path.rootfs stripping strips path.rootfs itself to the empty string

[dt-rush]

Host operating system: output of uname -a

all OS

node_exporter version: output of node_exporter --version

this is on master but not yet released.

node_exporter command line flags

See below

Are you running node_exporter in Docker?

Yes

What did you do that produced an error?

Dockerfile:

FROM golang

RUN apt-get update && apt-get -y install git build-essential

RUN git clone https://github.com/prometheus/node_exporter && \
	cd node_exporter && \
	make build && \
	cp node_exporter /usr/bin/

CMD ["node_exporter", "--web.listen-address=:9000", "--web.telemetry-path=/metrics", "--path.rootfs=/host"]

Build:

docker build -t node_exporter .

Then run the container:

docker run -d --rm -v /:/host:ro,rslave -p "9000:9000" node_exporter

Then, curl the container and grep for the empty string in the mountpoint label:

$ curl -s localhost:9000/metrics | grep 'mountpoint=""'

node_filesystem_avail_bytes{device="/dev/nvme0n1p2",fstype="ext4",mountpoint=""} 3.94300260352e+11
node_filesystem_device_error{device="/dev/nvme0n1p2",fstype="ext4",mountpoint=""} 0
node_filesystem_files{device="/dev/nvme0n1p2",fstype="ext4",mountpoint=""} 3.0130176e+07
node_filesystem_files_free{device="/dev/nvme0n1p2",fstype="ext4",mountpoint=""} 2.9022094e+07
node_filesystem_free_bytes{device="/dev/nvme0n1p2",fstype="ext4",mountpoint=""} 4.18995941376e+11
node_filesystem_readonly{device="/dev/nvme0n1p2",fstype="ext4",mountpoint=""} 1
node_filesystem_size_bytes{device="/dev/nvme0n1p2",fstype="ext4",mountpoint=""} 4.84756549632e+11

What did you expect to see?

The mountpoint label should strip down to "/", not the empty string.

What did you see instead?

mountpoint has "" as its value.

[SuperQ]

Fixed by #1464