ivankelly commented on a change in pull request #1192: BP-29 (task 3): use
metadata service uri for constructing registration client
URL: https://github.com/apache/bookkeeper/pull/1192#discussion_r170919448
##########
File path:
bookkeeper-server/src/main/java/org/apache/bookkeeper/meta/MetadataDrivers.java
##########
@@ -167,17 +167,28 @@ private static void loadInitialBookieDrivers() {
*/
public static void registerClientDriver(String metadataBackendScheme,
Class<? extends
MetadataClientDriver> driver) {
+ registerClientDriver(metadataBackendScheme, driver, false);
+ }
+
+ @VisibleForTesting
+ public static void registerClientDriver(String metadataBackendScheme,
+ Class<? extends
MetadataClientDriver> driver,
+ boolean allowOverride) {
if (!initialized) {
initialize();
}
String scheme = metadataBackendScheme.toLowerCase();
MetadataClientDriverInfo oldDriverInfo = clientDrivers.get(scheme);
- if (null != oldDriverInfo) {
+ if (null != oldDriverInfo && !allowOverride) {
return;
}
MetadataClientDriverInfo newDriverInfo = new
MetadataClientDriverInfo(driver);
- oldDriverInfo = clientDrivers.putIfAbsent(scheme, newDriverInfo);
+ if (allowOverride) {
Review comment:
My problem with this is that allowOverride is brought into the default flow
of the method. It's even the first branch from the if on L183. It means
multiple returns from the method. Logging only occurs if there is a race. The
existence in the map is checked twice. And what should be the non-default path
is intertwined with the default.
None of these are huge in themselves, but they combine to make me dislike
the current flow a lot. Another alternative, which would be a least deal with
some of the intertwining...
```
MetadataClientDriverInfo oldDriverInfo = clientDrivers.get(scheme);
if (null != oldDriverInfo && !allowOverride) {
return;
}
MetadataClientDriverInfo newDriverInfo = new
MetadataClientDriverInfo(driver);
oldDriverInfo = clientDrivers.putIfAbsent(scheme, newDriverInfo);
if (null != oldDriverInfo) {
log.debug("Metadata client driver for {} is already there.", scheme);
if (allowOverride) {
log.debug("Overriding client driver for {}", scheme);
clientDrivers.put(scheme, newDriverInfo);
}
}
```
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