Xata•6mo ago

Cannot perform I/O on behalf of a different request in Cloudflare Workers

Ok, so this may be a long one... I have several cloudflare workers that write or request data from Xata. When I do a single request using the TypeScript SDK, it works OK. When I do several requests like in a await Promise.all(array.map(async arrayElem => queryToXata(arrayElem))), then I get an error like:

 
  Unable to retrieve metrics for report rec_REDACTED Error: Cannot perform I/O
  on behalf of a different request. I/O objects (such as streams, request/response bodies, and
  others) created in the context of one request handler cannot be accessed from a different
  request's handler. This is a limitation of Cloudflare Workers which allows us to improve overall
  performance.

 
  Unable to retrieve metrics for report rec_REDACTED Error: Cannot perform I/O
  on behalf of a different request. I/O objects (such as streams, request/response bodies, and
  others) created in the context of one request handler cannot be accessed from a different
  request's handler. This is a limitation of Cloudflare Workers which allows us to improve overall
  performance.

This is coming from the Cloudflare Worker SDK, Wrangler. I have attached the stacktrace. I have tried creating the xata client on each method I call, so it is separated... but to no avail. If you request or need more information, i'll be happy to share code, or even do a screensharing session, etc. I want to discard if this is something from the Xata SDK, or it is something else,...

Stacktrace.txt

6 Replies

kostas•6mo ago

It looks like this issue is generic in the Workers runtime and not specific to using the Xata SDK I.e. it comes up with plain fetch in this article https://blog.cloudflare.com/miniflare-and-workerd/ Seems the worker can't handle multiple concurrent fetch requests in a promise. I'll ask around our team if we have any recommendations, but what Xata SDK calls are your running in it? If it is queries could they perhaps be combined to a single call with OR clauses ($any operator https://xata.io/docs/sdk/filtering#control-operators) ? Or if they are creates, send in bulk.

Eusebio Trigo•6mo ago

Yup, I have looked for this issue and it is common, but don't see a "straight answer". I've got queries like

const totals = await dbClient.sql<{ total_orders: number, total_sellers: number }>`
          SELECT COUNT(DISTINCT (transactions.order)) AS total_orders,
                 COUNT(DISTINCT (transactions.shop))  AS total_sellers
          FROM transactions
          WHERE transactions.report = ${report_id}`;

      const subquery = `SELECT DISTINCT (o.id)
                        FROM transactions t,
                             orders o
                        WHERE t.report = '${report_id}'
                          AND t.order = o.id`;

      const total_amounts = await dbClient.sql<{
        total_invoiced: number,
        total_commission: number;
      }>`SELECT SUM(orders.total_price) AS total_invoiced, SUM(orders.total_commission) AS total_commission
         FROM orders
         WHERE orders.id in (${subquery})`;

const totals = await dbClient.sql<{ total_orders: number, total_sellers: number }>`
          SELECT COUNT(DISTINCT (transactions.order)) AS total_orders,
                 COUNT(DISTINCT (transactions.shop))  AS total_sellers
          FROM transactions
          WHERE transactions.report = ${report_id}`;

      const subquery = `SELECT DISTINCT (o.id)
                        FROM transactions t,
                             orders o
                        WHERE t.report = '${report_id}'
                          AND t.order = o.id`;

      const total_amounts = await dbClient.sql<{
        total_invoiced: number,
        total_commission: number;
      }>`SELECT SUM(orders.total_price) AS total_invoiced, SUM(orders.total_commission) AS total_commission
         FROM orders
         WHERE orders.id in (${subquery})`;

And it happens to us both in a deployed worker and in local development.

kostas•6mo ago

Thanks for the details - I've asked around, and will let you know if we have some suggestions. My understanding is that a Promise and a fetch request (Xata call) should be mapped one-to-one though.

Eusebio Trigo•6mo ago

Yeah, that's my fear. Instead of a Promise.all( - send async requests using fetch -) that would send the requests in parallel, would need to send them using a good-old for loop with IO blocking, and getting each of the requests in sequence. Thanks for your help!

copper•4w ago

@Eusebio Trigo are you still on Cloudflare + Xata?

Eusebio Trigo•4w ago

We were using it in all our workers. But due to reasons, we stopped all activities, and found other jobs.

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Cannot perform I/O on behalf of a different request in Cloudflare Workers