Best Wireless Gaming Mouse - Goldensunsky 1000/1600/2000 dpi High Speed Wireless Gaming Optical Mouse with USB Mini Receiver, Plug and Play 2.4ghz is great for the price. There is anything to bad about it, it fits into your hand perfectly. I have been using it to play guild wars 2 and it has been working great after 5 hours of straight use.The mouse itself is not huge, and fits comfortably
Goldensunsky 1000/1600/2000 dpi High Speed Wireless Gaming Optical Mouse with USB Mini Receiver, Plug and Play 2.4ghz
Best Wireless Gaming Mouse - Goldensunsky 1000/1600/2000 dpi High Speed Wireless Gaming Optical Mouse with USB Mini Receiver, Plug and Play 2.4ghz is great for the price. There is anything to bad about it, it fits into your hand perfectly. I have been using it to play guild wars 2 and it has been working great after 5 hours of straight use.The mouse itself is not huge, and fits comfortably
MySQL error: last packet sent to the server was XXX ms ago
I just spent a few weeks battling a strange, infrequent, hard-to-reproduce error when using JDBC to talk to MySQL. After about a dozen experiments, I think I've finally found a solution and I've decided to capture the details here, since my online searches didn't turn up this particular answer anywhere else.
tldr: If you see a "last packet sent to the server was XXX ms ago" error, you may want to upgrade your version of the mysql-connector-java library.
The Symptoms
I had a simple Java app in production that was using JDBC to talk to a MySQL DB. Everything was running great: DB calls were taking 2 ms on average and 8 ms in the 99th percentile. However, once every 4-8 hours, a strange error would pop up that looked something like this:
I can understand the occasionally slow query, but 28800126 ms? EOFException? What's going on here?
Lots of ineffective options
As usual, I turned to a programmer's two best friends: Google and StackOverflow. I quickly found my way to the MySQL docs and found out that MySQL has two timeout settings that will close a connection if it is idle for too long: interactive_timeout and wait_timeout. The default value for these two settings is 28800000 ms or 8 hours.
The general advice online was to make sure that your connection management library was sending periodic "keep-alive" queries to prevent connections from going idle. I was using BoneCP, so I tried everything I could to make it behave properly, including a few configuration tweaks as well as workarounds for a connection leak bug and a releaseHelperThreads bug. Nothing worked.
Eventually, I swapped out BoneCP entirely for a different connection management library. Nevertheless, after a few hours, the dreaded "last packet sent to the server was XXX ms ago" error would pop up on the production box.
The solution at last
For a while, I was at a loss. I couldn't see how two entirely different DB connection management libraries could have the same bug. I began digging for what the two had in common and realized that, under the hood, both would be using the same JDBC driver. For MySQL, this is Connector/J.
It's at this point that I noticed that I was, for some reason, using Connector/J version 3.1.12, which is quite old. In fact, it is officially obsolete and only compatible with MySQL 5.0 and below. This is unfortunate, as I was using MySQL 5.5 in production.
I figured it was a long shot that this was the cause of the errors I was seeing, but I figured that using the "recommended" connector version was a good idea anyway. I updated from mysql-connector-java version 3.1.12 to version 5.1.22.
And just like that, all the errors were gone.
The final word
So, there you have it. If you see a "last packet sent to the server was XXX ms ago", it's likely one of two things:
tldr: If you see a "last packet sent to the server was XXX ms ago" error, you may want to upgrade your version of the mysql-connector-java library.
The Symptoms
I had a simple Java app in production that was using JDBC to talk to a MySQL DB. Everything was running great: DB calls were taking 2 ms on average and 8 ms in the 99th percentile. However, once every 4-8 hours, a strange error would pop up that looked something like this:
I can understand the occasionally slow query, but 28800126 ms? EOFException? What's going on here?
Lots of ineffective options
As usual, I turned to a programmer's two best friends: Google and StackOverflow. I quickly found my way to the MySQL docs and found out that MySQL has two timeout settings that will close a connection if it is idle for too long: interactive_timeout and wait_timeout. The default value for these two settings is 28800000 ms or 8 hours.
The general advice online was to make sure that your connection management library was sending periodic "keep-alive" queries to prevent connections from going idle. I was using BoneCP, so I tried everything I could to make it behave properly, including a few configuration tweaks as well as workarounds for a connection leak bug and a releaseHelperThreads bug. Nothing worked.
Eventually, I swapped out BoneCP entirely for a different connection management library. Nevertheless, after a few hours, the dreaded "last packet sent to the server was XXX ms ago" error would pop up on the production box.
