cmab client

Author: raju-opti

lib/core/decision_service/cmab/cmab_client.ts

@@ -0,0 +1,116 @@
+/**
+ * Copyright 2025, Optimizely
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { OptimizelyError } from "../../../error/optimizly_error";
+import { CMAB_FETCH_FAILED, INVALID_CMAB_FETCH_RESPONSE } from "../../../message/error_message";
+import { UserAttributes } from "../../../shared_types";
+import { runWithRetry } from "../../../utils/executor/backoff_retry_runner";
+import { sprintf } from "../../../utils/fns";
+import { RequestHandler } from "../../../utils/http_request_handler/http";
+import { isSuccessStatusCode } from "../../../utils/http_request_handler/http_util";
+import { BackoffController } from "../../../utils/repeater/repeater";
+import { Producer } from "../../../utils/type";
+
+export interface CmabClient {
+  fetchVariation(
+    experimentId: string,
+    userId: string,
+    attributes: UserAttributes,
+    cmabUuid: string
+  ): Promise<string>
+}
+
+const CMAB_PREDICTION_ENDPOINT = 'https://prediction.cmab.optimizely.com/predict/%s';
+
+export type RetryConfig = {
+  maxRetries: number,
+  backoffProvider?: Producer<BackoffController>;
+}
+
+export type CmabClientConfig = {
+  requestHandler: RequestHandler,
+  retryConfig?: RetryConfig;
+}
+
+export class DefaultCmabClient implements CmabClient {
+  private requestHandler: RequestHandler;
+  private retryConfig?: RetryConfig;
+
+  constructor(config: CmabClientConfig) {
+    this.requestHandler = config.requestHandler;
+    this.retryConfig = config.retryConfig;
+  }
+
+  async fetchVariation(
+    experimentId: string,
+    userId: string,
+    attributes: UserAttributes,
+    cmabUuid: string
+  ): Promise<string> {
+    const url = sprintf(CMAB_PREDICTION_ENDPOINT, experimentId);
+
+    const cmabAttributes = Object.keys(attributes).map((key) => ({
+      id: key,
+      value: attributes[key],
+      type: 'custom_attribute',
+    }));
+
+    const body = {
+      instances: [
+        {
+          visitorId: userId,
+          experimentId,
+          attributes: cmabAttributes,
+          cmabUUID: cmabUuid,
+        }
+      ]
+    }
+
+    const variation = await (this.retryConfig ?
+      runWithRetry(
+        () => this.doFetch(url, JSON.stringify(body)),
+        this.retryConfig.backoffProvider?.(),
+        this.retryConfig.maxRetries,
+      ).result : this.doFetch(url, JSON.stringify(body))
+    );
+
+    return variation;
+  }
+
+  private async doFetch(url: string, data: string): Promise<string> {
+    const response = await this.requestHandler.makeRequest(
+      url,
+      { 'Content-Type': 'application/json' },
+      'POST',
+      data,
+    ).responsePromise;
+
+    if (isSuccessStatusCode(response.statusCode)) {
+      return Promise.reject(new OptimizelyError(CMAB_FETCH_FAILED, response.statusCode));
+    }
+
+    const body = JSON.parse(response.body);
+    if (!this.validateResponse(body)) {
+      return Promise.reject(new OptimizelyError(INVALID_CMAB_FETCH_RESPONSE));
+    }
+
+    return String(body.predictions[0].variation_id);
+  }
+
+  private validateResponse(body: any): boolean {
+    return body.predictions && body.predictions.length > 0 && body.predictions[0].variation_id;
+  }
+}

lib/message/error_message.ts

@@ -106,5 +106,7 @@ export const ODP_EVENT_MANAGER_STOPPED = "ODP event manager stopped before it co
 export const DATAFILE_MANAGER_FAILED_TO_START = 'Datafile manager failed to start';
 export const UNABLE_TO_ATTACH_UNLOAD = 'unable to bind optimizely.close() to page unload event: "%s"';
 export const UNABLE_TO_PARSE_AND_SKIPPED_HEADER = 'Unable to parse & skipped header item';
+export const CMAB_FETCH_FAILED = 'CMAB variation fetch failed with status: %s';
+export const INVALID_CMAB_FETCH_RESPONSE = 'Invalid CMAB fetch response';
 
 export const messages: string[] = [];