codeconsole opened a new pull request, #16216:
URL: https://github.com/apache/grails-core/pull/16216
Follow-up to #16192.
### Problem
`EmbeddedMongoInitializer` hands a restart the server this JVM already
started when the settings match the ones it was started with:
```java
StartedServer started = discard(STARTED.get(port), settings);
```
`EmbeddedMongoSettings.equals` compares `port`, `version`, `databaseDir` and
`replicaSet`. **The backend is not among them**, and `StartedServer` does not
carry it either, so nothing in the reuse path knows which backend is running.
Switching `embedded.mongodb.backend` between `in-memory` and `flapdoodle`
across a devtools restart, changing nothing else, therefore keeps the old
server. An application that asked for a real `mongod` carries on against the
in-memory reimplementation, which implements neither transactions, change
streams nor `$text` — so the failure surfaces later and somewhere else, as a
missing feature rather than a backend that was never started.
Worth noting the shape of the omission: the check does compare `version`,
which `InMemoryMongoBackend` ignores entirely. The one setting that decides
what the server actually *is* was the one left out.
### Fix
Keep the backend the server was started with alongside its settings, and
compare it:
```java
private record StartedServer(RunningEmbeddedMongo running,
EmbeddedMongoSettings settings, String backend) { }
if (started == null || (started.settings().equals(settings) &&
started.backend().equals(backend))) {
return started;
}
```
The backend is resolved in `initialize` before the reuse question rather
than inside `start`, since it is part of that question, and passed to `start`
so it is selected once.
`EmbeddedMongoSettings` is public API and its constructor is unchanged; the
backend lives on the private `StartedServer` record instead.
**One behaviour change worth calling out:** asking for a backend whose
library is absent now fails even when a server is already running on that port,
because `selectBackend` runs before the reuse check. Previously such a restart
was silently handed the running server. The new behaviour matches what the same
configuration does when nothing is running.
### Tests
A restart that switches backend while holding version, database and replica
set unchanged now gets a new server. The assertion is behavioural — a document
written to the first server, then counted after the switch — because object
identity does not distinguish the two cases here: `initialize` constructs a
fresh `EmbeddedMongoLifecycle` on every call, reused server or not.
That last point applies to the existing test beside it. **`a restart that
asks for a different server is not handed the one already running` was
vacuous**: I removed `version` from `EmbeddedMongoSettings.equals` and it still
passed, so it was not verifying replacement at all. It is rewritten here with
the same behavioural assertion, and now fails when `version` is removed from
the comparison.
Both tests fail on unmodified `8.0.x` and pass with the fix;
`:grails-data-mongodb-embedded:test` is green.
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