Connection overload - system stalls

[funkahdafi]

Hi,

I am running 1.75 and ever since 1.7.something I believe Transmission is not obeying the settings for the maximum number of connections (and max. per new torrent). I have set mine to the recommended setting of 200/60 connections, but when I look at my firewall I see over 1000 connections related to Bittorrent.

To make things worse, as soon as more than 1000 connections are established, my system (10.6.1) kind of stalls, and does not allow me to establish any more new network connections (e.g. I can't browse the net or retrieve emails anymore).

Correct me if I am wrong, but if I tell Transmission to use a maximum of 200 connections, I should not see 1000 sessions on my firewall... I should see no more than 200.

Possible bug?

Thanks

[funkahdafi]

anyone? maybe some dev?

[jch]

What happens when you disable the DHT?

[funkahdafi]

Since I am only connected to private trackers that disallow DHT, DHT should be off, e.g. not be in use.

And even if it were... why are there more connections (many more) than I have allowed through Transmission's preferences?

[illyria]

This may have something to do with my current problem. Except I'm running 1.54, with OSX 10.4.11.

It's been ok up to now. But today I found I can't load any pages in my browser when Transmission is running. Upload and download, or just upload, doesn't matter. One torrent or five - doesn't matter. Firefox or Safari - ditto. I get blank pages for ages, followed by 'server not found'.

I was afraid my ISP was 'throttling' me, but the downloads are carrying on at my normal speed. If this is throttling, they're doing it wrong... So I came here to see if there was anything relevant.

This thread does describe my problem - except for the older versions I have of OSX and Transmission. I'd check how many connections I have for Transmission, only I don't know where to look for that information.....

[funkahdafi]

This may have something to do with my current problem. Except I'm running 1.54, with OSX 10.4.11.

That was quite common in the 1.5x branch. See the enourmously long thread here in the forum. Upgrade to 1.7x and you should be fine.

So.... anyone from the devs can answer why Transmission is opening about 10 times more connections than allowed?

Thanks

[illyria]

Thanks, I'll try that.

[illyria]

*sigh* 1.71 won't run with 10.4.11. When I downloaded it, the description said it would be compatible. But when I try to start, it tells me not with this version of OSX.
Anybody know what is the most recent version I can use with 10.4.11, please?

[funkahdafi]

Illyria, please check your questions elsewehere. This thread is about having too many connections open with 1.7x. Thanks.

[jch]

Since I am only connected to private trackers that disallow DHT, DHT should be off, e.g. not be in use.

If the DHT is enabled, you're still participating in DHT routing and serving as a tracker for other peers. You're just not using other peers for tracking.

So please disable the DHT, and tell us if this helps.

And even if it were... why are there more connections (many more) than I have allowed through Transmission's preferences?

The DHT is a connection-less protocol: it doesn't establish any connections, it just sends isolated packets to hundreds of other nodes around the Internet. Your router firmware is probably (incorrectly) accounting every of your communication partners as a ``connection''.

There's just no way around it -- the DHT needs to contact some 200 other nodes just for routing, plus some 20 nodes per public torrent. These are not ``connections'', however, whatever your router firmware may say.

[funkahdafi]

So please disable the DHT, and tell us if this helps.

Tried. I'm afraid it didn't help.

And even if it were... why are there more connections (many more) than I have allowed through Transmission's preferences?

The DHT is a connection-less protocol: it doesn't establish any connections, it just sends isolated packets to hundreds of other nodes around the Internet. Your router firmware is probably (incorrectly) accounting every of your communication partners as a ``connection''.

There's just no way around it -- the DHT needs to contact some 200 other nodes just for routing, plus some 20 nodes per public torrent. These are not ``connections'', however, whatever your router firmware may say.[/quote]

Well you are right in terms of "connections" as DHT is using UDP as it's transport protocol and thus is in fact "connectionless". However, there are still UDP sessions between peers, and that's what my firewall is counting - correctly. We're not talking about some el cheapo router from walmart's shelve here, this is a Cisco ASA, capable of handling 60.000 concurrent sessions and able to establish 3.000 new connections per second. If that thing tells me I have 1100 connections/sessions open, then that's a fact. So I think I can pretty much rule this one out as a potential point of failure.

Still... I am quite curious about DHT. Say I am not connected to any public trackers whatsoever, and the only trackers I am connected to are private, and Transmission automatically disabled PEX for all active torrents I got from that tracker.... Why would DHT still be working? To whom would it connect?

The configuration options for DHT and PEX clearly ask me to "Use DHT/PEX for *public* torrents" - If none of my torrents are public and DHT is still doing it's thing, then at least the configuration option should be named differently. DHT should automatically be off in my case. If it's not, then it's a bug or the config is described wrong.

[jch]

I am quite curious about DHT. Say I am not connected to any public trackers whatsoever, and the only trackers I am connected to are private, and Transmission automatically disabled PEX for all active torrents I got from that tracker.... Why would DHT still be working? To whom would it connect?

Think of the DHT as an overlay network -- a mesh of nodes that communicate with each other. A DHT node does three things:

1. keeping in touch with roughly 200 nodes, so that the DHT remains connected;

2. announcing every torrent it participates in to 8 DHT nodes, and retrieving peer information from those 8 nodes;

3. hosting peer information for other peers.

For a private torrent, (2) is disabled. However, even if all the torrents you use are private, you're still doing (1) and (3), unless you disable the DHT globally.

[funkahdafi]

Thanks for the explanation jch, apperciate it.

So I disabled DHT globally, but the problem remains.

To make things worse, Transmission takes down my whole machine in situations where it is under heavy workload (downloading 7-8 torrents at the same time with high speeds like 70-80 MB/sec.). Symptoms are loss of connection to other machines on the local LAN, loss of connection to the internet, Mac OS X completely freezing (GUI no longer responds, all dynamic items like menu bar icons that display time etc. freeze)... and more. I think there is another thread open about the same problem, so maybe both things are related.