Timezone in Docker Alpine not using environment variable TZ
I've started using alpine images in all my Docker containers, there are many blogs on why this is a good idea, lower container size (~5MB) which means faster to download and safer as there is less to be exploited.
Timezones
Dates are the bane of many a developer and javascript doesn't do them to well. Most languages allow you to set a timezone when creating dates but not Javascript it seems.
I didn't notice this problem until I started using Docker to run my node apps. Node will take the timezone of a running server and use your timezone when new Date() function is called.
docker run -it node /bin/bash
root@345245d:/# date // output Mon Sep 4 14:39:40 BST 2017
node:latest (base: Ubuntu)
At first I was using the Official Node image which has an Ubuntu base image. I originally had an issue where Dates where created in UTC but adding the environment variable TZ: 'Europe/London' solved that.
docker run -it -e "TZ=Europe/London" node /bin/bash
root@34543fs4:/# date // output Mon Sep 4 14:39:40 BST 2017
node:alpine
I changed all my images to node:alpine and at first I didn't notice any issues, but on further integration testing my validation on micro-services were failing when checking the current date is after a stored one. The client was sending the correct value, so when I looked in the logs of the server the dates were set to GMT, not BST (GMT+1).
docker run -it -e "TZ=Europe/London" node:alpine /bin/bash
root@34543fs4:/# date // output Mon Sep 4 13:39:40 GMT 2017 WHAT?!?!
From what I understand this isn't a "bug" with alpine but just not included in the base image to handle timezones. See "bug" details. The fix helpfully supplied by Christian Kampka is to install the package tzdata (at 3.34MB nearly as big as Alpine OS!) then node will pick up the timestamp setting.
New Dockerfile
To add the new package use apk add
FROM node:alpine
RUN apk add tzdata
Now when I use this Dockerfile with the env I get the correct timestamp
docker run -it -e "TZ=Europe/London" . /bin/bash
root@34543fs4:/# date // output Mon Sep 4 14:39:40 BST 2017 yey!