Question 121904 in Redis Question posted in
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Redis – ExpressJS: How to cache on demand

I’m trying to build a REST API with express, sequelize (PostgreSQL dialect) and node.

Essentially I have two endpoints:

Method Endpoint Desc.
GET /api/players To get players info, including assets
POST /api/assets To create an asset

And there is a mechanism which updates a property (say price) of assets, over a cycle of 30 seconds.

Goal

I want to cache the results of GET /api/players, but I want some control over it, so that whenever a user creates an asset (using POST /api/assets) and right after that a request to GET /api/players should give the updated data (i.e. including the property which updates for every 30 seconds) and cache it until it gets updated in the next cycle.

Expected

The following should demonstrate it:

  • GET /api/players

    JSON Response:

    [
  {
    "name": "John Doe"
    "assets": [
      {
        "id":1
        "price": 10
      }
    ]
  }
]

  • POST /api/assets

    JSON Request:

    {
  "id":2
}

  • GET /api/players

    JSON Response:

    {
  "name": "John Doe"
  "assets": [
    {
      "id":1
      "price": 10
    },
    {
      "id":2
      "price": 7.99
    }
  ]
}

What I have managed to do so far

I have made the routes, but GET /api/players has no cache mechanism and basically queries the database every time it is requested.

Some solutions I have found, but none seem to meet my scenario

Example implementation

I have seen (kind off) similar implementation (that I desire) in Github actions workflow for implementing cache, where you define a key and unless the key has changed it uses the same packages and doesn’t install packages everytime, (example: https://github.com/python-discord/quackstack/blob/6792fd5868f28573bb8f9565977df84e7ba50f42/.github/workflows/quackstack.yml#L39-L52)

Is there any package, to do that? So that while processing POST /api/assets I can change the key in its handler, and thus GET /api/players gives me the updated result (also I can change the key in that 30 seconds cycle too), and after that it gives me the cached result (until it is updated in the next cycle).

Note: If you have a solution please try to stick with some npm packages, rather than something like redis, unless its the only/best solution.

Thanks in advance!
(P.S. I’m a beginner and this is my first question in SO)

Tags:

2

Answers


  1. 0

    Typically caching is done with help of Redis. Redis is in-memory key-value store. You could handle the cache in the following manner.

    1. In your handler for POST operation update/reset cached entry for players.
    2. In your handler for GET operation if the Redis has the entry in cache return it, otherwise do the logic query the data, add the entry to the cache and return the data.

    Alternatively, you could use Memcached.

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  2. 0

    A bit late to this answer but I was looking for a similar solution. I found that the apicache library not only allows for caching for specified durations, but the cache can also be manually cleared.

    apicache.clear([target]) – clears cache target (key or group), or entire cache if no value passed, returns new index.

    Here is an example for your implementation:

    // POST /api/assets
app.post('/api/assets', function(req, res, next) {
  // update assets then clear cache
  apicache.clear()

  // or only clear the specific players cache by using a parameter 
  // apicache.clear('players')

  res.send(response)
})
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