pjfanning opened a new pull request, #618:
URL: https://github.com/apache/pekko-projection/pull/618
### Motivation
`JdbcSessionUtil.tryWithResource` takes the resource as a by-name parameter
and evaluates it **twice**: once when calling `func`, and once again in the
`finally` block.
```scala
def tryWithResource[T, C <: AutoCloseable](closeable: => C)(func: C => T): T
= {
try { func(closeable) } // evaluates the by-name arg -> resource
#1
finally { try closeable.close() // evaluates it AGAIN -> resource #2,
closes #2
```
So the resource handed to `func` is never closed, and a second one is
created just to be closed. Consequences:
* `JdbcOffsetStore` (lines 69, 80, 98, 114, 182, 200, 240, 281, 301) and
`SlickOffsetStore` (lines 169, 176, 187, 193) leak a
`Statement`/`PreparedStatement` on every call. When the `JdbcSession` is backed
by a connection pool (connection returned to the pool rather than physically
closed) these accumulate on the physical connection and can exhaust server-side
cursors.
* `tryWithResource(stmt.executeQuery())` in `JdbcOffsetStore.readOffset` and
`readManagementState` executes the query a second time and leaks the first
`ResultSet`.
### Modification
Evaluate the by-name parameter once into a local val, and use that instance
both for `func` and for `close()`.
### Result
The resource passed to `func` is the one that gets closed, no extra resource
is created, and each query is executed once.
### Tests
- New `JdbcSessionUtilSpec` asserts that exactly one resource is created and
that the instance passed to the function is the one closed (also on function
failure, and when `close()` throws `SQLException`). All 3 cases fail before the
fix.
- `sbt "jdbc/test"` - 31 passed
- `sbt "jdbc/mimaReportBinaryIssues"` - success
- `scalafmt --mode diff-ref=upstream/main` - no changes
- `sbt headerCreateAll` - header added to the new spec
### References
None - found during a resource-leak audit of the main sources
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