nodejs-base-image
JavaScript (Node.js) support for Dispatch
Latest image on Docker Hub
Usage
You need a recent version of Dispatch installed in your Kubernetes cluster, Dispatch CLI configured to use it.
Adding the Base Image
To add the base-image to Dispatch:
$ dispatch create base-image nodejs-base dispatchframework/nodejs-base:<tag>
Make sure the base-image status is READY
(it normally goes from INITIALIZED
to READY
):
$ dispatch get base-image nodejs-base
Adding Runtime Dependencies
Library dependencies listed in package.json
(npm dependency manifest) need to be wrapped into a Dispatch image. For example, suppose we need a math library:
$ cat ./package.json
{
"dependencies": {
"mathjs": "4.1.2"
}
}
$ dispatch create image nodejs-mylibs nodejs-base --runtime-deps ./package.json
Make sure the image status is READY
(it normally goes from INITIALIZED
to READY
):
$ dispatch get image nodejs-mylibs
Creating Functions
Using the Node.js base-image, you can create Dispatch functions from Node.js (javascript) source files. The file can require any libraries from the image (see above).
The only requirement is: module.exports
must be set to a function that accepts 2 arguments (context
and payload
), for example:
$ cat ./demo.js
const math = require('mathjs');
module.exports = function (context, payload) {
return { myField: math.chain(payload.val).add(4).divide(4).done() }
};
$ dispatch create function math-js ./demo.js --image=nodejs-mylibs --handler=demo.js
Make sure the function status is READY
(it normally goes from INITIALIZED
to READY
):
$ dispatch get function math-js
Running Functions
As usual:
$ dispatch exec --json --input '{"val": 12}' --wait math-js
{
"blocking": true,
"executedTime": 1524612028,
"faasId": "9ff4d69e-44e7-4ad3-a54c-6cfeb06729dd",
"finishedTime": 1524612028,
"functionId": "931828dc-87b8-43c7-b990-cb3f027f1e47",
"functionName": "math-js",
"input": {
"val": 12
},
"logs": {
"stderr": null,
"stdout": null
},
"name": "28d9acec-b9c2-408c-876a-1ef14611a803",
"output": {
"myField": 4
},
"reason": null,
"secrets": [],
"services": null,
"status": "READY",
"tags": []
}
Error Handling
There are three types of errors that can be thrown when invoking a function:
InputError
FunctionError
SystemError
SystemError
represents an error in the Dispatch infrastructure. InputError
represents an error in the input detected either early in the function itself or through input schema validation. FunctionError
represents an error in the function logic or an output schema validation error.
Functions themselves can either throw InputError
or FunctionError
Input Validation
For Node.js, the following exceptions thrown from the function are considered InputError
:
TypeError
All other exceptions thrown from the function are considered FunctionError
.
To validate input in the function body:
module.exports = function(context, payload) {
if (typeof payload !== 'string') {
throw new TypeError("payload is not of type string");
}
return payload.toLowerCase();
};
Note
Since TypeError
is considered an InputError
, functions should not throw it unless explicitly thrown due to an input validation error. Functions should catch and handle TypeError
accordingly if it should not be classified as an InputError
.
Running Tests
Unit tests are written in Jasmine
for both function-server
and validator
.
To run tests, ensure you have all the required dependencies:
npm install
Then run:
npm test