I should add that this isn’t the first time this has happened, but it is the first time since I reduced the allocation of RAM for PostgreSQL in the configuration file. I swore that that was the problem, but I guess not. It’s been almost a full week without any usage spikes or service interruptions of this kind, but all of a sudden, my RAM and CPU are maxing out again at regular intervals. When this occurs, the instance is unreachable until the issue resolves itself, which seemingly takes 5-10 minutes.
The usage spikes only started today out of a seven-day graph; they are far above my idle usage.
I thought the issue was something to do with Lemmy periodically fetching some sort of remote data and slamming the database, which is why I reduced the RAM allocation for PostgreSQL to 1.5 GB instead of the full 2 GB. As you can see in the above graph, my idle resource utilization is really low. Since it’s probably cut off from the image, I’ll add that my disk utilization is currently 25-30%. Everything seemed to be in order for basically an entire week, but this problem showed up again.
Does anyone know what is causing this? Clearly, something is happening that is loading the server more than usual.
Depending on your timezone, it is possibly a peak in traffic from the US, an overlap of July 4th, Reddit userbase jumping in, and the recent surge on shitposting about…sigh… beans.
interesting my new instance just had a 10ish minute cpu spike where ir was unresponsive. Even following a reboot.
Oh, and for completeness:
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We’ve deleted the vast majority of the spam bots that spammed our instance, are currently on closed registration with applications, and have had no anomalous activity since.
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Our server is essentially always at 50% memory (1GB/2GB), 10% CPU (2 vCPUs), and 30% disk (15-20GB/60GB) until a spike. Disk utilization does not change during a spike.
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Our instance is relatively quiet, and we probably have no more than ten truly active users at this point. We have a potential uptick in membership, but this is still relatively slow and negligible.
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This issue has happened before, but I assumed it was fixed when I changed the PostgreSQL configuration to utilize less RAM. This is still the longest lead-up time before the spikes started.
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When the spike resolves itself, the instance works as expected. The issues with service interruptions seems to stem from a drastic increase in resource utilization, which could be caused by some software component that I’m not aware of. I used the Ansible install for Lemmy, and have only modified certain configuration files as required. For the most part, I’ve only added a higher max_client_body_size in the nginx configs for larger images, and have added settings for an SMTP relay to the main config.hjson file. The spikes occured before these changes, which leads me to believe that they are caused by something I have not yet explored.
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These issues occured on both 0.17.4 and 0.18.0, which seems to indicate it’s not a new issue stemming from a recent source code change.
Here’s an update. I set up atop on my VPS and waited until the issue occurred again. Here’s the atop log from the event.
ATOP - ip-172-31-7-27 2023/07/22 18:40:02 ----------------- 10m0s elapsed
PRC | sys 9m49s | user 12.66s | #proc 134 | #zombie 0 | #exit 3 |
CPU | sys 99% | user 0% | irq 0% | idle 0% | wait 0% |
MEM | tot 957.1M | free 49.8M | buff 0.1M | slab 95.1M | numnode 1 |
SWP | tot 0.0M | free 0.0M | swcac 0.0M | vmcom 2.4G | vmlim 478.6M |
PAG | numamig 0 | migrate 0 | swin 0 | swout 0 | oomkill 0 |
PSI | cpusome 63% | memsome 99% | memfull 88% | iosome 99% | iofull 0% |
DSK | xvda | busy 100% | read 461505 | write 171 | avio 1.30 ms |
DSK | xvda1 | busy 100% | read 461505 | write 171 | avio 1.30 ms |
NET | transport | tcpi 2004 | tcpo 1477 | udpi 9 | udpo 11 |
NET | network | ipi 2035 | ipo 1521 | ipfrw 20 | deliv 2015 |
NET | eth0 ---- | pcki 2028 | pcko 1500 | si 4 Kbps | so 1 Kbps |
PID SYSCPU USRCPU VGROW RGROW RDDSK WRDSK CPU CMD
41 5m17s 0.00s 0B 0B 0B 0B 53% kswapd0
1 21.87s 0.00s 0B -80.0K 1.2G 0B 4% systemd
21681 20.28s 0.00s 0B 4.0K 4.2G 0B 3% lemmy
435 18.00s 0.00s 0B 392.0K 163.1M 0B 3% snapd
21576 17.20s 0.00s 0B 0B 4.2G 0B 3% pict-rs
The culprit seems to be kswapd0 trying to move memory to swap space, although there is no swap space.
I set memory swappiness to 0 on the system for now, I’ll check if that makes a difference.
I’ve been seeing similar since upgrading to 0.18. Upgraded to 0.18.1-rc.9 yesterday… haven’t seen it reoccur again… yet.
Here is an example I happened to be at my PC for:
The problem is that an update will inherently involve a restart of everything, which tends to solve the problem anyway. Whether the update fixed things or restarting things temporarily did is only something you can find out in a few days.
