On Thu, Nov 12, 2020 at 10:37 AM Ayub Khan <ayub...@gmail.com> wrote:
> Martin,
>
> These are file descriptors, some are related to the jar files which are
> included in the web application and some are related to the sockets from
> nginx to tomcat and some are related to database connections. I use the
> below command to count the open file descriptors
>
which type of connections increase ?
the sockets ? the DB ones ?
>
> watch "sudo ls /proc/`cat /var/run/tomcat8.pid`/fd/ | wc -l"
>
you can also use lsof command
>
>
>
> On Thu, Nov 12, 2020 at 10:56 AM Martin Grigorov <mgrigo...@apache.org>
> wrote:
>
> > On Wed, Nov 11, 2020 at 11:17 PM Ayub Khan <ayub...@gmail.com> wrote:
> >
> > > Chris,
> > >
> > > I was load testing using the ec2 load balancer dns. I have increased
> the
> > > connector timeout to 6000 and also gave 32gig to the JVM of tomcat. I
> am
> > > not seeing connection timeout in nginx logs now. No errors in
> kernel.log
> > I
> > > am not seeing any errors in tomcat catalina.out.
> > > During regular operations when the request count is between 4 to 6k
> > > requests per minute the open files count for the tomcat process is
> > between
> > > 200 to 350. Responses from tomcat are within 5 seconds.
> > > If the requests count goes beyond 6.5 k open files slowly move up to
> > 2300
> > > to 3000 and the request responses from tomcat become slow.
> > >
> > > I am not concerned about high open files as I do not see any errors
> > related
> > > to open files. Only side effect of open files going above 700 is the
> > > response from tomcat is slow. I checked if this is caused from elastic
> > > search, aws cloud watch shows elastic search response is within 5
> > > milliseconds.
> > >
> > > what might be the reason that when the open files goes beyond 600, it
> > slows
> > > down the response time for tomcat. I tried with tomcat 9 and it's the
> > same
> > > behavior
> > >
> >
> > Do you know what kind of files are being opened ?
> >
> >
> > >
> > >
> > >
> > >
> > >
> > >
> > > On Tue, Nov 3, 2020 at 9:40 PM Christopher Schultz <
> > > ch...@christopherschultz.net> wrote:
> > >
> > > > Ayub,
> > > >
> > > > On 11/3/20 10:56, Ayub Khan wrote:
> > > > > *I'm curious about why you are using all of cloudflare and ALB and
> > > > > nginx.Seems like any one of those could provide what you are
> getting
> > > from
> > > > > all3 of them. *
> > > > >
> > > > > Cloudflare is doing just the DNS and nginx is doing ssl termination
> > > >
> > > > What do you mean "Cloudflare is doing just the DNS?"
> > > >
> > > > So what is ALB doing, then?
> > > >
> > > > > *What is the maximum number of simultaneous requests that one
> > > > nginxinstance
> > > > > will accept? What is the maximum number of simultaneous
> > proxiedrequests
> > > > one
> > > > > nginx instance will make to a back-end Tomcat node? Howmany nginx
> > nodes
> > > > do
> > > > > you have? How many Tomcat nodes? *
> > > > >
> > > > > We have 4 vms each having nginx and tomcat running on them and each
> > > > tomcat
> > > > > has nginx in front of them to proxy the requests. So it's one Nginx
> > > > > proxying to a dedicated tomcat on the same VM.
> > > >
> > > > Okay.
> > > >
> > > > > below is the tomcat connector configuration
> > > > >
> > > > > <Connector port="8080"
> > > > > connectionTimeout="60000" maxThreads="2000"
> > > > >
> protocol="org.apache.coyote.http11.Http11NioProtocol"
> > > > > URIEncoding="UTF-8"
> > > > > redirectPort="8443" />
> > > >
> > > > 60 seconds is a *long* time for a connection timeout.
> > > >
> > > > Do you actually need 2000 threads? That's a lot, though not insane.
> > 2000
> > > > threads means you expect to handle 2000 concurrent (non-async,
> > > > non-Wewbsocket) requests. Do you need that (per node)? Are you
> > expecting
> > > > 8000 concurrent requests? Does your load-balancer understand the
> > > > topography and current-load on any given node?
