In this blog, I will provide answers to the Q & A for the Troubleshooting MySQL Concurrency Issues with Load Testing Tools webinar.

First, I want to thank everybody for attending my May 23, 2018, webinar on troubleshooting tools for MySQL. The recording and slides for the webinar are available here. Below is the list of your questions that I was unable to answer fully during the webinar.

Q: What do you recommend for benchmarking NDB cluster? Which should be used and how?

A: The issue with benchmarking NDB cluster is not the tool choice, …

Memcache access for MySQL Cluster (or NDBCluster) provides faster access to the data because it avoids the SQL parsing overhead for simple lookups – which is a great feature. But what happens if I try to get multiple records via memcache API (multi-GET) and via SQL (SELECT with IN())? I’ve encountered this a few times now, so I decided to blog about it. I did a very simple benchmark with the following script:

#!/bin/bash
mysql_server="192.168.56.75"
mc_server="192.168.56.75"
mysql_cmd="mysql -h${mysql_server} --silent --silent"
mysql_schema="percona"
mysql_table="memcache_t"
mc_port=11211
mc_prefix="mt:"
function populate_data () {
  nrec=$1
  $mysql_cmd -e "delete from ${mysql_table};" $mysql_schema > /dev/null 2>&1
  for rec in `seq 1 $nrec`
  do
    $mysql_cmd -e "insert into ${mysql_table} values ($rec, repeat('a',10), 0, 0);" $mysql_schema > /dev/null 2>&1
  done
}
function mget_via_sql() {
  nrec=$1
  in_list=''
  for rec in …

Ralf Gebhardt of SkySQL.

Cluster: shared nothing architecture (no single point of failure), synchronous replication between nodes, ACID transactions, row level locking. In-memory storage (some data can be stored on disk, but indexes must be in-memory). Checkpointing to disk for durability. It supports two types of indexes – ordered T-trees, unique hash indexes. Online operations like adding node groups, software upgrades, table alterations. Quick standard architecture diagram displayed about MySQL Cluster.

Network partitioning protocol is designed to avoid a split brain scenario. Is there at least one node from each node group? If not then this part cannot continue – graceful shutdown. Are all nodes present from any node group? If so, then this is the only viable cluster – continue to operate. Ask the arbitrator – the arbitrator which parts will continue if no arbitrator …

[HoneyMonitor is a GUI for MySQL™. Server Administration, Database and Database Objects Administration, Code Development, Server Monitoring, Performance Monitoring, Performance Auditing. Read more on http://www.honeysoftware.com/] Contents

• Introduction
• Log File Group & UndoFiles
• TableSpaces & DataFiles
• Cluster Disk Objects Metadata
• Creating Cluster Disk Tables
• Dropping Cluster Disk Data Objects
• The Cluster Monitor
• Cluster Disk Data Limitations
• Cluster Disk Data Quiz
• Other Resources

1. Introduction

Cluster Disk Data is a new …