# Multicast packets **URL:** \ **Category:** Elasticsearch\ **Created:** [April 20, 2010, 12:15pm UTC](https://discuss.elastic.co/t/multicast-packets/2921 "2010-04-20T12:15:12Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![Szymon\_Gwozdz](https://avatars.discourse-cdn.com/v4/letter/s/76d3ee/32.png) [@Szymon\_Gwozdz](https://discuss.elastic.co/u/Szymon_Gwozdz)\ **Post date:** [April 20, 2010, 12:15pm UTC](https://discuss.elastic.co/t/multicast-packets/2921/1 "2010-04-20T12:15:12Z")
Hi! When I'm launching ElasticSearch I get logs like this: [13:48:24,418][WARN][jgroups.UDP] send buffer of socket java.net.DatagramSocket@46b29c9d was set to 640KB, but the OS only allocated 167.77KB. This might lead to performance problems. Please set your max send buffer in the OS correctly (e.g. net.core.wmem\_max on Linux) [13:48:24,418][WARN][jgroups.UDP] receive buffer of socket java.net.DatagramSocket@46b29c9d was set to 20MB, but the OS only allocated 524.29KB. This might lead to performance problems. Please set your max receive buffer in the OS correctly (e.g. net.core.rmem\_max on Linux) [13:48:24,418][WARN][jgroups.UDP] send buffer of socket java.net.MulticastSocket@7846a55e was set to 640KB, but the OS only allocated 167.77KB. This might lead to performance problems. Please set your max send buffer in the OS correctly (e.g. net.core.wmem\_max on Linux) [13:48:24,418][WARN][jgroups.UDP] receive buffer of socket java.net.MulticastSocket@7846a55e was set to 25MB, but the OS only allocated 524.29KB. This might lead to performance problems. Please set your max receive buffer in the OS correctly (e.g. net.core.rmem\_max on Linux) How can I change this buffer in java (not in system, I don't want to change system values)? I've tried with something like this: discovery: jgroups: config: udp mcast\_send\_buf\_size: 10000 mcast\_recv\_buf\_size: 10000 ucast\_send\_buf\_size: 10000 ucast\_recv\_buf\_size: 10000 but it didn't work (i had the same values in logs as before) ☹ I have to get rid of these warnings, because network in my company is rejecting multicast messages with too many packets - admins sent me logs like this: Discard IP fragment set with more than 24 elements: src = 10.1.112.214, dest = 228.8.8.8, proto = udp, id = 18373 And probably because of this after few minutes of feeding elasticsearch with data I have logs like this: [12:28:16,346][WARN][jgroups.pbcast.NAKACK] test-4-16470: dropped message from test-5-22451 (not in xmit\_table), keys are [test-4-16470, test-3-24681, test-2-34614, test-1-48736], view=[test-1-48736|9] [test-1-48736, test-3-24681, test-4-16470, test-2-34614] ---
**Author:** ![kimchy](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/kimchy/32/44952_2.png) [@kimchy](https://discuss.elastic.co/u/kimchy)\ **Post date:** [April 20, 2010, 5:59pm UTC](https://discuss.elastic.co/t/multicast-packets/2921/2 "2010-04-20T17:59:29Z")
This values are recommended values for jgroups when using multicast. You can move to use unicast if you don't want to use multicast or change the values on the os level. cheers, shay.banon On Tue, Apr 20, 2010 at 3:15 PM, Szymon Gwóźdź [sz.gwozdz@gmail.com](mailto:sz.gwozdz@gmail.com) wrote: > Hi! > > When I'm launching Elasticsearch I get logs like this: > > [13:48:24,418][WARN][jgroups.UDP] send buffer of socket > java.net.DatagramSocket@46b29c9d was set to 640KB, but the OS only > allocated 167.77KB. This might lead to performance problems. Please set your > max send buffer in the OS correctly (e.g. net.core.wmem\_max on Linux) > [13:48:24,418][WARN][jgroups.UDP] receive buffer of socket > java.net.DatagramSocket@46b29c9d was set to 20MB, but the OS only > allocated 524.29KB. This might lead to performance problems. Please set your > max receive buffer in the OS correctly (e.g. net.core.rmem\_max on Linux) > [13:48:24,418][WARN][jgroups.UDP] send buffer of socket > java.net.MulticastSocket@7846a55e was set to 640KB, but the OS only > allocated 167.77KB. This might lead to performance problems. Please set your > max send buffer in the OS correctly (e.g. net.core.wmem\_max on Linux) > [13:48:24,418][WARN][jgroups.UDP] receive buffer of socket > java.net.MulticastSocket@7846a55e was set to 25MB, but the OS only > allocated 524.29KB. This might lead to performance problems. Please set your > max receive buffer in the OS correctly (e.g. net.core.rmem\_max on Linux) > > How can I change this buffer in java (not in system, I don't want to change > system values)? I've tried with something like this: > > discovery: > jgroups: > config: udp > mcast\_send\_buf\_size: 10000 > mcast\_recv\_buf\_size: 10000 > ucast\_send\_buf\_size: 10000 > ucast\_recv\_buf\_size: 10000 > > but it didn't work (i had the same values in logs as before) ☹ > > I have to get rid of these warnings, because network in my company is > rejecting multicast messages with too many packets - admins sent me logs > like this: > > Discard IP fragment set with more than 24 elements: src = 10.1.112.214, > dest = 228.8.8.8, proto = udp, id = 18373 > > And probably because of this after few minutes of feeding elasticsearch > with data I have logs like this: > > [12:28:16,346][WARN][jgroups.pbcast.NAKACK] test-4-16470: dropped > message from test-5-22451 (not in xmit\_table), keys are [test-4-16470, > test-3-24681, test-2-34614, test-1-48736], view=[test-1-48736|9] > [test-1-48736, test-3-24681, test-4-16470, test-2-34614] ---
**Author:** ![Szymon\_Gwozdz](https://avatars.discourse-cdn.com/v4/letter/s/76d3ee/32.png) [@Szymon\_Gwozdz](https://discuss.elastic.co/u/Szymon_Gwozdz)\ **Post date:** [April 21, 2010, 8:30am UTC](https://discuss.elastic.co/t/multicast-packets/2921/3 "2010-04-21T08:30:44Z")
Yes, but could you explain me why my discovery.jgroups config isn't working? Regards Szymon Gwóźdź ---
**Author:** ![kimchy](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/kimchy/32/44952_2.png) [@kimchy](https://discuss.elastic.co/u/kimchy)\ **Post date:** [April 21, 2010, 5:39pm UTC](https://discuss.elastic.co/t/multicast-packets/2921/4 "2010-04-21T17:39:42Z")
Yea, its because they are (sadly) not configured to be injected using system properties (which is what I do when you pass them in the elasticsearch.yml configuration). You can create your own copy of the udp.xml file, and place it under config/jgroups location, and change it. cheers, shay.banon 2010/4/21 Szymon Gwóźdź [sz.gwozdz@gmail.com](mailto:sz.gwozdz@gmail.com) > Yes, but could you explain me why my discovery.jgroups config isn't > working? > > Regards > Szymon Gwóźdź ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [July 6, 2017, 4:24am UTC](https://discuss.elastic.co/t/multicast-packets/2921/5 "2017-07-06T04:24:27Z")