Cache is a high-speed data storage layer that stores a subset of data, typically transient, so that future requests for that data are served up faster than is possible by accessing the data’s primary storage location. Caching allows you to reuse previously retrieved or computed data efficiently. It is very tedious to onboard cache into service, and a lot of boilerplate code and configuration are needed. We have an out-of-the-box caching solution, i.e. Flash, a library using Redis for in-memory central storage. It is built over ioredis so that services can onboard cache quickly and conveniently without writing boilerplate code.

Flash is currently published at npm registry as @uc-engg/flash, so to install it you need to set the registry as NPM and install flash.

npm set registry https://registry.npmjs.org/
npm get registry      // to list the set registry
npm install @uc-engg/flash

There are two ways to onboard Flash in your service

1. By using MARC
2. Without using MARC

It is integrated in Marc as one of the dependencies like Internal service, mysql, mongo etc. which is declared in

/configs/dependency.config.js

Declare Cache as dependency type in dependency.config.json under service or workflow block

[DEPENDENCY.TYPE.CACHE]: [{
        id     : DEPENDENCY.ID.cache,
        options: {}
  }]

Each type has a particular syntax it follows, for cache both id and options is required

Add @uc-engg/flash dependency in the service package.json file

Populate the options field with buckets configurations.

[DEPENDENCY.TYPE.CACHE]: [{
        id     : DEPENDENCY.ID.cache,
        options: {
          "bucketA": {
            "high_availability": true,
            "default_ttl": 86400,
            "registered_services": ["serviceA", "serviceB"]
          }
        }
  }]

1. high_availability - Its a boolean value and is true which refers to HIGH_AVAILABILITY cluster
2. default_ttl - If you didn't specify ttl(Time to Live) during setting of cache value then this vlaue is picked by default and is in seconds
3. registered_services - List of service_ids that are allowed to do an operation on a bucket

We have to create a config file with configs for initialising redis connection

1. connectionConfigs

  HIGH_AVAILABILITY: {
    config,
    default_options,
    cluster
  },

config - Connection config host, port where you want to host your cache

default_options - Default options for creating redis connection

cluster - Whether you want normal connection or cluster connection (boolean)

For Example

      "HIGH_AVAILABILITY": {
        "config": [
          {
            "host": "elasticache-cluster.cache.amazonaws.com",
            "port": 9002
          }
        ],
        "default_options": {
          "enableOfflineQueue": false
        },
        "cluster": true
      },

2. serviceConfig

"bucketA": {
	"high_availability": true,
	"default_ttl": 86400,
	"registered_services": ["serviceA", "serviceB"]
}
         

high_availability - Its a boolean value and is true which refers to HIGH_AVAILABILITY cluster

default_ttl - If you didn't specify ttl(Time to Live) during setting of cache value then this vlaue is picked by default and is in seconds

registered_services - List of service_ids that are allowed to do an operation on a bucket

Add @uc-engg/flash dependency in the service package.json file Initialize Cache

import Flash from '@uc-engg/flash'

const Cache = new Flash();
Cache.connect(connectionConfig, serviceConfig, serviceName)	//connectionConfig, serviceConfig initialized in step 1 

Now you can start using flash Library

  //To set data in Cache
	Cache.setData(serviceName, key, data, ttl)
    .then(function(result){
      console.log(result);
    });

  //To get data from Cache
  Cache.getData(serviceName, key) //returns object
    .then(function(data){
      console.log('Your data is', data);
    });
  
  //Check if key exists in Cache
  Cache.checkIfKeyExists(serviceName, key) //returns true/false
    .then(function(exists){
      console.log('Your key exists', exists);
    })

  //To set an array of values in Cache for a key
  Cache.setArrayValues(serviceName, key, values, ttl)
    .then(function(result){
      console.log(result);
    });

  //To get all values of array for a key
  Cache.getArrayValues(serviceName, key)
    .then(function(values){
      console.log(values);
    });
    // Add specified members with given scores to sorted set
    Cache.zadd(bucketName, key, score, data, ttl)
      .then(function (values) {
        console.log(values);
      });
    // Check if value is present in an array
    Cache.checkValueInArray(bucketName, key, value)
      .then(function (values) {
        console.log(values);
      });
    // Delete key from cache
    Cache.deleteKey(bucketName, key)
      .then(function (values) {
        console.log(values);
      });

// Set Json object as cache
    Cache.jsonSet(bucketName, key, data, path, ttl)
      .then(function (values) {
        console.log(values);
      });
    // Get json object as cache
    Cache.jsonGet(bucketName, key, path)  
      .then(function (values) {
        console.log(values);
      });

Here path refers to the depth at which you wish to store or retrieve data

    // {f1: 5, f2: {a : 10}} stored at "userKey"
    Cache.jsonSet(bucketName, "userKey", {f1: 5, f2: {a : 10}} , '$') 
    
    // {f1: 5, f2: {a : 10}} will become  {f1: 5, f2: {c: {a: 10}}
    Cache.jsonSet(bucketName, "userKey", {a: {c: 10}} , '$..f2') 
    
    // Same for jsonGet 
    
    // will return what is stored at key f2 {c: {a: 10}}
    Cache.jsonSet(bucketName, "userKey", '$..f2')