npm package: @koopjs/koop-core
Description: Serve, transform, and query geospatial data on the web
Latest version: 10.4.19

# Koop
[![npm version][npm-img]][npm-url]
![coverage](https://raw.githubusercontent.com/koopjs/koop/master/packages/core/coverage.svg)

> Transform, query, & download geospatial data on the web.  See [koopjs.github.io](https://koopjs.github.io) for details.

This is the core dependency for setting up a Koop instance.  By default it includes the Output-Geoservices plugin and an in-memory data cache.

## Install
```bash
# Install Koop npm and save to package.json
npm install --save @koopjs/koop-core
```

## Usage

The Koop [usage docs](https://koopjs.github.io/docs/usage/koop-core) and [quick start](https://koopjs.github.io/docs/basics/quickstart) provide usage information, but we'll give a quick overview here.

```js
// require koop-core
const Koop = require('@koopjs/koop-core')

// create a Koop instance
const koop = new Koop(options)

/* Register Koop data providers */
const provider = require('@koopjs/provider-github')
koop.register(provider)


// Start listening on port 8080
koop.server.listen(8080, () => console.log(`Koop listening on port 8080!`))
```

Every Koop instance includes the Geoservice output-plugin by default, so after startup noted above, you would have the following routes ready to receive requests:
[GET, POST] /github/rest/info
[GET, POST] /github/rest/services/:id/FeatureServer/:layer/:method
[GET, POST] /github/rest/services/:id/FeatureServer/layers
[GET, POST] /github/rest/services/:id/FeatureServer/:layer
[GET, POST] /github/rest/services/:id/FeatureServer

### Options
You can pass an `options` object when instantiating a Koop instance. 

```js
// create a Koop instance
const koop = new Koop(options)
```

#### disableCors
Koop enables CORS by default.  If you do not want CORS enabled, you can disable it by adding a `disableCors` boolean to your Koop config file:

```js
const options = {
  disableCors: true
}
```

#### disableCompression
Koop adds Express compression by default.  If you do not want Express compression (e.g., perhaps you are using Nginx for compression), you can disable it by adding a `disableCompression` boolean to your Koop config file:

```js
const options = {
  disableCompression: true
}
```

#### logger
Koop includes a Winston logger with a console transport by default.  If you have a custom logger that you want to use, you can pass it as an option:

```js

const logger = require('my-logger')
const options = {
  logger
}
```

#### logLevel
The default Koop logger uses a log-level of `info`.  If you want to change the log level, you can pass any of the standard Winston log-level values as an option:

```js
const options = {
  logLevel: 'debug'
}
```

#### cacheSize
The maximum number of items to store in the default memorey-cache. Defaults to 500:

```js
const options = {
  cacheSize: 1000
}
```

#### skipGeoservicesRegistration
By default, Koop will register the GeoServices output-plugin (a.k.a. FeatureServer).  If you do not want this plugin registered or want to register a specific version, you can skip the default registration by setting the option to `true`:

```js
const options = {
  skipGeoservicesRegistration: true
}
```


#### geoservicesDefaults
Koop registers the Geoservices output plugin (FeatureServer) by default.  This plugin takes its own options including those to set server and layer metadata (e.g., FeatureServer version, copyrightText, maxRecordCount, etc). These are useful for overriding defaults set in the FeatureServer codebase. You can have Koop set these options at start-up by passing the `geoservicesDefaults` option.  It should be a JSON object with the specification described in the [FeatureServer documentation](packages/featureserver#featureserver.setdefaults).

### Registering Providers
When registering a provider you can pass an options object that provides some useful functionality:

```js
const Koop = require('@koopjs/koop-core')
const koop = new Koop()

const providerOptions = {
  name: 'special-name',
  cacheTtl: 600,
  before: (req, callback) => {
    req.query.myHardCodedParam = 'foo';
    callback();
  }
  after: (req, geojson, callback) => {
    geojson.crs = 'my coordinate system';
    callback(null, geojson);
  }
}

/* Register Koop data providers with options */
const provider = require('@koopjs/provider-github')
koop.register(provider, providerOptions)
```

#### Provider registration options
##### name
Use this param to override the name of the provider.  If you supply a value for `name` it will be used in the path for routes registered to this provider.

##### cacheTtl
Use this param to set the default caching time (in seconds) for any data acquired by this provider. It can be overridden on a request-by-request basis by adding a `ttl` property to the root level of the geojson produced by the provider.

##### before
Supply a function that is executed _before_ a provider's `getData` method and has access to the Express request object.  This is useful is you want to modify incoming request params before they arrive in a providers `getData` method.

##### after
Supply a function that is executed _after_ a provider's `getData` method and has access to the Express request object.  This is useful is you want to modify the GeoJSON produce by the provider before it is passed on to the cache or any output plugin.  It's a way of modifying a provider's getData functionality without having to modify the code of the provider itself.

## Issues

Find a bug or want to request a new feature? Please let us know by submitting an [issue](https://github.com/koopjs/koop/issues).

## Contributing

Esri welcomes contributions from anyone and everyone. Please see our [guidelines for contributing](https://github.com/Esri/contributing).

## License

[Apache 2.0](LICENSE)

<!-- [](Esri Tags: ArcGIS Web Mapping GeoJson FeatureServices) -->
<!-- [](Esri Language: JavaScript) -->

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[npm-url]: https://www.npmjs.com/package/@koopjs/koop-core