Default value in collector config is interpreted as integer/float, where a string is expected. There is no way to typehint

[timbeemster]

What happened?

Description

In our setup we use the VERSION environment variable to set a dimension on metrics, so we can query our metrics based on the version of the application.
The version is sourced in the environment variables and consists of a combination of numbers and letters.
It has come to our attention that in a newer version (v109) the spanmetrics connector does not allow a default of only digits to be set.
Similarly, if there are only digits and the letter e, it will try to decode the value as a float.

For this problem I went ahead and opened a bug report in the spanmetrics project: open-telemetry/opentelemetry-collector-contrib#36786 - however, there it was suggested that the actual problem is probably in the confmap component.

A related issue: #10552

I have not found a way to force the environment variable to be interpreted as a string value.

Steps to Reproduce

I've created a minimal setup in a public repo: https://github.com/timbeemster/otelcol-custom/blob/main/README
Build the docker image and run the setup.

Expected Result

A running otel collector

Actual Result

Error message on startup (see log output section)

Let me know if I can assist in debugging the problem.

Collector version

v0.109.0

Environment information

Environment

OS: Golang base image for building + Debian12 (distroless variant for running)
Compiler(if manually compiled): golang:1.23.2

(see: https://github.com/timbeemster/otelcol-custom/blob/main/Dockerfile )

OpenTelemetry Collector configuration

builder config: https://github.com/timbeemster/otelcol-custom/blob/main/otel-builder-config.yml
collector config: https://github.com/timbeemster/otelcol-custom/blob/main/otel-collector-config.yml

Log output

Error: failed to get config: cannot unmarshal the configuration: decoding failed due to the following error(s):

error decoding 'connectors': error reading configuration for "spanmetrics": decoding failed due to the following error(s):

'dimensions[0].default' expected type 'string', got unconvertible type 'float64', value: '1.23e+06'
2024/12/11 15:45:40 collector server run finished with error: failed to get config: cannot unmarshal the configuration: decoding failed due to the following error(s):

error decoding 'connectors': error reading configuration for "spanmetrics": decoding failed due to the following error(s):

'dimensions[0].default' expected type 'string', got unconvertible type 'float64', value: '1.23e+06'

Additional context

No response

[mx-psi]

@timbeemster Thanks for reporting, I am able to reproduce in the latest version.

Looks like the type is *string for this field https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/f72ef07e008b03eb42363ed77296d9351bb34d81/connector/spanmetricsconnector/config.go#L31

which probably explains this.

The workaround is to use a YAML explicit tag, setting VERSION='!!str <version here>' works for me on the latest version.

[timbeemster]

Hi @mx-psi, thanks for reaching out.
I'm not 100% sure, but I think changing the config to:

default: '!!str ${VERSION}'

would simply set the version number to the actual string: !!str ${VERSION}

I've done a test with a config without the quotes:
default: !!str ${VERSION}
but this is not accepted in both 109 and 115.
I have the feeling it might have something to do with the extracting the environment variable..

[mx-psi]

Sorry I meant an environment variable with value !!str 1234, without the quotes (the quotes were just how I passed that value on bash).

[timbeemster]

I've found that this config is only a "default" that is used when the gitHash property is not available.
Funnily enough, our Spans always have the gitHash attribute already.
The workarond was dead simple: not use a default.