minute-metrics

README

MinuteMetrics

MinuteMetrics is a lightweight web service designed to provide both dynamic and static data. The dynamic data changes based on a predefined schedule, while the static data can be set and updated as needed. The application serves simple JSON responses that include a name and a value, with the value changing over time according to user-defined settings.

Features

• Dynamic value updates based on a customizable schedule.
• Static value endpoint for setting and updating a fixed value.
• Configurable through both environment variables and command-line arguments.
• Simple RESTful endpoints to fetch and update current values.

Configuration

MinuteMetrics can be configured using command-line arguments or environment variables. Command-line arguments take precedence over environment variables.

Command-Line Arguments

• -base: Sets the initial base value for calculations. Overrides the BASE environment variable if provided.
• -multiplier Similar to base, it scales the values by a factor. This is applied before adding the base. Overrides MULTIPLIER if provided.
• -lazy-start: Enables lazy start, delaying the schedule's start until the first request is received. Overrides the LAZY_START environment variable if provided.
• -schedule: Defines the value update schedule in a minute:value pairs format. Overrides the SCHEDULE environment variable if provided.
• -cycle-minutes: Repeat provided schedule every N minutes provided by this variable.
• -static-value: Sets the initial static value for static metrics. Overrides the STATIC_VALUE environment variable if provided.
• -time-relative-to-start: When enabled (default), it will use the time app is running for its calculations. Disabled takes the UTC time of a day - # of minutes since midnight. Overrides TIME_RELATIVE_TO_START if provided
• -interpolate-values: When enabled, it will interpolate the values between each schedule items. Overrides INTERPOLATE_VALUES if provided.
• -help: Displays help information about the application usage and options.

Environment Variables

• BASE: Sets the initial base value for calculations.
• MULTIPLIER: See cmd arg -multiplier. Takes a float.
• LAZY_START: Enables lazy start with "true".
• SCHEDULE: Defines the value update schedule in a minute:value pairs format.
• TIME_RELATIVE_TO_START: See cmd arg -time-relative-to-start. Disables with "false" (enabled by default).
• INTERPOLATE_VALUES: See cmd arg -interpolate-values. Enables with "true".
• STATIC_VALUE: Sets the initial static value for static metrics.

Endpoint

• /api/v1/minutemetrics: Returns the current name and value in JSON format. Example response:

{
  "name": "minute-metrics",
  "value": 10
}

• /api/v1/staticmetrics: GET returns the current static metric data in JSON format. PUT updates the static metric value.

{
  "name": "static-metrics",
  "value": 5
}

Schedule Examples

Schedules are defined as comma-separated minute:value pairs, where minute is the minute within a 10-minute cycle, and value is the value to be returned starting from that minute.

Example 1: Constant Increase

• Schedule: "0:10,1:20,2:30,3:40,4:50,5:60,6:70,7:80,8:90,9:100"
• Behavior: The value starts at 10 at the beginning of the cycle and increases by 10 every minute, reaching 100 at the 9th minute.

Example 2: Specific Changes

• Schedule: "0:10,3:0,7:50"
• Behavior: The value starts at 10, changes to 0 at the 3rd minute, and then to 50 at the 7th minute.

Example 3: Reset Mid-Cycle

• Schedule: "0:5,5:0"
• Behavior: The value starts at 5 and resets to 0 at the 5th minute of the cycle.

Example 4: Return number of minutes in a day multiplied by 3 and add 42 to it

go run . -cycle-minutes $[24*60] -base 42 -multiplier 3 -interpolate-values -time-relative-to-start=false -schedule "0:0,1440:1440"

Running MinuteMetrics

To run MinuteMetrics with a specific base value and schedule, you might use:

go run . -base 5 -lazy-start -schedule "0:10,5:20"

This sets the initial value to 5, enables lazy start, and uses a schedule where the value starts at 10 and changes to 20 at the 5th minute of every 10-minute cycle.

To set or update the static value at runtime, use the following curl command:

curl -X PUT -H "Content-Type: application/json" -d '{"value":5}' http://localhost:8080/api/v1/staticmetrics