Nextcloud Sync Diagnosis via Cloudflare Tunnel

2026-06-12 Incident

Symptoms

Doro reported "同步不流畅，更新很难顺利同步"
Multiple PDF files (~10MB each) failed to upload repeatedly over several hours
Desktop client (mirall/33.0.5, Windows 10) kept retrying

Log Evidence

Nextcloud log (/var/www/html/data/nextcloud.log):

level:3 | user:doro | method:PUT | BadRequest
"预期文件大小为10821497字节，实际从Nextcloud客户端读入并写入Nextcloud存储空间的大小为5758976字节。
 可能是发送端发生了网络问题，或者是服务器写入存储设备时发生错误。"

Expected: ~10.8MB, actual written: 3-7MB (varies per attempt)
Same file attempted 10+ times between 02:12-08:03 UTC (10:12-16:03 BJT)

Cloudflared log (journalctl -u cloudflared-nextcloud.service):

ERR error="Incoming request ended abruptly: context canceled" connIndex=2
ERR Request failed error="Incoming request ended abruptly: context canceled"
    dest=https://maggie-share.shazhou.work/remote.php/dav/files/doro/...万禹案-再审申请书附件材料.pdf

Also: failed to run the datagram handler error="timeout: no recent network activity"
QUIC stream acceptance failures

Root Cause Analysis

Cloudflare free-tier 100-second timeout: Hard limit on edge nodes for single HTTP requests. Not configurable via tunnel YAML.
No chunked upload: Desktop client uploaded 10MB files as single PUT requests. At Doro's upload bandwidth, 100s wasn't enough.
connectTimeout: 120s in tunnel config only governs connection establishment, not transfer duration.
Server-side chunking was already enabled (chunking: 1.0, bigfilechunking: true) — the problem was purely client-side threshold.

Failed Files

万禹案-再审申请书附件材料-完整版.pdf (~10.8MB, multiple renamed versions)
万禹案-再审申请书附件材料.pdf (~9.9MB)
万禹行政诉讼及撤销材料-书签版.pdf (~33MB, different error path)
0612_万禹案-再审申请书附件材料.pdf (~11.2MB)

Fix Applied

Client-side: %APPDATA%\Nextcloud\nextcloud.cfg → [General] → chunkSize=5242880 (5MB per chunk)

Diagnostic Commands

# 1. Check server capabilities
curl -s -u USER:PASS "http://localhost:5000/ocs/v1.php/cloud/capabilities?format=json" \
  -H "OCS-APIRequest: true" | python3 -c "
import sys,json; d=json.load(sys.stdin)
caps=d['ocs']['data']['capabilities']
print('DAV:', json.dumps(caps.get('dav',{}), indent=2))
print('Files:', json.dumps(caps.get('files',{}), indent=2))"

# 2. Test chunked upload endpoint
curl -s -o /dev/null -w "%{http_code}" -X MKCOL \
  -u USER:PASS http://localhost:5000/remote.php/dav/uploads/USER/test-chunk
# Should return 201

# 3. Nextcloud error log (today's level 3+ errors)
docker exec nextcloud-nextcloud-1 bash -c \
  "cat /var/www/html/data/nextcloud.log" | grep "$(date -u +%Y-%m-%d)" | grep '"level":3'

# 4. Cloudflared errors
journalctl -u cloudflared-nextcloud.service --since today | grep -i "ERR\|error\|timeout\|cancel"

# 5. Tunnel config
cat /home/maggie/.cloudflared/maggie-share.yml

Infrastructure Context

Tunnel config: /home/maggie/.cloudflared/maggie-share.yml
Service: cloudflared-nextcloud.service (systemd)
Tunnel ID: 1af48f57-9e20-41d6-a09c-0ef9547eeb88
Hostnames: maggie-share.shazhou.work (Nextcloud), office.shazhou.work (OnlyOffice)
PHP limits: upload_max=512M, post_max=512M, memory=512M — not the bottleneck
Disk: 8% used (412GB free) — not the bottleneck

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