1 | const murmurhash = require('murmurhash');
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2 | const cookie = require('cookie');
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3 | const url = require('url');
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4 | const uuidv4 = require('uuid/v4');
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5 |
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6 | const pkg = require('../package.json');
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7 | const sync = require('./sync');
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8 | const expressionEvaluator = require('./expressionEvaluator');
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9 |
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10 | const Logger = require('./logger');
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11 |
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12 | const HASH_SEED = 1;
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13 | const MAX_HASH_VALUE = Math.pow(2, 32);
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14 | const MAX_TRAFFIC_VALUE = 10000;
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15 | const COOKIE_NAME = 'ABBY_EXPERIMENTS';
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16 | const COOKIE_SESSION = 'ABBY_SESSION';
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17 | const COOKIE_MAX_AGE = 60 * 60 * 24 * 7 * 52;
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18 | const COOKIE_SESSION_MAX_AGE = 60 * 45;
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19 | const CONTROL_VARIANT = 'control';
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20 | const SEPARATOR = '|';
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21 |
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96 |
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97 |
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98 |
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99 |
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100 | function experimentHash(experimentCode, experiment) {
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101 | return experiment && isFinite(parseInt(experiment.hash))
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102 | ? experiment.hash
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103 | : generateHash(`${uuidv4()}_${experimentCode}`);
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104 | }
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105 |
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106 |
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107 |
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108 |
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109 |
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110 |
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111 | function generateHash(experimentID) {
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112 | let hashValue = murmurhash.v3(experimentID, HASH_SEED),
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113 | ratio = hashValue / MAX_HASH_VALUE;
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114 | return parseInt(ratio * MAX_TRAFFIC_VALUE, 10);
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115 | }
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116 |
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117 |
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118 |
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119 |
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120 |
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121 |
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122 |
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123 | function getVariantCode(experiment, hash, currentExperiment) {
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124 | var percentage = Math.floor((hash * 100) / MAX_TRAFFIC_VALUE),
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125 | variants = experiment.variants.filter(variant => {
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126 | let { start, end } = variant.range;
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127 | return percentage >= start && percentage <= end;
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128 | });
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129 |
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130 | if (variants.length === 0) {
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131 | return CONTROL_VARIANT;
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132 | } else if (!currentExperiment || currentExperiment.variantCode === CONTROL_VARIANT) {
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133 | return variants[0].code;
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134 | } else {
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135 | return currentExperiment.variantCode;
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136 | }
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137 | }
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138 |
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139 |
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140 |
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141 |
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142 |
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143 |
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144 |
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145 |
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146 | function getVariant(experiment, variantCode) {
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147 | let variants = experiment.variants;
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148 | if (Array.isArray(variants)) {
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149 | for (let i = 0, ii = variants.length; i < ii; i++) {
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150 | if (variants[i].code === variantCode) {
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151 | return variants[i];
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152 | }
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153 | }
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154 | }
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155 | return null;
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156 | }
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157 |
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158 |
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159 |
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160 |
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161 |
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162 |
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163 | function assignToRequest(req, experiments) {
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164 | req.experiments = {};
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165 | for (let experiment of experiments) {
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166 | if(experiment.paused) {
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167 | continue;
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168 | }
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169 | req.experiments[experiment.experimentCode] = experiment;
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170 | }
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171 | }
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172 |
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173 |
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174 |
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175 |
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176 |
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177 |
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178 |
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179 |
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180 | function experimentsCookieValue(experiments) {
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181 | let path = '/',
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182 | maxAge = COOKIE_MAX_AGE,
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183 | expires = new Date(Date.now() + maxAge);
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184 |
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185 | let value = experiments
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186 | .map(item => `${item.experimentCode}${SEPARATOR}${item.variantCode}${SEPARATOR}${item.hash}`)
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187 | .join(',');
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188 |
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189 | return cookie.serialize(COOKIE_NAME, value,
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190 | {
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191 | path,
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192 | maxAge,
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193 | expires
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194 | });
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195 | }
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196 |
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197 |
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198 |
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199 |
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200 |
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201 |
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202 |
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203 | function assignVersion(res, pk, synchroniser) {
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204 | if (typeof pkg.version === 'string') {
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205 | res.setHeader('X-Abby-Version', pkg.version);
