File Uploads fail with "Connection to Server Lost" "An Unknown Error has Occured"

ℹ️ Support
1

Problem:

I’m running nextcloud on a home server behind an nginx proxy. When I try to upload large binary (~10mb) files, the upload fails. The upload succeeds if I upload the files via gnome files or the mobile app.

Attempted fix:

My initial thought was that nginx or php was rejecting the file because it was too large, so I added client_max_body_size 16G; to nginx’s http, server, and location sections. I also ran

* snap set nextcloud php.post-max-execution-time=100000
* snap set php.upload-max-filesize 16G
* snap set php.post-max-size 16G
* snap set php.max-input-time 100000
* snap set php.max-execution-time 100000

Versions:

Nextcloud version: Nextcloud Snap 20.0.4
Operating system: Ubuntu Server 20.04
Nginx version: 1.18.0

Repro Steps:

  1. Install a clean copy of ubuntu 20.04
  2. Install Nextcloud Snap and and nginx
  3. Set up a reverse proxy to Nextcloud
  4. Attempt to upload a file

config.php file:

<?php
$CONFIG = array (
  'apps_paths' => 
  array (
    0 => 
    array (
      'path' => '/snap/nextcloud/current/htdocs/apps',
      'url' => '/apps',
      'writable' => false,
    ),
    1 => 
    array (
      'path' => '/var/snap/nextcloud/current/nextcloud/extra-apps',
      'url' => '/extra-apps',
      'writable' => true,
    ),
  ),
  'supportedDatabases' => 
  array (
    0 => 'mysql',
  ),
  'memcache.locking' => '\\OC\\Memcache\\Redis',
  'memcache.local' => '\\OC\\Memcache\\Redis',
  'redis' => 
  array (
    'host' => '/tmp/sockets/redis.sock',
    'port' => 0,
  ),
  'log_type' => 'file',
  'logfile' => '/var/snap/nextcloud/current/logs/nextcloud.log',
  'logfilemode' => 416,
  'passwordsalt' => '<redacted>',
  'secret' => '<redacted>',
  'trusted_domains' => 
  array (
    0 => 'localhost',
    1 => '<redacted>',
  ),
  'trusted_proxies' => 
  array (
	  0 => '127.0.0.1',
  ),
  'datadirectory' => '<redacted>',
  'dbtype' => '<redacted>',
  'version' => '<redacted>',
  'overwrite.cli.url' => '<redacted>',
  'overwriteprotocol' => 'https',
  'overwritehost' => '<redacted>',
  'dbname' => '<redacted>',
  'dbhost' => '<redacted>',
  'dbport' => '',
  'dbtableprefix' => '<redacted>',
  'mysql.utf8mb4' => true,
  'dbuser' => '<redacted>',
  'dbpassword' => '<redacted>',
  'installed' => true,
  'instanceid' => '<redacted>',
  'maintenance' => false,
  'loglevel' => 2,
  'app_install_overwrite' => 
  array (
    0 => '<redacted>',
    1 => '<redacted>',
  ),
);

Relevent nginx logs:

146.115.145.110 - - [27/Dec/2020:18:31:37 +0000] "MKCOL /remote.php/dav/uploads/ajl/web-file-upload-373c038a410bb3edd463edde5843dd04-1609093897581 HTTP/1.1" 201 0 "-" "Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:84.0) Gecko/20100101 Firefox/84.0"
146.115.145.110 - - [27/Dec/2020:18:31:37 +0000] "PUT /remote.php/dav/uploads/ajl/web-file-upload-373c038a410bb3edd463edde5843dd04-1609093897581/0 HTTP/1.1" 400 0 "-" "Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:84.0) Gecko/20100101 Firefox/84.0"
146.115.145.110 - - [27/Dec/2020:18:31:37 +0000] "PUT /remote.php/dav/uploads/ajl/web-file-upload-373c038a410bb3edd463edde5843dd04-1609093897581/0 HTTP/1.1" 400 0 "-" "Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:84.0) Gecko/20100101 Firefox/84.0"
146.115.145.110 - - [27/Dec/2020:18:31:38 +0000] "DELETE /remote.php/dav/uploads/ajl/web-file-upload-373c038a410bb3edd463edde5843dd04-1609093897581 HTTP/1.1" 204 0 "-" "Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:84.0) Gecko/20100101 Firefox/84.0"
146.115.145.110 - - [27/Dec/2020:18:31:38 +0000] "GET /index.php/apps/files/ajax/getstoragestats.php?dir=%2F HTTP/1.1" 200 202 "-" "Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:84.0) Gecko/20100101 Firefox/84.0"

Relevent apache snap logs:

127.0.0.1 - - [27/Dec/2020:18:45:00 +0000] "MKCOL /remote.php/dav/uploads/ajl/web-file-upload-373c038a410bb3edd463edde5843dd04-1609094700787 HTTP/1.0" 201 525 "-" "Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:84.0) Gecko/20100101 Firefox/84.0"
127.0.0.1 - - [27/Dec/2020:18:45:00 +0000] "POST /index.php/apps/text/session/sync HTTP/1.0" 200 959 "-" "Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:84.0) Gecko/20100101 Firefox/84.0"
127.0.0.1 - - [27/Dec/2020:18:45:01 +0000] "DELETE /remote.php/dav/uploads/ajl/web-file-upload-373c038a410bb3edd463edde5843dd04-1609094700787 HTTP/1.0" 204 469 "-" "Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:84.0) Gecko/20100101 Firefox/84.0"
127.0.0.1 - - [27/Dec/2020:18:45:01 +0000] "GET /index.php/apps/files/ajax/getstoragestats.php?dir=%2F HTTP/1.0" 200 930 "-" "Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:84.0) Gecko/20100101 Firefox/84.0"

I think the problem is those “PUT” requests that are returning 400. They appear in nginx logs, but don’t appear in the apache logs. I’m a little out of my depth here, though. Any advise would be greatly appreciated.

2

I solved this problem myself, although the solution probably won’t be helpful to other people.

This appears to have been a problem with my laptop’s operating system. I don’t know why, but it was dropping large file uploads prematurely. The upload worked fine from every other computer I tested it on, but failed with every application I tried (chrome, firefox, curl, nautilus files) on my laptop. I re-installed my laptop’s OS and the problem went away.