#
key_buffer_size + tmp_table_size + (read_buffer_size + sort_buffer_size + read_rnd_buffer_size +join_buffer_size )*max_connections = 21215973024
大于物理内存16G,所以导致out of memory
最近mysql(5.0.45)偶尔出现"Got error 127 when reading table"的错误.原来是bug,在5.0.51已fix.
Release Notes for MySQL Community Server 5.0.51
If one thread was performing concurrent inserts, other threads reading from the same table using equality key searches could see the index values for new rows before the data values had been written, leading to reports of table corruption. (
Bug#29838)
tail -f sql.log | grep 'table_name', 非常快
tail -f sql.log | grep 'table_name' | awk '{print substr($0,0,150)}',非常慢
select table_name, engine, row_format, table_rows, data_length, index_length, max_data_length, data_free
from information_schema.tables
order by table_rows desc, data_length desc limit 100
mysql 5.x 增加information_schema
VisualVM is a visual tool that integrates several existing JDK software tools and lightweight memory and CPU profiling capabilities. This tool is designed for both production and development time use and further enhances the capability of monitoring and performance analysis for the Java SE platform.
目前还是用jconsole远程观察jvm. visualvm不知是否像听上去那么好.此项目还在beta2状态.好像dev.java.net的项目都不怎么样.
Adobe AIR is a cross-operating system runtime that enables you to use your existing HTML/Ajax, Flex, or Flash web development skills and tools to build and deploy rich Internet applications to the desktop.
air就像客户端的jvm,现在大家都喜欢提供api给developer,希望air能更加open一些,或许能获得像jvm一样的成功.
fisheye: 代码仓库查看工具. changelog非常方便查看团队成员提交的代码. 当然还有rss功能. search也非常强大. 不过statistic功能就比较简单些.
show variables like 'table_cache'
show variables like 'key_buffer_size'
show variables like 'thread_cache_size'
show variables like 'tmp_table_size'
SHOW STATUS LIKE 'open%tables%';
SHOW STATUS LIKE '%key_read%';
SHOW STATUS LIKE '%qc%';
SHOW STATUS LIKE '%Threads_created%';
SHOW STATUS LIKE '%Created_tmp_disk_tables%';
set GLOBAL max_connections = 2048
set GLOBAL table_cache=2048
set GLOBAL key_buffer_size=4294967296;
set GLOBAL query_cache_size=536870912;
set GLOBAL thread_cache_size=400;
http://trac.symfony-project.com/wiki/MysqlOptimization
使用fileupload上传文件,有些浏览器会出现乱码. 使用setHeaderEncoding就可以解决.
ServletFileUpload upload = new ServletFileUpload(factory);
String charset = request.getCharacterEncoding();
if (charset != null) {
upload.setHeaderEncoding(charset);
}
String charset = request.getCharacterEncoding();
if (charset!=null) value = item.getString(charset);
else value = item.getString();