278 lines
8.9 KiB
Markdown
278 lines
8.9 KiB
Markdown
# strong-error-handler
|
|
|
|
This package is an error handler for use in both development (debug) and production environments.
|
|
|
|
In production mode, `strong-error-handler` omits details from error responses to prevent leaking sensitive information:
|
|
|
|
- For 5xx errors, the output contains only the status code and the status name from the HTTP specification.
|
|
- For 4xx errors, the output contains the full error message (`error.message`) and the contents of the `details`
|
|
property (`error.details`) that `ValidationError` typically uses to provide machine-readable details
|
|
about validation problems. It also includes `error.code` to allow a machine-readable error code to be passed
|
|
through which could be used, for example, for translation.
|
|
|
|
In debug mode, `strong-error-handler` returns full error stack traces and internal details of any error objects to the client in the HTTP responses.
|
|
|
|
## Supported versions
|
|
|
|
Current|Long Term Support|Maintenance
|
|
:-:|:-:|:-:
|
|
3.x|2.x|1.x
|
|
|
|
Learn more about our LTS plan in [docs](http://loopback.io/doc/en/contrib/Long-term-support.html).
|
|
|
|
## Installation
|
|
|
|
```bash
|
|
$ npm install --save strong-error-handler
|
|
```
|
|
|
|
## Use
|
|
|
|
In an Express-based application:
|
|
|
|
```js
|
|
var express = require('express');
|
|
var errorHandler = require('strong-error-handler');
|
|
|
|
var app = express();
|
|
// setup your routes
|
|
// `options` are set to default values. For more info, see `options` below.
|
|
// app.use(errorHandler({ /* options, see below */ }));
|
|
app.use(errorHandler({
|
|
debug: app.get('env') === 'development',
|
|
log: true,
|
|
}));
|
|
|
|
app.listen(3000);
|
|
```
|
|
|
|
The module also exports `writeErrorToResponse`, a non-middleware flavor of the
|
|
error handler:
|
|
|
|
```js
|
|
const http = require('http');
|
|
const writeErrorToResponse = require('strong-error-handler')
|
|
.writeErrorToResponse;
|
|
const errHandlingOptions = {debug: process.env.NODE_ENV === 'development'}
|
|
|
|
http
|
|
.createServer((req, res) => {
|
|
if (errShouldBeThrown) {
|
|
writeErrorToResponse(
|
|
new Error('something went wrong'),
|
|
req,
|
|
res,
|
|
errHandlingOptions,
|
|
);
|
|
}
|
|
})
|
|
.listen(3000);
|
|
```
|
|
|
|
In LoopBack applications, add the following entry to `server/middleware.json`:
|
|
|
|
```json
|
|
{
|
|
"final:after": {
|
|
"strong-error-handler": {
|
|
"params": {
|
|
"debug": false,
|
|
"log": true
|
|
}
|
|
}
|
|
}
|
|
}
|
|
```
|
|
|
|
In general, `strong-error-handler` must be the last middleware function registered.
|
|
|
|
The above configuration will log errors to the server console, but not return stack traces in HTTP responses.
|
|
For details on configuration options, see below.
|
|
|
|
### Response format and content type
|
|
|
|
The `strong-error-handler` package supports JSON, HTML and XML responses:
|
|
|
|
- When the object is a standard Error object, it returns the string provided by the stack property in HTML/text
|
|
responses.
|
|
- When the object is a non-Error object, it returns the result of `util.inspect` in HTML/text responses.
|
|
- For JSON responses, the result is an object with all enumerable properties from the object in the response.
|
|
|
|
The content type of the response depends on the request's `Accepts` header.
|
|
|
|
- For Accepts header `json` or `application/json`, the response content type is JSON.
|
|
- For Accepts header `html` or `text/html`, the response content type is HTML.
|
|
- For Accepts header `xml` or `text/xml`, the response content type is XML.
|
|
|
|
*There are plans to support other formats such as Plain-text.*
|
|
|
|
## Options
|
|
|
|
| Option | Type | Default | Description |
|
|
| ---- | ---- | ---- | ---- |
|
|
| debug | Boolean | `false` | If `true`, HTTP responses include all error properties, including sensitive data such as file paths, URLs and stack traces. See [Example output](#example) below. |
|
|
| log | Boolean | `true` | If `true`, all errors are printed via `console.error`, including an array of fields (custom error properties) that are safe to include in response messages (both 4xx and 5xx). <br/> If `false`, sends only the error back in the response. |
|
|
| safeFields | [String] | `[]` | Specifies property names on errors that are allowed to be passed through in 4xx and 5xx responses. See [Safe error fields](#safe-error-fields) below. |
|
|
| defaultType | String | `"json"` | Specify the default response content type to use when the client does not provide any Accepts header.
|
|
| negotiateContentType | Boolean | true | Negotiate the response content type via Accepts request header. When disabled, strong-error-handler will always use the default content type when producing responses. Disabling content type negotiation is useful if you want to see JSON-formatted error responses in browsers, because browsers usually prefer HTML and XML over other content types.
|
|
|
|
### Customizing log format
|
|
|
|
**Express**
|
|
|
|
To use a different log format, add your own custom error-handling middleware then disable `errorHandler.log`.
|
|
For example, in an Express application:
|
|
|
|
```js
|
|
app.use(myErrorLogger());
|
|
app.use(errorHandler({ log: false }));
|
|
```
|
|
|
|
In general, add `strong-error-handler` as the last middleware function, just before calling `app.listen()`.
