UserSessionExercise.md

User Session Exercise

In this activity we will describe something a little more advanced for interested students to apply themselves to. We will discuss an application known as user session storage/management. This is something that riak is commonly used for so we figured it would be perhaps the best activity for this.

Prompt

Keeping track of user data is a serious task for most modern applications. You can reduce the problem quite a bit by taking a sort of simplified approach to what user data is. For example you could only count how often a user creates, deletes, updates, fetches, logins, etc. These are all simple counters that Riak is well suited to handle.

1. Keep track of a user's login number
2. Keep track of a user's number of submitted updates
3. Keep track of a user's number of submitted creates
4. Keep track of a user's number of submitted fetches
5. Keep track of a user's number of submitted deletes

Try the exercise yourself and check our solution below!

Solution

We've done it in the javascript driver to show the versatility of the platform. Content is the incoming data from the server.

const client = new Riak.Client(IP, (error, c) => // Remember to use the IP of your server!
{
    if (error) {
          this.logger.error(`[ RIAK ] failed to connect: ${error}`);
          reject(false);
          return;
        }
      switch (content.action) {
          case "LOGIN":
            return this.handleLogin(content, c)
              .then((result) => resolve(result));
          case "REGISTRATION":
            return this.handleRegistration(content, c)
              .then((result) => resolve(result));
          case "COURSE_CREATE":
          case "COURSE_DELETE":
            return this.handleCreateOrDelete("COURSE", content, c)
              .then((result) => resolve(result));
          case "COURSE_FETCH":
          case "COURSE_UPDATE":
            return this.handleFetchOrUpdate("COURSE", content, c)
              .then((result) => resolve(result));
          case "WISH_CREATE":
          case "WISH_DELETE":
            return this.handleCreateOrDelete("WISH", content, c)
              .then((result) => resolve(result));
          case "WISH_UPDATE":
          case "WISH_FETCH":
            return this.handleFetchOrUpdate("WISH", content, c);
          default:
            this.logger.warn(`[ RIAK ] Unexpected type ${content.action}.`);
            return resolve(true);
        }
});
 
  handleLogin(content, client) {
    return new Promise((resolve, reject) => {
      const logTag = "LOGIN";
      this.logger.info(`[ ${logTag} ] handling login`);
      const mapOp = new Riak.Commands.CRDT.UpdateMap.MapOperation();
      mapOp.incrementCounter(content.username, 1);
      const datum = {
        bucketType: "maps",
        bucket: content.action,
        key: content.ip,
        op: mapOp
      };
      client.updateMap(datum, (error, result) => {
        let status;
        if (error) {
          this.logger.error(`[ ${logTag} ] failed to store value ${error}`);
          status = false;
        } else {
          this.logger.info(`[ ${logTag} ] successfully stored value ${JSON.stringify(result)}`);
          status = true;
        }
        this.stop(logTag, client);
        resolve(status);
      });
    });
  }
  
    handleRegistration(content, client) {
    return new Promise((resolve, reject) => {
      const logTag = "REGISTRATION";
      const datum = {
        bucketType: "counters",
        bucket: content.action,
        key: content.ip,
        increment: 1
      };
      this.updateCounter(logTag, client, datum, resolve, reject);
    });
  }

  handleCreateOrDelete(logTag, content, client) {
    return new Promise((resolve, reject) => {
      const datum = {
        bucketType: "counters",
        bucket: content.action,
        key: content.username,
        increment: 1
      };
      this.updateCounter(logTag, client, datum, resolve, reject);
    });
  }

  handleFetchOrUpdate(logTag, content, client) {
    return new Promise((resolve, reject) => {
      const datum = {
        bucketType: "counters",
        bucket: content.action,
        key: content.id,
        increment: 1
      };
      this.updateCounter(logTag, client, datum, resolve, reject);
    });
  }

  updateCounter(logTag, client, datum, resolve, reject) {
    client.updateCounter(datum, (error, result) => {
      let status;
      if (error) {
        this.logger.error(`[ ${logTag} ] failed to store value ${error}`);
        status = false;
      } else {
        this.logger.info(`[ ${logTag} ] successfully stored value ${JSON.stringify(result)}`);
        status = true;
      }
      this.stop(logTag, client);
      resolve(status);
    });
  }