使用 Firebase 快取

目標： 提高資訊主頁效能，並避免外部 API 頻率限制， 為連接器部署自訂快取。

Looker Studio 有報表專屬的快取系統。製作專屬廣告活動時 連接器可以導入自訂快取，以加快報表製作速度， 避免年利率限制

例如，假設您正在建立提供歷史天氣資料的連接器 特定郵遞區號最近 7 天的資料你的連接器品質良好 但您擷取資料的外部 API 採用嚴格的頻率 API 只會每天更新資料，因此如特定郵遞區號， 不必在一天內多次擷取相同的資料使用此應用程式 解決方案指南，為每個郵遞區號實作每日快取。

需求條件

• Firebase 即時資料庫。如果沒有存取權，請建立 Google Cloud Platform (GCP) 專案，並追蹤 入門指南：自行建立 Firebase 即時資料庫執行個體。
• 可讀取及寫入 Firebase Realtime 資料的 GCP 服務帳戶 資料庫。
• 可從來源擷取資料的社群連接器。

限制

• 這項解決方案無法與 Looker Studio 進階服務搭配使用。時間 使用 Looker Studio 進階服務，也就是應用程式中的連接器程式碼 指令碼無法存取資料。因此無法快取資料 使用 Apps Script。
• 報表編輯者和檢視者無法重設這個快取。

解決方案

實作服務帳戶

1. 在 Google Cloud 專案中建立服務帳戶。
2. 請確認這個服務帳戶具備雲端專案中的 BigQuery 存取權。
   • 必要的 Identity and Access Management (IAM) 角色：Firebase Admin
3. 下載 JSON 檔案即可取得服務帳戶金鑰。儲存檔案的 資源指令碼屬性中所列的內容。將 金鑰，應在 Apps Script UI 中類似：
   
4. 在您的 Apps Script 專案中加入 Apps Script 的 OAuth2 程式庫。
5. 為服務帳戶實作必要的 OAuth2 程式碼：

firestore-cache/src/firebase.js

前往 GitHub 查看

var SERVICE_ACCOUNT_CREDS = 'SERVICE_ACCOUNT_CREDS';
var SERVICE_ACCOUNT_KEY = 'private_key';
var SERVICE_ACCOUNT_EMAIL = 'client_email';
var BILLING_PROJECT_ID = 'project_id';

var scriptProperties = PropertiesService.getScriptProperties();

/**
 * Copy the entire credentials JSON file from creating a service account in GCP.
 * Service account should have `Firebase Admin` IAM role.
 */
function getServiceAccountCreds() {
  return JSON.parse(scriptProperties.getProperty(SERVICE_ACCOUNT_CREDS));
}

function getOauthService() {
  var serviceAccountCreds = getServiceAccountCreds();
  var serviceAccountKey = serviceAccountCreds[SERVICE_ACCOUNT_KEY];
  var serviceAccountEmail = serviceAccountCreds[SERVICE_ACCOUNT_EMAIL];

  return OAuth2.createService('FirebaseCache')
    .setAuthorizationBaseUrl('https://accounts.google.com/o/oauth2/auth')
    .setTokenUrl('https://accounts.google.com/o/oauth2/token')
    .setPrivateKey(serviceAccountKey)
    .setIssuer(serviceAccountEmail)
    .setPropertyStore(scriptProperties)
    .setCache(CacheService.getScriptCache())
    .setScope([
      'https://www.googleapis.com/auth/userinfo.email',
      'https://www.googleapis.com/auth/firebase.database'
    ]);
}

實作要在 Firebase 中讀取及寫入的程式碼

您將使用 Firebase Database REST API 來讀取和寫入 Firebase 即時資料庫。下列程式碼實作 存取這個 API

實作 getData()

不含快取的現有 getData() 程式碼的結構應如下所示 輸入：

firestore-cache/src/without-caching.js

前往 GitHub 查看

/*
 * This file is only to demonstrate how the `getData()` fucntion would look
 * like without the Firebase Realtime Database caching. It is not a part of
 * the connector code and should not be included in Apps Script / Clasp.
 */

function getData(request) {
  var requestedFields = getFields().forIds(
    request.fields.map(function(field) {
      return field.name;
    })
  );

  var fetchedData = fetchAndParseData(request);
  var data = getFormattedData(fetchedData, requestedFields);

  return {
    schema: requestedFields.build(),
    rows: data
  };
}

如要在 getData() 程式碼中使用快取，請按照下列步驟操作：

1. 判斷「區塊」或「unit」代表應快取的資料

2. 建立一個不重複的鍵，用於在快取中儲存最低資料單位。
   實作範例時，使用的是來自 configparams 的 zipcode 做為鍵
   選用：針對每位使用者的快取，請建立含有基準金鑰和 使用者身分。導入範例：
   js var baseKey = getBaseKey(request); var userEmail = Session.getEffectiveUser().getEmail(); var hasheduserEmail = getHashedValue(userEmail); var compositeKey = baseKey + hasheduserEmail;

