bbeaudreault commented on a change in pull request #3536:
URL: https://github.com/apache/hbase/pull/3536#discussion_r679472058
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File path: hbase-client/src/main/java/org/apache/hadoop/hbase/client/Admin.java
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@@ -1253,6 +1253,15 @@ default boolean balancer() throws IOException {
*/
boolean balance() throws IOException;
+ /**
+ * Invoke the balancer in dry run mode. Will show plan but not actually move
any regions.
+ * Can NOT run for various reasons. Check logs.
+ *
+ * @return <code>true</code> if dry run ran, <code>false</code> otherwise.
+ * @throws IOException if a remote or network exception occurs
+ */
+ boolean dryRunBalance() throws IOException;
Review comment:
I could do that. I didn't initially do that for a few reasons:
- There are already a lot of overloads of `balance()`, between the
deprecated `balancer()` and the `boolean force`.
- I didn't want to add another boolean argument. IMO an interface
`balance(boolean, boolean)` can be easily messed up. I could expose a
client-side version of RunMode enum though, but in order to preserve backwards
compatibility we'd have to add a whole set of new overloads.
- In the comments of HBASE-26147 we discussed enhancing dry run mode to
accept config overrides for cost functions. This would make it much more
intuitive to iterate on cost functions without doing a bunch of gymnastics. If
we wanted to do that, we'd need to add another argument that would be specific
to dry run mode which would further complicate the interface of `balance()`.
To the last reason, I could plan ahead for that and have `balance()` take a
BalancerConfig object instead of an enum. That'd give us the future flexibility
to add config overrides to just dry run mode, but it's a more complex interface
and not _that_ much better than having 2 separate methods.
Do you have any opinions on the above? I'm not sure how the hbase devs weigh
interface change questions like this.
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