Builds on Travis will fail at random due to a gpg key server issue

[rbreslow]

An example of a failed build log:

gpg: keybox '/tmp/tmp.68k2oubm9U/pubring.kbx' created
gpg: keyserver receive failed: Cannot assign requested address

Can be resolved by restarting the job, sometimes multiple times.

[rbreslow]

https://docs.travis-ci.com/user/common-build-problems/#travis_retry

[rbreslow]

My mind is blown:

> rbreslow@maiden docker-django (master *) $ CI=1 VERSION=2.0 PYTHON_VERSION=3.6   PG_MAJOR=10 PG_VERSION=10.4-2.pgdg90+1 VARIANT=slim   ./scripts/cibuild
+ '[' ./scripts/cibuild = ./scripts/cibuild ']'
+ '[' '' = --help ']'
+ pushd 2.0
~/Projects/docker-django/2.0 ~/Projects/docker-django
+ sed -e s/%%PYTHON_VERSION%%/3.6/ -e s/%%PG_MAJOR%%/10/ -e s/%%PG_VERSION%%/10.4-2.pgdg90+1/ ../Dockerfile-slim.template
+ docker build -t quay.io/azavea/django:2.0-python3.6-slim .
Sending build context to Docker daemon  4.096kB
Step 1/10 : FROM python:3.6-slim-stretch
 ---> 29ea9c0b39c6
Step 2/10 : MAINTAINER Azavea <systems@azavea.com>
 ---> Using cache
 ---> 4652a1a9d4c6
Step 3/10 : RUN set -ex; 	if ! command -v gpg > /dev/null; then 		apt-get update; 		apt-get install -y --no-install-recommends 			gnupg 			dirmngr ; 		rm -rf /var/lib/apt/lists/*; 	fi
 ---> Using cache
 ---> e4485cb6be8d
Step 4/10 : RUN set -ex; 	key='B97B0AFCAA1A47F044F244A07FCC7D46ACCC4CF8'; 	apt-key adv --keyserver ha.pool.sks-keyservers.net --recv-keys "$key";
 ---> Running in 9a6c1ef9826f
+ key=B97B0AFCAA1A47F044F244A07FCC7D46ACCC4CF8
+ apt-key adv --keyserver ha.pool.sks-keyservers.net --recv-keys B97B0AFCAA1A47F044F244A07FCC7D46ACCC4CF8
Warning: apt-key output should not be parsed (stdout is not a terminal)
Executing: /tmp/apt-key-gpghome.3OK9uEUyrG/gpg.1.sh --keyserver ha.pool.sks-keyservers.net --recv-keys B97B0AFCAA1A47F044F244A07FCC7D46ACCC4CF8
gpg: keyserver receive failed: Cannot assign requested address
The command '/bin/sh -c set -ex; 	key='B97B0AFCAA1A47F044F244A07FCC7D46ACCC4CF8'; 	apt-key adv --keyserver ha.pool.sks-keyservers.net --recv-keys "$key";' returned a non-zero code: 2

I ran this locally and switched to the old import method of using apt-key adv. It failed three times in a row.

[rbreslow]

I believe this is happening because IPv6 networking for Docker is disabled by default, and the SKS Keyservers high-availability pool contains some IPv6-only servers:

• gpg: keyserver receive failed: Address not available nodejs/docker-node#380 (comment)
• IPv6 sockets returning "Cannot assign requested address" travis-ci/travis-ci#8711 (closed due to inactivity)
• https://sks-keyservers.net/status/

This would explain why builds were failing, seemingly at random, and even locally.

I am testing a work around:

diff --git a/Dockerfile-slim.template b/Dockerfile-slim.template
index 423b752..82b0ae9 100644
--- a/Dockerfile-slim.template
+++ b/Dockerfile-slim.template
@@ -18,7 +18,8 @@ RUN set -ex; \
 # uid                  PostgreSQL Debian Repository
        key='B97B0AFCAA1A47F044F244A07FCC7D46ACCC4CF8'; \
        export GNUPGHOME="$(mktemp -d)"; \
-       gpg --keyserver ha.pool.sks-keyservers.net --recv-keys "$key"; \
+       (gpg --keyserver ha.pool.sks-keyservers.net --recv-keys "$key" \
+           || gpg --keyserver ipv4.pool.sks-keyservers.net --recv-keys "$key"); \
        gpg --export "$key" > /etc/apt/trusted.gpg.d/postgres.gpg; \
        rm -rf "$GNUPGHOME"; \
        apt-key list