The solution at last
For a while, I was at a loss. I couldn't see how two entirely different DB connection management libraries could have the same bug. I began digging for what the two had in common and realized that, under the hood, both would be using the same JDBC driver. For MySQL, this is Connector/J.
It's at this point that I noticed that I was, for some reason, using Connector/J version 3.1.12, which is quite old. In fact, it is officially obsolete and only compatible with MySQL 5.0 and below. This is unfortunate, as I was using MySQL 5.5 in production.
I figured it was a long shot that this was the cause of the errors I was seeing, but I figured that using the "recommended" connector version was a good idea anyway. I updated from mysql-connector-java version 3.1.12 to version 5.1.22.
And just like that, all the errors were gone.
The final word
So, there you have it. If you see a "last packet sent to the server was XXX ms ago", it's likely one of two things:
- Your DB connection management library is leaving idle connections open too long
- You're hitting an incompatibility bug between the Connector/J version and the MySQL DB version
Logitech M510 Wireless Mouse Review
Best Wireless Gaming Mouse - I have been seeking a fully-featured wireless mouse for the past two weeks and have finally found my optimum choice in the Logitech M510 Wireless Mouse. This mouse is just large enough to be a comfortable fit for virtually any hand. The battery life is outstanding! The package says the batteries will last 2 years. I have been using it for gaming and normal computer
Seven Languages in Seven Weeks: Erlang, Day 2
After learning some basic Erlang syntax on Day 1, I take on the second Erlang chapter, which introduces some more interesting concepts.
Erlang, Day 2: Thoughts
I'm finding it very easy to dive into Erlang. After going through the Prolog and Scala chapters of this book, as well as making heavy use of Scala at work, the functional constructs used in Erlang feel natural. I've grown very fond of pattern matching in the last few months and have found it to be a very powerful tool for expressing complex concepts in a very concise and readable manner. Erlang's heavy reliance on pattern matching makes me happy.
However, the syntax does feel slightly clunky: I constantly forget to end lines with dots and separating clauses of control structures with semi-colons gets annoying. I suspect this is something you get used to. Moreover, the end result, at least in the dead-simple code snippets I've looked at so far, is pleasantly readable.
Erlang, Day 2: Problems
List lookup
Consider a list of keyword-value tuples, such as [{erlang, "a functional language"}, {ruby, "an OO language"}]. Write a function that accepts the list and a keyword and returns the associated value for the keyword.
My implementation:
Shopping list price
Consider a shopping list that looks like [{item, quantity, price}, ...]. Write a list comprehension that builds a list of items of the form [{item, total_price}, ...] where total_price is quantity times the price.
My implementation:
Sample usage:
Tic-tac-toe
Write a program that reads a tic-tac-toe board presented as a list or a tuple of size nine. Return the winner (x or o) if a winner has been determined, cat if there are no more possible moves, or no_winner if no player has won yet.
My implementation:
Sample usage:
My first tic-tac-toe solution was a bit more complex, using recursion to scan all rows, columns and diagonals. However, I found that for a 3x3 board, the simple pattern matching approach, while somewhat verbose, was much easier to read.
Erlang, Day 2: Thoughts
I'm finding it very easy to dive into Erlang. After going through the Prolog and Scala chapters of this book, as well as making heavy use of Scala at work, the functional constructs used in Erlang feel natural. I've grown very fond of pattern matching in the last few months and have found it to be a very powerful tool for expressing complex concepts in a very concise and readable manner. Erlang's heavy reliance on pattern matching makes me happy.
However, the syntax does feel slightly clunky: I constantly forget to end lines with dots and separating clauses of control structures with semi-colons gets annoying. I suspect this is something you get used to. Moreover, the end result, at least in the dead-simple code snippets I've looked at so far, is pleasantly readable.
Erlang, Day 2: Problems
List lookup
Consider a list of keyword-value tuples, such as [{erlang, "a functional language"}, {ruby, "an OO language"}]. Write a function that accepts the list and a keyword and returns the associated value for the keyword.
My implementation:
Shopping list price
Consider a shopping list that looks like [{item, quantity, price}, ...]. Write a list comprehension that builds a list of items of the form [{item, total_price}, ...] where total_price is quantity times the price.
My implementation:
Sample usage:
Tic-tac-toe
Write a program that reads a tic-tac-toe board presented as a list or a tuple of size nine. Return the winner (x or o) if a winner has been determined, cat if there are no more possible moves, or no_winner if no player has won yet.
My implementation:
Sample usage:
My first tic-tac-toe solution was a bit more complex, using recursion to scan all rows, columns and diagonals. However, I found that for a 3x3 board, the simple pattern matching approach, while somewhat verbose, was much easier to read.
