[CASSANDRA-15158] Wait for schema agreement rather than in flight schema requests when bootstrapping

• Type: Bug
• Status: Resolved
• Priority: Normal
• Resolution: Fixed
• Fix Version/s: 3.0.24, 3.11.10, 4.0-beta4, 4.0
• Component/s: Cluster/Gossip, Cluster/Schema
• Bug Category: Correctness - Consistency
• Severity: Normal
• Complexity: Challenging
• Discovered By: User Report
• Platform: All
• Since Version: 3.0.0

Source Control Link

https://github.com/apache/cassandra/commit/08450080614250a8bfaba23dbca741a4d9315e3c

Test and Documentation Plan

There are unit tests as part of PR testing this feature.

• Assignee: Blake Eggleston
• Reporter: Vincent White

Authors

Blake Eggleston, Stefan Miklosovic

Reviewers

Aleksey Yeschenko, Blake Eggleston

• Created: 13/Jun/19 09:18
• Updated: 21/Oct/22 14:03
• Resolved: 09/Nov/20 20:26

Description

Currently when a node is bootstrapping we use a set of latches (org.apache.cassandra.service.MigrationTask#inflightTasks) to keep track of in-flight schema pull requests, and we don't proceed with bootstrapping/stream until all the latches are released (or we timeout waiting for each one). One issue with this is that if we have a large schema, or the retrieval of the schema from the other nodes was unexpectedly slow then we have no explicit check in place to ensure we have actually received a schema before we proceed.

While it's possible to increase "migration_task_wait_in_seconds" to force the node to wait on each latche longer, there are cases where this doesn't help because the callbacks for the schema pull requests have expired off the messaging service's callback map (org.apache.cassandra.net.MessagingService#callbacks) after request_timeout_in_ms (default 10 seconds) before the other nodes were able to respond to the new node.

This patch checks for schema agreement between the bootstrapping node and the rest of the live nodes before proceeding with bootstrapping. It also adds a check to prevent the new node from flooding existing nodes with simultaneous schema pull requests as can happen in large clusters.

Removing the latch system should also prevent new nodes in large clusters getting stuck for extended amounts of time as they wait `migration_task_wait_in_seconds` on each of the latches left orphaned by the timed out callbacks.

 

3.11
PoC
dtest

 

Issue Links

• causes: CASSANDRA-17972 nodetool resetlocalschema does not sync schema
• is related to: CASSANDRA-11748 Schema version mismatch may leads to Casandra OOM at bootstrap during a rolling upgrade process
• relates to: CASSANDRA-16732 Unable to replace node if cluster is in mixed major version