[mysql] ERROR 2006 (HY000): MySQL server has gone away

I get this error when I try to source a large SQL file (a big INSERT query).

mysql>  source file.sql
ERROR 2006 (HY000): MySQL server has gone away
No connection. Trying to reconnect...
Connection id:    2
Current database: *** NONE ***

ERROR 2006 (HY000): MySQL server has gone away
No connection. Trying to reconnect...
Connection id:    3
Current database: *** NONE ***

Nothing in the table is updated. I've tried deleting and undeleting the table/database, as well as restarting MySQL. None of these things resolve the problem.

Here is my max-packet size:

+--------------------+---------+
| Variable_name      | Value   |
+--------------------+---------+
| max_allowed_packet | 1048576 |
+--------------------+---------+

Here is the file size:

$ ls -s file.sql 
79512 file.sql

When I try the other method...

$ ./mysql -u root -p my_db < file.sql
Enter password: 
ERROR 2006 (HY000) at line 1: MySQL server has gone away

You can increase Max Allowed Packet

SET GLOBAL max_allowed_packet=1073741824;

http://dev.mysql.com/doc/refman/5.5/en/server-system-variables.html#sysvar_max_allowed_packet

If it's reconnecting and getting connection ID 2, the server has almost definitely just crashed.

Contact the server admin and get them to diagnose the problem. No non-malicious SQL should crash the server, and the output of mysqldump certainly should not.

It is probably the case that the server admin has made some big operational error such as assigning buffer sizes of greater than the architecture's address-space limits, or more than virtual memory capacity. The MySQL error-log will probably have some relevant information; they will be monitoring this if they are competent anyway.

You can also log into the database as root (or SUPER privilege) and do

set global max_allowed_packet=64*1024*1024;

doesn't require a MySQL restart as well. Note that you should fix your my.cnf file as outlined in other solutions:

[mysqld]
max_allowed_packet=64M

And confirm the change after you've restarted MySQL:

show variables like 'max_allowed_packet';

You can use the command-line as well, but that may require updating the start/stop scripts which may not survive system updates and patches.

As requested, I'm adding my own answer here. Glad to see it works!

If you are on Mac and installed mysql through brew like me, the following worked.

1. cp $(brew --prefix mysql)/support-files/my-default.cnf /usr/local/etc/my.cnf

Source: For homebrew mysql installs, where's my.cnf?

2. add max_allowed_packet=1073741824 to /usr/local/etc/my.cnf

3. mysql.server restart

The global update and the my.cnf settings didn't work for me for some reason. Passing the max_allowed_packet value directly to the client worked here:

mysql -h <hostname> -u username -p --max_allowed_packet=1073741824 <databasename> < db.sql

I solved the error ERROR 2006 (HY000) at line 97: MySQL server has gone away and successfully migrated a >5GB sql file by performing these two steps in order:

1. Created /etc/my.cnf as others have recommended, with the following contents:

   [mysql]
   connect_timeout = 43200
   max_allowed_packet = 2048M
   net_buffer_length = 512M
   debug-info = TRUE
   

2. Appending the flags --force --wait --reconnect to the command (i.e. mysql -u root -p -h localhost my_db < file.sql --verbose --force --wait --reconnect).

Important Note: It was necessary to perform both steps, because if I didn't bother making the changes to /etc/my.cnf file as well as appending those flags, some of the tables were missing after the import.

System used: OSX El Capitan 10.11.5; mysql Ver 14.14 Distrib 5.5.51 for osx10.8 (i386)

For Drupal 8 users looking for solution for DB import failure:

At end of sql dump file there can commands inserting data to "webprofiler" table. That's I guess some debug log file and is not really important for site to work so all this can be removed. I deleted all those inserts including LOCK TABLES and UNLOCK TABLES (and everything between). It's at very bottom of the sql file. Issue is described here:

https://www.drupal.org/project/devel/issues/2723437

But there is no solution for it beside truncating that table.

BTW I tried all solutions from answers above and nothing else helped.

I've tried all of above solutions, all failed.

I ended up with using -h 127.0.0.1 instead of using default var/run/mysqld/mysqld.sock.

A couple things could be happening here;

• Your INSERT is running long, and client is disconnecting. When it reconnects it's not selecting a database, hence the error. One option here is to run your batch file from the command line, and select the database in the arguments, like so;

$ mysql db_name < source.sql

• Another is to run your command via php or some other language. After each long - running statement, you can close and re-open the connection, ensuring that you're connected at the start of each query.

For amazon RDS (it's my case), you can change the max_allowed_packet parameter value to any numeric value in bytes that makes sense for the biggest data in any insert you may have (e.g.: if you have some 50mb blob values in your insert, set the max_allowed_packet to 64M = 67108864), in a new or existing parameter-group. Then apply that parameter-group to your MySQL instance (may require rebooting the instance).

Just in case, to check variables you can use

$> mysqladmin variables -u user -p 

This will display the current variables, in this case max_allowed_packet, and as someone said in another answer you can set it temporarily with

mysql> SET GLOBAL max_allowed_packet=1072731894

In my case the cnf file was not taken into account and I don't know why, so the SET GLOBAL code really helped.

This is more of a rare issue but I have seen this if someone has copied the entire /var/lib/mysql directory as a way of migrating their DB to another server. The reason it doesn't work is because the database was running and using log files. It doesn't work sometimes if there are logs in /var/log/mysql. The solution is to copy the /var/log/mysql files as well.

I had the same problem but changeing max_allowed_packet in the my.ini/my.cnf file under [mysqld] made the trick.

add a line

max_allowed_packet=500M

now restart the MySQL service once you are done.

