Cherry pick #95466 to 25.8: Avoid possible crash for distributed queries in case of cancellation#95601
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robot-ch-test-poll1 merged 7 commits intobackport/25.8/95466from Jan 30, 2026
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The race condition causes a crash when reading from a disconnected
connection in distributed queries.
The `in` buffer:
```
(gdb) frame 1
(gdb) print this->in
$19 = {__ptr_ = 0x0, __cntrl_ = 0x0}
(gdb) print this->connected
$18 = false
```
But the same time:
```
(gdb) frame 2
async_callback=...) at ./ci/tmp/build/./src/Client/MultiplexedConnections.cpp:398
(gdb) print this->sent_query
$15 = true
(gdb) print this->cancelled
$16 = false
(gdb) print this->active_connection_count
$17 = 1
```
Current solution will not fix the issue, it just apply a check like in
`sendCancel()`.
Related PRs:
- #89740
- #92807
- #93029
Avoid possible crash for distributed queries in case of cancellation
1a05360
into
backport/25.8/95466
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Original pull-request #95466
Do not merge this PR manually
This pull-request is a first step of an automated backporting.
It contains changes similar to calling
git cherry-picklocally.If you intend to continue backporting the changes, then resolve all conflicts if any.
Otherwise, if you do not want to backport them, then just close this pull-request.
The check results does not matter at this step - you can safely ignore them.
Troubleshooting
If the conflicts were resolved in a wrong way
If this cherry-pick PR is completely screwed by a wrong conflicts resolution, and you want to recreate it:
pr-cherrypicklabel from the PRYou also need to check the Original pull-request for
pr-backports-createdlabel, and delete if it's presented thereThe PR source
The PR is created in the CI job