Batching with API Mesh for Adobe Developer App Builder

Batching allows you to combine a group of requests into a single request, turning multiple queries into a single one. Compared to sending multiple queries simultaneously, batched requests result in better response times. They also avoid issues with rate-limiting.

The n+1 problem

The n+1 problem occurs when you request multiple pieces of information that cause the system to make multiple (n) queries to a source instead of using a single query. Since each query takes approximately the same amount of time, processing many queries can lead to degraded performance. In this example, a Reviews API contains reviews of your products by SKU. Without batching, you would need to query each SKU individually to return the corresponding reviews.

Example (without batching)

Consider a scenario where you are using the following mesh, where the Reviews source is a third-party API that contains reviews for your products by SKU. Each review consists of a review, customer_name, and rating field.

Copy
{
  "meshConfig": {
    "sources": [
      {
        "name": "Products",
        "handler": {
          "graphql": {
            "endpoint": "https://venia.magento.com/graphql"
          }
        }
      },
      {
        "name": "Reviews",
        "handler": {
          "graphql": {
            "endpoint": "<Reviews_API_URL>",
            "useGETForQueries": true
          }
        }
      }
    ],
    "additionalTypeDefs": "extend type ConfigurableProduct { customer_reviews: [productReviewslist]} ",
    "additionalResolvers": [
      {
        "targetFieldName": "customer_reviews",
        "targetTypeName": "ConfigurableProduct",
        "sourceName": "Reviews",
        "sourceTypeName": "Query",
        "sourceFieldName": "productsReviews",
        "requiredSelectionSet": "{ sku }",
        "sourceArgs": {
          "sku": "{root.sku}"
        }
      }
    ],
    "responseConfig": {
      "includeHTTPDetails": true
    }
  }
}
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{
  "meshConfig": {
    "sources": [
      {
        "name": "Products",
        "handler": {
          "graphql": {
            "endpoint": "https://venia.magento.com/graphql"
          }
        }
      },
      {
        "name": "Reviews",
        "handler": {
          "graphql": {
            "endpoint": "<Reviews_API_URL>",
            "useGETForQueries": true
          }
        }
      }
    ],
    "additionalTypeDefs": "extend type ConfigurableProduct { customer_reviews: [productReviewslist]} ",
    "additionalResolvers": [
      {
        "targetFieldName": "customer_reviews",
        "targetTypeName": "ConfigurableProduct",
        "sourceName": "Reviews",
        "sourceTypeName": "Query",
        "sourceFieldName": "productsReviews",
        "requiredSelectionSet": "{ sku }",
        "sourceArgs": {
          "sku": "{root.sku}"
        }
      }
    ],
    "responseConfig": {
      "includeHTTPDetails": true
    }
  }
}

The custom resolver extends the type ConfigurableProdcut with a new customer_reviews field, which allows nesting review fields inside of queries against the Venia source. The resolver is composed of the following components:

• The target (targetTypeName, targetFieldName) - describes the queried field.
• The source (sourceName, sourceTypeName, sourceFieldName) - describes where the data is resolved for the target field.
• requiredSelectionSet fetches the required arguments.
• sourceArgs maps the requiredSelectionSet argument to the source.

The following query causes multiple calls to the Reviews API:

Copy
{
  products(filter: { sku: { in: ["VD03", "VT12"] } }) {
    items {
      ... on ConfigurableProduct {
        sku
        name
        customer_reviews {
          sku
          reviews {
            review
            customer_name
            rating
          }
        }
        __typename
      }
    }
  }
}
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{
  products(filter: { sku: { in: ["VD03", "VT12"] } }) {
    items {
      ... on ConfigurableProduct {
        sku
        name
        customer_reviews {
          sku
          reviews {
            review
            customer_name
            rating
          }
        }
        __typename
      }
    }
  }
}

Batching example

The Reviews source takes an array of product SKUs and returns an array of reviews for each SKU. To make a single network request to the Reviews source for multiple SKUs, add keysArg and keyField to your mesh.

Copy
{
    "meshConfig": {
        "sources": [
            {
                "name": "Products",
                "handler": {
                    "graphql": {
                        "endpoint": " https://venia.magento.com/graphql"
                    }
                }
            },
            {
                "name": "Reviews",
                "handler": {
                    "graphql": {
                        "endpoint": "<Reviews_API_URL>",
                        "useGETForQueries":true
                    }
                }
            }
        ],
        "additionalTypeDefs": "extend type ConfigurableProduct { customer_reviews: productReviewslist} " ,
        "additionalResolvers" : [
          {
            "targetFieldName" : "customer_reviews",
            "targetTypeName" : "ConfigurableProduct",
            "sourceName": "Reviews",
            "sourceTypeName": "Query",
            "sourceFieldName": "productsReviews",
            "keysArg": "sku",
            "keyField": "sku"
        }],
        "responseConfig": {
            "includeHTTPDetails": true
        }
    }
}
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{
    "meshConfig": {
        "sources": [
            {
                "name": "Products",
                "handler": {
                    "graphql": {
                        "endpoint": " https://venia.magento.com/graphql"
                    }
                }
            },
            {
                "name": "Reviews",
                "handler": {
                    "graphql": {
                        "endpoint": "<Reviews_API_URL>",
                        "useGETForQueries":true
                    }
                }
            }
        ],
        "additionalTypeDefs": "extend type ConfigurableProduct { customer_reviews: productReviewslist} " ,
        "additionalResolvers" : [
          {
            "targetFieldName" : "customer_reviews",
            "targetTypeName" : "ConfigurableProduct",
            "sourceName": "Reviews",
            "sourceTypeName": "Query",
            "sourceFieldName": "productsReviews",
            "keysArg": "sku",
            "keyField": "sku"
        }],
        "responseConfig": {
            "includeHTTPDetails": true
        }
    }
}

requiredSelectionSet and sourceArgs are replaced with keysarg and keyField:

• keysArg provides the name of the primary key argument. For this example, the keysArg field is the argument name used when sending an array of SKUs to fetch multiple reviews.
• keyField provides the key value for each item in the batched query. For this example, the keyField indicates which Product field provides the SKU value to the review service.

With the updated mesh, using the previous query returns the same information, but only makes one call to the Reviews source for multiple SKUs.

Last updated 12/7/2023

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