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Today's Topics:
1. ISC DHCP performance, an example (Peter Rathlev)
2. DHCP Server Fails When Forking (Jay Foster)
3. Re: DHCP Server Fails When Forking (Christopher Barry)
4. Re: DHCP Server Fails When Forking (Jay Foster)
5. Re: DHCP Server Fails When Forking (Christopher Barry)
----------------------------------------------------------------------
Message: 1
Date: Mon, 06 Jan 2020 18:20:05 +0100
From: Peter Rathlev <pe...@rathlev.dk>
To: dhcp-users <dhcp-us...@isc.org>
Subject: ISC DHCP performance, an example
Message-ID:
<56ca38f6ea49ee77e5fedd7fabae753e748af8e1.ca...@rathlev.dk>
Content-Type: text/plain; charset="UTF-8"
I've been reading up on some (rather old) mails on this list and I can
see that there have been a few discussions about performance. I thought
I would post what we have at my current job, just as an example for
future reference.
We have two sets of DHCP servers, one set serving guests and the other
set serving everything else. Each set have a standard failover config.
Extra info follow below the stats.
Stats for the set servicing everything but guests:
ISC DHCP version 4.4.1
Number of range statements: 3048
Total number of addresses in range statements: 1641487
Leases in lease file (touched leases): 959816 (58%)
Primary server:
Server type: Physical
Processors: 2 x Intel Xeon E5-2640 @2.40 GHz (20 cores)
RAM: 16 GB
Load average (24h): 0.6
Lease file storage: RAM-disk with periodic backup to HDD
DISCOVERS per day: 127732 (1621 unique clients)
Restart time: 21.2 seconds
Secondary server:
Server type: Virtual
Processors (vCPUs): 4 x Intel Xeon E7-4880 v2 @2.5GHz
RAM: 4 GB
Load average (24h): 0.3
Lease file storage: SSD based virtual disk
DISCOVERS per day: 119340 (1632 unique clients)
Restart time: 16.0 seconds
Stats for the set servicing guests:
ISC DHCP version 4.3.6b1
Number of range statements: 516
Total number of addresses in range statements: 236146
Leases in lease file (touched leases): 194592 (82%)
Primary server:
Server type: Virtual
Processors (vCPUs): 4 x Intel Xeon Gold 6154 @3.00 GHz
RAM: 4 GB
Load average (24h): 0.5
Restart time: 6.5 seconds
DISCOVERS per day: 98265 (4564 unique clients)
Lease file storage: SSD based virtual disk
Secondary server:
Server type: Virtual
Processors (vCPUs): 4 x Intel Xeon E7-4880 v2 @2.50 GHz
RAM: 4 GB
Load average (24h): 0.1
Restart time: 5.7 seconds
DISCOVERS per day: 119340 (4627 unique clients)
Lease file storage: SSD based virtual disk
Restart times are measured with "time systemctl restart dhcpd". I have
only measured this once on every server for these numbers, but it's my
impression that it's nominal.
I have included the number of DHCP DISCOVER messages logged and number
of unique clients as a measure of their approximate load. Data was for
what I hope is a "typical" day, Tuesday December 10th 2019.
There are always at least two DHCP relays and often four, multiplying
the number of DISCOVER messages logged compared to actual client
DISCOVERs. Default lease times are typically 8 days with a few
exceptions.
We have a bunch of misbehaving clients that result in a lot more
DISCOVERs that unique clients per day even though the lease time is
much longer. (We have top-talkers warnings and send requests for
inspection to local people when one client sticks out.)
All the servers also act as a caching resolvers (BIND + anycast) for
all our clients and record (via a rotating "tshark") at least the last
24 hours of all DNS and DHCP traffic for troubleshooting purposes. This
adds a bit to the load average but not much.
We normally restart the secondary server immediately after the primary
and have never seen any problems with this. After a normal restart they
enter functional state with no pause.
