I'm looking into aborted connection -
2022-11-21T20:10:43.215738Z 640870 [Note] Aborted connection 640870 to db: '' user: '' host: '10.0.0.**' (Got timeout reading communication packets)
My understanding is that I need to figure out whether it is an interactive or not connection, and increase wait_timeout (or interactive_timeout) accordingly. If it has no effect, then I'll need to adjust net_read_timeout or net_write_timeout and see.
I'd like to ask:
Is there a meta table that I can query for the connection type
(interactive or not)?
There are how-to's on the internet on adjusting wait_timeout (or
interactive_timeout) and all of them have rebooting the database as
the last step. Is that really required? Given that immediate effect
is not required, the sessions are supposed to come and go, and new
sessions will pick up the new value (after the system value is set),
I suppose if there is a way to track how many connections are left
with the old values, then it will be ok?
Finally, can someone suggest any blog (strategy) on handling aborted
connection or adjusting the timeout values?
Thank you!
RDS MySQL version 5.7
There is only one client that sets the interactive flag by default: the mysql command-line client. All other client tools and connectors do not set this flag by default. You can choose to set the interactive flag, because it's a flag in the MySQL client API mysql_real_connect(). So you would know if you did it. In some connectors, you aren't calling the MySQL client API directly, and it isn't even an option to set this flag.
So for practical purposes, you can ignore the difference between wait_timeout and interactive_timeout, unless you're trying to tune the timeout of the mysql client in a shell window.
You should never need to restart the MySQL Server. The timeout means the client closed the session after there has been no activity for wait_timeout seconds. The default value is 28800, which is 8 hours.
The proper way of handling this in application code is to catch exceptions, reconnect if necessary, and then retry whatever query was interrupted.
Some connectors have an auto-reconnect option. Auto-reconnect does not automatically retry the query.
In many applications, you are borrowing a connection from a connection pool, and the connection pool manager is supposed to test the connection before returning it to the caller. For example running SELECT 1; is a common test. The action of testing the connection causes a reconnect if the connection was not used for 8 hours.
If you don't use a connection pool (for example if your client program is PHP, which doesn't support connection pools as far as I know), then your client opens a new connection on request, so naturally it can't be idle for 8 hours if it's a new connection. Then the connection is closed as the request finishes, and presumably this request lasts less than 8 hours.
So this comes up only if your client opens a long-lived MySQL connection that is inactive for periods of 8 hours or more. In such cases, it's your responsibility to test the connection and reopen it if necessary before running a query.
I get the following error accessing to a MySql Database from Jdbc:
java.sql.SQLNonTransientConnectionException: Too many connections
At the same time I am monitoring my connections. I added a counter that counts any opening and closing. The error ouccurs when I get to 380 opened and closed connections within 3 minutes.
Is it possible that it takes some time for MySql to acutally close the connection so that there are still too many opened even though I have send a command to close them?
I am just assuming certain points that might be the reason.
MySql Connections are maintained by MySql Connection Manager so once connection is released Manager will decide to kill that thread or return it back to pool.
In some cases if MySql Resultset is not closed after retrieving data and connection has been close on that time sending it back to pool might have some latency issue.
These two are points that i think might cause that, but i am not sure if these are correct or not.
There could be other reasons that i am not knowing about.
Hope it gives you some idea.
I've a MySQL 5.1.41 Server installed on a Ubuntu machine. I get connected to it through Workbench from my Windows machine over TCP/IP. I run a bigger query, after 900 seconds I got the below message, (there is no wait_timeout defined in the server's configuration file my.cnf)
Error Code: 2013. Lost connection to MySQL server during query
But when I look into the process list by using show processlist; command, I can still see my query running.
I got this link http://dev.mysql.com/doc/refman/5.0/en/gone-away.html where I found the below lines,
The problem on Windows is that in some cases MySQL does not get an
error from the OS when writing to the TCP/IP connection to the server,
but instead gets the error when trying to read the answer from the
connection.
I'm not sure whether this is the reason for my observation.
Please clarify me on this.
Thanks in advance!!
Closing connection is not a reason to stop a query. A query might be update, or kind of transaction, or select with output to remote (server) file.
Closed connection is just is just means, that you will not receive any data from DBMS after executing query (data, timings - nothing).
