Connection timeout at startup

[idlmn]

I am running dnscrypt-proxy in version 2.0.19 installed from the Debian sid repository on an minimal raspbian installation. I want to use it to encrypt dns queries through DNS over HTTPS but it does not matter what server I want it to use (Quad9, Cloudflare), every time after a system startup/restart the following is showing up in the system log:

Apr 25 04:51:50 raspi dnscrypt-proxy[1700]: [2019-04-25 04:51:50] [ERROR] Get https://dns.quad9.net/dns-query?ct=&dns=yv4BAAABAAAAAAABAAACAAEAACkQAAAAgAAAAA: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)
Apr 25 04:51:50 raspi dnscrypt-proxy[1700]: [2019-04-25 04:51:50] [NOTICE] dnscrypt-proxy is waiting for at least one server to be reachable
Apr 25 04:53:45 raspi dnscrypt-proxy[1700]: [2019-04-25 04:53:45] [NOTICE] [quad9-doh-ip4-pri] OK (DoH) - rtt: 11ms
Apr 25 04:53:45 raspi dnscrypt-proxy[1700]: [2019-04-25 04:53:45] [NOTICE] Server with the lowest initial latency: quad9-doh-ip4-pri (rtt: 11ms)

At startup dnscrypt-proxy can't reach the server and resolving is impossible and exact 1 min and 55 sec later it is no problem.

[incognico]

Is it because the clock is off and gets synced ~2min after boot?

[idlmn]

Is it because the clock is off and gets synced ~2min after boot?

That would be a good catch but unfortunately that is not the case. To make it perfectly sure, I disabled the the systemd unit and waited for systemd-timesyncd to synchronize the time. After this I started it manually over the command line but the problem still remains.

When I (re)boot the system, wait for 2 minutes and start it manually, erverthing is fine. So there is something in the background that keeps dnscrypt-proxy away from working correctly but I don't know what it could be.

UPDATE:
I have found the problem. In the system log I saw that dnycrypt-proxy started successfully one second after crng (kernel component for cryptographic random numbers) initialization had been done.
Google says that this component could cause some trouble. So I think that dnscrypt-proxy wants to retrieve some random content for https and/or maybe other things but because of the fact that the entropy queue isn't filled enough it has to wait until it is.
The Solution is to install rng-tools, so rngd fills up the entropy queue and dnscrypt-proxy is served with enough random content to work properly.

[jedisct1]

Duplicate of #760