ctubbsii commented on a change in pull request #341: ACCUMULO-3902 Ensure
[Batch]Scanners are closed in ITs
URL: https://github.com/apache/accumulo/pull/341#discussion_r157503827
##########
File path: test/src/main/java/org/apache/accumulo/test/CleanWalIT.java
##########
@@ -136,11 +136,13 @@ private int countLogs(String tableName, Connector conn)
throws TableNotFoundExce
log.debug("Saw {}={}", entry.getKey(), entry.getValue());
count++;
}
+ scanner.close();
return count;
}
int count(String tableName, Connector conn) throws Exception {
Scanner s = conn.createScanner(tableName, Authorizations.EMPTY);
+ s.close();
Review comment:
This is a good example to highlight three different possibilities. In all
three cases, the scanner instance never leaves the method (we never do `return
s;` or `callOtherMethodToFinish(s);`), so we should always try to close it
within the method.
The first is the best because it guarantees the scanner is closed before the
method returns, but also doesn't require all the complicated syntax of the old
finally block in the second example. The third example is the worst, because it
can leave the scanner unclosed.
```java
// using try-with-resources
try (Scanner s = conn.createScanner(tableName, Authorizations.EMPTY)) {
return Iterators.size(s.iterator());
}
```
```java
// make sure it's closed, using old finally syntax
Scanner s = null;
try {
s = conn.createScanner(tableName, Authorizations.EMPTY);
return Iterators.size(s.iterator());
} finally {
if (s != null) {
s.close;
}
}
```
```java
// does not guarantee it is closed if it has an exception, but does
try before it returns from the method
Scanner s = conn.createScanner(tableName, Authorizations.EMPTY);
int size = Iterators.size(s.iterator());
s.close();
return size;
```
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