Public Python Apps

This repository contains my collection of Python applications that run inside of a Docker container.

Table of Contents

• Applications
  • Environment Variable Logger
    • Configuration
    • Examples

Applications

Environment Variable Logger

This is a Python app which runs inside a container, periodically emitting JSON formatted messages to the console, using the Kubernetes Recommended Labels format as inspiration.

I say "inspriation" because the labels emitted are an extension to the Kubernetes Recommended Labels, to support multiple name, component, and version pairs. Actually, there's no limitation to what the label keys are and which have multiple values.

Configuration

The following environment variables are supported:

Name	Value	Description
EV_LOGGER_PREFIX	(string)	Mandatory. The prefix all other environment variables need to use.
EV_LOGGER_SYSLOG	(number)	Optional. Set this to 1 to enable logging to syslog. Anything else will use stdout/err. Default is 0.
EV_LOGGER_INTERVAL	(number)	Optional. The interval in seconds the log is emitted to the console. Default is 300 (5 minutes). It must be greater than 0 and less than 604800 (1 week). Setting this to 0 will result in logging once only and then exiting successfully.
EV_LOGGER_INDENT	(number)	Optional. The number of spaces to indent the JSON message. Default is 0. Must be greater than or equal to 0.
<EV_LOGGER_PREFIX>_<KEY>	(string)	Mandatory. The label key and value to log (see below). Must have at least 1.

The label key and value to log are configured via environment variables, using the following syntax:

<EV_LOGGER_PREFIX>_<KEY>="<VALUE>"

Where...

Field	Description
<KEY>	Represents the key name.
<VALUE>	Represents the key value.

If <VALUE> contains a string formatted as <PARENT_KEY>[__<ID>_]_<CHILD_KEY>, it indicates a JSON array of objects, where:

Field	Description
<PARENT_KEY>	Represents the parent key name.
<ID>	Represents the index of the array element.
<CHILD_KEY>	Represents the child key name.

Note: All label keys and sub-keys are converted to lower case.

Examples

Example 1

The following is an example of the environment variable syntax in practice:

EV_LOGGER_PREFIX="APP_CONTOSO_MS"
EV_LOGGER_SYSLOG=0
EV_LOGGER_INDENT=2
EV_LOGGER_INTERVAL=600
APP_CONTOSO_MS_INSTANCE="my-instance"
APP_CONTOSO_MS_MANAGED_BY="my-team"
APP_CONTOSO_MS_PART_OF="my-collection"
APP_CONTOSO_MS_INVENTORY__0__NAME="my-app"
APP_CONTOSO_MS_INVENTORY__0__VERSION="v1"
APP_CONTOSO_MS_INVENTORY__0__COMPONENT="my-component"
APP_CONTOSO_MS_INVENTORY__1__NAME="my-app2"
APP_CONTOSO_MS_INVENTORY__1__VERSION="v2"
APP_CONTOSO_MS_INVENTORY__1__COMPONENT="my-component2"

The above configuration will produce the following JSON string (pretty formatted), every 10 minutes:

{
  "time": "2024-04-27 01:39:30",
  "level": "INFO",
  "message": "Starting Kubernetes Label Emitter v2.1.0. Interval: 600 seconds"
}
{
  "app.contoso.ms/interval": "600",
  "app.contoso.ms/instance": "my-instance",
  "app.contoso.ms/managed.by": "my-team",
  "app.contoso.ms/part.of": "my-collection",
  "app.contoso.ms/inventory": [
    {
      "name": "my-app",
      "version": "v1",
      "component": "my-component"
    },
    {
      "name": "my-app2",
      "version": "v2",
      "component": "my-component2"
    }
  ]
}

Example 2

The following is the same as Example 1 but without any JSON indentation:

EV_LOGGER_PREFIX="APP_CONTOSO_MS"
EV_LOGGER_SYSLOG=0
EV_LOGGER_INDENT=0
EV_LOGGER_INTERVAL=600
APP_CONTOSO_MS_INSTANCE="my-instance"
APP_CONTOSO_MS_MANAGED_BY="my-team"
APP_CONTOSO_MS_PART_OF="my-collection"
APP_CONTOSO_MS_INVENTORY__0__NAME="my-app"
APP_CONTOSO_MS_INVENTORY__0__VERSION="v1"
APP_CONTOSO_MS_INVENTORY__0__COMPONENT="my-component"
APP_CONTOSO_MS_INVENTORY__1__NAME="my-app2"
APP_CONTOSO_MS_INVENTORY__1__VERSION="v2"
APP_CONTOSO_MS_INVENTORY__1__COMPONENT="my-component2"

The above configuration will produce the following JSON string to the console, every 10 minutes:

{"time": "2024-04-27 01:39:30", "level": "INFO", "message": "Starting Kubernetes Label Emitter v2.1.0. Interval: 600 seconds"}
{"time": "2024-04-27 01:39:30", "level": "INFO", "message": {"app.contoso.ms/instance": "my-instance", "app.contoso.ms/managed.by": "my-team", "app.contoso.ms/part.of": "my-collection", "app.contoso.ms/inventory": [{"name": "my-app", "version": "v1", "component": "my-component"}, {"name": "my-app2", "version": "v2", "component": "my-component2"}]}}