Extension generates huge amounts of DNS traffic

[boeremak]

Hi,

Whenever I have the docker extension tab open in VS Code it generates huge amounts of DNS traffic. Like every second it will resolve the docker host it seems.

I don't know why, but it seems a bit excessive.

Is this a known issue?

I tested it by closing the tab and reopening it again while running tcpdump port 53 on the host.

14:02:58.555296 IP (tos 0x0, ttl 64, id 4595, offset 0, flags [DF], proto UDP (17), length 74) computer1.37430 > 45387544169d.domain: 34017+ AAAA? computer2. (46) 14:02:58.556758 IP (tos 0x0, ttl 64, id 60761, offset 0, flags [DF], proto UDP (17), length 74) 45387544169d.domain > computer1.37430: 34017* 0/0/0 (46) 14:02:59.555871 IP (tos 0x0, ttl 64, id 4783, offset 0, flags [DF], proto UDP (17), length 74) computer1.43205 > 45387544169d.domain: 37882+ AAAA? computer2. (46) 14:02:59.557476 IP (tos 0x0, ttl 64, id 60987, offset 0, flags [DF], proto UDP (17), length 74) 45387544169d.domain > computer1.43205: 37882* 0/0/0 (46) 14:02:59.558387 IP (tos 0x0, ttl 64, id 4784, offset 0, flags [DF], proto UDP (17), length 74) computer1.54991 > 45387544169d.domain: 37631+ AAAA? computer2. (46) 14:02:59.559639 IP (tos 0x0, ttl 64, id 60988, offset 0, flags [DF], proto UDP (17), length 74) 45387544169d.domain > computer1.54991: 37631* 0/0/0 (46) 14:03:00.557342 IP (tos 0x0, ttl 64, id 4979, offset 0, flags [DF], proto UDP (17), length 74) computer1.48462 > 45387544169d.domain: 20099+ AAAA? computer2. (46) 14:03:00.558728 IP (tos 0x0, ttl 64, id 61220, offset 0, flags [DF], proto UDP (17), length 74) 45387544169d.domain > computer1.48462: 20099* 0/0/0 (46) 14:03:00.559082 IP (tos 0x0, ttl 64, id 4980, offset 0, flags [DF], proto UDP (17), length 74) computer1.51060 > 45387544169d.domain: 16870+ AAAA? computer2. (46) 14:03:00.560197 IP (tos 0x0, ttl 64, id 61221, offset 0, flags [DF], proto UDP (17), length 74) 45387544169d.domain > computer1.51060: 16870* 0/0/0 (46) 14:03:01.558345 IP (tos 0x0, ttl 64, id 5065, offset 0, flags [DF], proto UDP (17), length 74) computer1.34690 > 45387544169d.domain: 35754+ AAAA? computer2. (46) 14:03:01.559449 IP (tos 0x0, ttl 64, id 61227, offset 0, flags [DF], proto UDP (17), length 74) 45387544169d.domain > computer1.34690: 35754* 0/0/0 (46) 14:03:01.559894 IP (tos 0x0, ttl 64, id 5066, offset 0, flags [DF], proto UDP (17), length 74) computer1.57271 > 45387544169d.domain: 41870+ AAAA? computer2. (46) 14:03:01.560733 IP (tos 0x0, ttl 64, id 61228, offset 0, flags [DF], proto UDP (17), length 74) 45387544169d.domain > computer1.57271: 41870* 0/0/0 (46) 14:03:02.559186 IP (tos 0x0, ttl 64, id 5133, offset 0, flags [DF], proto UDP (17), length 74) computer1.56776 > 45387544169d.domain: 54764+ AAAA? computer2. (46) 14:03:02.560743 IP (tos 0x0, ttl 64, id 61260, offset 0, flags [DF], proto UDP (17), length 74) 45387544169d.domain > computer1.56776: 54764* 0/0/0 (46) 14:03:02.561055 IP (tos 0x0, ttl 64, id 5134, offset 0, flags [DF], proto UDP (17), length 74) computer1.58752 > 45387544169d.domain: 17352+ AAAA? computer2. (46) 14:03:02.562655 IP (tos 0x0, ttl 64, id 61261, offset 0, flags [DF], proto UDP (17), length 74) 45387544169d.domain > computer1.58752: 17352* 0/0/0 (46) 14:03:03.559994 IP (tos 0x0, ttl 64, id 5329, offset 0, flags [DF], proto UDP (17), length 74) computer1.42790 > 45387544169d.domain: 37436+ AAAA? computer2. (46) 14:03:03.561522 IP (tos 0x0, ttl 64, id 61415, offset 0, flags [DF], proto UDP (17), length 74) 45387544169d.domain > computer1.42790: 37436* 0/0/0 (46) 14:03:04.561236 IP (tos 0x0, ttl 64, id 5362, offset 0, flags [DF], proto UDP (17), length 74) computer1.56471 > 45387544169d.domain: 39504+ AAAA? computer2. (46) 14:03:04.562809 IP (tos 0x0, ttl 64, id 61499, offset 0, flags [DF], proto UDP (17), length 74) 45387544169d.domain > computer1.56471: 39504* 0/0/0 (46)

And so on.

OS: Kubuntu 19. Latest VS Code.

Edit: I really do like the extension, thanks for making it.

[ejizba]

Likely duplicate of #1225 (not sure why that one was closed).

As mentioned there, you can modify docker.explorerRefreshInterval. It defaults to 1 second, which I agree seems excessive

[boeremak]

I don't really mind the refresh speed, it is just that my host does not change its IP address every second. :) Is it possible to just cache the IP address of the docker host?

I'll take a look, thanks.

[bwateratmsft]

I can reproduce. It seems to be a long-standing, controversial issue with Node itself, wherein for every single HTTP request it does a DNS lookup: nodejs/node#5893 ?

From what I understand, in order to actually make use of caching, it sounds like one must configure a system-wide DNS cache (e.g. dnsmasq) or otherwise, use userland packages like dnscache.

It would be possible for docker-modem to resolve it by using dnscache but I will leave that decision to docker-modem.

[bwateratmsft]

@boeremak I filed apocas/docker-modem#111 for docker-modem to consider doing DNS caching for their HTTP requests (or making it an option). In the meantime, you can reduce the refresh speed if you want, or set up a local DNS cache.

[bwateratmsft]

I'll close this one as external to apocas/docker-modem#111; and we can consider changing the refresh speed in #1351.