Storefront graphql concurrent question

[Trick99]

Hi！

I have a question about Shopify Graphql，If I make two graphql requests at the same time. One is `cartLinesAdd` and the other is `cartLinesRemove`，Then I found that the products I added were not in the final shopping cart.

For example, the original shopping cart has two products, and `cartLinesAdd`and `cartLinesRemove` are called at the same time. Normally, there should be two products in the cart, but in the end, only one product is left in the shopping cart.

I don’t know if the problem is caused by concurrency. Is there any solution?

[PageFly-Richard]

Hi,
This is Richard at PageFly - Shopify Advanced Page Builder app.

You're likely encountering concurrency issues with your Shopify GraphQL mutations. Here's a breakdown of the problem and potential solutions:

Understanding the Issue

• Concurrent Mutations: When you execute cartLinesAdd and cartLinesRemove simultaneously, Shopify's GraphQL API might not process them in the order you intended.
• Data Inconsistency: This can lead to unexpected results, such as products being removed before they are added, resulting in an incorrect final cart state.

Solutions

1. Sequential Execution:

   • Implement Logic: Introduce logic to ensure sequential execution of mutations. For example:

     • Wait for the cartLinesAdd mutation to complete successfully before executing the cartLinesRemove mutation.
     • Use a mechanism like a promise chain or async/await (if using JavaScript) to handle the order of operations.

2. Optimistic Updates (with Caution):

   • Optimistically Update Client-Side: After a successful cartLinesAdd mutation, update your local cart state (in your frontend application) immediately.

   • Handle Rollbacks: If the server-side mutation fails, roll back the optimistic update on the client-side.

   • Caution: Optimistic updates can lead to inconsistencies if not implemented carefully. Thoroughly test and handle potential race conditions.

3. Shopify API Limitations:

   • Acknowledge Limitations: Be aware that there might be inherent limitations in how Shopify's GraphQL API handles concurrent mutations.
   • Contact Shopify Support: If you suspect a bug or limitation in the API itself, reach out to Shopify Support for clarification.

Hoping my solution helps you solve your problem.
Best regards,
Richard | PageFly