--
Peter
------------------------------
Message: 2
Date: Mon, 6 Jan 2020 10:42:05 -0800
From: Jay Foster <j...@systech.com>
To: dhcp-users@lists.isc.org
Subject: DHCP Server Fails When Forking
Message-ID: <a4839503-a7e0-feac-0a5c-957a7eeff...@systech.com>
Content-Type: text/plain; charset=utf-8; format=flowed
I am using the ISC DHCP server (dhcpd) version 4.3.6 from a rocko Yocto
build.? When dhcpd is started without the '-f' or '-d' options (forks to
the background) it does not work.? DHCP DISCOVER requests are sent, but
the dhcpd application does not respond.? I can attach strace to the
dhcpd process and see that dhcpd just sleeps in an futex() call.
If I start dhcpd with either the '-f' or '-d' options so it does not
fork, then it works properly.
I have run dhcpd (both forking and non forking) using strace to see if I
could spot any differences.? The only thing I notice is that when
forking, the parent process terminates (expected) along with 3 other
child processes/threads.? It looks like these other threads are supposed
to handle the ISC tasks/messages, but are not cloned by the fork and are
not present after forking.
For reference, with an older version of ISC DHCP server (4.1.1-P1) on an
older product, this problem does not occur.
Any ideas where to look?
------------------------------
Message: 3
Date: Mon, 6 Jan 2020 15:58:32 -0500
From: Christopher Barry <christopher.r.ba...@gmail.com>
To: Users of ISC DHCP <dhcp-users@lists.isc.org>
Subject: Re: DHCP Server Fails When Forking
Message-ID:
<caoajpmrdq2ew+owdgucwbur99ehwtlwp9vdaipsa+vzv3je...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
Make sure user/group perms are valid.
On Mon, Jan 6, 2020, 1:42 PM Jay Foster <j...@systech.com> wrote:
> I am using the ISC DHCP server (dhcpd) version 4.3.6 from a rocko Yocto
> build. When dhcpd is started without the '-f' or '-d' options (forks to
> the background) it does not work. DHCP DISCOVER requests are sent, but
> the dhcpd application does not respond. I can attach strace to the
> dhcpd process and see that dhcpd just sleeps in an futex() call.
>
> If I start dhcpd with either the '-f' or '-d' options so it does not
> fork, then it works properly.
>
> I have run dhcpd (both forking and non forking) using strace to see if I
> could spot any differences. The only thing I notice is that when
> forking, the parent process terminates (expected) along with 3 other
> child processes/threads. It looks like these other threads are supposed
> to handle the ISC tasks/messages, but are not cloned by the fork and are
> not present after forking.
>
> For reference, with an older version of ISC DHCP server (4.1.1-P1) on an
> older product, this problem does not occur.
>
> Any ideas where to look?
>
>
>
>
>
> _______________________________________________
> dhcp-users mailing list
> dhcp-users@lists.isc.org
> https://lists.isc.org/mailman/listinfo/dhcp-users
>
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Message: 4
Date: Mon, 6 Jan 2020 13:14:53 -0800
From: Jay Foster <j...@systech.com>
To: Users of ISC DHCP <dhcp-users@lists.isc.org>, Christopher Barry
<christopher.r.ba...@gmail.com>
Subject: Re: DHCP Server Fails When Forking
Message-ID: <e5d0a2ba-d8f3-b6ca-bf69-85fdcb8ed...@systech.com>
Content-Type: text/plain; charset="utf-8"; Format="flowed"
Can you be more specific?? /usr/sbin/dhcpd is root:root. /usr/sbin/dhcpd
is being run as root.
On 1/6/2020 12:58 PM, Christopher Barry wrote:
> Make sure user/group perms are valid.