The reason of closing connection could be different, as SO-User posted. Try increasing
on server side:
wait_timeout
max_allowed_packet
on client side:
any kinds of timeout you find in your client (i.e. that SO-User suggests)
Do not forget to reload DBMS config and restart client (for sure)
In MySQL WorkBench we have an option to change timeout.
Find it under
Edit → Preferences → SQL Editor → DBMS connection read time out (in seconds): 600
Changed the value to 6000 or something higher.
Update
Lost connection to MySQL server
There are three likely causes for this error message.
Usually it indicates network connectivity trouble and you should check
the condition of your network if this error occurs frequently. If the
error message includes “during query,” this is probably the case you
are experiencing.
Sometimes the “during query” form happens when millions of rows are
being sent as part of one or more queries. If you know that this is
happening, you should try increasing net_read_timeout from its default
of 30 seconds to 60 seconds or longer, sufficient for the data
transfer to complete.
More rarely, it can happen when the client is attempting the initial
connection to the server. In this case, if your connect_timeout value
is set to only a few seconds, you may be able to resolve the problem
by increasing it to ten seconds, perhaps more if you have a very long
distance or slow connection. You can determine whether you are
experiencing this more uncommon cause by using SHOW GLOBAL STATUS LIKE
'Aborted_connects'. It will increase by one for each initial
connection attempt that the server aborts. You may see “reading
authorization packet” as part of the error message; if so, that also
suggests that this is the solution that you need.
If the cause is none of those just described, you may be experiencing
a problem with BLOB values that are larger than max_allowed_packet,
which can cause this error with some clients. Sometime you may see an
ER_NET_PACKET_TOO_LARGE error, and that confirms that you need to
increase max_allowed_packet.
Doc link: Error lost connection
and also check here
for some reason when I open a connection the the Percona MySQL database on my HostGator website, after fetching the query, it will disconnect/ close the connection about 10 seconds later.
I typically wouldn't care, but HeidiSQL freezes up, preventing exporting or sorting the returned rows with it's UI unless I connect again.
Any thoughts on making the connection last longer? is it something I can do myself, or will it require a dedicated server or some upgrade? (I'm currently on a shared one). Thanks!
Sounds like it may be the "wait" timeout on the MySQL connection.
SHOW VARIABLES LIKE 'wait_timeout'
That's the amount of time (in seconds) that MySQL will leave the session (the database connection) open while it's idle, waiting for another statement to be issued. After this amount of time expires, MySQL can close the connection.
You should be able to change this for a session, to change the timeout to 5 minutes
SET wait_timeout = 300
Verify the setting with the SHOW VARIABLES statement again.
NOTE: This is per connection. It only affects the current session. Every new connection will inherit their own wait_timeout value from the global setting.
(This is only a guess. There's insufficient information in the question to make a precise diagnosis. It could be something other than MySQL server that's closing the database connection, e.g. it could be your connection pool settings (if you are using a connection pool).
After our Ruby on Rails application has run for a while, it starts throwing 500s with "MySQL server has gone away". Often this happens overnight. It's started doing this recently, with no obvious change in our server configuration.
Mysql::Error: MySQL server has gone away: SELECT * FROM `widgets`
Restarting the mongrels (not the MySQL server) fixes it.
How can we fix this?
Ruby on Rails 2.3 has a reconnect option for your database connection:
production:
# Your settings
reconnect: true
See:
Ruby on Rails 2.3 Release Notes, sub section 4.8 Reconnecting MySQL Connections.
MySQL auto-reconnect revisited
Good luck!
This is probably caused by the persistent connections to MySQL going away (time out is likely if it's happening over night) and Ruby on Rails is failing to restore the connection, which it should be doing by default:
In the file vendor/rails/actionpack/lib/action_controller/dispatcher.rb is the code:
if defined?(ActiveRecord)
before_dispatch { ActiveRecord::Base.verify_active_connections! }
to_prepare(:activerecord_instantiate_observers) {ActiveRecord::Base.instantiate_observers }
end
The method verify_active_connections! performs several actions, one of which is to recreate any expired connections.
The most likely cause of this error is that this is because a monkey patch has redefined the dispatcher to not call verify_active_connections!, or verify_active_connections! has been changed, etc.
Try ActiveRecord::Base.connection.verify! in Ruby on Rails 4. Verify pings the server and reconnects if it is not connected.
