[util/getAllDocs] extract getAllDocs to util

src/scripts/migrations/createBackendUsers.js

@@ -34,6 +34,7 @@
 
 import 'dotenv/config';
 import client from 'util/client';
+import getAllDocs from 'util/getAllDocs';
 import Bulk from 'util/bulk';
 import rollbar from 'rollbarInstance';
 import {
@@ -295,30 +296,15 @@ export default class CreateBackendUsers {
    * @yields {Object} the document
    */
   async *getAllDocs(indexName, hasAdditionalUserFields = false) {
-    let resp = await client.search({
-      index: indexName,
-      scroll: SCROLL_TIMEOUT,
-      size: this.batchSize,
-      body: {
-        query: hasAdditionalUserFields ? matchAllQuery : backendUserQuery,
-      },
-    });
-
-    while (true) {
-      const docs = resp.body.hits.hits;
-      if (docs.length === 0) break;
-      for (const doc of docs) {
-        yield doc;
-      }
-
-      if (!resp.body._scroll_id) {
-        break;
-      }
-
-      resp = await client.scroll({
+    for await (const doc of getAllDocs(
+      indexName,
+      hasAdditionalUserFields ? matchAllQuery : backendUserQuery,
+      {
         scroll: SCROLL_TIMEOUT,
-        scrollId: resp.body._scroll_id,
-      });
+        size: this.batchSize,
+      }
+    )) {
+      yield doc;
     }
   }
 

src/util/getAllDocs.js

@@ -0,0 +1,45 @@
+import client from 'util/client';
+
+/**
+ * A generator that fetches all docs in the specified index and yield 1 doc at a time.
+ *
+ * @param {String} index The name of the index to fetch
+ * @param {Object} query The elasticsearch query. Fetches all doc in the specified index if not given.
+ * @param {Object} settings Query param settings in ES.
+ * @param {number} settings.size Number of docs per batch. Default to 1000.
+ * @param {string} settings.scroll The scroll timeout setting. Default to 30s.
+ * @yields {Object} the document
+ */
+async function* getAllDocs(
+  index,
+  query = { match_all: {} },
+  { scroll = '30s', size = 1000 } = {}
+) {
+  let resp = await client.search({
+    index,
+    scroll,
+    size,
+    body: {
+      query,
+    },
+  });
+
+  while (true) {
+    const docs = resp.body.hits.hits;
+    if (docs.length === 0) break;
+    for (const doc of docs) {
+      yield doc;
+    }
+
+    if (!resp.body._scroll_id) {
+      break;
+    }
+
+    resp = await client.scroll({
+      scroll,
+      scrollId: resp.body._scroll_id,
+    });
+  }
+}
+
+export default getAllDocs;