[KAFKA-3014] Integer overflow causes incorrect node iteration in leastLoadedNode()

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.9.0.1
• Assignee: Jason Gustafson
• Reporter: Jason Gustafson
• Created: 18/Dec/15 19:14
• Updated: 21/Dec/15 18:54
• Resolved: 21/Dec/15 18:54

Description

The leastLoadedNode() implementation iterates over all the known nodes to find a suitable candidate for sending metadata. The loop looks like this:

for (int i = 0; i < nodes.size(); i++) {
  int idx = Utils.abs((this.nodeIndexOffset + i) % nodes.size());
  Node node = nodes.get(idx);
  ...
}

Unfortunately, this doesn't handle integer overflow correctly, which can result in some nodes in the list being passed over. For example, if the size of the node list is 5 and the random offset is Integer.MAX_VALUE, then the loop will iterate over the following indices: 2, 3, 2, 1, 0.

In pathological cases, this can prevent the client from being able to connect to good nodes in order to refresh metadata.