I had this problem when sending really large statements to MySQL. MySQL limits the size of statements and will close the connection if you go over the limit.
set global max_allowed_packet = 1048576; # 2^20 bytes (1 MB) was enough in my case
As the other contributors to this thread have said, it is most likely that MySQL server has closed the connection to your Ruby on Rails application because of inactivity. The default timeout is 28800 seconds, or 8 hours.
set-variable = wait_timeout=86400
Adding this line to your /etc/my.cnf will raise the timeout to 24 hours
http://dev.mysql.com/doc/refman/5.0/en/server-system-variables.html#option_mysqld_wait_timeout.
Although the documentation doesn't indicate it, a value of 0 may disable the timeout completely, but you would need to experiment as this is just speculation.
There are however three other situations that I know of that can generate that error. The first is the MySQL server being restarted. This will obviously drop all the connections, but as the MySQL client is passive, and this won't be noticed till you do the next query.
The second condition is if someone kills your query from the MySQL command line, and this also drops the connection, because it could leave the client in an undefined state.
The last is if your MySQL server restarts itself due to a fatal internal error. That is, if you are doing a simple query against a table and instantly see 'MySQL has gone away', I'd take a close look at your server's logs to check for hardware error, or database corruption.
First, determine the max_connections in MySQL:
show variables like "max_connections";
You need to make sure that the number of connections you're making in your Ruby on Rails application is less than the maximum allowed number of connections. Note that extra connections can be coming from your cron jobs, delayed_job processes (each would have the same pool size in your database.yml), etc.
Monitor the SQL connections as you go through your application, run processes, etc. by doing the following in MySQL:
show status where variable_name = 'Threads_connected';
You might want to consider closing connections after a Thread finishes execution as database connections do not get closed automatically (I think this is less of an issue with Ruby on Rails 4 applications Reaper):
Thread.new do
begin
# Thread work here
ensure
begin
if (ActiveRecord::Base.connection && ActiveRecord::Base.connection.active?)
ActiveRecord::Base.connection.close
end
rescue
end
end
end
The connection to the MySQL server is probably timing out.
You should be able to increase the timeout in MySQL, but for a proper fix, have your code check that the database connection is still alive, and re-connect if it's not.
Using reconnect: true in the database.yml will cause the database connection to be re-established AFTER the ActiveRecord::StatementInvalid error is raised (As Dave Cheney mentioned).
Unfortunately adding a retry on the database operation seemed necessary to guard against the connection timeout:
begin
do_some_active_record_operation
rescue ActiveRecord::StatementInvalid => e
Rails.logger.debug("Got statement invalid #{e.message} ... trying again")
# Second attempt, now that db connection is re-established
do_some_active_record_operation
end
Do you monitor the number of open MySQL connections or threads? What is your mysql.ini settings for max_connections?
mysql> show status;
Look at Connections, Max_used_connections, Threads_connected, and Threads_created.
You may need to increase the limits in your MySQL configuration, or perhaps rails is not closing the connection properly*.
Note: I've only used Ruby on Rails briefly...
The MySQL documentation for server status is in http://dev.mysql.com/doc/refman/5.0/en/server-status-variables.html.
Something else to check is Unicorn config is correct. See before_fork and after_fork handling of ActiveRecord connection here: https://gist.github.com/nebiros/2776085#file-unicorn-rb
I had this problem in a Ruby on Rails 3 application, using the mysql2 gem. I copied out the offending query and tried running it in MySQL directly, and I got the same error, "MySQL server has gone away.".
The query in question was very, very large. A very large insert (+1 MB). The field I was trying to insert into was a TEXT column and their max size is 64 KB. Rather than throwing an errorm, the connection went away.
I increased the size of the field and got the same thing, so I'm still not sure what the exact issue was. The point is that it was in the database due to some strange query. Anyway!
While forking in Rails.
For anyone running into this while forking in Rails, try clearing the existing connections before forking and then establish a new connection for each fork, like this:
# Clear existing connections before forking to ensure they do not get inherited.
::ActiveRecord::Base.clear_all_connections!
fork do
# Establish a new connection for each fork.
::ActiveRecord::Base.establish_connection
# The rest of the code for each fork...
end
See this StackOverflow answer here: https://stackoverflow.com/a/8915353/293280