Cached routes significantly decrease throughput

[InstantlyMoist]

Environment

Node v22.2.0
Nitro latest (as of posting)

Reproduction

https://github.com/InstantlyMoist/nitro-throughput

Describe the bug

Currently it appears that using a cached event handler reduces the throughput of a route by around 40% this is tested with

https://github.com/fomalhaut88/winrk but can also be tested with wrk for linux.

My findings (based on reproduction)
For all endpoints I used the same settings (t = 4, d = 10, c = 200), tested 3 times

/simple = ~16k requests per second
/simple_cached = ~11k requests per second
/big_payload = ~100 requests per second
/big_payload_cached = ~60 request per second

While nitro's throughput seems to significantly decrease with a higher payload, it seems to decrease even further with the use of a cached event route.

Additional context

No response

Logs

No response

[manniL]

(Linking Discord discussion here)

[pi0]

Hi dear @InstantlyMoist. You should use caching when the computation cost is more than cache retrieval like when making a costly database query or long-time fetch.

In the /simple example, computing a simple new Date() is actually cheaper than more instructions needed to store and retrieve the cache.

In the /big_payload case, we are actually not computing anything. Returning a JS object is also significantly cheaper than serializing it to store it in the cache and deserializing it before sending a response.

We can improve Nitro DX though to show some info in about it ~> #2559

[manniL]

As an addition to the difference in time. This is because of the gigantic JSON. As comparison, express does even worse on my machine compared to what I get for the payload on Nitro

You should definitely paginate your content and not bring out all of them at once. Or you might want to serve the content fully static, or use a different caching option than in-memory.

[cjpearson]

I've also been testing out the performance of Nitro's cachedEventHandler. I noticed that as the payload grows, a larger percentage of the execution time is taken up by serializing and deserializing the JSON.

When profiling /big_payload_cached I see destr taking up a bit over 50% of the time (compared to ~2% for /simple_cached). This JSON is admittedly gigantic, but it's also noticeable in more realistic scenarios. For returning cached pages in our Nuxt application, about a third of the time is spent by destr.

One idea is to use getItemRaw/setItemRaw to avoid serialization. I made a quick test patch to save the cached payload in the raw format and save the metadata in JSON. With these changes, the performance of /big_payload and /big_payload_cached is comparable.

Before Patch

Running 10s test @ http:https://localhost:3000/big_payload
10 connections


┌─────────┬───────┬───────┬────────┬────────┬──────────┬──────────┬────────┐
│ Stat    │ 2.5%  │ 50%   │ 97.5%  │ 99%    │ Avg      │ Stdev    │ Max    │
├─────────┼───────┼───────┼────────┼────────┼──────────┼──────────┼────────┤
│ Latency │ 46 ms │ 49 ms │ 101 ms │ 105 ms │ 54.67 ms │ 16.73 ms │ 145 ms │
└─────────┴───────┴───────┴────────┴────────┴──────────┴──────────┴────────┘
┌───────────┬────────┬────────┬────────┬────────┬────────┬───────┬────────┐
│ Stat      │ 1%     │ 2.5%   │ 50%    │ 97.5%  │ Avg    │ Stdev │ Min    │
├───────────┼────────┼────────┼────────┼────────┼────────┼───────┼────────┤
│ Req/Sec   │ 169    │ 169    │ 181    │ 186    │ 180.7  │ 4.95  │ 169    │
├───────────┼────────┼────────┼────────┼────────┼────────┼───────┼────────┤
│ Bytes/Sec │ 481 MB │ 481 MB │ 515 MB │ 530 MB │ 514 MB │ 14 MB │ 481 MB │
└───────────┴────────┴────────┴────────┴────────┴────────┴───────┴────────┘
┌──────┬───────┐
│ Code │ Count │
├──────┼───────┤
│ 200  │ 1807  │
└──────┴───────┘

