There is definitely a resource risk to having thousands of open connections to
each node. Some of the drivers have (had?) less than optimal default settings,
like acquiring 50 connections per Cassandra node. This is usually overkill. I
think 5-10/node is much more reasonable. It depends on your app architecture
and cluster node count. If there are lots of small micro-services, maybe they
only need 2 connections per node.
Sean Durity – Staff Systems Engineer, Cassandra
From: Sergio <lapostadiser...@gmail.com>
Sent: Wednesday, October 30, 2019 5:39 PM
To: user@cassandra.apache.org
Subject: [EXTERNAL] Re: Cassandra 3.11.4 Node the load starts to increase after
few minutes to 40 on 4 CPU machine
Hi Reid,
I don't have anymore this loading problem.
I solved by changing the Cassandra Driver Configuration.
Now my cluster is pretty stable and I don't have machines with crazy CPU Load.
The only thing not urgent but I need to investigate is the number of
ESTABLISHED TCP connections. I see just one node having 7K TCP connections
ESTABLISHED while the others are having around 4-6K connection opened. So the
newest nodes added into the cluster have a higher number of ESTABLISHED TCP
connections.
default['cassandra']['sysctl'] = {
'net.ipv4.tcp_keepalive_time' => 60,
'net.ipv4.tcp_keepalive_probes' => 3,
'net.ipv4.tcp_keepalive_intvl' => 10,
'net.core.rmem_max' => 16777216,
'net.core.wmem_max' => 16777216,
'net.core.rmem_default' => 16777216,
'net.core.wmem_default' => 16777216,
'net.core.optmem_max' => 40960,
'net.ipv4.tcp_rmem' => '4096 87380 16777216',
'net.ipv4.tcp_wmem' => '4096 65536 16777216',
'net.ipv4.ip_local_port_range' => '10000 65535',
'net.ipv4.tcp_window_scaling' => 1,
'net.core.netdev_max_backlog' => 2500,
'net.core.somaxconn' => 65000,
'vm.max_map_count' => 1048575,
'vm.swappiness' => 0
}
These are my tweaked value and I used the values recommended from datastax.
Do you have something different?
Best,
Sergio
Il giorno mer 30 ott 2019 alle ore 13:27 Reid Pinchback
<rpinchb...@tripadvisor.com<mailto:rpinchb...@tripadvisor.com>> ha scritto:
Oh nvm, didn't see the later msg about just posting what your fix was.
R
On 10/30/19, 4:24 PM, "Reid Pinchback"
<rpinchb...@tripadvisor.com<mailto:rpinchb...@tripadvisor.com>> wrote:
Message from External Sender
Hi Sergio,
Assuming nobody is actually mounting a SYN flood attack, then this sounds
like you're either being hammered with connection requests in very short
periods of time, or your TCP backlog tuning is off. At least, that's where
I'd start looking. If you take that log message and google it (Possible SYN
flooding... Sending cookies") you'll find explanations. Or just googling "TCP
backlog tuning".
R
On 10/30/19, 3:29 PM, "Sergio Bilello"
<lapostadiser...@gmail.com<mailto:lapostadiser...@gmail.com>> wrote:
>
>Oct 17 00:23:03 prod-personalization-live-data-cassandra-08 kernel:
TCP: request_sock_TCP: Possible SYN flooding on port 9042. Sending cookies.
Check SNMP counters.
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