I have a Dockerfile which builds a Rust application and puts it in a scratch image.
# build application
FROM ubuntu:latest as system-deps
RUN apt-get update && apt-get install -y tzdata
FROM scratch
COPY --from=system-deps /usr/share/zoneinfo /usr/share/zoneinfo
COPY --from=app-builder --chown=myuser:myuser /app/ryot /app
ENTRYPOINT ["/app"]
However, regardless of what timezone I specify using the --env TZ="<a valid timezone>" docker flag, I always get the current UTC.
How can I make it respect the timezone?
Here is an article I found pertaining to Go projects: Using local time in a Golang Docker container built from Scratch | by Chris Binder | Medium https://github.com/IgnisDa/ryot/blob/ec3194eee6840f4eed902d7fa1a78a6824d8f878/Dockerfile#L45
This question is not specific to Rust. Add a /etc/localtime symlink via the Dockerfile. See localtime(5) - Linux manual page
But that makes me have to hardcore the value at docker build time. I want the users to be able to set the TZ environment variable.
Ok, do it the hard way.
You aren’t really supposed to change the environment in Rust, but you can if you isolate it. It just ends up being code that is completely unnecessary.
As I said in my original post, I am already settings the environment variable.
My question is why is Rust not respecting it?
Hyeonu
July 14, 2023, 1:18am
10
Wht does it mean by Rust not respecting it? Are you using crates like time or chrono?
The chrono crate uses types like Local and Utc to set the timezone, where Local comes from the system (i.e. /etc/localtime). For example, chrono::DateTime<Utc> will give you UTC times.
If you want it dynamically configured via a $TZ environment variable then create your own TimeZone$TZ environment variable for setting the timezone, so it's not surprising that --env TZ=... does nothing.
mpol
July 14, 2023, 8:59pm
13
But doesn't chrono use TZ?
#[cfg(not(target_os = "android"))]
let bytes = fs::read(format!("{}/{}", TZDB_LOCATION, tz_name)).ok()?;
#[cfg(target_os = "android")]
let bytes = android_tzdata::find_tz_data(&tz_name).ok()?;
TimeZone::from_tz_data(&bytes).ok()
}
impl Default for Cache {
fn default() -> Cache {
// default to UTC if no local timezone can be found
let env_tz = env::var("TZ").ok();
let env_ref = env_tz.as_deref();
Cache {
last_checked: SystemTime::now(),
source: Source::new(env_ref),
zone: current_zone(env_ref),
}
}
}
fn current_zone(var: Option<&str>) -> TimeZone {
1 Like
bjorn3
July 15, 2023, 8:17am
14
I think the issue is that the scratch layer doesn't contain the timezone database, so it fails to load the timezone file for the TZ you specified causing a fallback to UTC. https://github.com/chronotope/chrono/blob/38b19bbe4e21c402f81edfa2932a43831e679a35/src/offset/local/tz_info/timezone.rs#L614 Chrono looks in /usr/share/zoneinfo, /share/zoneinfo, /etc/zoneinfo and /usr/share/lib/zoneinfo in that order. Try copying the timezone database from your host system or download it from Time Zone Database
3 Likes
riking
July 18, 2023, 7:38pm
15
Build FROM gcr.io/distroless/base instead of FROM scratch. That will include the time zone database and libc.
# Documentation for `gcr.io/distroless/base` and `gcr.io/distroless/static`
## Image Contents
This image contains a minimal Linux, glibc-based system. It is intended for use directly by "mostly-statically compiled" languages like Go, Rust or D.
Statically compiled applications (Go) that do not require libc can use the `gcr.io/distroless/static` image, which contains:
* ca-certificates
* A /etc/passwd entry for a root user
* A /tmp directory
* tzdata
Most other applications (and Go apps that require libc/cgo) should start with `gcr.io/distroless/base`, which contains all
of the packages in `gcr.io/distroless/static`, and
* glibc
* libssl
* openssl
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