Services or capabilities described in Amazon Web Services documentation might vary by Region. To see the differences applicable to the China Regions, see Getting Started with Amazon Web Services in China (PDF).

Tutorial: Amazon OpenSearch Service Resolvers

Amazon AppSync supports using Amazon OpenSearch Service from domains that you have provisioned in your own Amazon account, provided they don’t exist inside a VPC. After your domains are provisioned, you can connect to them using a data source, at which point you can configure a resolver in the schema to perform GraphQL operations such as queries, mutations, and subscriptions. This tutorial will take you through some common examples.

For more information, see the Resolver Mapping Template Reference for OpenSearch.

One-Click Setup

To automatically set up a GraphQL endpoint in Amazon AppSync with Amazon OpenSearch Service configured you can use this Amazon CloudFormation template:

After the Amazon CloudFormation deployment completes you can skip directly to running GraphQL queries and mutations.

Create a New OpenSearch Service Domain

To get started with this tutorial, you need an existing OpenSearch Service domain. If you don’t have one, you can use the following sample. Note that it can take up to 15 minutes for an OpenSearch Service domain to be created before you can move on to integrating it with an Amazon AppSync data source.

aws cloudformation create-stack --stack-name AppSyncOpenSearch \
--template-url https://s3.us-west-2.amazonaws.com/awsappsync/resources/elasticsearch/ESResolverCFTemplate.yaml \
--parameters ParameterKey=OSDomainName,ParameterValue=ddtestdomain ParameterKey=Tier,ParameterValue=development \
--capabilities CAPABILITY_NAMED_IAM

You can launch the following Amazon CloudFormation stack in the US West 2 (Oregon) region in your Amazon account:

Configure Data Source for OpenSearch Service

After the OpenSearch Service domain is created, navigate to your Amazon AppSync GraphQL API and choose the Data Sources tab. Choose New and enter a friendly name for the data source, such as “oss”. Then choose Amazon OpenSearch domain for Data source type, choose the appropriate region, and you should see your OpenSearch Service domain listed. After selecting it you can either create a new role and Amazon AppSync will assign the role-appropriate permissions, or you can choose an existing role, which has the following inline policy:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "Stmt1234234",
            "Effect": "Allow",
            "Action": [
                "es:ESHttpDelete",
                "es:ESHttpHead",
                "es:ESHttpGet",
                "es:ESHttpPost",
                "es:ESHttpPut"
            ],
            "Resource": [
                "arn:aws:es:REGION:ACCOUNTNUMBER:domain/democluster/*"
            ]
        }
    ]
}

You’ll also need to set up a trust relationship with Amazon AppSync for that role:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Principal": {
                "Service": "appsync.amazonaws.com"
            },
            "Action": "sts:AssumeRole"
        }
    ]
}

Additionally, the OpenSearch Service domain has it’s own Access Policy which you can modify through the Amazon OpenSearch Service console. You will need to add a policy similar to the following, with the appropriate actions and resource for the OpenSearch Service domain. Note that the Principal will be the AppSync data source role, which if you let the console create this, can be found in the IAM console.

{
    "Version": "2012-10-17",
    "Statement": [
        {
        "Effect": "Allow",
        "Principal": {
            "AWS": "arn:aws:iam::ACCOUNTNUMBER:role/service-role/APPSYNC_DATASOURCE_ROLE"
        },
        "Action": [
            "es:ESHttpDelete",
            "es:ESHttpHead",
            "es:ESHttpGet",
            "es:ESHttpPost",
            "es:ESHttpPut"
        ],
        "Resource": "arn:aws:es:REGION:ACCOUNTNUMBER:domain/DOMAIN_NAME/*"
        }
    ]
}

Connecting a Resolver

Now that the data source is connected to your OpenSearch Service domain, you can connect it to your GraphQL schema with a resolver, as shown in the following example:

 schema {
   query: Query
   mutation: Mutation
 }

 type Query {
   getPost(id: ID!): Post
   allPosts: [Post]
 }

 type Mutation {
   addPost(id: ID!, author: String, title: String, url: String, ups: Int, downs: Int, content: String): AWSJSON
 }

type Post {
  id: ID!
  author: String
  title: String
  url: String
  ups: Int
  downs: Int
  content: String
}
...

Note that there is a user-defined Post type with a field of id. In the following examples, we assume there is a process (which can be automated) for putting this type into your OpenSearch Service domain, which would map to a path root of /post/_doc, where post is the index. From this root path, you can perform individual document searches, wildcard searches with /id/post*, or multi-document searches with a path of /post/_search. For example, if you have another type called User, you can index documents under a new index called user, then perform searches with a path of /user/_search.

