Test Message Generator

This small tool helps to generate (test) messages based on a Mustache template. It can act as a simple replacement for message source systems and allows to send on regular time intervals some data, based on a template that gets altered before sending.

Docker

The generator can be run as a Docker container, after creating a Docker image for it. The Docker container will keep running until stopped.

To create a Docker image, run the following command:

docker build --tag vsds/test-message-generator .

To run the generator, you can use:

docker run -v $(pwd)/data:/tmp/data -e TEMPLATEFILE=/tmp/data/template.json vsds/test-message-generator

You can also pass the following arguments when running the container:

• SILENT=true to display no logging to the console
• TARGETURL=<target-uri> to POST the output to the target URI instead of to the console
• MIMETYPE=<mime-type> to specify a mime-type when POSTing
• RANGE=<range> allows to create the same range of values (1 to range) on each tick instead of an increasing index

Alternatively, you can also pass the template as string instead of as file, use TEMPLATE.

Build the Generator

The generator is implemented as a Node.js application. You need to run the following commands to build it:

npm i
npm run build

Run the Generator

The generator works based on a template, defining the structure to use for each generated item. It can send the generated data to a target URL or simply send it to the console.

The generator takes the following command line arguments:

• --silent=<true|false> prevents any console debug output if true, defaults to false (not silent, logging all debug info)
• --targetUrl defines the target URL to where the generated message is POST'ed as the configured mime-type, no default (if not provided, sends output to console independant of --silent)

Note: alternatively, you can provide the target URL as a plain text in a file named TARGETURL (located in the current working directory) allowing to change the target URL at runtime as the file is read at cron schedule time (see below), e.g.:

echo http://example.org/my-ingest-endpoint > ./TARGETURL

Note: for testing the target URL you can use a webhook service, e.g. using command line arguments --targetUrl=https://webhook.site/f140204a-9514-4bfa-8d3e-fd18ba325ee3 or using the TARGETURL file:

echo https://webhook.site/f140204a-9514-4bfa-8d3e-fd18ba325ee3 > ./TARGETURL

• --mimeType=<mime-type> mime-type of message send to target URL, no default
• --cron defines the time schedule, defaults to * * * * * * (every second)
• --template='<content>' allows to provide the template on the command line, no default (if not provided, you MUST provide --templateFile)
• --templateFile=<partial-or-full-pathname> allows to provide the template in a file, no default (if not provided, you MUST provide --template)
• --range=<range> allows to create a range of values (1 to <range>) on every tick instead of an increasing index
• --maxRetries=<number> allows to retry some (possibly retryable) HTTP status codes (429, 500 & 503) a maximum number of times
• --retryTimeout=<ms> the amount of time (in milliseconds) to wait between retrying to send the message again

The template or template file should simply contain a message with mustache variables (between {{ and }}). E.g.:

[
    { "id": "my-id-{{index}}", "type": "Something", "modifiedAt": "{{timestamp}}" },
    { "id": "my-other-id-{{index}}", "type": "SomethingElse", "modifiedAt": "{{timestamp}}" }
]

Currently the only allowed variables are:

• index: on each tick, increasing integer value starting from 1 OR a range of values [1 .. N] given by --range=N
• timestamp: on each tick, current date and time formatted as ISO 8601 in UTC, e.g. 2007-04-05T14:30:00.000Z (all values in the range have the same timestamp)

You can run the generator after building it, e.g.:

Using this template and with silent output to console:

node ./dist/index.js --templateFile ./data/template.json --silent

This results in something like the following:

{"id":"my-id-1","type":"Something","modifiedAt":"2022-09-12T13:15:42.009Z"}
{"id":"my-id-2","type":"Something","modifiedAt":"2022-09-12T13:15:43.003Z"}
{"id":"my-id-3","type":"Something","modifiedAt":"2022-09-12T13:15:44.003Z"}
...

By specifying the template (containing multiple objects) and mapping on the command file:

node ./dist/index.js --template '[{"id": "my-id-{{index}}", "type": "Something", "modifiedAt": "{{timestamp}}" },{ "id": "my-other-id-{{index}}", "type": "SomethingElse", "modifiedAt": "{{timestamp}}" }]' --silent

This results in something like:

[{"id":"my-id-1","type":"Something","modifiedAt":"2022-09-12T13:44:12.010Z"},{"id":"my-other-id-2","type":"SomethingElse","modifiedAt":"2022-09-12T13:44:12.010Z"}]
[{"id":"my-id-3","type":"Something","modifiedAt":"2022-09-12T13:44:13.005Z"},{"id":"my-other-id-4","type":"SomethingElse","modifiedAt":"2022-09-12T13:44:13.005Z"}]
[{"id":"my-id-5","type":"Something","modifiedAt":"2022-09-12T13:44:14.004Z"},{"id":"my-other-id-6","type":"SomethingElse","modifiedAt":"2022-09-12T13:44:14.004Z"}]
...

Alternatively you can generate the output using a different time schedule (e.g. every 2 seconds) to a dummy HTTP server (including debugging to the console):

node ./dist/index.js --templateFile ./data/template.json --cron '*/2 * * * * *' --targetUrl https://webhook.site/ce3065f5-2f0b-49d8-8856-330ae3c6e737 --mimeType application/json

This results in:

Arguments:  {
  _: [],
  templateFile: './data/template.json',
  cron: '*/2 * * * * *',
  targetUrl: 'https://webhook.site/ce3065f5-2f0b-49d8-8856-330ae3c6e737'
}
Runs at:  */2 * * * * *
Sending to 'https://webhook.site/ce3065f5-2f0b-49d8-8856-330ae3c6e737': {"id":"my-id-1","type":"Something","modifiedAt":"2023-04-06T08:34:56.005Z"}
Response: OK
Next run at:  2023-04-06T10:34:58.000+02:00
Sending to 'https://webhook.site/ce3065f5-2f0b-49d8-8856-330ae3c6e737': {"id":"my-id-2","type":"Something","modifiedAt":"2023-04-06T08:34:58.003Z"}
Response: OK
Next run at:  2023-04-06T10:35:00.000+02:00
...