Can't enable Memcached on php:7.4-fpm-alpine

[LucianoVandi]

Hello, i'm trying to add memcached support to php:7.4-fpm-alpine, below my Dockerfile.

FROM php:7.4-fpm-alpine

RUN apk update && apk add --no-cache --allow-untrusted \
    apache2 apache2-ssl apache2-proxy \
    memcached php7-pecl-memcached

ENTRYPOINT [ "httpd", "-DFOREGROUND"]

The container build without any error, but if from within the container I do php -mcan't see the memcached module loaded.

[PHP Modules]
Core
ctype
curl
date
dom
fileinfo
filter
ftp
hash
iconv
json
libxml
mbstring
mysqlnd
openssl
pcre
PDO
pdo_sqlite
Phar
posix
readline
Reflection
session
SimpleXML
sodium
SPL
sqlite3
standard
tokenizer
xml
xmlreader
xmlwriter
zlib

[Zend Modules]

I'm on Mac OS 10.11.6, Docker CE Version 18.06.1-ce-mac73 (26764).

[wglambert]

There's a docs entry for installing extensions https://github.com/docker-library/docs/tree/master/php#how-to-install-more-php-extensions

$ docker build -t php:test - << EOF
FROM php:7.4-fpm-alpine
RUN apk add libmemcached-dev libmemcached autoconf pkgconfig g++ zlib-dev make && pecl install memcached && \ 
docker-php-ext-enable memcached && apk del make g++ autoconf pkgconfig 
EOF

Sending build context to Docker daemon  2.048kB
Step 1/2 : FROM php:7.4-fpm-alpine
 ---> 597b78d02952
Step 2/2 : RUN apk add libmemcached-dev libmemcached autoconf pkgconfig g++ zlib-dev make && pecl install memcached && docker-php-ext-enable memcached && apk del make g++ autoconf pkgconfig
 ---> Using cache
 ---> 3408f876001f
Successfully built 3408f876001f
Successfully tagged php:test

$ docker run --rm php:test php -m | grep memcached
memcached

See also #575 (comment)

I'd recommend instead running memcached in a separate container

And any reason why you're opting to install Apache in the fpm variant instead of using the default apache variant?

[LucianoVandi]

@wglambert this solved my issue, thanks! Basically I can't install extensions with apk add? I need to reproduce an environment with php-fpm and apache2 through mpm_event_module/proxy_pass, but the apache variant uses mod_php.

[tianon]

When you install via apk, you send up with two versions of PHP in the image (ours and Alpine's), with a very low chance of compatible extensions. You might be interested in the CLI variant (which is roughly the same as FPM but without the FPM binary).

[LucianoVandi]

@tianon thanks for the explanation. What are the advantage of using CLI variant? I need fpm anyway...

[tianon]

Ah sorry, I misunderstood and thought FPM was just dead weight for your use case; my apologies!