> > > >
> > > > > When I am doing a load test of 2000 concurrent users I see the open
> > > files
> > > > > increase to 10,320 and when I take thread dump I see the threads
> are
> > > in a
> > > > > waiting state.Slowly as the requests are completed I see the open
> > files
> > > > > come down to normal levels.
> > > >
> > > > Are you performing your load-test against the CF/ALB/nginx/Tomcat
> > stack,
> > > > or just hitting Tomcat (or nginx) directly?
> > > >
> > > > Are you using HTTP keepalive in your load-test (from the client to
> > > > whichever server is being contacted)?
> > > >
> > > > > The output of the below command is
> > > > > sudo cat /proc/sys/kernel/pid_max
> > > > > 131072
> > > > >
> > > > > I am testing this on a c4.8xlarge VM in AWS.
> > > > >
> > > > > below is the config I changed in nginx.conf file
> > > > >
> > > > > events {
> > > > > worker_connections 50000;
> > > > > # multi_accept on;
> > > > > }
> > > >
> > > > This will allow 50k incoming connections, and Tomcat will accept an
> > > > unbounded number of connections (for NIO connector). So limiting your
> > > > threads to 2000 only means that the work of each request will be done
> > in
> > > > groups of 2000.
> > > >
> > > > > worker_rlimit_nofile 30000;
> > > >
> > > > I'm not sure how many connections are handled by a single nginx
> worker.
> > > > If you accept 50k connections and only allow 30k file handles, you
> may
> > > > have a problem if that's all being done by a single worker.
> > > >
> > > > > What would be the ideal config for tomcat and Nginx so this setup
> on
> > > > > c4.8xlarge vm could serve at least 5k or 10k requests
> simultaneously
> > > > > without causing the open files to spike to 10K.
> > > >
> > > > You will never be able to serve 10k simultaneous requests without
> > having
> > > > 10k open files on the server. If you mean 10k requests across the
> whole
> > > > 4-node environment, then I'd expect 10k requests to open (roughly)
> 2500
> > > > open files on each server. And of course, you need all kinds of other
> > > > files open as well, from JAR files to DB connections or other network
> > > > connections.
> > > >
> > > > But each connection needs a file descriptor, full stop. If you need
> to
> > > > handle 10k connections, then you will need to make it possible to
> open
> > > > 10k file handles /just for incoming network connections/ for that
> > > > process. There is no way around it.
> > > >
> > > > Are you trying to hit a performance target or are you actively
> getting
> > > > errors with a particular configuration? Your subject says "Connection
> > > > Timed Out". Is it nginx that is reporting the connection timeout?
> Have
> > > > you checked on the Tomcat side what is happening with those requests?
> > > >
> > > > -chris
> > > >
> > > > > On Thu, Oct 29, 2020 at 10:29 PM Christopher Schultz <
> > > > > ch...@christopherschultz.net> wrote:
> > > > >
> > > > >> Ayub,
> > > > >>
> > > > >> On 10/28/20 23:28, Ayub Khan wrote:
> > > > >>> During high load of 16k requests per minute, we notice below
> error
> > in
> > > > >> log.
> > > > >>>
> > > > >>> [error] 2437#2437: *13335389 upstream timed out (110:
> Connection
> > > > timed
> > > > >>> out) while reading response header from upstream, server:
> > jahez.net
> > > ,
> > > > >>> request: "GET /serviceContext/ServiceName?callback= HTTP/1.1",
> > > > upstream:
> > > > >> "
> > > > >>> http://127.0.0.1:8080/serviceContext/ServiceName
> > > > >>>
> > > > >>> Below is the flow of requests:
> > > > >>>
> > > > >>> cloudflare-->AWS ALB--> NGINX--> Tomcat-->Elastic-search
> > > > >>
> > > > >> I'm curious about why you are using all of cloudflare and ALB and
> > > nginx.
> > > > >> Seems like any one of those could provide what you are getting
> from
> > > all
> > > > >> 3 of them.