Req/Bytes counts sampled once per second.
# of samples: 10

2k requests in 10.01s, 5.14 GB read

Running 10s test @ http:https://localhost:3000/big_payload_cached
10 connections


┌─────────┬───────┬────────┬────────┬────────┬───────────┬──────────┬────────┐
│ Stat    │ 2.5%  │ 50%    │ 97.5%  │ 99%    │ Avg       │ Stdev    │ Max    │
├─────────┼───────┼────────┼────────┼────────┼───────────┼──────────┼────────┤
│ Latency │ 98 ms │ 103 ms │ 209 ms │ 231 ms │ 115.42 ms │ 35.87 ms │ 265 ms │
└─────────┴───────┴────────┴────────┴────────┴───────────┴──────────┴────────┘
┌───────────┬────────┬────────┬────────┬────────┬────────┬─────────┬────────┐
│ Stat      │ 1%     │ 2.5%   │ 50%    │ 97.5%  │ Avg    │ Stdev   │ Min    │
├───────────┼────────┼────────┼────────┼────────┼────────┼─────────┼────────┤
│ Req/Sec   │ 74     │ 74     │ 86     │ 90     │ 85.8   │ 4.45    │ 74     │
├───────────┼────────┼────────┼────────┼────────┼────────┼─────────┼────────┤
│ Bytes/Sec │ 211 MB │ 211 MB │ 245 MB │ 256 MB │ 244 MB │ 12.6 MB │ 211 MB │
└───────────┴────────┴────────┴────────┴────────┴────────┴─────────┴────────┘
┌──────┬───────┐
│ Code │ Count │
├──────┼───────┤
│ 200  │ 858   │
└──────┴───────┘

Req/Bytes counts sampled once per second.
# of samples: 10

868 requests in 10.04s, 2.44 GB read

After Patch

Running 10s test @ http:https://localhost:3000/big_payload
10 connections


┌─────────┬───────┬───────┬───────┬────────┬──────────┬──────────┬────────┐
│ Stat    │ 2.5%  │ 50%   │ 97.5% │ 99%    │ Avg      │ Stdev    │ Max    │
├─────────┼───────┼───────┼───────┼────────┼──────────┼──────────┼────────┤
│ Latency │ 44 ms │ 48 ms │ 98 ms │ 104 ms │ 53.75 ms │ 15.88 ms │ 116 ms │
└─────────┴───────┴───────┴───────┴────────┴──────────┴──────────┴────────┘
┌───────────┬────────┬────────┬────────┬────────┬────────┬─────────┬────────┐
│ Stat      │ 1%     │ 2.5%   │ 50%    │ 97.5%  │ Avg    │ Stdev   │ Min    │
├───────────┼────────┼────────┼────────┼────────┼────────┼─────────┼────────┤
│ Req/Sec   │ 177    │ 177    │ 183    │ 189    │ 184    │ 3.77    │ 177    │
├───────────┼────────┼────────┼────────┼────────┼────────┼─────────┼────────┤
│ Bytes/Sec │ 504 MB │ 504 MB │ 521 MB │ 538 MB │ 524 MB │ 10.7 MB │ 504 MB │
└───────────┴────────┴────────┴────────┴────────┴────────┴─────────┴────────┘
┌──────┬───────┐
│ Code │ Count │
├──────┼───────┤
│ 200  │ 1840  │
└──────┴───────┘

Req/Bytes counts sampled once per second.
# of samples: 10

2k requests in 10.02s, 5.24 GB read

Running 10s test @ http:https://localhost:3000/big_payload_cached
10 connections


┌─────────┬───────┬───────┬────────┬────────┬─────────┬──────────┬────────┐
│ Stat    │ 2.5%  │ 50%   │ 97.5%  │ 99%    │ Avg     │ Stdev    │ Max    │
├─────────┼───────┼───────┼────────┼────────┼─────────┼──────────┼────────┤
│ Latency │ 45 ms │ 48 ms │ 100 ms │ 105 ms │ 54.1 ms │ 16.04 ms │ 120 ms │
└─────────┴───────┴───────┴────────┴────────┴─────────┴──────────┴────────┘
┌───────────┬────────┬────────┬────────┬────────┬────────┬─────────┬────────┐
│ Stat      │ 1%     │ 2.5%   │ 50%    │ 97.5%  │ Avg    │ Stdev   │ Min    │
├───────────┼────────┼────────┼────────┼────────┼────────┼─────────┼────────┤
│ Req/Sec   │ 172    │ 172    │ 183    │ 188    │ 182.6  │ 4.32    │ 172    │
├───────────┼────────┼────────┼────────┼────────┼────────┼─────────┼────────┤
│ Bytes/Sec │ 490 MB │ 490 MB │ 521 MB │ 535 MB │ 520 MB │ 12.3 MB │ 490 MB │
└───────────┴────────┴────────┴────────┴────────┴────────┴─────────┴────────┘
┌──────┬───────┐
│ Code │ Count │
├──────┼───────┤
│ 200  │ 1826  │
└──────┴───────┘

Req/Bytes counts sampled once per second.
# of samples: 10

2k requests in 10.01s, 5.2 GB read

Would an approach like this make sense?