DNS challenges with Kubernetes and Alpine

[olvlvl]

Hi,

Alpine has a known issue regarding DNS resolving. Our only solution right now is to use Debian images instead, but they are bigger, like ~5 times bigger. Would you consider adding support for ubuntu:bionic? Its file size is comparable to Alpine's and it's working fine, at least on our infrastructure.

[tianon]

Would you consider adding support for ubuntu:bionic? Its file size is comparable to Alpine's ...

I'm not sure where this idea comes from, but I don't think it's accurate:

alpine:3.8           4.41MB
alpine:3.7           4.21MB
ubuntu:xenial        115MB
ubuntu:trusty        188MB
ubuntu:cosmic        71.3MB
ubuntu:bionic        84.1MB
debian:wheezy-slim   46.9MB
debian:stretch-slim  55.3MB
debian:sid-slim      66.6MB
debian:jessie-slim   79.2MB
debian:buster-slim   66.1MB

(We're currently based on debian:stretch-slim.)

[olvlvl]

I tried to create an image using ubuntu:bionic but it failed on COPY docker-php-source /usr/local/bin/. I see that debian's base image is pretty slim, bionic might not be an improvement. Still, what's up with the resulting image?

Base image	Size	With CLI	Increase
alpine:3.8	4.41MB	77.5MB	73MB
debian:stretch-slim	55.3MB	368MB	312MB

[tianon]

For Alpine-based images we're able to get a lot more aggressive about removing packages and re-adding them at runtime when users need them since packages typically install very quickly (see PHPIZE_DEPS for what I'm talking about) -- I imagine those are probably a pretty sizeable contributor to that difference in increase.

[tianon]

If you do docker history on each image, you should be able to get a little more granular:

$ docker history php:7.2-cli-alpine
IMAGE               CREATED             CREATED BY                                      SIZE                COMMENT
1163be6aecce        44 hours ago        /bin/sh -c #(nop)  CMD ["php" "-a"]             0B                  
<missing>           44 hours ago        /bin/sh -c #(nop)  ENTRYPOINT ["docker-php-e…   0B                  
<missing>           44 hours ago        /bin/sh -c docker-php-ext-enable sodium         168kB               
<missing>           44 hours ago        /bin/sh -c #(nop) COPY multi:2cdcedabcf5a3b9…   6.42kB              
<missing>           44 hours ago        /bin/sh -c set -xe  && apk add --no-cache --…   58.1MB              
<missing>           44 hours ago        /bin/sh -c #(nop) COPY file:207c686e3fed4f71…   587B                
<missing>           44 hours ago        /bin/sh -c set -xe;   apk add --no-cache --v…   12.2MB              
<missing>           44 hours ago        /bin/sh -c #(nop)  ENV PHP_SHA256=3585c1222e…   0B                  
<missing>           44 hours ago        /bin/sh -c #(nop)  ENV PHP_URL=https://secur…   0B                  
<missing>           44 hours ago        /bin/sh -c #(nop)  ENV PHP_VERSION=7.2.9        0B                  
<missing>           44 hours ago        /bin/sh -c #(nop)  ENV GPG_KEYS=1729F83938DA…   0B                  
<missing>           45 hours ago        /bin/sh -c #(nop)  ENV PHP_LDFLAGS=-Wl,-O1 -…   0B                  
<missing>           45 hours ago        /bin/sh -c #(nop)  ENV PHP_CPPFLAGS=-fstack-…   0B                  
<missing>           45 hours ago        /bin/sh -c #(nop)  ENV PHP_CFLAGS=-fstack-pr…   0B                  
<missing>           45 hours ago        /bin/sh -c mkdir -p $PHP_INI_DIR/conf.d         0B                  
<missing>           45 hours ago        /bin/sh -c #(nop)  ENV PHP_INI_DIR=/usr/loca…   0B                  
<missing>           45 hours ago        /bin/sh -c set -x  && addgroup -g 82 -S www-…   4.85kB              
<missing>           45 hours ago        /bin/sh -c apk add --no-cache --virtual .per…   2.69MB              
<missing>           45 hours ago        /bin/sh -c #(nop)  ENV PHPIZE_DEPS=autoconf …   0B                  
<missing>           47 hours ago        /bin/sh -c #(nop)  CMD ["/bin/sh"]              0B                  
<missing>           47 hours ago        /bin/sh -c #(nop) ADD file:25c10b1d1b41d46a1…   4.41MB              

$ docker history php:7.2-cli
IMAGE               CREATED             CREATED BY                                      SIZE                COMMENT
71c6a3058357        6 days ago          /bin/sh -c #(nop)  CMD ["php" "-a"]             0B                  
<missing>           6 days ago          /bin/sh -c #(nop)  ENTRYPOINT ["docker-php-e…   0B                  
<missing>           6 days ago          /bin/sh -c docker-php-ext-enable sodium         20B                 
<missing>           6 days ago          /bin/sh -c #(nop) COPY multi:2cdcedabcf5a3b9…   6.42kB              
<missing>           6 days ago          /bin/sh -c set -eux;   savedAptMark="$(apt-m…   89.6MB              
<missing>           8 days ago          /bin/sh -c #(nop) COPY file:207c686e3fed4f71…   587B                
<missing>           8 days ago          /bin/sh -c set -xe;   fetchDeps='   wget  ';…   13.4MB              
<missing>           8 days ago          /bin/sh -c #(nop)  ENV PHP_SHA256=3585c1222e…   0B                  
<missing>           8 days ago          /bin/sh -c #(nop)  ENV PHP_URL=https://secur…   0B                  
<missing>           8 days ago          /bin/sh -c #(nop)  ENV PHP_VERSION=7.2.9        0B                  
<missing>           8 days ago          /bin/sh -c #(nop)  ENV GPG_KEYS=1729F83938DA…   0B                  
<missing>           8 days ago          /bin/sh -c #(nop)  ENV PHP_LDFLAGS=-Wl,-O1 -…   0B                  
<missing>           8 days ago          /bin/sh -c #(nop)  ENV PHP_CPPFLAGS=-fstack-…   0B                  
<missing>           8 days ago          /bin/sh -c #(nop)  ENV PHP_CFLAGS=-fstack-pr…   0B                  
<missing>           8 days ago          /bin/sh -c mkdir -p $PHP_INI_DIR/conf.d         0B                  
<missing>           8 days ago          /bin/sh -c #(nop)  ENV PHP_INI_DIR=/usr/loca…   0B                  
<missing>           8 days ago          /bin/sh -c apt-get update && apt-get install…   209MB               
<missing>           8 days ago          /bin/sh -c #(nop)  ENV PHPIZE_DEPS=autoconf …   0B                  
<missing>           8 days ago          /bin/sh -c set -eux;  {   echo 'Package: php…   46B                 
<missing>           9 days ago          /bin/sh -c #(nop)  CMD ["bash"]                 0B                  
<missing>           9 days ago          /bin/sh -c #(nop) ADD file:e6ca98733431f75e9…   55.3MB              

[tianon]

Closing given that there's not really much we can do here (as far as I can see).

One other thing you could try is to use something like https://github.com/frol/docker-alpine-glibc in order to get an Alpine build of PHP + glibc (to try and overcome the DNS issues), but that's definitely out of scope for this repository. 👍