Switch to the multi-stage build pattern

[dkarlovi]

Looking at the Dockerfile and the image's history (see below), it seems we can save quite a bit of space by switching to the multi-stage build pattern.

It should allow us to avoid having a 250MB+ intermediate layer in the image:

$ docker history jakzal/phpqa:alpine 
IMAGE               CREATED             CREATED BY                                      SIZE                COMMENT
76b1555a30f9        19 hours ago        /bin/sh -c #(nop)  CMD ["/bin/sh" "-c" "php …   0B                  
<missing>           19 hours ago        /bin/sh -c apk add --no-cache --virtual .too…   252MB               
<missing>           19 hours ago        /bin/sh -c #(nop) COPY file:60fad6cf4445b0d0…   1.88MB              
<missing>           19 hours ago        /bin/sh -c #(nop) COPY file:287ae7377cdad1b1…   23.6kB              
<missing>           19 hours ago        /bin/sh -c #(nop) COPY file:850923d8354d1f73…   18.7kB              
<missing>           19 hours ago        /bin/sh -c #(nop)  ENV TOOLS_JSON=/tools/too…   0B                  
<missing>           19 hours ago        /bin/sh -c #(nop)  ENV PATH=/usr/local/sbin:…   0B                  
<missing>           19 hours ago        /bin/sh -c #(nop)  ENV TOOL_DEPS=git graphvi…   0B                  
<missing>           19 hours ago        /bin/sh -c #(nop)  ENV LIB_DEPS=zlib-dev        0B                  
<missing>           19 hours ago        /bin/sh -c #(nop)  ENV BUILD_DEPS=autoconf f…   0B                  
<missing>           19 hours ago        /bin/sh -c #(nop)  ENV COMPOSER_HOME=/tools/…   0B                  
<missing>           19 hours ago        /bin/sh -c #(nop)  ENV COMPOSER_ALLOW_SUPERU…   0B                  
<missing>           19 hours ago        /bin/sh -c #(nop)  LABEL maintainer=Jakub Za…   0B                  
<missing>           2 weeks ago         /bin/sh -c #(nop)  CMD ["php" "-a"]             0B                  
<missing>           2 weeks ago         /bin/sh -c #(nop)  ENTRYPOINT ["docker-php-e…   0B                  
<missing>           2 weeks ago         /bin/sh -c docker-php-ext-enable sodium         168kB               
<missing>           2 weeks ago         /bin/sh -c #(nop) COPY multi:2cdcedabcf5a3b9…   6.42kB              
<missing>           2 weeks ago         /bin/sh -c set -xe  && apk add --no-cache --…   58.1MB              
<missing>           2 weeks ago         /bin/sh -c #(nop) COPY file:207c686e3fed4f71…   587B                
<missing>           2 weeks ago         /bin/sh -c set -xe;   apk add --no-cache --v…   12.2MB              
<missing>           2 weeks ago         /bin/sh -c #(nop)  ENV PHP_SHA256=da1a705c0b…   0B                  
<missing>           2 weeks ago         /bin/sh -c #(nop)  ENV PHP_URL=https://secur…   0B                  
<missing>           2 weeks ago         /bin/sh -c #(nop)  ENV PHP_VERSION=7.2.11       0B                  
<missing>           6 weeks ago         /bin/sh -c #(nop)  ENV GPG_KEYS=1729F83938DA…   0B                  
<missing>           6 weeks ago         /bin/sh -c #(nop)  ENV PHP_LDFLAGS=-Wl,-O1 -…   0B                  
<missing>           6 weeks ago         /bin/sh -c #(nop)  ENV PHP_CPPFLAGS=-fstack-…   0B                  
<missing>           6 weeks ago         /bin/sh -c #(nop)  ENV PHP_CFLAGS=-fstack-pr…   0B                  
<missing>           6 weeks ago         /bin/sh -c mkdir -p $PHP_INI_DIR/conf.d         0B                  
<missing>           6 weeks ago         /bin/sh -c #(nop)  ENV PHP_INI_DIR=/usr/loca…   0B                  
<missing>           6 weeks ago         /bin/sh -c set -x  && addgroup -g 82 -S www-…   4.85kB              
<missing>           6 weeks ago         /bin/sh -c apk add --no-cache --virtual .per…   2.69MB              
<missing>           6 weeks ago         /bin/sh -c #(nop)  ENV PHPIZE_DEPS=autoconf …   0B                  
<missing>           6 weeks ago         /bin/sh -c #(nop)  CMD ["/bin/sh"]              0B                  
<missing>           6 weeks ago         /bin/sh -c #(nop) ADD file:25c10b1d1b41d46a1…   4.41MB   

[jakzal]

Are you happy to prepare a POC? Is it a lot of work? Are there any drawbacks?

[dkarlovi]

There shouldn't be any, we'll just split the process in two (using the same FROM image) and the run the build in the first and copy the build artifacts into the second.

I'll create a POC.

[jakzal]

Since I now learned more about multistage I think it might be a good thing to implement 👍

[dkarlovi]

Yes, it allows your final image to be quite lean, we can move all the build stuff into a separate step and just copy artifacts.

If you have time to move forward with the toolbox merge, we can wrap up quite a bit of work. 👍

[jakzal]

I'll have time around Xmas ;)

[ostrolucky]

I don't see any concrete proposal here. @dkarlovi For what build steps exactly do you want to use multi stage?

[dkarlovi]

I worked on this a bit for the holiday, but it's a bit more complex than anticipated (some problems with adding the zip extension) which made me run out of time. Will continue on this once we're migrated to Toolbox.

@ostrolucky for building the PHP modules.

[jakzal]

@dkarlovi do you have a WIP somewhere we could look at?

[dkarlovi]

Yes, will push later today.

[jakzal]

No rush, I'm just interested to look at it at some point :)

[dkarlovi]

Yes, will push later today.

I'm really bad at estimates. :)

[dkarlovi]

Closed by #302.