Persisted operations

Persisted operations (also known as trusted documents) let you pre-register all required operations of your clients. You extract the operations from your client applications at build time and place them in the server's operation document storage.

Extracting operations is supported by client libraries like Relay and in the case of Strawberry Shake no additional work is needed.

How It Works#

• All operations that your clients execute are extracted during the client build process. Individual operation documents are hashed to generate a unique identifier for each operation.
• Before your server is deployed, the extracted operation documents are placed in the server's operation document storage.
• After the server has been deployed, clients execute persisted operations by specifying the operation ID (hash) in their requests.
• If Hot Chocolate finds an operation that matches the specified hash in the operation document storage, it executes the operation and returns the result to the client.

Benefits#

There are two main benefits to using persisted operations:

Performance

• Only a hash and optionally variables need to be sent to the server, reducing network traffic.
• Operations no longer need to be embedded into the client code, reducing the bundle size in the case of websites.
• Hot Chocolate can optimize the execution of persisted operations because they are always the same.

Security

The server can be configured to only execute persisted operations and refuse any other operation provided by a client. This eliminates a whole class of potential attack vectors because malicious actors can no longer craft and execute harmful operations against your GraphQL server.

Usage#

Instruct your server to handle persisted operations by calling UsePersistedOperationPipeline() on the IRequestExecutorBuilder:

builder
    .AddGraphQL()
    .AddQueryType<Query>()
    .UsePersistedOperationPipeline();

Production-Ready Persisted Operations#

Setting up a persisted operation file is not sufficient for a robust production environment. A key aspect of managing persisted operations at scale involves version management and ensuring compatibility with your GraphQL schema. The client registry is the resource for this purpose.

The client registry simplifies the management of your GraphQL clients. It stores and retrieves persisted operation documents through their hashes and ensures that operations are validated against the current schema on publish, preventing runtime errors due to schema-operation mismatches. It also supports versioning of your clients, allowing updates and maintenance without disrupting existing operations.

Check out the client registry documentation for more information.

Storage Mechanisms#

Hot Chocolate supports several operation document storages for persisted operations.

Filesystem#

To load persisted operation documents from the filesystem, add the following package:

dotnet add package HotChocolate.PersistedOperations.FileSystem

Specify where the persisted operation documents are located. The argument to AddFileSystemOperationDocumentStorage() specifies the directory containing the operation documents.

builder
    .AddGraphQL()
    .AddQueryType<Query>()
    .UsePersistedOperationPipeline()
    .AddFileSystemOperationDocumentStorage("./persisted_operations");

When presented with an operation document hash, Hot Chocolate checks the specified folder for a file in the format: {Hash}.graphql.

Example: 0c95d31ca29272475bf837f944f4e513.graphql

This file is expected to contain the operation document that the hash was generated from.

Redis#

To load persisted operation documents from Redis, add the following package:

dotnet add package HotChocolate.PersistedOperations.Redis

Specify where the persisted operation documents are located. Using AddRedisOperationDocumentStorage(), point to a specific Redis database containing the operation documents.

builder
    .AddGraphQL()
    .AddQueryType<Query>()
    .UsePersistedOperationPipeline()
    .AddRedisOperationDocumentStorage(services =>
        ConnectionMultiplexer.Connect("host:port").GetDatabase());

Keys in the specified Redis database are expected to be operation IDs (hashes) and contain the actual operation document as the value.

Azure Blob Storage#

To load persisted operation documents from Azure Blob Storage, add the following package:

dotnet add package HotChocolate.PersistedOperations.AzureBlobStorage

Specify where the persisted operation documents are located. Using AddAzureBlobStorageOperationDocumentStorage(), point to a specific Azure Blob Storage container. The blob's name is the hash of the query, and its content is the corresponding GraphQL query.

builder
    .AddGraphQL()
    .AddQueryType<Query>()
    .UsePersistedOperationPipeline()
    .AddAzureBlobStorageOperationDocumentStorage(services =>
        services.GetService<BlobServiceClient>().GetBlobContainerClient("hotchocolate"));

Unlike Redis, a Blob Storage client has no built-in way to set the expiration of files in Azure Blob Storage. However, you can define a Lifecycle Management Policy. The following sample policy instructs Azure to remove all files from the hotchocolate container when they have not been accessed for 10 days.

{
  "rules": [
    {
      "enabled": true,
      "name": "remove-after-10d",
      "type": "Lifecycle",
      "definition": {
        "actions": {
          "baseBlob": {
            "delete": {
              "daysAfterLastAccessTimeGreaterThan": 10
            }
          }
        },
        "filters": {
          "blobTypes": ["blockBlob"],
          "prefixMatch": ["hotchocolate/"]
        }
      }
    }
  ]
}

Hashing Algorithms#

By default, Hot Chocolate uses the MD5 hashing algorithm. You can override this default by specifying a DocumentHashProvider:

builder
    .AddGraphQL()
    .AddQueryType<Query>()
    // choose one of the following providers
    .AddMD5DocumentHashProvider()
    .AddSha256DocumentHashProvider()
    .AddSha1DocumentHashProvider()
    .UsePersistedOperationPipeline()
    .AddFileSystemOperationDocumentStorage("./persisted_operations");

You can also configure how these hashes are encoded by specifying a HashFormat as argument:

AddSha256DocumentHashProvider(HashFormat.Hex)
AddSha256DocumentHashProvider(HashFormat.Base64)

Blocking Regular Operations#

If you want to disallow any dynamic operations, enable OnlyAllowPersistedDocuments:

builder
    .AddGraphQL()
    // Omitted for brevity
    .ModifyRequestOptions(
        options => options
            .PersistedOperations
            .OnlyAllowPersistedDocuments = true);

This blocks any dynamic operations that do not contain the id of a persisted operation.

You might still want to allow the execution of dynamic operations in certain circumstances. Override the OnlyAllowPersistedDocuments rule on a per-request basis using the AllowNonPersistedOperation method on the OperationRequestBuilder. Implement a custom IHttpRequestInterceptor and call AllowNonPersistedOperation if a certain condition is met:

builder
    .AddGraphQL()
    // Omitted for brevity
    .AddHttpRequestInterceptor<CustomHttpRequestInterceptor>()
    .ModifyRequestOptions(
        options => options
            .PersistedOperations
            .OnlyAllowPersistedDocuments = true);

public class CustomHttpRequestInterceptor
    : DefaultHttpRequestInterceptor
{
    public override ValueTask OnCreateAsync(
        HttpContext context,
        IRequestExecutor requestExecutor,
        OperationRequestBuilder requestBuilder,
        CancellationToken cancellationToken)
    {
        if (context.Request.Headers.ContainsKey("X-Developer"))
        {
            requestBuilder.AllowNonPersistedOperation();
        }

        return base.OnCreateAsync(
            context,
            requestExecutor,
            requestBuilder,
            cancellationToken);
    }
}

In the above example, requests containing the X-Developer header can execute dynamic operations. In your production application, replace this check with an authorization policy, an API key, or whatever fits your requirements.

Client Expectations#

A client is expected to send an id field containing the operation document hash instead of a query field.

HTTP POST

{
  "id": "0c95d31ca29272475bf837f944f4e513",
  "variables": {
    // ...
  }
}

Next Steps#

• Automatic Persisted Operations for dynamically storing operations at runtime.
• Interceptors for per-request customization.
• Client Registry for production-ready persisted operation management.