Ensure that schedule is a valid Cron expression

[adamconnelly]

I've added the framework to perform additional validation on a field, and implemented a Cron expression validator for the scraping schedule.

Each field can have a collection of zero or more validators that implement IFieldValidator, and the validator uses the error reporter to report any validation errors.

Fixes #1103

If we use the following example config:

version: v1
azureMetadata:
  tenantId: <tenant-id>
  subscriptionId: <subscription-id>
  resourceGroupName: promitor
metricDefaults:
  aggregation:
    interval: 00:05:00
  scraping:
    # Every minute
    schedule: "12345"

We'll now get the following error message:

[13:24:35 ERR] The following problems were found with the metric configuration:
Error 11:15: '12345' is not a valid value for 'schedule'. The value must be a valid Cron expression.

[promitor-bot]

Docker image for this PR was built and is available on Docker Hub.

You can pull it locally via the CLI:

docker pull tomkerkhove/promitor-agent-scraper-ci:pr1104-linux

Want to verify the new version? Run it locally:

docker run -d -p 8999:80 --name promitor-agent-scraper-pr1104-linux \
                         --env PROMITOR_AUTH_APPID='<azure-ad-app-id>' \
                         --env-file C:/Promitor/az-mon-auth.creds \
                         --volume C:/Promitor/metrics-declaration.yaml:/config/metrics-declaration.yaml  \
                         --volume C:/Promitor/runtime-config.yaml:/config/runtime.yaml \
                         tomkerkhove/promitor-agent-scraper-ci:pr1104-linux

You can find a CI version of our Helm chart on hub.helm.sh

[tomkerkhove]

Will this happen during startup validation or before? Just asking to see if we should merge them or not to provide a consistent experience.

For the rest it looks great!

[adamconnelly]

It happens just after the config is deserialized and we check if there's any errors before proceeding. The error appears in the same place as the errors in the examples I've added to the PR about suggestions.

[promitor-bot]

Docker image for this PR was built and is available on Docker Hub.

You can pull it locally via the CLI:

docker pull tomkerkhove/promitor-agent-scraper-ci:pr1104-linux

Want to verify the new version? Run it locally:

docker run -d -p 8999:80 --name promitor-agent-scraper-pr1104-linux \
                         --env PROMITOR_AUTH_APPID='<azure-ad-app-id>' \
                         --env-file C:/Promitor/az-mon-auth.creds \
                         --volume C:/Promitor/metrics-declaration.yaml:/config/metrics-declaration.yaml  \
                         --volume C:/Promitor/runtime-config.yaml:/config/runtime.yaml \
                         tomkerkhove/promitor-agent-scraper-ci:pr1104-linux

You can find a CI version of our Helm chart on hub.helm.sh

[promitor-bot]

Docker image for this PR was built and is available on Docker Hub.

You can pull it locally via the CLI:

docker pull tomkerkhove/promitor-agent-scraper-ci:pr1104-linux

Want to verify the new version? Run it locally:

docker run -d -p 8999:80 --name promitor-agent-scraper-pr1104-linux \
                         --env PROMITOR_AUTH_APPID='<azure-ad-app-id>' \
                         --env-file C:/Promitor/az-mon-auth.creds \
                         --volume C:/Promitor/metrics-declaration.yaml:/config/metrics-declaration.yaml  \
                         --volume C:/Promitor/runtime-config.yaml:/config/runtime.yaml \
                         tomkerkhove/promitor-agent-scraper-ci:pr1104-linux

You can find a CI version of our Helm chart on hub.helm.sh

[tomkerkhove]

Cool, thanks man!

[promitor-bot]

Docker image for this PR was built and is available on Docker Hub.

You can pull it locally via the CLI:

docker pull tomkerkhove/promitor-agent-scraper-ci:pr1104-linux

Want to verify the new version? Run it locally:

docker run -d -p 8999:80 --name promitor-agent-scraper-pr1104-linux \
                         --env PROMITOR_AUTH_APPID='<azure-ad-app-id>' \
                         --env-file C:/Promitor/az-mon-auth.creds \
                         --volume C:/Promitor/metrics-declaration.yaml:/config/metrics-declaration.yaml  \
                         --volume C:/Promitor/runtime-config.yaml:/config/runtime.yaml \
                         tomkerkhove/promitor-agent-scraper-ci:pr1104-linux

You can find a CI version of our Helm chart on hub.helm.sh