Alerting Rules

Promgen supports the concept of a global set of rules and then configuring overrides at the Service or Project level

When working with many services, there are times that a global rule will not cover all use cases. In this case, Promgen allows the user to override a parent rule using an <exclude> tag.

For example, we may want to check overall file system usage across all of our machines

node_filesystem_free / node_filesystem_size < 0.20

This may be an acceptable default for our service, but perhaps a different service wants to be warned at only 10%. Since the global rule already warns us at 20% we need to do something different. Promgen supports a special <exclude> tag to handle this use case

Original Rules

node_filesystem_free{<exclude>}
    / node_filesystem_size{<exclude>} < 0.20
node_filesystem_free{service="A", <exclude>}
    / node_filesystem_size{service="A", <exclude>} < 0.10
node_filesystem_free{service="B"}
    / node_filesystem_size{service="B"} < 0.15

This will be properly expanded into the following rules so that we can have a general default but be more specific with certain services

Expanded Rules

node_filesystem_free{service=~"A|B"}
    / node_filesystem_size{service=~"A|B"} < 0.20
node_filesystem_free{service="A",}
    / node_filesystem_size{service="A",} < 0.10
node_filesystem_free{service="B"}
   / node_filesystem_size{service="B"} < 0.15

Visuallizing it as a hiarchy it would look like this

# Global Rule excludes children
example_rule{service!~"A|B",}:
    # Service A override includes self
    - example_rule{service="A",}
    # Service B override includes self, but excludes children
    - example_rule{service="B", project!~"C"}:
        # Project Override
        - example_rule{project="C"}