> > > > >>
> > > > >>> In NGINX we have the below config
> > > > >>>
> > > > >>> location /serviceContext/ServiceName{
> > > > >>>
> > > > >>> proxy_pass
> > > > >> http://localhost:8080/serviceContext/ServiceName;
> > > > >>> proxy_http_version 1.1;
> > > > >>> proxy_set_header Connection
> $connection_upgrade;
> > > > >>> proxy_set_header Upgrade $http_upgrade;
> > > > >>> proxy_set_header Host $host;
> > > > >>> proxy_set_header X-Real-IP $remote_addr;
> > > > >>> proxy_set_header X-Forwarded-For
> > > > $proxy_add_x_forwarded_for;
> > > > >>>
> > > > >>>
> > > > >>> proxy_buffers 16 16k;
> > > > >>> proxy_buffer_size 32k;
> > > > >>> }
> > > > >>
> > > > >> What is the maximum number of simultaneous requests that one nginx
> > > > >> instance will accept? What is the maximum number of simultaneous
> > > proxied
> > > > >> requests one nginx instance will make to a back-end Tomcat node?
> How
> > > > >> many nginx nodes do you have? How many Tomcat nodes?
> > > > >>
> > > > >>> below is tomcat connector config
> > > > >>>
> > > > >>> <Connector port="8080"
> > > > >>>
> > > protocol="org.apache.coyote.http11.Http11NioProtocol"
> > > > >>> connectionTimeout="200" maxThreads="50000"
> > > > >>> URIEncoding="UTF-8"
> > > > >>> redirectPort="8443" />
> > > > >>
> > > > >> 50,000 threads is a LOT of threads.
> > > > >>
> > > > >>> We monitor the open file using *watch "sudo ls /proc/`cat
> > > > >>> /var/run/tomcat8.pid`/fd/ | wc -l" *the number of tomcat open
> files
> > > > keeps
> > > > >>> increasing slowing the responses. the only option to recover from
> > > this
> > > > is
> > > > >>> to restart tomcat.
> > > > >>
> > > > >> So this looks like Linux (/proc filesystem). Linux kernels have a
> > > 16-bit
> > > > >> pid space which means a theoretical max pid of 65535. In practice,
> > the
> > > > >> max pid is actually to be found here:
> > > > >>
> > > > >> $ cat /proc/sys/kernel/pid_max
> > > > >> 32768
> > > > >>
> > > > >> (on my Debian Linux system, 4.9.0-era kernel)
> > > > >>
> > > > >> Each thread takes a pid. 50k threads means more than the maximum
> > > allowed
> > > > >> on the OS. So you will eventually hit some kind of serious problem
> > > with
> > > > >> that many threads.
> > > > >>
> > > > >> How many fds do you get in the process before Tomcat grinds to a
> > halt?
> > > > >> What does the CPU usage look like? The process I/O? Disk usage?
> What
> > > > >> does a thread dump look like (if you have the disk space to dump
> > it!)?
> > > > >>
> > > > >> Why do you need that many threads?
> > > > >>
> > > > >> -chris
> > > > >>
> > > > >>
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> > > >
> > > >
> > >
> > > --
> > > --------------------------------------------------------------------
> > > Sun Certified Enterprise Architect 1.5
> > > Sun Certified Java Programmer 1.4
> > > Microsoft Certified Systems Engineer 2000
> > > http://in.linkedin.com/pub/ayub-khan/a/811/b81
> > > mobile:+966-502674604
> > > ----------------------------------------------------------------------
> > > It is proved that Hard Work and kowledge will get you close but
> attitude
> > > will get you there. However, it's the Love
> > > of God that will put you over the top!!
> > >
> >
>
>
> --
> --------------------------------------------------------------------
> Sun Certified Enterprise Architect 1.5
> Sun Certified Java Programmer 1.4
> Microsoft Certified Systems Engineer 2000
> http://in.linkedin.com/pub/ayub-khan/a/811/b81
> mobile:+966-502674604
> ----------------------------------------------------------------------
> It is proved that Hard Work and kowledge will get you close but attitude
> will get you there. However, it's the Love
> of God that will put you over the top!!
>
