Delay fetching notes via API

[sciurius]

Describe the bug
When I fetch a note (or note information) using the API, there seems to be a 2-3 second delay. This is consistent, independent of server load, so it may indicate some internal time-out

To Reproduce
Steps to reproduce the behavior:

1. Use curl to fetch note info, e.g. `curl -u "user:password" https://cloud.squirrel.nl/index.php/apps/notes/api/v1/notes/141980
2. Response after 3 seconds.

Expected behavior
Output within a reasonable amount of time. Since this is a lightly loaded server on a local LAN I'd expect a response in milliseconds.

Server (please complete the following information):

• Notes app version: 3.6.2
• Nextcloud version: 19.0.1
• OS: Raspbian
• Web server: nginx
• PHP version: 7.3
• Database: PostgreSQL

Client (please complete the following information):

• Browser (incl. version): curl 7.66.0
• OS: Fedora 31

Log files
A message similar to this is written to the NC log for each request:

{"reqId":"c4dvydfNm08qhTtBCKb2","level":3,"time":"2020-08-22T18:35:38+00:00","remoteAddr":"192.168.1.251","user":"--","app":"PHP","method":"GET","url":"/index.php/apps/notes/api/v1/notes?exclude=content","message":"session_start(): A session had already been started - ignoring at /var/www/nextcloud/lib/private/Session/Internal.php#209","userAgent":"curl/7.66.0","version":"19.0.1.1"}

[korelstar]

I can confirm this. However, I don't know when this was introduced. Recently, I did some work in order to improve the speed, see #525 (Notes app 3.5.0). I remember, that I measured a time of around 200ms for API requests. However, I don't remember the exact Nextcloud server version. I think it was something in 18. Now, with Nextcloud server 19 and Notes 3.6.3, I get something around 2.200 ms.

Hence, we have to investigate in which version of Nextcloud server or the Notes app the slowness was introduced.

I did a quick test on this using Nextcloud's docker images, but I couldn't find any difference between versions. Any help is appreciated, since it seems to be a time consuming investigation.

[korelstar]

Oh, and you can safely ignore the session error message. It's a bug in Nextcloud server (see nextcloud/server#20490) which was fixed in nextcloud/server#22243 (will be part of 19.0.2).

[sciurius]

There are similar delays when using webdav so the problem may be more general.

[korelstar]

Interestingly, I can't see a delay anymore, when using the Android App. However, when doing a request using curl, it still takes about 2 seconds (even in my test account with very few notes).

Does the problem still occurs to you with the latest server version?

[stefan-niedermann]

@korelstar maybe the ETags distort the results from the Android App... I guess you make full requests without If-Modified-Since headers and such stuff, maybe this causes (or prevents) the delay?

[korelstar]

No, I used ETags (If-None-Match) and pruneBefore. But I had no time to dig into the details ...

[korelstar]

In practice, I can't see any delay since a long time. I'll close this issue for now. If it will happen again, we can re-open it.