If you have tried all these solutions, esp. increasing max_allowed_packet up to the maximum supported amount of 1GB and you are still seeing these errors, it might be that your server literally does not have enough free RAM memory available...

The solution = upgrade your server to more RAM memory, and try again.

Note: I'm surprised this simple solution has not been mentioned after 8+ years of discussion on this thread... sometimes we developers tend to overthink things.

I encountered this error when I use Mysql Cluster, I do not know this question is from a cluster usage or not. As the error is exactly the same, so give my solution here. Getting this error because the data nodes suddenly crash. But when the nodes crash, you can still get the correct result using cmd:

ndb_mgm -e 'ALL REPORT MEMORYUSAGE'

And the mysqld also works correctly.So at first, I can not understand what is wrong. And about 5 mins later, ndb_mgm result shows no data node working. Then I realize the problem. So, try to restart all the data nodes, then the mysql server is back and everything is OK.

But one thing is weird to me, after I lost mysql server for some queries, when I use cmd like show tables, I can still get the return info like 33 rows in set (5.57 sec), but no table info is displayed.

This error message also occurs when you created the SCHEMA with a different COLLATION than the one which is used in the dump. So, if the dump contains

CREATE TABLE `mytab` (
..
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;

you should also reflect this in the SCHEMA collation:

CREATE SCHEMA myschema COLLATE utf8_unicode_ci;

I had been using utf8mb4_general_ci in the schema, cause my script came from a fresh V8 installation, now loading a DB on old 5.7 crashed and drove me nearly crazy.

So, maybe this helps you saving some frustating hours... :-)

(MacOS 10.3, mysql 5.7)

In general the error:

Error: 2006 (CR_SERVER_GONE_ERROR) - MySQL server has gone away

means that the client couldn't send a question to the server.

mysql import

In your specific case while importing the database file via mysql, this most likely mean that some of the queries in the SQL file are too large to import and they couldn't be executed on the server, therefore client fails on the first occurred error.

So you've the following possibilities:

• Add force option (-f) for mysql to proceed and execute rest of the queries.

  This is useful if the database has some large queries related to cache which aren't relevant anyway.

• Increase max_allowed_packet and wait_timeout in your server config (e.g. ~/.my.cnf).

• Dump the database using --skip-extended-insert option to break down the large queries. Then import it again.

• Try applying --max-allowed-packet option for mysql.

Common reasons

In general this error could mean several things, such as:

• a query to the server is incorrect or too large,

  Solution: Increase max_allowed_packet variable.

  • Make sure the variable is under [mysqld] section, not [mysql].

  • Don't afraid to use large numbers for testing (like 1G).

  • Don't forget to restart the MySQL/MariaDB server.

  • Double check the value was set properly by:

    mysql -sve "SELECT @@max_allowed_packet" # or:
    mysql -sve "SHOW VARIABLES LIKE 'max_allowed_packet'"
    

• You got a timeout from the TCP/IP connection on the client side.

  Solution: Increase wait_timeout variable.

• You tried to run a query after the connection to the server has been closed.

  Solution: A logic error in the application should be corrected.

• Host name lookups failed (e.g. DNS server issue), or server has been started with --skip-networking option.

  Another possibility is that your firewall blocks the MySQL port (e.g. 3306 by default).

• The running thread has been killed, so retry again.

• You have encountered a bug where the server died while executing the query.

• A client running on a different host does not have the necessary privileges to connect.

• And many more, so learn more at: B.5.2.9 MySQL server has gone away.

Debugging

Here are few expert-level debug ideas:

• Check the logs, e.g.

  sudo tail -f $(mysql -Nse "SELECT @@GLOBAL.log_error")
  

• Test your connection via mysql, telnet or ping functions (e.g. mysql_ping in PHP).

• Use tcpdump to sniff the MySQL communication (won't work for socket connection), e.g.:

  sudo tcpdump -i lo0 -s 1500 -nl -w- port mysql | strings
  

• On Linux, use strace. On BSD/Mac use dtrace/dtruss, e.g.

  sudo dtruss -a -fn mysqld 2>&1
  

  See: Getting started with DTracing MySQL

Learn more how to debug MySQL server or client at: 26.5 Debugging and Porting MySQL.

For reference, check the source code in sql-common/client.c file responsible for throwing the CR_SERVER_GONE_ERROR error for the client command.

MYSQL_TRACE(SEND_COMMAND, mysql, (command, header_length, arg_length, header, arg));
if (net_write_command(net,(uchar) command, header, header_length,
          arg, arg_length))
{
  set_mysql_error(mysql, CR_SERVER_GONE_ERROR, unknown_sqlstate);
  goto end;
}

The solution is increasing the values given the wait_timeout and the connect_timeout parameters in your options file, under the [mysqld] tag.

I had to recover a 400MB mysql backup and this worked for me (the values I've used below are a bit exaggerated, but you get the point):

[mysqld]
port=3306
explicit_defaults_for_timestamp = TRUE
connect_timeout = 1000000
net_write_timeout = 1000000
wait_timeout = 1000000
max_allowed_packet = 1024M
interactive_timeout = 1000000
net_buffer_length = 200M
net_read_timeout = 1000000
set GLOBAL delayed_insert_timeout=100000

Blockquote

if none of this answers solves you the problem, I solved it by removing the tables and creating them again automatically in this way:

when creating the backup, first backup structure and be sure of add:
DROP TABLE / VIEW / PROCEDURE / FUNCTION / EVENT
CREATE PROCEDURE / FUNCTION / EVENT
IF NOT EXISTS
AUTO_INCREMENT

then just use this backup with your db and it will remove and recreate the tables you need.

Then you backup just data, and do the same, and it will work.

How about using the mysql client like this:

mysql -h <hostname> -u username -p <databasename> < file.sql