remove sync response cache #380
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This cache can serve invalid responses, and has an extremely low hit rate. It serves invalid responses because because it's only keyed off the `since` parameter, but many of the other request parameters also affect the response or it's side effects. This will become worse once we implement filtering, because there will be a wider space of parameters with different responses. This problem is fixable, but not worth it because of the low hit rate. The low hit rate is because normal clients will always issue the next sync request with `since` set to the `prev_batch` value of the previous response. The only time we expect to see multiple requests with the same `since` is when the response is empty, but we don't cache empty responses. This was confirmed experimentally by logging cache hits and misses over 15 minutes with a wide variety of clients. This test was run on matrix.computer.surgery, which has only a few active users, but a large volume of sync traffic from many rooms. Over the test period, we had 3 hits and 5309 misses. All hits occurred in the first minute, so I suspect that they had something to do with client recovery from an offline state. The clients that were connected during the test are: - element web - schildichat web - iamb - gomuks - nheko - fractal - fluffychat web - fluffychat android - cinny web - element android - element X android Fixes: girlbossceo#336
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CI is now fixed on the main branch, so rebased and removed the lockfile commit. |
girlbossceo
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May 17, 2024
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This cache can serve invalid responses, and has an extremely low hit rate.
It serves invalid responses because because it's only keyed off the
sinceparameter, but many of the other request parameters also affect the response or it's side effects. This will become worse once we implement filtering, because there will be a wider space of parameters with different responses. This problem is fixable, but not worth it because of the low hit rate.The low hit rate is because normal clients will always issue the next sync request with
sinceset to theprev_batchvalue of the previous response. The only time we expect to see multiple requests with the samesinceis when the response is empty, but we don't cache empty responses.This was confirmed experimentally by logging cache hits and misses over 15 minutes with a wide variety of clients. This test was run on matrix.computer.surgery, which has only a few active users, but a large volume of sync traffic from many rooms. Over the test period, we had 3 hits and 5309 misses. All hits occurred in the first minute, so I suspect that they had something to do with client recovery from an offline state. The clients that were connected during the test are:
Fixes: #336