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206 | }
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207 | if (typeof synchroniser.lastSync === 'string') {
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208 | res.setHeader('X-Abby-Sync', synchroniser.lastSync);
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209 | }
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210 | }
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211 |
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212 |
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213 |
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214 |
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215 |
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216 |
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217 |
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218 |
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219 | function sessionCookieValue(newSession, sessionId) {
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220 | let path = '/',
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221 | maxAge = COOKIE_SESSION_MAX_AGE,
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222 | expires = new Date(Date.now() + (maxAge * 1000));
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223 | return cookie.serialize(COOKIE_SESSION, newSession ? uuidv4() : sessionId, {
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224 | path,
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225 | maxAge,
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226 | expires
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227 | });
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228 | }
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229 |
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230 |
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231 |
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232 |
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233 |
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234 | function getCookieData(req) {
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235 | return req.headers.cookie ? cookie.parse(req.headers.cookie) : {};
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236 | }
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237 |
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238 |
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239 |
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240 |
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241 |
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242 | function getCurrentExperiments(data) {
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243 |
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244 | if (typeof data !== 'string') {
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245 | return {};
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246 | }
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247 | let experiments = {};
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248 | data.split(',').forEach(value => {
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249 | let [experimentCode, variantCode, hash] = value.split(SEPARATOR);
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250 | experiments[experimentCode] = { experimentCode, variantCode, hash };
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251 | });
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252 | return experiments;
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253 | }
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254 |
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255 |
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256 |
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257 |
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258 |
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259 |
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260 | function getForcedExperimentsFromQuery(req) {
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261 | const { query: { abby_experiment: query } } = url.parse(req.url, true);
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262 |
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263 | if (typeof query !== 'string') {
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264 | return {};
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265 | }
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266 |
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267 | let experiments = {};
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268 | query.split(',').forEach(value => {
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269 | let [experimentCode, variantCode] = value.split(SEPARATOR);
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270 | experiments[experimentCode] = variantCode;
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271 | });
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272 | return experiments;
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273 | }
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274 |
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275 |
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276 |
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277 |
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278 |
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279 | function validateSession(sessionId) {
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280 | return typeof sessionId !== 'string' || sessionId.trim().length === 0;
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281 | }
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282 |
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283 |
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284 |
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285 |
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286 |
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287 |
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288 |
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289 |
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290 |
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291 |
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292 | function buildUserExperiment(experiment, variant, hash) {
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293 | return {
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294 | experimentCode: experiment.code,
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295 | experiment: {
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296 | code: experiment.code,
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297 | tags: experiment.tags.map(tag => tag.name),
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298 | audience: experiment.audience,
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299 | targeting: experiment.targeting
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300 | },
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301 | variantCode: variant.code,
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302 | variant: {
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303 | code: variant.code,
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304 | properties: Object.assign({}, variant.properties),
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305 | original: variant.original
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306 | },
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307 | hash,
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308 | paused: !experiment.active
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309 | };
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310 | }
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311 |
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312 |
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313 |
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314 |
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315 |
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316 |
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317 | function filterUserExperiments(experiments, filter = {}) {
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318 | let result = experiments;
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319 | if (filter.tags) {
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320 | result = result.filter(({ experiment }) =>
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321 | filter.tags.every(tag => experiment.tags.find(value => value === tag))
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322 | );
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323 | }
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324 | return result;
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325 | }
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326 |
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327 |
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328 |
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329 |
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330 |
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331 |
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332 |
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333 |
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334 |
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335 |
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336 |
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337 | function getTargetedExperiments(userExperiments, props, filter = {}) {
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338 | return filterUserExperiments(userExperiments, filter)
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339 | .filter(({ experiment, variant }) => !variant.original && expressionEvaluator.evaluate(experiment.targeting, props));
