Ubuntu – How to quiet stdout when I rsync in a remote docker container

I host some personal services on a remote server running docker. This service is storing it’s data in a docker volume.

I’m doing some backups from my NAS at home using rsync:

rsync --recursive --archive --stats 
      --rsync-path="docker run -v my_vol:/my/path rsync-image rsync --quiet --log-file=/dev/null" 
      -e ssh user@host:/my/path /local/directory

It works well, but rsync writes a massive amount of things on the container stdout, which are then forwarded to my Datadog account and ends up in way too much logs stored there.

I know I can disable logs capture from this specific container but then I would miss potential errors, so I’m looking for a way to make the rsync server less verbose.

The Dockerfile for rsync-image is very basic:

FROM alpine:latest

# Install Rsync and SSH.
RUN apk update 
 && apk upgrade 
 && apk add --no-cache 
            rsync 
            openssh-client-default 
            sshpass 
            ca-certificates tzdata 
 && update-ca-certificates 
 && rm -rf /var/cache/apk/*

# The UID:GID for www-data in Debian/Ubuntu doesn't match with the IDs in Alpine:
#
# | user : group        | Debian/Ubuntu (uid:gid) | Alpine (uid:gid) |
# | www-data : www-data |         33 : 33         |     82 : 82      |
# | xfs : xfs           |            -            |     33 : 33      |
RUN addgroup nobody xfs

# Run unprivileged
USER nobody

I already tried with –quiet in both –rsync-path and the main rsync command, but it did not change anything

What am I missing?