fix: Metrics without a timeseries are not reported

[tomkerkhove]

fix: Metrics without a timeseries are not reported with the metricSinks.prometheusScrapingEndpoint.metricUnavailableValue

Fixes #1197

Before:

# HELP azure_event_hubs_incoming_messages_discovery The number of incoming messages on an Azure Event Hub namespace
# TYPE azure_event_hubs_incoming_messages_discovery gauge
azure_event_hubs_incoming_messages_discovery{resource_group="promitor-sources",subscription_id="0f9d7fea-99e8-4768-8672-06a28514f77e",resource_uri="subscriptions/0f9d7fea-99e8-4768-8672-06a28514f77e/resourceGroups/promitor-sources/providers/Microsoft.EventHub/namespaces/promitor-streaming",instance_name="promitor-streaming",entity_name="topic-1"} 1 1606049042395

For the other dimension that does not have a value triggered an exception:

[12:44:02 FTL] Failed to scrape resource for metric 'azure_event_hubs_incoming_messages_discovery'
Promitor.Integrations.AzureMonitor.Exceptions.MetricInformationNotFoundException: No metric information was found for 'IncomingMessages'. Reason: 'No time series was found'
at Promitor.Integrations.AzureMonitor.AzureMonitorClient.QueryMetricAsync(String metricName, String metricDimension, AggregationType aggregationType, TimeSpan aggregationInterval, String resourceId, String metricFilter) in C:\Code\GitHub\promitor\src\Promitor.Integrations.AzureMonitor\AzureMonitorClient.cs:line 88
at Promitor.Core.Scraping.AzureMonitorScraper1.ScrapeResourceAsync(String subscriptionId, ScrapeDefinition1 scrapeDefinition, TResourceDefinition resourceDefinition, AggregationType aggregationType, TimeSpan aggregationInterval) in C:\Code\GitHub\promitor\src\Promitor.Core.Scraping\AzureMonitorScraper.cs:line 46
at Promitor.Core.Scraping.Scraper1.ScrapeAsync(ScrapeDefinition1 scrapeDefinition) in C:\Code\GitHub\promitor\src\Promitor.Core.Scraping\Scraper.cs:line 69

After:

# HELP azure_event_hubs_incoming_messages_discovery The number of incoming messages on an Azure Event Hub namespace
# TYPE azure_event_hubs_incoming_messages_discovery gauge
azure_event_hubs_incoming_messages_discovery{resource_group="dapr-actors",subscription_id="0f9d7fea-99e8-4768-8672-06a28514f77e",resource_uri="subscriptions/0f9d7fea-99e8-4768-8672-06a28514f77e/resourceGroups/dapr-actors/providers/Microsoft.EventHub/namespaces/dapr-actors",instance_name="dapr-actors",entity_name="unknown"} -1 1606048322048
azure_event_hubs_incoming_messages_discovery{resource_group="promitor-sources",subscription_id="0f9d7fea-99e8-4768-8672-06a28514f77e",resource_uri="subscriptions/0f9d7fea-99e8-4768-8672-06a28514f77e/resourceGroups/promitor-sources/providers/Microsoft.EventHub/namespaces/promitor-streaming",instance_name="promitor-streaming",entity_name="topic-1"} 1 1606048322133

[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:pr1369-linux

Want to verify the new version? Run it locally:

docker run -d -p 8999:80 --name promitor-agent-scraper-pr1369-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:pr1369-linux

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