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181 lines
6.8 KiB
Markdown
181 lines
6.8 KiB
Markdown
# `hafas-client` documentation
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**[API documentation](api.md)**
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## Migrating from an old `hafas-client` version
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- [`4` → `5` migration guide](migrating-to-5.md)
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## Throttling requests
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There's opt-in support for throttling requests to the endpoint.
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```js
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import {createClient} from 'hafas-client'
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import {withThrottling} from 'hafas-client/throttle.js'
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import {dbProfile} from 'hafas-client/p/db.js'
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// create a throttled HAFAS client with Deutsche Bahn profile
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const client = createClient(withThrottling(dbProfile), 'my-awesome-program')
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// Berlin Jungfernheide to München Hbf
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await client.journeys('8011167', '8000261', {results: 1})
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```
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You can pass custom values for the nr of requests (`limit`) per interval into `withThrottling`:
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```js
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// 2 requests per second
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const throttledDbProfile = withThrottling(dbProfile, 2, 1000)
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const client = createClient(throttledDbProfile, 'my-awesome-program')
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```
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## Retrying failed requests
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There's opt-in support for retrying failed requests to the endpoint.
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```js
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import {createClient} from 'hafas-client'
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import {withRetrying} from 'hafas-client/retry.js'
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import {dbProfile} from 'hafas-client/p/db.js'
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// create a client with Deutsche Bahn profile that will retry on HAFAS errors
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const client = createClient(withRetrying(dbProfile), 'my-awesome-program')
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```
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You can pass custom options into `withRetrying`. They will be passed into [`retry`](https://github.com/tim-kos/node-retry#tutorial).
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```js
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// retry 2 times, after 10 seconds & 30 seconds
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const retryingDbProfile = withRetrying(dbProfile, {
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retries: 2,
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minTimeout: 10 * 1000,
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factor: 3
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})
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const client = createClient(retryingDbProfile, 'my-awesome-program')
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```
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## User agent randomization
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By default, `hafas-client` randomizes the client name that you pass into `createClient`, and sends it as [`User-Agent`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/User-Agent) in a randomized form:
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```js
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import {createClient} from 'hafas-client'
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// …
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const client = createClient(someProfile, 'my-awesome-program')
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await client.journeys(/* … */)
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// User-Agent: my-awee70429some-pre70429ogram
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await client.journeys(/* … */)
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// User-Agent: my-awesom9bb8e2e-prog9bb8e2ram
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```
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You can turn this off by setting `profile.randomizeUserAgent` to `false`:
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```js
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const client = createClient({
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...someProfile,
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randomizeUserAgent: false,
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}, 'my-awesome-program')
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```
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## Logging requests
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You can use `profile.logRequest` and `profile.logResponse` to process the raw [Fetch](https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API) [`Request`](https://developer.mozilla.org/en-US/docs/Web/API/Request) and [`Response`](https://developer.mozilla.org/en-US/docs/Web/API/Response), respectively.
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As an example, we can implement a custom logger:
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```js
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const createClient = require('hafas-client')
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const dbProfile = require('hafas-client/p/db')
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const logRequest = (ctx, fetchRequest, requestId) => {
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// ctx looks just like with the other profile.* hooks:
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const {profile, opt} = ctx
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console.debug(requestId, fetchRequest.headers, fetchRequest.body + '')
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}
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const logResponse = (ctx, fetchResponse, body, requestId) => {
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console.debug(requestId, fetchResponse.headers, body + '')
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}
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// create a client with Deutsche Bahn profile that debug-logs
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const client = createClient({
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...dbProfile,
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logRequest,
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logResponse,
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}, 'my-awesome-program')
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```
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```js
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// logRequest output:
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'29d0e3' {
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accept: 'application/json',
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'accept-encoding': 'gzip, br, deflate',
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'content-type': 'application/json',
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connection: 'keep-alive',
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'user-agent': 'hafas842c51-clie842c51nt debug C842c51LI'
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} {"lang":"de","svcReqL":[{"cfg":{"polyEnc":"GPA"},"meth":"LocMatch",…
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// logResponse output:
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'29d0e3' {
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'content-encoding': 'gzip',
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'content-length': '1010',
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'content-type': 'application/json; charset=utf-8',
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date: 'Thu, 06 Oct 2022 12:31:09 GMT',
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server: 'Apache',
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vary: 'User-Agent'
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} {"ver":"1.45","lang":"deu","id":"sb42zgck4mxtxm4s","err":"OK","graph"…
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```
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The default `profile.logRequest` [`console.error`](https://nodejs.org/docs/latest-v10.x/api/console.html#console_console_error_data_args)s the request body, if you have set `$DEBUG` to `hafas-client`. Likewise, `profile.logResponse` `console.error`s the response body.
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## Error handling
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Unexpected errors – e.g. due to bugs in `hafas-client` itself – aside, its methods may reject with the following errors:
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- `HafasError` – A generic error to signal that something HAFAS-related went wrong, either in the client, or in the HAFAS endpoint.
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- `HafasAccessDeniedError` – The HAFAS endpoint has rejected your request because you're not allowed to access it (or the specific API call). Subclass of `HafasError`.
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- `HafasInvalidRequestError` – The HAFAS endpoint reports that an invalid request has been sent. Subclass of `HafasError`.
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- `HafasNotFoundError` – The HAFAS endpoint does not know about such stop/trip/etc. Subclass of `HafasError`.
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- `HafasServerError` – An error occured within the HAFAS endpoint, so that it can't fulfill the request; For example, this happens when HAFAS' internal backend is unavailable. Subclass of `HafasError`.
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Each error has the following properties:
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- `isHafasError` – Always `true`. Allows you to differente HAFAS-related errors from e.g. network errors.
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- `code` – A string representing the error type for all other error classes, e.g. `INVALID_REQUEST` for `HafasInvalidRequestError`. `null` for plain `HafasError`s.
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- `isCausedByServer` – Boolean, telling you if the HAFAS endpoint says that it couldn't process your request because *it* is unavailable/broken.
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- `hafasCode` – A HAFAS-specific error code, if the HAFAS endpoint returned one; e.g. `H890` when no journeys could be found. `null` otherwise.
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- `request` – The [Fetch API `Request`](https://developer.mozilla.org/en-US/docs/Web/API/Request) of the request.
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- `url` – The URL of the request.
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- `response` – The [Fetch API `Response`](https://developer.mozilla.org/en-US/docs/Web/API/Response).
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To check **if an error from `hafas-client` is HAFAS-specific, use `error instanceof HafasError`**:
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```js
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import {HafasError} from 'hafas-client/lib/errors.js'
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try {
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await client.journeys(/* … */)
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} catch (err) {
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if (err instanceof HafasError) {
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// HAFAS-specific error
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} else {
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// different error, e.g. network (ETIMEDOUT, ENETDOWN)
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}
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}
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```
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To determine **if you should automatically retry an error, use `!error.causedByServer`**.
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## Using `hafas-client` from another language
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If you want to use `hafas-client` to access HAFAS APIs but work with non-Node.js environments, you can use [`hafas-client-rpc`](https://github.com/derhuerst/hafas-client-rpc) to create a [JSON-RPC](https://www.jsonrpc.org) interface that you can send commands to.
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## Writing a profile
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Check [the guide](writing-a-profile.md).
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## General documentation for `mgate.exe` APIs
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[`hafas-mgate-api.md`](hafas-mgate-api.md)
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