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340 | }
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341 |
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342 |
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343 |
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344 |
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345 |
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346 |
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347 |
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348 |
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349 |
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350 | function assignCookies(res, ...values) {
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351 | let cookies = [],
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352 | cookieHeader = res.getHeader('Set-Cookie');
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353 |
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354 | if (typeof cookieHeader !== 'undefined' && cookieHeader !== null) {
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355 | if (Array.isArray(cookieHeader)) {
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356 | cookies = cookie.concat(cookieHeader);
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357 | } else {
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358 | cookies.push(cookieHeader);
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359 | }
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360 | }
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361 |
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362 | cookies = cookies.filter(cookie => !cookie.startsWith('ABBY_'));
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363 |
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364 | cookies = cookies.concat(values);
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365 | res.setHeader('Set-Cookie', cookies);
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366 | }
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367 |
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368 |
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369 |
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370 |
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371 |
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372 |
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373 |
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374 | function rebalanceExperiment(experiment, rebalance = []) {
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375 | if (Array.isArray(rebalance)) {
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376 | return rebalance.find(code => code === experiment.code);
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377 | }
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378 | return false;
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379 | }
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380 |
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381 | function abby(logger, synchroniser, configs) {
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382 |
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383 | |
384 |
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385 |
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386 |
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387 |
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388 |
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389 |
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390 |
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391 |
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392 |
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393 |
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394 | function handle(req, res, props = {}, config = {}) {
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395 | let cookies = getCookieData(req),
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396 | sessionCookie = cookies[COOKIE_SESSION],
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397 | newSession = validateSession(sessionCookie),
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398 | currentExperiments = getCurrentExperiments(cookies[COOKIE_NAME]),
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399 | forcedExperiments = getForcedExperimentsFromQuery(req);
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400 |
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401 |
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402 | let experimentMap = {};
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403 | for (let experiment of synchroniser.data) {
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404 | let experimentCode = experiment.code,
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405 | hash,
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406 | variantCode,
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407 | |
408 |
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409 |
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410 | currentExperiment = currentExperiments[experimentCode],
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411 | forced = forcedExperiments[experimentCode],
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412 | rebalance = rebalanceExperiment(experiment, config.rebalance);
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413 |
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414 | if (forced || rebalance) {
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415 | hash = currentExperiment ? currentExperiment.hash : experimentHash(experimentCode, currentExperiment);
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416 | if (rebalance) {
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417 | variantCode = getVariantCode(experiment, hash, null);
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418 | } else {
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419 | variantCode = forced;
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420 | }
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421 | } else if (newSession) {
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422 | if (!expressionEvaluator.evaluate(experiment.audience, props)) {
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423 | continue;
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424 | }
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425 | hash = experimentHash(experimentCode, currentExperiment);
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426 | variantCode = getVariantCode(experiment, hash, currentExperiment);
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427 | } else if (currentExperiment) {
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428 | hash = currentExperiment.hash;
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429 | variantCode = currentExperiment.variantCode;
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430 | }
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431 |
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432 | let variant = getVariant(experiment, variantCode);
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433 | if (variant === null) {
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434 | continue;
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435 | }
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436 |
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437 | experimentMap[experimentCode] = buildUserExperiment(experiment, variant, hash);
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438 | }
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439 | let userExperiments = Object.values(experimentMap);
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440 | assignToRequest(req, userExperiments);
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441 | assignVersion(res, pkg, synchroniser);
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442 |
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443 | assignCookies(res, experimentsCookieValue(userExperiments), sessionCookieValue(newSession, sessionCookie));
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444 | }
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445 | handle.ready = () => synchroniser.load(configs);
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446 | handle.getTargetedExperiments = getTargetedExperiments;
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447 | return handle;
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448 | }
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449 |
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450 | module.exports = function (/**Configs*/configs, /**Synchroniser?*/synchroniser = sync) {
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451 | let { tags, apiEndpoint, logger } = Object.assign({}, configs);
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452 | let logger_ = Logger.instance(logger ? logger : console);
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453 |
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454 | if (!tags) {
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455 | logger.error(new Error('You should pass <tags>'));
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456 | return;
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457 | }
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458 | if (!apiEndpoint) {
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459 | logger.error(new Error('You should pass <apiEndpoint>'));
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460 | return;
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461 | }
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462 | return abby(logger_, synchroniser, configs);
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463 | };
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