3. 如果有快取資料，請檢查快取是否為最新資料。
   在這個範例中，特定郵遞區號的快取資料會與 目前日期。從快取擷取資料時，快取的日期就是 系統會對照目前日期進行檢查

   var cacheForZipcode = {
     data: <data being cached>,
     ymd: <current date in YYYYMMDD format>
   }
   

4. 如果快取資料不存在，或是快取資料不是最新資料，請擷取資料 並儲存在快取中

在以下範例中，main.js 包含具有快取的 getData() 程式碼

範例程式碼

以下是使用 FireBase 進行快取的連接器的完整範例：

main.js

firestore-cache/src/main.js

前往 GitHub 查看

// [start common_connector_code]
var cc = DataStudioApp.createCommunityConnector();

function getAuthType() {
  return cc
    .newAuthTypeResponse()
    .setAuthType(cc.AuthType.NONE)
    .build();
}

function getConfig(request) {
  var config = cc.getConfig();

  config
    .newTextInput()
    .setId('zipcode')
    .setName('Enter Zip Code')
    .setPlaceholder('eg. 95054');

  return config.build();
}

function getFields() {
  var fields = cc.getFields();
  var types = cc.FieldType;
  var aggregations = cc.AggregationType;

  fields
    .newDimension()
    .setId('zipcode')
    .setName('Zip code')
    .setType(types.TEXT);

  fields
    .newDimension()
    .setId('date')
    .setName('Date')
    .setType(types.YEAR_MONTH_DAY);

  fields
    .newMetric()
    .setId('temperature')
    .setName('Temperature (F)')
    .setType(types.NUMBER)
    .setIsReaggregatable(false);

  return fields;
}

function getSchema(request) {
  return {
    schema: getFields().build()
  };
}
// [end common_connector_code]

// [start caching_implementation]
function getData(request) {
  var requestedFields = getFields().forIds(
    request.fields.map(function(field) {
      return field.name;
    })
  );

  var cacheUpdateNeeded = true;
  var url = buildFirebaseUrl(request.configParams.zipcode);
  var cache = firebaseCache('get', url);

  if (cache) {
    var currentYmd = getCurrentYmd();
    cacheUpdateNeeded = currentYmd > cache.ymd;
  }

  if (cacheUpdateNeeded) {
    var fetchedData = fetchAndParseData(request);
    cache = {};
    cache.data = fetchedData;
    cache.ymd = currentYmd;
    firebaseCache('delete', url);
    firebaseCache('post', url, cache);
  }

  var data = getFormattedData(cache.data, requestedFields);

  var requestedFields = getFields().forIds(
    request.fields.map(function(field) {
      return field.name;
    })
  );

  var cache = getCachedData(request);
  var data = getFormattedData(cache, requestedFields);

  return {
    schema: requestedFields.build(),
    rows: data
  };
}

function getCachedData(request) {
  var cacheUpdateNeeded = true;
  var url = buildFirebaseUrl(request.configParams.zipcode);
  var cachedData = getFromCache(url);
  var currentYmd = getCurrentYmd();

  if (cachedData) {
    cacheUpdateNeeded = currentYmd > cachedData.ymd;
  }

  if (cacheUpdateNeeded) {
    var fetchedData = fetchAndParseData(request);
    freshData = {};
    freshData.data = fetchedData;
    freshData.ymd = currentYmd;
    deleteFromCache(url);
    putInCache(url, freshData);
    cachedData = freshData;
  }

  return cachedData.data;
}

function getCurrentYmd() {
  var currentDate = new Date();
  var year = currentDate.getFullYear();
  var month = ('0' + (currentDate.getMonth() + 1)).slice(-2);
  var date = ('0' + currentDate.getDate()).slice(-2);
  var currentYmd = year + month + date;
  return currentYmd;
}

// [end caching_implementation]

// [start common_getdata_implementation]
function fetchAndParseData(request) {
  // TODO: Connect to your own API endpoint and parse the fetched data.
  // To keep this example simple, we are returning dummy data instead of
  // connecting to an enpoint. This does not affect the caching.
  var parsedData = sampleData;
  return parsedData;
}

function getFormattedData(fetchedData, requestedFields) {
  var data = fetchedData.map(function(rowData) {
    return formatData(rowData, requestedFields);
  });
  return data;
}

function formatData(rowData, requestedFields) {
  var row = requestedFields.asArray().map(function(requestedField) {
    switch (requestedField.getId()) {
      case 'date':
        return rowData.date;
      case 'zipcode':
        return rowData.zipcode;
      case 'temperature':
        return rowData.temperature;
      default:
        return '';
    }
  });
  return {values: row};
}
// [end common_getdata_implementation]

