
158 |
|
159 |
|
160 |
|
161 |
|
162 |
|
163 |
|
164 | function assignToRequest(req, experiments) {
|
165 | req.experiments = {};
|
166 | for (let experiment of experiments) {
|
167 | if (experiment.paused) {
|
168 | continue;
|
169 | }
|
170 | req.experiments[experiment.experimentCode] = experiment;
|
171 | }
|
172 | }
|
173 |
|
174 |
|
175 |
|
176 |
|
177 |
|
178 |
|
179 |
|
180 |
|
181 | function experimentsCookieValue(experiments) {
|
182 | let path = '/',
|
183 | maxAge = COOKIE_MAX_AGE,
|
184 | expires = new Date(Date.now() + maxAge);
|
185 |
|
186 | let value = experiments
|
187 | .map(item => `${item.experimentCode}${SEPARATOR}${item.variantCode}${SEPARATOR}${item.hash}`)
|
188 | .join(',');
|
189 |
|
190 | return cookie.serialize(COOKIE_NAME, value,
|
191 | {
|
192 | path,
|
193 | maxAge,
|
194 | expires,
|
195 | secure: true
|
196 | });
|
197 | }
|
198 |
|
199 |
|
200 |
|
201 |
|
202 |
|
203 |
|
204 |
|
205 | function assignVersion(res, pk, synchroniser) {
|
206 | if (typeof pkg.version === 'string') {
|
207 | res.setHeader('X-Abby-Version', pkg.version);
|
208 | }
|
209 | if (typeof synchroniser.lastSync === 'string') {
|
210 | res.setHeader('X-Abby-Sync', synchroniser.lastSync);
|
211 | }
|
212 | }
|
213 |
|
214 |
|
215 |
|
216 |
|
217 |
|
218 |
|
219 |
|
220 |
|
221 | function sessionCookieValue(newSession, sessionId) {
|
222 | let path = '/',
|
223 | maxAge = COOKIE_SESSION_MAX_AGE,
|
224 | expires = new Date(Date.now() + (maxAge * 1000));
|
225 | return cookie.serialize(COOKIE_SESSION, newSession ? uuidv4() : sessionId, {
|
226 | path,
|
227 | maxAge,
|
228 | expires,
|
229 | secure: true
|
230 | });
|
231 | }
|
232 |
|
233 |
|
234 |
|
235 |
|
236 |
|
237 | function getCookieData(req) {
|
238 | return req.headers.cookie ? cookie.parse(req.headers.cookie) : {};
|
239 | }
|
240 |
|
241 |
|
242 |
|
243 |
|
244 |
|
245 | function getCurrentExperiments(data) {
|
246 |
|
247 | if (typeof data !== 'string') {
|
248 | return {};
|
249 | }
|
250 | let experiments = {};
|
251 | data.split(',').forEach(value => {
|
252 | let [experimentCode, variantCode, hash] = value.split(SEPARATOR);
|
253 | experiments[experimentCode] = { experimentCode, variantCode, hash };
|
254 | });
|
255 | return experiments;
|
256 | }
|
257 |
|
258 |
|
259 |
|
260 |
|
261 |
|
262 |
|
263 | function getForcedExperimentsFromQuery(req) {
|
264 | const { query: { abby_experiment: query } } = url.parse(req.url, true);
|
265 |
|
266 | if (typeof query !== 'string') {
|
267 | return {};
|
268 | }
|
269 |
|
270 | let experiments = {};
|
271 | query.split(',').forEach(value => {
|
272 | let [experimentCode, variantCode] = value.split(SEPARATOR);
|
273 | experiments[experimentCode] = variantCode;
|
274 | });
|
275 | return experiments;
|
276 | }
|
277 |
|
278 |
|
279 |
|
280 |
|
281 |
|
282 | function validateSession(sessionId) {
|
283 | return typeof sessionId !== 'string' || sessionId.trim().length === 0;
|
284 | }
|
285 |
|
286 |
|
287 |
|
288 |
|
289 |
|
290 |
|
291 |
|
292 |
|
293 |
|
294 |
|
295 | function buildUserExperiment(experiment, variant, hash) {
|
296 | return {
|
297 | experimentCode: experiment.code,
|
298 | experiment: {
|
299 | code: experiment.code,
|
300 | tags: experiment.tags.map(tag => tag.name),
|
301 | audience: experiment.audience,
|
302 | targeting: experiment.targeting
|
303 | },
|
304 | variantCode: variant.code,
|
305 | variant: {
|
306 | code: variant.code,
|
307 | properties: Object.assign({}, variant.properties),
|
308 | original: variant.original
|
309 | },
|
310 | hash,
|
311 | paused: !experiment.active
|
312 | };
|
313 | }
|
314 |
|
315 |
|
316 |
|
317 |
|
318 |
|
319 |
|
320 | function filterUserExperiments(experiments, filter = {}) {
|
321 | let result = experiments;
|
322 | if (filter.tags) {
|
323 | result = result.filter(({ experiment }) =>
|
324 | filter.tags.every(tag => experiment.tags.find(value => value === tag))
|
325 | );
|
326 | }
|
327 | return result;
|
328 | }
|
329 |
|
330 |
|
331 |
|
332 |
|
333 |
|
334 |
|
335 |
|
336 |
|
337 |
|
338 |
|
339 |
|
340 | function getTargetedExperiments(userExperiments, props, filter = {}) {
|
341 | return filterUserExperiments(userExperiments, filter)
|
342 | .filter(({ experiment, variant }) => !variant.original && expressionEvaluator.evaluate(experiment.targeting, props));
|
343 | }
|
344 |
|
345 |
|
346 |
|
347 |
|
348 |
|
349 |
|
350 |
|
351 |
|
352 |
|
353 | function assignCookies(res, ...values) {
|
