So many sFTP connections...

[theseus]

Hello!

One of my clients has a cloud subscription with data on it. I've been tasked to backup this data for redundancy.
I've contacted the cloud provider and they started to send me the data via sFTP: I've set up a small sFTP server on a VM and they transfer the data (delta every day).
From there, all good, except that I find there are so many sFTP connections established to transfer the data!
I've asked them, they sent me a log and I saw they are using Syncovery.
For example, here's a (redacted) extract of the log which shows many connection established and nothing is sent through (or at least that's what I can see) before seeing something being copied:

Code: Select all

Syncovery v9.50a, build 431 (64-bit CL)

Licensed to: <REDACTED>
Running on : <REDACTED>
Running as : <REDACTED>
System Info: Microsoft Windows Server 2016 Standard Build 14393
Using Backup Privilege

Log for profile<REDACTED> Common, started at 19:20:00 on 24-04-24

LEFT: \\<REDACTED>\e$\Storage\FG\COMMON\FG
RIGHT: sftp://<REDACTED>/backup/<REDACTED>

The profile is run by the scheduler in a separate thread.

Previous run was at 23-04-24 19:20:01: 141 copied (104,6MB)

Total System Memory at 24-04-24 19:20:00: 10240 MB, Available: 1189 MB, Memory Load: 88%


Left Side Volume Name:                DATA

RIGHT SIDE: Using client certificate "<REDACTED>" with C:\IT\<REDACTED>
Connecting with <REDACTED>

***** RIGHT SIDE: SFTP CONNECTION STARTS *****
Using tgputtylib build 20 based on PuTTY Release 0.76
Accepted SSH server MD5 fingerprint:  <REDACTED>
Accepted SSH server SHA1 fingerprint: <REDACTED>
Copying Direction : Left To Right

Scanning Folders Started At 24-04-24 19:20:01
RIGHT SIDE: Using client certificate "<REDACTED>" with C:\IT\<REDACTED>.ppk
Connecting with <REDACTED>

***** RIGHT SIDE: SFTP CONNECTION STARTS *****
RIGHT SIDE: Using client certificate "<REDACTED>" with C:\IT\<REDACTED>.ppk
Connecting with <REDACTED>

***** RIGHT SIDE: SFTP CONNECTION STARTS *****
RIGHT SIDE: Using client certificate "<REDACTED>" with C:\IT\<REDACTED>.ppk
Connecting with <REDACTED>

***** RIGHT SIDE: SFTP CONNECTION STARTS *****
RIGHT SIDE: Using client certificate "<REDACTED>" with C:\IT\<REDACTED>.ppk
Connecting with <REDACTED>

***** RIGHT SIDE: SFTP CONNECTION STARTS *****
RIGHT SIDE: Using client certificate "<REDACTED>" with C:\IT\<REDACTED>.ppk
Connecting with <REDACTED>

***** RIGHT SIDE: SFTP CONNECTION STARTS *****
RIGHT SIDE: Using client certificate "<REDACTED>" with C:\IT\<REDACTED>.ppk
Connecting with <REDACTED>

[...]

***** RIGHT SIDE: SFTP CONNECTION STARTS *****
Copy L->R \\<REDACTED>\e$\Storage\FG\COMMON\FG\<REDACTED>  (533,0kB)
Copy L->R \\<REDACTED>\e$\Storage\FG\COMMON\FG\<REDACTED>  (170,1kB)
RIGHT SIDE: Using client certificate "<REDACTED>" with C:\IT\<REDACTED>.ppk
Connecting with <REDACTED>

***** RIGHT SIDE: SFTP CONNECTION STARTS *****
Created folder: sftp://<REDACTED>/backup/<REDACTED>
Copy L->R \\<REDACTED>\e$\Storage\FG\COMMON\FG\<REDACTED>  (537,9kB)
RIGHT SIDE: Using client certificate "<REDACTED>" with C:\IT\<REDACTED>.ppk
Connecting with <REDACTED>

[...]

At the end, there are 90 "Connecting with ..." in that log file (which is consistent with what I see in my sFTP server log file) for sending 24 files.
I've performed tests with "scp" and "rsync" (sending ~700 files for a total of ~700MB) and they just establish 1 connection, send everything through it and then disconnect.
The issue I see is that it sometimes generate so many connections (400+ in less than 5 minutes), that my sFTP server starts dropping as a defence mechanism (to avoid DoS).

Is this normal for Syncovery to establish so many connections for sending so little? Or did they miss something in their configuration?


Thanks for clarifying the matter!

[tobias]

Hello,
no, it's not normal.

In general Syncovery uses multiple threads for scanning folders and for copying files, so there will be multiple connection. But not 90 connections for 24 files.

Syncovery will sometimes close a connection and reconnect if there has been an unexpected error.

Can you ask the client to update Syncovery at least to version 9.50d? The latest version is actually 10.14, which is even better.

The multithreading can be configured. But to discover the reason for many extra connections, I would need to see an original log file. Maybe you can send one to support@syncovery.com where you don't need to redact so much.