AIO 12.x: Elasticsearch 8.19 breaks Fulltext Search (bulk indexing rejected)

[harryv1]

After resolving the previous fulltextsearch incompatibility via
fulltextsearch_elasticsearch 32.0.2 (which fixed the earlier AIO-12.x mapping bug), fulltext indexing is still not working in AIO 12.x.

Environment
Nextcloud AIO 12.x
ghcr.io/nextcloud-releases/aio-fulltextsearch:latest (bundled Elasticsearch 8.19.x)
fulltextsearch_elasticsearch 32.0.2
PHP memory_limit = 1024M
PDF limit = 50 MB
vm.max_map_count = 262144

Observed behavior
Running
occ fulltextsearch:index

produces:
Results: 1/1
Status: ok
Errors: 68708 / 68708
Exception: ClientResponseException
Message: "unknown error"

Elasticsearch shows:
GET /_cat/indices
nextcloud-aio docs.count = 1–2

even though tens of thousands of files are being indexed.

Only the very first single document is written successfully; all subsequent bulk requests fail.
Elasticsearch logs remain empty (no server-side errors), indicating HTTP-level rejection.

Analysis / suspicion
Elasticsearch ≥ 8.12 enforces
Content-Type: application/x-ndjson
for _bulk requests.
fulltextsearch_elasticsearch (via the PHP client) still appears to send:
Content-Type: application/json
which causes Elasticsearch 8.19 to reject all bulk writes with 4xx (silently from the server side).
Nextcloud only sees ClientResponseException: unknown error.

This matches the exact pattern:
single-document indexing works
all bulk indexing fails
index stays almost empty

Why this is an AIO problem
AIO 12.x ships Elasticsearch 8.19.x by default.
fulltextsearch_elasticsearch is the officially recommended fulltext backend.
This combination currently makes fulltext search unusable for real workloads (PDFs, OCR, attachments).

Requested action
AIO should either:
pin Elasticsearch to a version still compatible with fulltextsearch (e.g. 8.11.x), or
ship a fulltextsearch-compatible Elasticsearch build, or
block / warn about this broken combination.

Right now AIO 12.x silently deploys an Elasticsearch version that breaks fulltext search completely.

[harryv1]

Update (root cause identified)

Recent versions of fulltextsearch_elasticsearch (incl. 32.0.2) no longer support Elasticsearch 8 and now require Elasticsearch 9.
This is confirmed by community reports and upgrade guides (e.g. https://decatec.de/home-server/nextcloud-volltextsuche-upgrade-auf-elasticsearch-9/), while the official Nextcloud documentation still lists Elasticsearch 8 as a supported requirement.
Nextcloud AIO 12.x currently ships Elasticsearch 8.19, which creates a silent but complete incompatibility:
single-document indexing works, all bulk indexing fails with ClientResponseException "unknown error", the Elasticsearch index stays almost empty, no server-side errors are logged (HTTP-level rejection).
This explains the observed behavior and means that fulltext search is effectively broken in AIO 12.x with current app versions.

AIO should either ship Elasticsearch 9, pin the fulltext app to an ES-8-compatible release, or clearly block/warn about this invalid combination.

[szaimen]

Hi, see #7341 (reply in thread)