[Bug] broadcast.fail.percent=0 does not stop the broadcast at the first failure #16515

Apache Dubbo Component

Java SDK (apache/dubbo)

Dubbo Version

3.3 branch (ae809de), OpenJDK 21, macOS. The threshold check has not changed since broadcast.fail.percent was added in #7174 (2.7.9).

Steps to reproduce this issue

BroadcastClusterInvoker documents broadcast.fail.percent=0 as "throw as soon as an exception occurs":

// The value range of broadcast.fail.threshold must be 0～100.
// 100 means that an exception will be thrown last, and 0 means that as long as an exception occurs, it will be
// thrown.

Export one service on four Dubbo-protocol ports, with an implementation that always throws, and call it through a broadcast reference:

ReferenceConfig<Echo> reference = new ReferenceConfig<>();
reference.setInterface(Echo.class);
reference.setUrl("dubbo://127.0.0.1:21081;dubbo://127.0.0.1:21082;dubbo://127.0.0.1:21083;dubbo://127.0.0.1:21084");
reference.setCluster("broadcast");
reference.setParameters(Collections.singletonMap("broadcast.fail.percent", "0"));

Number of providers invoked for one call, depending on broadcast.fail.percent:

broadcast.fail.percent=0    -> 4 of 4 providers invoked
broadcast.fail.percent=25   -> 1 of 4
broadcast.fail.percent=75   -> 3 of 4
broadcast.fail.percent=100  -> 4 of 4

So 0 stops later than 25 and behaves like the default of 100. Any percentage that rounds down to a threshold of 0 behaves the same way, for example 10 with four providers.

What you expected to happen

With broadcast.fail.percent=0, the broadcast should throw right after the first failed provider, so only one of the four providers is invoked.

Anything else

The threshold is computed as invokers.size() * broadcastFailPercent / 100, which is 0 here, and the loop stops only when failIndex == failThresholdIndex. failIndex is incremented before that comparison, so it is at least 1 and never equals 0: the loop never stops early.

Comparing with >= fixes the zero case and leaves every non-zero threshold unchanged.

Are you willing to submit a pull request to fix on your own?

• Yes I am willing to submit a pull request on my own!