From the schema editor in the Amazon AppSync console, modify the preceding Posts schema to include a searchPosts query:

type Query {
  getPost(id: ID!): Post
  allPosts: [Post]
  searchPosts: [Post]
}

Save the schema. On the right side, for searchPosts, choose Attach resolver. In the Action menu, choose Update runtime, then choose Unit Resolver (VTL only). Then, choose your OpenSearch Service data source. Under the request mapping template section, select the drop-down for Query posts to get a base template. Modify the path to be /post/_search. It should look like the following:

{
    "version":"2017-02-28",
    "operation":"GET",
    "path":"/post/_search",
    "params":{
        "headers":{},
        "queryString":{},
        "body":{
            "from":0,
            "size":50
        }
    }
}

This assumes that the preceding schema has documents that have been indexed in OpenSearch Service under the post field. If you structure your data differently, then you’ll need to update accordingly.

Under the response mapping template section, you need to specify the appropriate _source filter if you want to get back the data results from an OpenSearch Service query and translate to GraphQL. Use the following template:

[
    #foreach($entry in $context.result.hits.hits)
    #if( $velocityCount > 1 ) , #end
    $utils.toJson($entry.get("_source"))
    #end
]

Modifying Your Searches

The preceding request mapping template performs a simple query for all records. Suppose you want to search by a specific author. Further, suppose you want that author to be an argument defined in your GraphQL query. In the schema editor of the Amazon AppSync console, add an allPostsByAuthor query:

type Query {
  getPost(id: ID!): Post
  allPosts: [Post]
  allPostsByAuthor(author: String!): [Post]
  searchPosts: [Post]
}

Now choose Attach resolver and select the OpenSearch Service data source, but use the following example in the response mapping template:

{
    "version":"2017-02-28",
    "operation":"GET",
    "path":"/post/_search",
    "params":{
        "headers":{},
        "queryString":{},
        "body":{
            "from":0,
            "size":50,
            "query":{
                "match" :{
                    "author": $util.toJson($context.arguments.author)
                }
            }
        }
    }
}

Note that the body is populated with a term query for the author field, which is passed through from the client as an argument. You could optionally have prepopulated information, such as standard text, or even use other utilities.

If you’re using this resolver, fill in the response mapping template with the same information as the previous example.

Adding Data to OpenSearch Service

You may want to add data to your OpenSearch Service domain as the result of a GraphQL mutation. This is a powerful mechanism for searching and other purposes. Because you can use GraphQL subscriptions to make your data real-time, it serves as a mechanism for notifying clients of updates to data in your OpenSearch Service domain.

Return to the Schema page in the Amazon AppSync console and select Attach resolver for the addPost() mutation. Select the OpenSearch Service data source again and use the following response mapping template for the Posts schema:

{
    "version":"2017-02-28",
    "operation":"PUT",
    "path": $util.toJson("/post/_doc/$context.arguments.id"),
    "params":{
        "headers":{},
        "queryString":{},
        "body":{
            "id": $util.toJson($context.arguments.id),
            "author": $util.toJson($context.arguments.author),
            "ups": $util.toJson($context.arguments.ups),
            "downs": $util.toJson($context.arguments.downs),
            "url": $util.toJson($context.arguments.url),
            "content": $util.toJson($context.arguments.content),
            "title": $util.toJson($context.arguments.title)
        }
    }
}

As before, this is an example of how your data might be structured. If you have different field names or indexes, you need to update the path and body as appropriate. This example also shows how to use $context.arguments to populate the template from your GraphQL mutation arguments.

Before moving on, use the following response mapping template, which will return the result of the mutation operation or error information as output:

#if($context.error)
    $util.toJson($ctx.error)
#else
    $util.toJson($context.result)
#end

Retrieving a Single Document

Finally, if you want to use the getPost(id:ID) query in your schema to return an individual document, find this query in the schema editor of the Amazon AppSync console and choose Attach resolver. Select the OpenSearch Service data source again and use the following mapping template:

{
    "version":"2017-02-28",
    "operation":"GET",
    "path": $util.toJson("post/_doc/$context.arguments.id"),
    "params":{
        "headers":{},
        "queryString":{},
        "body":{}
    }
}

Because the path above uses the id argument with an empty body, this returns the single document. However, you need to use the following response mapping template, because now you’re returning a single item and not a list:

$utils.toJson($context.result.get("_source"))

Perform Queries and Mutations

You should now be able to perform GraphQL operations against your OpenSearch Service domain. Navigate to the Queries tab of the Amazon AppSync console and add a new record:

mutation addPost {
    addPost (
        id:"12345"
        author: "Fred"
        title: "My first book"
        content: "This will be fun to write!"
        url: "publisher website",
        ups: 100,
        downs:20 
       )
}

You’ll see the result of the mutation on the right. Similarly, you can now run a searchPosts query against your OpenSearch Service domain:

query searchPosts {
    searchPosts {
        id
        title
        author
        content
    }
}

Best Practices