Mysql2 Error MySQL server has gone away

问题

I am getting this error occasionally. I have read some solutions in stackoverflow but they were about rails 2 or mysql. Any help will be appreciated.

ActiveRecord::StatementInvalid (Mysql2::Error: MySQL server has gone away

回答1:

There are numerous causes for the error. See below page for possible causes. Perhaps your packet size is set too small.

http://dev.mysql.com/doc/refman/5.0/en/gone-away.html

回答2:

I got this error while trying to import a large file through seeds.rb with rake db:seed by calling one statement:

ActiveRecord::Base.connection.execute(IO.read("path/to/file.sql"))

And I kept on getting ActiveRecord::StatementInvalid (Mysql2::Error: MySQL server has gone away...

---

SOLUTION

I resolved this by a combination of two things:

1. Add reconnect: true to the database specification in database.yml

2. Read the SQL file and execute the statement individually, as such:

   f = File.new('path/to/file.sql')
   
   while statements = f.gets("") do
     ActiveRecord::Base.connection.execute(statements)
   end  
   

I had to modify to remove some comments from my SQL file -- they made ActiveRecord throw errors for some reason, but that resolved my problem.

回答3:

I experience exactly same issue when I run "rake db:reset" command on my development environment. But I never see this error message when I run "rake db:migrate:reset && rake db:seed".

Though it is very strange, but this may throw some lights on this issue. I am glad if my post leads to a solution somehow.

回答4:

Maybe the server you are hosted on is overloaded and in some cases the MySQL server can not execute a query. Ask your hosting provider about performance monitoring tools, or tell him about this problem directly. This error message should be enough for them to give you an answer.

来源：https://stackoverflow.com/questions/6807012/mysql2-error-mysql-server-has-gone-away