Parallel products feed data fetching (#465)

* Parallel products feed data fetching

* Create strong-peas-begin.md

.changeset/strong-peas-begin.md

@@ -0,0 +1,5 @@
+---
+"saleor-app-products-feed": patch
+---
+
+Query for the product details run now in paralell to speed up overall feed generation

apps/products-feed/graphql/queries/FetchProductCursors.graphql

@@ -0,0 +1,9 @@
+query FetchProductCursors($first:Int!, $after: String, $channel: String!){
+  productVariants(first:$first, after: $after, channel: $channel){
+    pageInfo{
+      hasNextPage
+      startCursor
+      endCursor
+    }
+  }
+}

apps/products-feed/src/lib/google-feed/fetch-product-data.ts

@@ -2,10 +2,64 @@ import { url } from "inspector";
 import { Client } from "urql";
 import { createLogger } from "@saleor/apps-shared";
 import {
+  FetchProductCursorsDocument,
   FetchProductDataForFeedDocument,
   GoogleFeedProductVariantFragment,
 } from "../../../generated/graphql";
 
+const getCursors = async ({ client, channel }: { client: Client; channel: string }) => {
+  let result = await client
+    .query(FetchProductCursorsDocument, { channel: channel as string, first: 100 })
+    .toPromise();
+
+  // First page is queried without the `after` param, so we start an array with `undefined`
+  const cursors: Array<string | undefined> = [undefined];
+
+  while (result.data?.productVariants?.pageInfo.hasNextPage) {
+    result = await client
+      .query(FetchProductCursorsDocument, {
+        channel: channel as string,
+        first: 100,
+        after: result.data.productVariants.pageInfo.endCursor,
+      })
+      .toPromise();
+
+    const endCursor = result.data?.productVariants?.pageInfo.endCursor;
+
+    if (endCursor) {
+      cursors.push(endCursor);
+    }
+  }
+  return cursors;
+};
+
+const fetchVariants = async ({
+  client,
+  after,
+  channel,
+}: {
+  client: Client;
+  after?: string;
+  channel: string;
+}): Promise<GoogleFeedProductVariantFragment[]> => {
+  const logger = createLogger({ saleorApiUrl: url, channel, fn: "fetchVariants" });
+
+  const result = await client
+    .query(FetchProductDataForFeedDocument, {
+      channel: channel as string,
+      first: 100,
+      after,
+    })
+    .toPromise();
+
+  if (result.error) {
+    logger.error(`Error during the GraphqlAPI call: ${result.error.message}`);
+    return [];
+  }
+
+  return result.data?.productVariants?.edges.map((e) => e.node) || [];
+};
+
 interface FetchProductDataArgs {
   client: Client;
   channel: string;
@@ -14,40 +68,13 @@ interface FetchProductDataArgs {
 export const fetchProductData = async ({ client, channel }: FetchProductDataArgs) => {
   const logger = createLogger({ saleorApiUrl: url, channel, route: "Google Product Feed" });
 
-  let result = await client
-    .query(FetchProductDataForFeedDocument, { channel: channel as string, first: 100 })
-    .toPromise();
+  const cursors = await getCursors({ client, channel });
 
-  if (result.error) {
-    logger.error(`Error during the GraphqlAPI call: ${result.error.message}`);
-    throw new Error("Error during the GraphQL API call");
-  }
+  logger.debug(`Query generated ${cursors.length} cursors`);
 
-  let variants: GoogleFeedProductVariantFragment[] =
-    result.data?.productVariants?.edges.map((e) => e.node) || [];
+  const promises = cursors.map((cursor) => fetchVariants({ client, after: cursor, channel }));
 
-  while (result.data?.productVariants?.pageInfo.hasNextPage) {
-    logger.debug("Fetching the next page of products");
+  const results = await Promise.all(promises);
 
-    result = await client
-      .query(FetchProductDataForFeedDocument, {
-        channel: channel as string,
-        first: 100,
-        after: result.data.productVariants.pageInfo.endCursor,
-      })
-      .toPromise();
-
-    if (result.error) {
-      logger.error(`Error during the GraphqlAPI call: ${result.error.message}`);
-      throw new Error("Error during the GraphQL API call");
-    }
-
-    if (!result.data?.productVariants?.edges.length) {
-      logger.warn("Fetching the second page of results resulted in no entries");
-      break;
-    }
-    variants = variants?.concat(result.data?.productVariants?.edges.map((e) => e.node));
-  }
-
-  return variants;
+  return results.flat();
 };