A better way to implement in-memory-cache in javascript / nodejs

Question

I had a question. The following code has a memory leak:

let inMemoryCache = {};

app.get("/hello",(req, resp) => {
   inMemoryCache[unixTimeStamp] = {"foo":"bar"}
   resp.json({});
});

Isn't it? The size of the object inMemoryCache will keep on increasing with each request until it hits the ceiling and the heap size explodes.

What then is the best to implement in-memory-caches?

jmrk · Accepted Answer · 2021-04-22 18:17:13Z

2

Manage the size of your cache somehow. For example, you could keep a fixed number of entries, and once the cache has reached its maximum size and a new entry comes in, delete the oldest (or least frequently used, or least recently used, or some other selection criteria).

Caching is harder than it seems :-)

answered Apr 22, 2021 at 18:17

jmrk

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7 Comments

Suhail Gupta Over a year ago

Yeah, I realized this recently. I was reading about weakmap While I am not clear enough, but does that help here?

jmrk Over a year ago

WeakMaps don't keep their contents "alive" in the GC sense, i.e. if there are no other references to them, then the next GC cycle will clear them. Whether that's desirable behavior very much depends on what you want your cache to do.

Suhail Gupta Over a year ago

I specifically want to cache the results from database calls. Like big JSON documents. What will you suggest?

jmrk Over a year ago

I don't know enough about your situation to recommend something specific, so I can only recommend a generic strategy: try any one approach that seems reasonable to you, measure how well it works, and if it's not satisfactory, try something else. Repeat as needed.

Suhail Gupta Over a year ago

Yeah, doing the same!

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