npm package: @fluidframework/driver-web-cache
Description: Implementation of the driver caching API for a web browser
Author: Microsoft and contributors
Latest version: 2.92.0

# @fluidframework/driver-web-cache

This package provides an implementation of the `IPersistedCache` interface in the odsp-driver package. This cache enables
storing of user content on the user's machine in order to provide faster boot experiences when opening the same Fluid
containers more than once. This implementation has a dependency on indexeddb, so it is intended to only be used in a browser
context.

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## Using Fluid Framework libraries

When taking a dependency on a Fluid Framework library's public APIs, we recommend using a `^` (caret) version range, such as `^1.3.4`.
While Fluid Framework libraries may use different ranges with interdependencies between other Fluid Framework libraries,
library consumers should always prefer `^`.

If using any of Fluid Framework's unstable APIs (for example, its `beta` APIs), we recommend using a more constrained version range, such as `~`.

## Installation

To get started, install the package by running the following command:

```bash
npm i @fluidframework/driver-web-cache
```

## Importing from this package

This package leverages [package.json exports](https://nodejs.org/api/packages.html#exports) to separate its APIs by support level.
For more information on the related support guarantees, see [API Support Levels](https://fluidframework.com/docs/build/releases-and-apitags/#api-support-levels).

To access the `public` ([SemVer](https://semver.org/)) APIs, import via `@fluidframework/driver-web-cache` like normal.

To access the `legacy` APIs, import via `@fluidframework/driver-web-cache/legacy`.

## API Documentation

API documentation for **@fluidframework/driver-web-cache** is available at <https://fluidframework.com/docs/apis/driver-web-cache>.

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## Usage

```typescript
import { FluidCache } from "@fluidframework/driver-web-cache";

new FluidCache({
	partitionKey: userId,
	logger,
	maxCacheItemAge,
});
```

### Parameters

-   `partitionKey` - Used to determine what partition of the cache is being used, and can prevent multiple users on the
    same machine from sharing a snapshot cache. If you absolutely know that users will not share the cache,
    can also be set to `null`. Currently optional, but is proposed to be required in the next major bump.
    The recommendation is to use this key to differentiate users for the cache data.
-   `logger` - An optional implementation of the logger contract where diagnostic data can be logged.
-   `maxCacheItemAge` - The cache tracks a timestamp with each entry. This flag specifies the maximum age (in milliseconds)
    for a cache entry to be used. This flag does not control when cached content is deleted since different scenarios and
    applications may have different staleness thresholds for the same data.

## Clearing cache entries

Whenever any Fluid content is loaded with the web cache enabled, a task is scheduled to clear out all "stale" cache
entries. This task is scheduled with the `setIdleCallback` browser API. We define stale cache entries as any cache
entries that have not been used (read or written to) within the last 4 weeks. The cache is cleared of all stale cache
entries corresponding to all documents, not just the ones corresponding to the Fluid document being loaded.

The `deleteFluidCacheIndexDbInstance` API that an application can use to clear out the entire contents of the snapshot
cache at any time. We recommend calling this API when the user explicitly signs out. Hosting applications
are on point for ensuring responsible usage of the snapshot caching capability to still meet any relevant
customer promises, such as clearing out storage when appropriate or disabling snapshot caching under certain circumstances,
such as when it is known the user is logged in to a public computer.

```typescript
import { deleteFluidCacheIndexDbInstance } from "@fluidframework/driver-web-cache";

// We put a catch here because Firefox Incognito will throw an error here. This is why we claim this method is a "best effort", since sometimes the browser won't let us access storage
deleteFluidCacheIndexDbInstance().catch(() => {});
```

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## Minimum Client Requirements

These are the platform requirements for the current version of Fluid Framework Client Packages.
These requirements err on the side of being too strict since within a major version they can be relaxed over time, but not made stricter.
For Long Term Support (LTS) versions this can require supporting these platforms for several years.

It is likely that other configurations will work, but they are not supported: if they stop working, we do not consider that a bug.
If you would benefit from support for something not listed here, file an issue and the product team will evaluate your request.
When making such a request please include if the configuration already works (and thus the request is just that it becomes officially supported), or if changes are required to get it working.

