Gitlab merge request metrics produce connection error

[nvanloon92]

Describe the bug
Since yesterday, we see the following Connection error for all our merge requests metrics:

Traceback (most recent call last):
File "/home/collector/base_collectors/source_collector.py", line 106, in __safely_get_source_responses
responses = await asyncio.wait_for(self._get_source_responses(api_url), timeout=self._session.timeout.total)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.14/asyncio/tasks.py", line 488, in wait_for
return await fut
^^^^^^^^^
File "/home/collector/source_collectors/gitlab/merge_requests.py", line 89, in _get_source_responses
approved_field = await self._approved_field(client)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/collector/source_collectors/gitlab/merge_requests.py", line 101, in _approved_field
fields = [field["name"] for field in json["data"]["__type"]["fields"]]
~~~~~~~~~~~~^^^^^^^^^^
KeyError: '__type'

This seems to have something to do with a Gitlab upgrade.

To Reproduce
Steps to reproduce the behaviour:

1. Click on 'ADD METRIC'
2. Select 'Merge requests'
3. Click on 'SOURCES'
4. Add 'GitLab' as Source type
5. Enter a GitLab instance URL, private token and project name

Expected behaviour
Number of merge requests should be displayed.

Screenshots

Your environment (please complete the following information):

• Operating system: -
• Browser: Chrome v145.0.7632.117
• Quality-time: v5.48.2
• Source version: Gitlab v18.9.1

Additional context
Yesterday, our Gitlab was upgraded to version 18.9.1, but I am not entirely sure this error message did pop up earlier on.

[fniessink]

Reading the documentation for the GitLab GraphQL API, I suspect the introspection query that Quality-time does to find out the fields that are available on merge requests fails because introspection queries may be prohibited on production installations of GitLab. Note sure why we haven't seen this before, though. Can you find out whether introspection queries have been turned off on your GitLab installation?

Also, can you please try this so we get the full output of the response?

export GITLAB_PAT=...
curl --request POST \
     --url "https://gitlab.at.rws.nl/api/graphql" \
     --header "Authorization: Bearer $GITLAB_PAT" \
     --header "Content-Type: application/json" \
     --data '{"query": "query {__type(name: \"MergeRequest\") {fields {name}}}"}'

[nvanloon92]

@fniessink I just checked the Gitlab project itself and I think it has something to do with this MR: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/223088. I do not think this change is already in the version that we run, so I will keep an eye out when we have a new version deployed.

[wkoot]

@nvanloon92 the issue appears to be that the entire __schema is also returned by the GraphQL api.
Perhaps we can avoid this by passing fetch_schema_from_transport=False somewhere, but I'm not sure if the GLQL listens to it.

So far, they don't seem to be fixing this explicitly although some GLQL bugs have been addressed:

• https://about.gitlab.com/releases/2026/03/25/patch-release-gitlab-18-10-1-released/
• https://about.gitlab.com/releases/2026/03/11/patch-release-gitlab-18-9-2-released/

Can you verify if the new version (I presume 18.9.3 in your case) still has this issue?

Also, I'd be interested to know how large the resultset is exactly; perhaps an ingress or proxy is truncating it.
During testing, I typically saw response sizes of 6.36 Mb which were being truncated to 1 Mb leading to invalid JSON.

You can test this by POST'ing {"query":"{__type(name: \"MergeRequest\") {fields {name}}}"} to the /api/graphql endpoint (in a valid session).

[nvanloon92]

@wkoot At first, we still see this issue while running Gitlab version 18.10.1. I just did a curl request with the data you suggested and this indeed ends up in a json file of 6,5 Mb. What would be the next step?

[wkoot]

Does the full json output contain the ['data']['__type'] node, or is it only ['data']['__schema'] ?

Since QT is searching for ['data']['__type']['fields'], I wouldn't expect this to be available in your json..
But in my tests, I've only gotten output truncated to 1Mb - not sure if this is a limitation somehow imposed by GitLab.

[nvanloon92]

It only contains ['data]['__schema']. This is the top level of the json:

[wkoot]

I'm not sure if there actually is a bugreport on the GitLab issue tracker, I can't really find something that matches.
The ticket you mentioned before has been addressed, but the bug persists in 18.10.1.
Can you find any related issue? If not, we'll need to raise a bugreport with them and hope for a fix - or find a workaround.

[nvanloon92]

Nope, I could also not pinpoint which ticket that would be. Can you please chase this?