|
|
|
|
**LoopBack**
|
|
|
|
For LoopBack applications, put custom error-logging middleware in a separate file; for example, `server/middleware/error-logger.js`:
|
|
|
|
```
|
|
module.exports = function(options) {
|
|
return function logError(err, req, res, next) {
|
|
console.log('unhandled error' ,err);
|
|
next(err);
|
|
};
|
|
};
|
|
```
|
|
|
|
Then in `server/middleware.json`, specify your custom error logging function as follows:
|
|
|
|
```
|
|
{
|
|
// ...
|
|
"final:after": {
|
|
"./middleware/error-logger": {},
|
|
"strong-error-handler": {
|
|
"params": {
|
|
"log": false
|
|
}
|
|
}
|
|
}
|
|
```
|
|
|
|
The default `middleware.development.json` file explicitly enables logging in strong-error-handler params, so you will need to change that file too.
|
|
|
|
### Safe error fields
|
|
|
|
By default, `strong-error-handler` will only pass through the `name`, `message` and `details` properties of an error. Additional error
|
|
properties may be allowed through on 4xx and 5xx status code errors using the `safeFields` option to pass in an array of safe field names:
|
|
|
|
```
|
|
{
|
|
"final:after": {
|
|
"strong-error-handler": {
|
|
"params": {
|
|
"safeFields": ["errorCode"]
|
|
}
|
|
}
|
|
}
|
|
```
|
|
|
|
Using the above configuration, an error containing an `errorCode` property will produce the following response:
|
|
|
|
```
|
|
{
|
|
"error": {
|
|
"statusCode": 500,
|
|
"message": "Internal Server Error",
|
|
"errorCode": "INTERNAL_SERVER_ERROR"
|
|
}
|
|
}
|
|
```
|
|
|
|
## Migration from old LoopBack error handler
|
|
|
|
NOTE: This is only required for applications scaffolded with old versions of the `slc loopback` tool.
|
|
|
|
To migrate a LoopBack 2.x application to use `strong-error-handler`:
|
|
|
|
1. In `package.json` dependencies, remove `"errorhandler": "^x.x.x”,`
|
|
1. Install the new error handler by entering the command:
|
|
<pre>npm install --save strong-error-handler</pre>
|
|
1. In `server/config.json`, remove:
|
|
<pre>
|
|
"remoting": {
|
|
...
|
|
"errorHandler": {
|
|
"disableStackTrace": false
|
|
}</pre>
|
|
and replace it with:
|
|
<pre>
|
|
"remoting": {
|
|
...,
|
|
"rest": {
|
|
"handleErrors": false
|
|
}</pre>
|
|
1. In `server/middleware.json`, remove:
|
|
<pre>
|
|
"final:after": {
|
|
"loopback#errorHandler": {}
|
|
}</pre>
|
|
and replace it with:
|
|
<pre>
|
|
"final:after": {
|
|
"strong-error-handler": {}
|
|
}</pre>
|
|
1. Delete `server/middleware.production.json`.
|
|
1. Create `server/middleware.development.json` containing:
|
|
<pre>
|
|
"final:after": {
|
|
"strong-error-handler": {
|
|
"params": {
|
|
"debug": true,
|
|
"log": true
|
|
}
|
|
}
|
|
}
|
|
</pre>
|
|
|
|
For more information, see
|
|
[Migrating apps to LoopBack 3.0](http://loopback.io/doc/en/lb3/Migrating-to-3.0.html#update-use-of-rest-error-handler).
|
|
|
|
## Example
|
|
|
|
5xx error generated when `debug: false` :
|
|
|
|
```
|
|
{ error: { statusCode: 500, message: 'Internal Server Error' } }
|
|
```
|
|
|
|
The same error generated when `debug: true` :
|
|
|
|
```
|
|
{ error:
|
|
{ statusCode: 500,
|
|
name: 'Error',
|
|
message: 'a test error message',
|
|
stack: 'Error: a test error message
|
|
at Context.<anonymous> (User/strong-error-handler/test/handler.test.js:220:21)
|
|
at callFnAsync (User/strong-error-handler/node_modules/mocha/lib/runnable.js:349:8)
|
|
at Test.Runnable.run (User/strong-error-handler/node_modules/mocha/lib/runnable.js:301:7)
|
|
at Runner.runTest (User/strong-error-handler/node_modules/mocha/lib/runner.js:422:10)
|
|
at User/strong-error-handler/node_modules/mocha/lib/runner.js:528:12
|
|
at next (User/strong-error-handler/node_modules/mocha/lib/runner.js:342:14)
|
|
at User/strong-error-handler/node_modules/mocha/lib/runner.js:352:7
|
|
at next (User/strong-error-handler/node_modules/mocha/lib/runner.js:284:14)
|
|
at Immediate._onImmediate (User/strong-error-handler/node_modules/mocha/lib/runner.js:320:5)
|
|
at tryOnImmediate (timers.js:543:15)
|
|
at processImmediate [as _immediateCallback] (timers.js:523:5)' }}
|
|
```
|
|
|
|
4xx error generated when `debug: false` :
|
|
|
|
```
|
|
{ error:
|
|
{ statusCode: 422,
|
|
name: 'Unprocessable Entity',
|
|
message: 'Missing required fields',
|
|
code: 'MISSING_REQUIRED_FIELDS' }}
|
|
```
|