354 | let cookies = [],
|
355 | cookieHeader = res.getHeader('Set-Cookie');
|
356 |
|
357 | if (typeof cookieHeader !== 'undefined' && cookieHeader !== null) {
|
358 | if (Array.isArray(cookieHeader)) {
|
359 | cookies = cookie.concat(cookieHeader);
|
360 | } else {
|
361 | cookies.push(cookieHeader);
|
362 | }
|
363 | }
|
364 |
|
365 | cookies = cookies.filter(cookie => !cookie.startsWith('ABBY_'));
|
366 |
|
367 | cookies = cookies.concat(values);
|
368 | res.setHeader('Set-Cookie', cookies);
|
369 | }
|
370 |
|
371 |
|
372 |
|
373 |
|
374 |
|
375 |
|
376 |
|
377 | function rebalanceExperiment(experiment, rebalance = []) {
|
378 | if (experiment.rebalance) {
|
379 | return true;
|
380 | }
|
381 | if (Array.isArray(rebalance)) {
|
382 | return rebalance.find(code => code === experiment.code);
|
383 | }
|
384 | return false;
|
385 | }
|
386 |
|
387 |
|
388 |
|
389 |
|
390 |
|
391 |
|
392 | function isExperimentsEnforcedToControl(req) {
|
393 | const { query: { abby_enforce_control } } = url.parse(req.url, true);
|
394 |
|
395 | return abby_enforce_control === 'true';
|
396 | }
|
397 |
|
398 |
|
399 |
|
400 |
|
401 |
|
402 | function setExperimentsToControl(experiments) {
|
403 | for (let experiment in experiments) {
|
404 | experiments[experiment].variantCode = 'control';
|
405 | }
|
406 | }
|
407 |
|
408 | function abby(logger, synchroniser, configs) {
|
409 |
|
410 | |
411 |
|
412 |
|
413 |
|
414 |
|
415 |
|
416 |
|
417 |
|
418 |
|
419 |
|
420 |
|
421 | function handle(req, res, props = {}, config = {}) {
|
422 | const cookies = getCookieData(req);
|
423 | const sessionCookie = cookies[COOKIE_SESSION];
|
424 | const newSession = validateSession(sessionCookie);
|
425 | |
426 |
|
427 |
|
428 |
|
429 | const forcedExperiments = getForcedExperimentsFromQuery(req);
|
430 | let currentExperiments = getCurrentExperiments(cookies[COOKIE_NAME]);
|
431 | let experimentMap = {};
|
432 |
|
433 | if (isExperimentsEnforcedToControl(req)) {
|
434 | setExperimentsToControl(currentExperiments);
|
435 | }
|
436 |
|
437 | |
438 |
|
439 |
|
440 |
|
441 | for (let experiment of synchroniser.data) {
|
442 | let experimentCode = experiment.code,
|
443 | hash,
|
444 | variantCode,
|
445 | |
446 |
|
447 |
|
448 | currentExperiment = currentExperiments[experimentCode],
|
449 | forced = forcedExperiments[experimentCode];
|
450 |
|
451 |
|
452 | if (forced) {
|
453 | hash = currentExperiment ? currentExperiment.hash : experimentHash(experimentCode, currentExperiment);
|
454 | variantCode = forced;
|
455 | } else if (newSession) {
|
456 | if (!expressionEvaluator.evaluate(experiment.audience, props)) {
|
457 | continue;
|
458 | }
|
459 | hash = experimentHash(experimentCode, currentExperiment);
|
460 | variantCode = getVariantCode(experiment, hash, currentExperiment);
|
461 | } else if (currentExperiment) {
|
462 | hash = currentExperiment.hash;
|
463 | if (rebalanceExperiment(experiment, config.rebalance)) {
|
464 | variantCode = getVariantCode(experiment, hash, null);
|
465 | } else {
|
466 | variantCode = currentExperiment.variantCode;
|
467 | }
|
468 | }
|
469 |
|
470 | let variant = getVariant(experiment, variantCode);
|
471 | if (variant === null) {
|
472 | continue;
|
473 | }
|
474 |
|
475 | experimentMap[experimentCode] = buildUserExperiment(experiment, variant, hash);
|
476 | }
|
477 | let userExperiments = Object.values(experimentMap);
|
478 | assignToRequest(req, userExperiments);
|
479 | assignVersion(res, pkg, synchroniser);
|
480 |
|
481 | assignCookies(res, experimentsCookieValue(userExperiments), sessionCookieValue(newSession, sessionCookie));
|
482 | }
|
483 | handle.ready = () => synchroniser.load(configs);
|
484 | handle.getTargetedExperiments = getTargetedExperiments;
|
485 | handle.isExperimentsEnforcedToControl = isExperimentsEnforcedToControl;
|
486 | handle.setExperimentsToControl = setExperimentsToControl;
|
487 | return handle;
|
488 | }
|
489 |
|
490 | module.exports = function (/**Configs*/configs, /**Synchroniser?*/synchroniser = sync) {
|
491 | let { tags, apiEndpoint, logger } = Object.assign({}, configs);
|
492 | let logger_ = Logger.instance(logger ? logger : console);
|
493 |
|
494 | if (!tags) {
|
495 | logger_.error(new Error('You should pass <tags>'));
|
496 | return;
|
497 | }
|
498 | if (!apiEndpoint) {
|
499 | logger_.error(new Error('You should pass <apiEndpoint>'));
|
500 | return;
|
501 | }
|
502 | return abby(logger_, synchroniser, configs);
|
503 | };
|