### Supported Runtimes

-   NodeJs ^20.10.0 except that we will drop support for it [when NodeJs 20 loses its upstream support on 2026-04-30](https://github.com/nodejs/release#release-schedule), and will support a newer LTS version of NodeJS (22) at least 1 year before 20 is end-of-life. This same policy applies to NodeJS 22 when it is end of life (2027-04-30).
    -   Running Fluid in a Node.js environment with the `--no-experimental-fetch` flag is not supported.
-   Modern browsers supporting the es2022 standard library: in response to asks we can add explicit support for using babel to polyfill to target specific standards or runtimes (meaning we can avoid/remove use of things that don't polyfill robustly, but otherwise target modern standards).

### Supported Tools

-   TypeScript 5.4:
    -   All [`strict`](https://www.typescriptlang.org/tsconfig) options are supported.
    -   [`strictNullChecks`](https://www.typescriptlang.org/tsconfig) is required.
    -   [Configuration options deprecated in 5.0](https://github.com/microsoft/TypeScript/issues/51909) are not supported.
    -   `exactOptionalPropertyTypes` is currently not fully supported.
        If used, narrowing members of Fluid Framework types types using `in`, `Reflect.has`, `Object.hasOwn` or `Object.prototype.hasOwnProperty` should be avoided as they may incorrectly exclude `undefined` from the possible values in some cases.
-   [webpack](https://webpack.js.org/) 5
    -   We are not intending to be prescriptive about what bundler to use.
        Other bundlers which can handle ES Modules should work, but webpack is the only one we actively test.

### Module Resolution

[`Node16`, `NodeNext`, or `Bundler`](https://www.typescriptlang.org/tsconfig#moduleResolution) resolution should be used with TypeScript compilerOptions to follow the [Node.js v12+ ESM Resolution and Loading algorithm](https://nodejs.github.io/nodejs.dev/en/api/v20/esm/#resolution-and-loading-algorithm).
Node10 resolution is not supported as it does not support Fluid Framework's API structuring pattern that is used to distinguish stable APIs from those that are in development.

### Module Formats

-   ES Modules:
    ES Modules are the preferred way to consume our client packages (including in NodeJs) and consuming our client packages from ES Modules is fully supported.
-   CommonJs:
    Consuming our client packages as CommonJs is supported only in NodeJS and only for the cases listed below.
    This is done to accommodate some workflows without good ES Module support.
    If you have a workflow you would like included in this list, file an issue.
    Once this list of workflows motivating CommonJS support is empty, we may drop support for CommonJS one year after notice of the change is posted here.

    -   Testing with Jest (which lacks [stable ESM support](https://jestjs.io/docs/ecmascript-modules) due to [unstable APIs in NodeJs](https://github.com/nodejs/node/issues/37648))

## Contribution Guidelines

There are many ways to [contribute](https://github.com/microsoft/FluidFramework/blob/main/CONTRIBUTING.md) to Fluid.

-   Participate in Q&A in our [GitHub Discussions](https://github.com/microsoft/FluidFramework/discussions).
-   [Submit bugs](https://github.com/microsoft/FluidFramework/issues) and help us verify fixes as they are checked in.
-   Review the [source code changes](https://github.com/microsoft/FluidFramework/pulls).
-   [Contribute bug fixes](https://github.com/microsoft/FluidFramework/blob/main/CONTRIBUTING.md).

Detailed instructions for working in the repo can be found in the [Wiki](https://github.com/microsoft/FluidFramework/wiki).

This project has adopted the [Microsoft Open Source Code of Conduct](https://opensource.microsoft.com/codeofconduct/).
For more information see the [Code of Conduct FAQ](https://opensource.microsoft.com/codeofconduct/faq/) or contact [opencode@microsoft.com](mailto:opencode@microsoft.com) with any additional questions or comments.

This project may contain Microsoft trademarks or logos for Microsoft projects, products, or services.
Use of these trademarks or logos must follow Microsoft’s [Trademark & Brand Guidelines](https://www.microsoft.com/trademarks).
Use of Microsoft trademarks or logos in modified versions of this project must not cause confusion or imply Microsoft sponsorship.

## Help

Not finding what you're looking for in this README? Check out [fluidframework.com](https://fluidframework.com/docs/).

Still not finding what you're looking for? Please [file an issue](https://github.com/microsoft/FluidFramework/wiki/Submitting-Bugs-and-Feature-Requests).

Thank you!

## Trademark

This project may contain Microsoft trademarks or logos for Microsoft projects, products, or services.

Use of these trademarks or logos must follow Microsoft's [Trademark & Brand Guidelines](https://www.microsoft.com/en-us/legal/intellectualproperty/trademarks/usage/general).

Use of Microsoft trademarks or logos in modified versions of this project must not cause confusion or imply Microsoft sponsorship.

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