Intermittent non-ASCII (emoji/Georgian) corruption in large responses

[GiorgiZanqaidze]

🐛 Bug report

Large _search responses occasionally corrupt arbitrary non-ASCII characters (e.g., Georgian text, emoji, or any extended Unicode). Smaller responses always look correct. The same request may succeed or fail across runs, so this appears to be a transport/streaming issue surfaced through the default @elastic/elasticsearch client.

To reproduce

1. Populate an index (e.g., persons) with documents that include any non-ASCII strings (Georgian, emoji, accented Latin, etc.). Sample document:

   {
     "id": "person-001",
     "firstName": "ანა",
     "lastName": "ტესტაშვილი",
     "personalId": "00000000001",
     "lists": [
       {
         "id": "list-entry-001",
         "content": "😄 🎉 🚀 👍 ❤️ 🙌 Greeting"
       }
     ]
   }

2. Run:

   import { Client } from '@elastic/elasticsearch';
   
   async function repro() {
     const client = new Client({
       headers: {
         accept: 'application/vnd.elasticsearch+json; compatible-with=8',
         'content-type': 'application/vnd.elasticsearch+json; compatible-with=8',
       },
       nodes: ['http://elastic:******@<REDACTED-HOST>:9200'],
       requestTimeout: 0,
     });
   
     const res = await client.search({
       index: 'persons',
       size: 200, // ensures >50 hits
       query: { match_all: {} },
     });
   
     res.hits.hits.forEach((hit) =>
       console.log(hit._source?.content ?? hit._source?.firstName),
     );
   }
   
   repro().catch(console.error);

3. Run the script several times. Some runs log the correct text; others log corrupted output such as ��ამარჯობა, გიორგი or 😄 🎉 🚀 👍 ��️ 🙌 Greeting (any non-ASCII characters can be affected).

Expected behavior

Responses should consistently return the original UTF-8 text (Georgian and emoji) regardless of payload size. Example expected output:

გამარჯობა, გიორგი
😄 🎉 🚀 👍 ❤️ 🙌 Greeting

Environment

Node.js version: 20.19.5

@elastic/elasticsearch version: 9.1.1

Operating system: Windows 10/11 x64

[GiorgiZanqaidze]

Also have pull request on elastic-transport-js repo: elastic/elastic-transport-js#324

added issue also on elastic-transport-js: elastic/elastic-transport-js#323

[JoshMock]

Going to close this one in favor of elastic/elastic-transport-js#323.