var sampleData = [
  {
    date: '20190601',
    zipcode: '95054',
    temperature: 80
  },
  {
    date: '20190602',
    zipcode: '95054',
    temperature: 82
  },
  {
    date: '20190603',
    zipcode: '95054',
    temperature: 82
  },
  {
    date: '20190604',
    zipcode: '95054',
    temperature: 85
  },
  {
    date: '20190605',
    zipcode: '95054',
    temperature: 84
  },
  {
    date: '20190606',
    zipcode: '95054',
    temperature: 83
  },
  {
    date: '20190607',
    zipcode: '95054',
    temperature: 81
  }
];

firebase.js

firestore-cache/src/firebase.js

前往 GitHub 查看

// [start firebase_access_implementation]

var FIREBASE_REALTIME_DB_BASE_URL = '.firebaseio.com';
var FIREBASE_REALTIME_DB_COLLECTION = '/cache';

/**
 * Returns the URL for a file in a firebase database.
 *
 * @param {string} fileName The filename in the database
 * @returns {string} The url for the file in the database
 */
function buildFirebaseUrl(fileName) {
  var serviceAccountCreds = getServiceAccountCreds();
  var projectId = serviceAccountCreds[BILLING_PROJECT_ID];

  if (fileName) {
    fileName = '/' + fileName;
  }
  var urlElements = [
    'https://',
    projectId,
    FIREBASE_REALTIME_DB_BASE_URL,
    FIREBASE_REALTIME_DB_COLLECTION,
    fileName,
    '.json'
  ];
  var url = urlElements.join('');
  return url;
}

/**
 * Generic method for handling the Firebase Realtime Database REST API.
 * For `get`: returns the data at the given url.
 * For `post`: posts the data in in firestore db at the given url and returns `undefined`.
 * For `delete`: deletes the data at the given url and returns `undefined`.
 *
 * @param {string} method Method for the REST API: `get`, `post`, or `delete`
 * @param {string} url REST endpoint
 * @param {string} [data] Data to be stored for `post` method
 * @returns {undefined|object} Returns data from the REST endpoint for `get`
 *          method. For other methods, returns `undefined`.
 */
function firebaseCache(method, url, data) {
  var oAuthToken = getOauthService().getAccessToken();

  var responseOptions = {
    headers: {
      Authorization: 'Bearer ' + oAuthToken
    },
    method: method,
    contentType: 'application/json'
  };

  // Add payload for post method
  if (method === 'post') {
    responseOptions['payload'] = JSON.stringify(data);
  }

  var response = UrlFetchApp.fetch(url, responseOptions);

  // Return value only for `get`.
  if (method === 'get') {
    var responseObject = JSON.parse(response);
    if (responseObject === null) {
      return null;
    } else {
      var autoKey = Object.keys(responseObject)[0];
      var returnValue = responseObject[autoKey];
    }
    return returnValue;
  }
}

function getFromCache(url) {
  return firebaseCache('get', url);
}

function deleteFromCache(url) {
  return firebaseCache('delete', url);
}

function putInCache(url, data) {
  return firebaseCache('put', url, data);
}

// [end firebase_access_implementation]

var SERVICE_ACCOUNT_CREDS = 'SERVICE_ACCOUNT_CREDS';
var SERVICE_ACCOUNT_KEY = 'private_key';
var SERVICE_ACCOUNT_EMAIL = 'client_email';
var BILLING_PROJECT_ID = 'project_id';

var scriptProperties = PropertiesService.getScriptProperties();

/**
 * Copy the entire credentials JSON file from creating a service account in GCP.
 * Service account should have `Firebase Admin` IAM role.
 */
function getServiceAccountCreds() {
  return JSON.parse(scriptProperties.getProperty(SERVICE_ACCOUNT_CREDS));
}

function getOauthService() {
  var serviceAccountCreds = getServiceAccountCreds();
  var serviceAccountKey = serviceAccountCreds[SERVICE_ACCOUNT_KEY];
  var serviceAccountEmail = serviceAccountCreds[SERVICE_ACCOUNT_EMAIL];

  return OAuth2.createService('FirebaseCache')
    .setAuthorizationBaseUrl('https://accounts.google.com/o/oauth2/auth')
    .setTokenUrl('https://accounts.google.com/o/oauth2/token')
    .setPrivateKey(serviceAccountKey)
    .setIssuer(serviceAccountEmail)
    .setPropertyStore(scriptProperties)
    .setCache(CacheService.getScriptCache())
    .setScope([
      'https://www.googleapis.com/auth/userinfo.email',
      'https://www.googleapis.com/auth/firebase.database'
    ]);
}

其他資源

Chrome 使用者體驗連接器提供約 20 GB BigQuery 的資訊主頁 提供給數千名使用者使用這個連接器使用 Firebase 即時資料庫 以及 Apps Script Cache Service，兩者都適用雙層快取方法。詳情請見 code。