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➕ Calculation Property

Calculation properties allow you to use existing properties defined on blueprints, either directly or by using relations and mirror properties, in order to create new properties by using the jq processor for JSON.

  • Filter/Select/Slice/Concatenate data from an existing property;
  • Create math equations or modifications. For example, calculate required disk storage by specifying page size, and number of pages needed.
  • Merge complex properties, including deep-merge and overriding.

💡 Common calculation usage​

Calculation properties make it easier to define properties that are based on values from other properties, with the added ability to transform the data, for example:

  • Construct custom URLs based on templates - for example:
    • https://slack.com/ + {my_parameter};
    • https://datadog.com/ + {my_parameter};
    • https://launchdarkly.com/ + {my_parameter};
  • Merge service configurations templates to create a real service config;
  • Calculate the number of code owners;
  • etc.

In this live demo example, we can see the Slack Notifications calculation property. 🎬

Definition​

The calculationProperties key is a top-level key in the JSON of an entity (similar to identifier, title, properties, etc..)

You can access properties as part of the calculation by using .properties

{
  "calculationProperties": {
    "myCalculationProp": {
      "title": "My calculation property",
      "type": "string",
      "calculation": ".properties.myStringProp + .properties.myStringProp"
    }
  }
}

Check out Port's API reference to learn more.

Supported Types​

Calculation properties support the following output types: string, number, object, array, and boolean. For example:

{
  "calculationProperties": {
    "myCalculationProp": {
      "title": "My calculation property",
      "type": "my_output_type",
      "calculation": ".properties.myStringProp + .properties.myStringProp"
    }
  }
}

Using meta properties in calculation properties​

It is possible to use meta properties as template values for calculation properties.

For example, if you want to concatenate a template URL (for example https://datadog.com) with the identifier meta property:

Given the following notification-service entity:

{
  "identifier": "notification-service",
   "title": "Notification Service",
  "properties": {
   ...
  },
}

And the following calculation property definition for the blueprint:

{
  "calculationProperties": {
    "monitorUrl": {
      "title": "Monitor url",
      "type": "string",
      "format": "url",
      "calculation": "'https://datadog.com/' + .identifier"
    }
  }
}

The value of the property monitorUrl will be https://datadog.com/notification-service

Using mirror properties in calculation properties​

It is possible to use mirror properties as template values for calculation properties.

For example, if an entity has a mirror property called owningSquad:

"mirrorProperties": {
    "owningSquad": {
        "path": "microservice-to-squad.$title"
    }
}

A calculation property that links to the slack channel of the squad can be:

"owning_squad_slack": {
    "title": "Owning Squad Channel",
    "calculation": "'https://slack.com/' + .properties.owningSquad",
}

Colorized calculation properties​

You can colorize calculation properties according to their value, by adding a colorized key with the value true to the calculation property object. You can also add a colors key to specify the colors of the different values, otherwise, the colors will be chosen automatically for you.

For example, if you want to colorize a calculation property called status-calculation with the values OK, WARNING, and CRITICAL:

"properties":{
    "status":{
        "type": "string"
    },
},
"calculationProperties": {
    "status-calculation": {
        "title": "Status",
        "type": "string",
        "calculation": ".properties.status",
        "colorized": true,
        "colors": {
            "OK": "green",
            "WARNING": "yellow",
            "CRITICAL": "red"
        }
    }
}
Parameters with special characters

Parameter contains special characters (for example: -) or starts with a digit (for example: @/#/$/1/2/3), should be surrounded with single quotes.


"properties":{
    "prop-with-special-char":{
        "type": "string"
    },
},
"calculationProperties": {
    "myCalculatedProp": {
        "title": "My Calculated Property",
        "type": "string",
        "calculation": ".properties.'prop-with-special-char'",
    }
}

Examples​

Refer to the calculation property examples page.