>
>
> On Mon, Jan 6, 2020, 1:42 PM Jay Foster <j...@systech.com
> <mailto:j...@systech.com>> wrote:
>
> I am using the ISC DHCP server (dhcpd) version 4.3.6 from a rocko
> Yocto
> build.? When dhcpd is started without the '-f' or '-d' options
> (forks to
> the background) it does not work.? DHCP DISCOVER requests are
> sent, but
> the dhcpd application does not respond.? I can attach strace to the
> dhcpd process and see that dhcpd just sleeps in an futex() call.
>
> If I start dhcpd with either the '-f' or '-d' options so it does not
> fork, then it works properly.
>
> I have run dhcpd (both forking and non forking) using strace to
> see if I
> could spot any differences.? The only thing I notice is that when
> forking, the parent process terminates (expected) along with 3 other
> child processes/threads.? It looks like these other threads are
> supposed
> to handle the ISC tasks/messages, but are not cloned by the fork
> and are
> not present after forking.
>
> For reference, with an older version of ISC DHCP server (4.1.1-P1)
> on an
> older product, this problem does not occur.
>
> Any ideas where to look?
>
>
>
>
>
> _______________________________________________
> dhcp-users mailing list
> dhcp-users@lists.isc.org <mailto:dhcp-users@lists.isc.org>
> https://lists.isc.org/mailman/listinfo/dhcp-users
>
>
> _______________________________________________
> dhcp-users mailing list
> dhcp-users@lists.isc.org
> https://lists.isc.org/mailman/listinfo/dhcp-users
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Message: 5
Date: Mon, 6 Jan 2020 16:49:04 -0500
From: Christopher Barry <christopher.r.ba...@gmail.com>
Cc: Users of ISC DHCP <dhcp-users@lists.isc.org>
Subject: Re: DHCP Server Fails When Forking
Message-ID:
<CAOajpmq43V72OCZ8bvNmE9jiAHQo6qofFNb61E9+=14icpk...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
Generally, when backgrounded, dhcpd runs with reduced privs, e.g. as
dhcpd:dhcpd (your configured user/group may be different). Can you su as
that user and run dhcpd in the foreground? I'm suspecting that user may not
have write perms to the leases file.
On Mon, Jan 6, 2020, 4:15 PM Jay Foster <j...@systech.com> wrote:
> Can you be more specific? /usr/sbin/dhcpd is root:root. /usr/sbin/dhcpd
> is being run as root.
>
> On 1/6/2020 12:58 PM, Christopher Barry wrote:
>
> Make sure user/group perms are valid.
>
>
> On Mon, Jan 6, 2020, 1:42 PM Jay Foster <j...@systech.com> wrote:
>
>> I am using the ISC DHCP server (dhcpd) version 4.3.6 from a rocko Yocto
>> build. When dhcpd is started without the '-f' or '-d' options (forks to
>> the background) it does not work. DHCP DISCOVER requests are sent, but
>> the dhcpd application does not respond. I can attach strace to the
>> dhcpd process and see that dhcpd just sleeps in an futex() call.
>>
>> If I start dhcpd with either the '-f' or '-d' options so it does not
>> fork, then it works properly.
>>
>> I have run dhcpd (both forking and non forking) using strace to see if I
>> could spot any differences. The only thing I notice is that when
>> forking, the parent process terminates (expected) along with 3 other
>> child processes/threads. It looks like these other threads are supposed
>> to handle the ISC tasks/messages, but are not cloned by the fork and are
>> not present after forking.
>>
>> For reference, with an older version of ISC DHCP server (4.1.1-P1) on an
>> older product, this problem does not occur.
>>
>> Any ideas where to look?
>>
>>
>>
>>
>>
>> _______________________________________________
>> dhcp-users mailing list
>> dhcp-users@lists.isc.org
>> https://lists.isc.org/mailman/listinfo/dhcp-users
>>
>
> _______________________________________________
> dhcp-users mailing
> listdhcp-us...@lists.isc.orghttps://lists.isc.org/mailman/listinfo/dhcp-users
>
>
>
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