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Re: [Sks-devel] Peering Issues - High IO ending with Eventloop.SigAlarm


From: Steffen Kaiser
Subject: Re: [Sks-devel] Peering Issues - High IO ending with Eventloop.SigAlarm always occur with 1 peer
Date: Thu, 13 Dec 2018 07:28:50 +0100 (CET)
User-agent: Alpine 2.11 (DEB 23 2013-08-11)

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On Wed, 12 Dec 2018, Todd Fleisher wrote:

Looks like the issue has spread to other peers as the behavior returned

when I started my server initially, it was hit by the same problem with great I/O and CPU consumption. I had to throow more and more RAM to it. Actually building up the database from scratch required me to give it 4GB or 8GB RAM, then I lowered the limit and it looks like that some keys require the same amount. For my server "the problem suddenly stopped", I don't know why, except to assume the bad keys are included now.

Wasn't there a thread some monthes back telling that some index will be read into memory or something like that?

Well, it's a strange user experience that users cannot query the server, when it is adding keys and stalls like that.

when reconciling with yet another peer (pgpkeys.co.uk <http://pgpkeys.co.uk/>), so I’ve uncommented the previous peer (sks.infcs.de <http://sks.infcs.de/>) and will wait for someone to advise if there’s anything that can be done to reduce this extra IO load (https://imgur.com/a/wHPYGsK <https://imgur.com/a/wHPYGsK>)

-T

On Dec 11, 2018, at 10:10 AM, Todd Fleisher <address@hidden> wrote:

Signed PGP part
I had gotten things under control after sending this, but starting yesterday it 
came back when reconciling with a different peer. I commented that peer out for 
now and things are back to normal.

Is anyone else seeing similar behavior? Is there anything that can be done 
other than pausing reconciliation with peers that bring on the issue?

Here is a graph of my IO during the issue. You can see it drop back to normal 
immediately after I commented out the problem peer.



-T

On Oct 19, 2018, at 11:38 PM, Paul Fawkesley <address@hidden 
<mailto:address@hidden>> wrote:

Hi Todd, for what it's worth, I've been experiencing this too since March.

The hangs are so severe my keyserver would fail to respond to requests. In 
order not to provide a poor experience to users of the pool, I removed myself 
from it.

Anecdotally it appears other keyservers still in the pool are similarly 
affected: I experience high rates of timeout and failure when using the pool 
these days.

I installed Hockeypuck on another server and peered it with my SKS instance. It 
syncs successfully but Hockeypock *also* goes nuts periodically while syncing. 
Its memory and CPU use rockets, often pushing into gigabytes of swap space, so 
that server is pretty unresponsive too.

I'm about to arrive at the OpenPGP Email summit in Brussels, I'm sure this will 
come up as a topic, I shall report back...

Paul

On Wed, 10 Oct 2018, at 19:00, Todd Fleisher wrote:
Hi All,
I wanted to follow up on this and add some new data points. I tried
building some new SKS instances based on a more recent dump
(specifically 2018-10-07 from https://keyserver.mattrude.com/dump/ 
<https://keyserver.mattrude.com/dump/>
<https://keyserver.mattrude.com/dump/ <https://keyserver.mattrude.com/dump/>>) 
and found those instances were
plagued by the same issue when I began peering with my existing
instances. When I re-built the new instances from an older dump
(specifically 2018-10-01 from the same source), the issues went away.
This seems to imply some problematic data was introduced into the pool
during the first week of October that is causing the issues.

I found an existing issue logged about this behavior @
https://bitbucket.org/skskeyserver/sks-keyserver/issues/61/key-addition-failed-blocks-web-interface
 
<https://bitbucket.org/skskeyserver/sks-keyserver/issues/61/key-addition-failed-blocks-web-interface>
<https://bitbucket.org/skskeyserver/sks-keyserver/issues/61/key-addition-failed-blocks-web-interface
 
<https://bitbucket.org/skskeyserver/sks-keyserver/issues/61/key-addition-failed-blocks-web-interface>>

For now, I’m able to keep my instances stable by building them from the
earlier 2018-10-01 dump and not adding the second peer to my membership
file. I would like to better understand why this is happening and figure
out how to go about fixing it, in part so I can begin peering with more
servers to improve the mesh.

-T

On Oct 8, 2018, at 1:54 PM, Todd Fleisher <address@hidden 
<mailto:address@hidden>> wrote:

Hi All,
I recently joined the pool and started having an issue after adding a second external peer to my membership file. The symptoms 
are abnormally high IO load on the disk whenever my server tries to reconcile with the second peer (149.28.198.86), ending with 
a failure message "add_keys_merge failed: Eventloop.SigAlarm”. It appears it tries to reconcile a large number of keys 
(100) consistently when this happens. I’ve read previous list threads about this message (e.g. 
https://lists.nongnu.org/archive/html/sks-devel/2018-06/msg00051.html 
<https://lists.nongnu.org/archive/html/sks-devel/2018-06/msg00051.html> 
<https://lists.nongnu.org/archive/html/sks-devel/2018-06/msg00051.html 
<https://lists.nongnu.org/archive/html/sks-devel/2018-06/msg00051.html>> & 
https://lists.nongnu.org/archive/html/sks-devel/2011-06/msg00077.html 
<https://lists.nongnu.org/archive/html/sks-devel/2011-06/msg00077.html> 
<https://lists.nongnu.org/archive/html/sks-devel/2011-06/msg00077.html 
<https://lists.nongnu.org/archive/html/sks-devel/2011-06/msg00077.html>>) which mention the cause potentially being a 
large key trying to be processed and failing. I tried increasing my client_max_body_size from 8m -> 32m in NGINX, but the 
issue persisted. For now, I have removed the second peer from my membership file to keep from over-taxing my server with no 
apparent benefits. I have included an excerpt of my logs showing the behavior. Can someone please advise what might be causing 
this issue and what can be done to resolve it? Thanks in advance.

<skslog2.txt>

- -- Steffen Kaiser
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