I like that this book is small; 150 pages means you can carry it easily. It’s also very no nonsense. It does not dig too deeply into theory unless it directly relates to your day-to-day needs. And those needs probably cluster heavily around optimizing SQL queries, as those pesky developers are always breaking things 😉
Jokes aside, this new book out on Oracle Press is a very readable volume. Bradford has drawn directly from real-world experience to give you the right bite size morsels you need in your day-to-day MySQL activities.
To be sure, this has raised waves of concern among the community, but on the whole I suspect it will be a good thing for MySQL. This brings more commercial addons to the table, which only increases the options for customers. Many will continue to use the core database product only, and avoid license hassles while others will surely embark on a hybrid approach if it solves their everyday business problems.
3 ways your MySQL migration project can shake you up
Once a development or operations team gets over the hurdle of open-source, and start to feel comfortable with the way software works outside of the enterprise world, they will likely start to settle in and feel comfortable. Best not to get too cushy though for there are more surprises hiding around the corner. Here are a few of the biggest ones.
ORMs are popular among developers but not among performance experts. Why is that? Primarily these two engineers experience a web application from entirely different perspectives. One is building functionality, delivering features, and results are measured on fitting business requirements. Performance and scalability are often low priorities at this stage. ORMs allow developers to be much more productive, abstracting away the SQL difficulties of interacting with the backend datastore, and allowing them to concentrate on building the features and functionality.
Scalability is about application, architecture and infrastructure design, and careful management of server components.
On the performance side the picture is a bit different. By leaving SQL query writing to an ORM, you are faced with complex queries that the database cannot optimize well. What’s more ORMs don’t allow easy tweaking of queries, slowing down the tuning process further.
2. Synchronous, Serial, Coupled or Locking Processes
Locking in a web application operates something like traffic lights in the real world. Replacing a traffic light with a traffic circle often speeds up traffic dramatically. That’s because when you’re out somewhere in the country where there’s very little traffic, no one is waiting idly at a traffic light for no reason. What’s more even when there’s a lot of traffic, a traffic circle keeps things flowing. If you need locking, better to use InnoDB tables as they offer granular row level locking than table level locking like MyISAM tables.
Avoid things like semi-synchronous replication that will wait for a message from another node before allowing the code to continue. Such waits can add up in a highly transactional web application with many thousands of concurrent sessions.
Avoid any type of two-phase commit mechanism that we see in clustered databases quite often. Multi-phase commit provides a serialization point so that multiple nodes can agree on what data looks like, but they are toxic to scalability. Better to use technologies that employ an eventually consistent algorithm.
Without replication, you rely on only one copy of your database. In this configuration, you limit all of your webservers to using a single backend datastore, which becomes a funnel or bottleneck. It’s like a highway that is under construction, forcing all the cars to squeeze into one lane. It’s sure to slow things down. Better to build parallel roads to start with, and allow the application aka the drivers to choose alternate routes as their schedule and itinerary dictate.
Having no metrics in place is toxic to scalability because you can’t visualize what is happening on your systems. Without this visual cue, it is hard to get business units, developers and operations teams all on the same bandwagon about scalability issues. If teams are having trouble groking this, realize that these tools simple provide analytics for infrastructure.
There are tons of solutions too, that use SNMP and are non-invasive. Consider Cacti, Munin, OpenNMS, Ganglia and Zabbix to name a few. Metrics collections can involve business metrics like user registrations, accounts or widgets sold. And of course they should also include low level system cpu, memory, disk & network usage as well as database level activity like buffer pool, transaction log, locking sorting, temp table and queries per second activity.
Applications built without feature flags make it much more difficult to degrade gracefully. If your site gets bombarded by a spike in web traffic and you aren’t magically able to scale and expand capacity, having inbuilt feature flags gives the operations team a way to dial down the load on the servers without the site going down. This can buy you time while you scale your webservers and/or database tier or even retrofit your application to allow multiple read and write databases.
Without these switches in place, you limit scalability and availability.
Deploying new code that includes changes to your database schema doesn’t have to be a process fraught with stress and burned fingers. Follow these five tips and enjoy a good nights sleep.
1. Deploy with Roll Forward & Rollback Scripts
When developers check-in code that requires schema changes, that release should also require two scripts to perform database changes. One script will apply those changes, alter tables to add columns, change data types, seed data, clean data, create new tables, views, stored procedures, functions, triggers and so forth. A release should also include a rollback script, which would return tables to their previous state.
Software development has always made use of libraries, off-the-shelf components that are shared between different projects. These allow you to stand on the shoulders of others and build bigger things. Frameworks do the same thing, they provide a context from which to build on. Ruby on Rails for example provides a great starting framework from which to build web applications, managing sessions in an elegant way.
1. This page or area of the website is very slow, why?
There are a lot of components that make up modern internet websites, and a lot of places to get stuck in the mud. Website performance starts with the browser, what caching it is doing, their bandwidth to your server, what the webserver is doing (caching or not and how), if the webserver has sufficient memory, and then what the application code is doing and lastly how it is interacting with the backend database.
Does anyone remember 15 years ago when the dot-com boom was just starting? A lot of companies were running on Sun. Sun was the best hardware you could buy for the price. It was reliable and a lot of engineers had experience with the operating system, SunOS a flavor of Unix.
Yet suddenly companies were switching to cheap crappy hardware. The stuff failed more often, had lower quality control, and cheaper and slower buses. Despite all of that, cutting edge firms and startups were moving to commodity hardware in droves. Why was it so?
MySQL databases are great work horses of the internet. They back tons of modern websites, from blogs and checkout carts, to huge sites like Facebook. But these technologies don’t run themselves. When you’re faced with a system that is slowing down, you’ll need the right tools to diagnose and troubleshoot the problem. MySQL has a huge community following and that means scores of great tools for your toolbox. Here are 7 ways to troubleshoot MySQL.