# Performance optimizations

There are a few ways in which the performance of `@lumieducation/h5p-server` can be improved:

* [Caching library storage](#caching-library-storage)
* [Serving the library files from a different system](#serving-the-library-files-from-a-different-system)
* [Horizontal scaling](#horizontal-scaling)
* [Database-based content storage](#database-based-content-storage)

## Caching library storage

The [`CachedLibraryStorage`](https://github.com/Lumieducation/H5P-Nodejs-library/blob/release/packages/h5p-server/src/implementation/cache/CachedLibraryStorage.ts) class can be used to cache the most common calls to the library storage. This will improve the overall performance of the library quite a bit, as many functions need library metadata, semantics or language files, which they get from the library storage. When used for complex content types like Course Presentation, the `GET /ajax?action=libraries` endpoint becomes around 40x faster if you use the cached library storage!

The class uses [the NPM package `cache-manager`](https://www.npmjs.com/package/cache-manager) to abstract the caching, so you can pass in any of the store engines supported by it (e.g. redis, mongodb, fs, memcached). See the documentation page of `cache-manager` for more details.

This is how you use the storage:

```javascript
import * as H5P from '@lumieducation/h5p-server';
// const H5P = require('@lumieducation/h5p-server'); // old-style require alternative

const cachedStorage = new H5P.cacheImplementations.CachedLibraryStorage(
    new H5P.fsImplementations.FileLibraryStorage(localLibraryPath)
    // you can also pass in other implementation of ILibraryStorage
);
```

Check out how to construct the H5PEditor with the storage [here](/usage/h5p-editor-constructor.md).

## Serving the library files from a different system

While you can use the inbuilt methods of `@lumieducation/h5p-server` to serve the library files (JavaScript and CSS files used by the actual content types) to the browser of the user, it is also possible to serve them directly, as they are simple static files.

If you construct [`FileLibraryStorage`](https://github.com/Lumieducation/H5P-Nodejs-library/blob/release/packages/h5p-server/src/implementation/fs/FileLibraryStorage.ts) with

`new FileLibraryStorage('/directory/in/filesystem')`

all libraries will be stored in `/directory/in/filesystem`. You can simply serve this directory under the URL specified in `IH5PConfig.librariesUrl` (defaults to `/libraries`). If you put this directory into a NFS storage or a shared volume, you can even use different machines to serve the library files (vertical scaling)!

You must make sure that patches to libraries that have changed the library files aren't lost due to caching.

## Horizontal scaling

It is possible to use `@lumieducation/h5p-server` in a setup in which multiple instances of it are executed in parallel (on a single machine to make use of multi-core processors or on multiple machines). When doing this, pay attention to this:

* If you use [caching](#caching-library-storage), you have to use a cache like Redis or memcached. Cache invalidation across multiple instances will not work with the simple default in-memory cache.
* If you run multiple instances on a single machine, the library storage directory can be on the local filesystem and all instances can share it.
* If you run multiple instances on multiple machines, the library storage directory must be put into a network share (NFS) or you must use shared volumes (Docker).
* It is advised to use the Mongo/S3 content storage classes. [See below](#database-based-content-storage) for details.

## Database-based content storage

The simple [`FileContentStorage`](https://github.com/Lumieducation/H5P-Nodejs-library/blob/release/packages/h5p-server/src/implementation/fs/FileContentStorage.ts) and [`DirectoryTemporaryFileStorage`](https://github.com/Lumieducation/H5P-Nodejs-library/blob/release/packages/h5p-server/src/implementation/fs/DirectoryTemporaryFileStorage.ts) are not suitable for production use, as they suffer from serious scaling issues when listing content objects. They should only be used for development and testing purposes or in very small deployments.

It is advised to use the [MongoS3ContentStorage](/npm-packages/h5p-mongos3/mongo-s3-content-storage.md) and [S3TemporaryFileStorage](/npm-packages/h5p-mongos3/s3-temporary-file-storage.md) classes of the h5p-mongos3 package. You can also write your own custom content storage and temporary file storage classes for other databases.


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