Mysql 服务器消失但在清除浏览器缓存时解决
Mysql server gone away but resolved when clear browser cache
我有 mysql serve gone away 错误，但如果我清除浏览器缓存，然后问题就解决了。我不明白为什么？
查看错误图片 link http://veenas.com/beta/error.jpg
来自 MySQL 文档：
The most common reason for the MySQL server has gone away error is that the server timed out and closed the connection.
Some other common reasons for the MySQL server has gone away error
are:
You (or the db administrator) has killed the running thread with a
KILL statement or a mysqladmin kill command.
You tried to run a query after closing the connection to the server.
This indicates a logic error in the application that should be
corrected.
A client application running on a different host does not have the
necessary privileges to connect to the MySQL server from that host.
You got a timeout from the TCP/IP connection on the client side. This
may happen if you have been using the commands: mysql_options(...,
MYSQL_OPT_READ_TIMEOUT,...) or mysql_options(...,
MYSQL_OPT_WRITE_TIMEOUT,...). In this case increasing the timeout may
help solve the problem.
You have encountered a timeout on the server side and the automatic
reconnection in the client is disabled (the reconnect flag in the
MYSQL structure is equal to 0).
You are using a Windows client and the server had dropped the
connection (probably because wait_timeout expired) before the command
was issued.
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.
Prior to MySQL 5.0.19, even if the reconnect flag in the MYSQL
structure is equal to 1, MySQL does not automatically reconnect and
re-issue the query as it doesn't know if the server did get the
original query or not.
The solution to this is to either do a mysql_ping() on the connection
if there has been a long time since the last query (this is what
Connector/ODBC does) or set wait_timeout on the mysqld server so high
that it in practice never times out.
You can also get these errors if you send a query to the server that
is incorrect or too large. If mysqld receives a packet that is too
large or out of order, it assumes that something has gone wrong with
the client and closes the connection. If you need big queries (for
example, if you are working with big BLOB columns), you can increase
the query limit by setting the server's max_allowed_packet variable,
which has a default value of 1MB. You may also need to increase the
maximum packet size on the client end. More information on setting the
packet size is given in Section B.5.2.10, “Packet Too Large”.
An INSERT or REPLACE statement that inserts a great many rows can also
cause these sorts of errors. Either one of these statements sends a
single request to the server irrespective of the number of rows to be
inserted; thus, you can often avoid the error by reducing the number
of rows sent per INSERT or REPLACE.
You also get a lost connection if you are sending a packet 16MB or
larger if your client is older than 4.0.8 and your server is 4.0.8 and
above, or the other way around.
It is also possible to see this error if host name lookups fail (for
example, if the DNS server on which your server or network relies goes
down). This is because MySQL is dependent on the host system for name
resolution, but has no way of knowing whether it is working—from
MySQL's point of view the problem is indistinguishable from any other
network timeout.
You may also see the MySQL server has gone away error if MySQL is
started with the --skip-networking option.
Another networking issue that can cause this error occurs if the MySQL
port (default 3306) is blocked by your firewall, thus preventing any
connections at all to the MySQL server.
You can also encounter this error with applications that fork child
processes, all of which try to use the same connection to the MySQL
server. This can be avoided by using a separate connection for each
child process.
You have encountered a bug where the server died while executing the
query.
You can check whether the MySQL server died and restarted by executing
mysqladmin version and examining the server's uptime. If the client
connection was broken because mysqld crashed and restarted, you should
concentrate on finding the reason for the crash. Start by checking
whether issuing the query again kills the server again. See Section
B.5.4.2, “What to Do If MySQL Keeps Crashing”.
You can get more information about the lost connections by starting
mysqld with the --log-warnings=2 option. This logs some of the
disconnected errors in the hostname.err file. See Section 5.2.1, “The
Error Log”.
If you want to create a bug report regarding this problem, be sure
that you include the following information:
Indicate whether the MySQL server died. You can find information about
this in the server error log. See Section B.5.4.2, “What to Do If
MySQL Keeps Crashing”.
If a specific query kills mysqld and the tables involved were checked
with CHECK TABLE before you ran the query, can you provide a
reproducible test case? See Section 21.3, “Debugging and Porting
MySQL”.
What is the value of the wait_timeout system variable in the MySQL
server? (mysqladmin variables gives you the value of this variable.)
Have you tried to run mysqld with the general query log enabled to
determine whether the problem query appears in the log? (See Section
5.2.2, “The General Query Log”.)
我有 mysql serve gone away 错误，但如果我清除浏览器缓存，然后问题就解决了。我不明白为什么？
查看错误图片 link http://veenas.com/beta/error.jpg
来自 MySQL 文档：
The most common reason for the MySQL server has gone away error is that the server timed out and closed the connection.
Some other common reasons for the MySQL server has gone away error are:
You (or the db administrator) has killed the running thread with a KILL statement or a mysqladmin kill command.
You tried to run a query after closing the connection to the server. This indicates a logic error in the application that should be corrected.
A client application running on a different host does not have the necessary privileges to connect to the MySQL server from that host.
You got a timeout from the TCP/IP connection on the client side. This may happen if you have been using the commands: mysql_options(..., MYSQL_OPT_READ_TIMEOUT,...) or mysql_options(..., MYSQL_OPT_WRITE_TIMEOUT,...). In this case increasing the timeout may help solve the problem.
You have encountered a timeout on the server side and the automatic reconnection in the client is disabled (the reconnect flag in the MYSQL structure is equal to 0).
You are using a Windows client and the server had dropped the connection (probably because wait_timeout expired) before the command was issued.
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.
Prior to MySQL 5.0.19, even if the reconnect flag in the MYSQL structure is equal to 1, MySQL does not automatically reconnect and re-issue the query as it doesn't know if the server did get the original query or not.
The solution to this is to either do a mysql_ping() on the connection if there has been a long time since the last query (this is what Connector/ODBC does) or set wait_timeout on the mysqld server so high that it in practice never times out.
You can also get these errors if you send a query to the server that is incorrect or too large. If mysqld receives a packet that is too large or out of order, it assumes that something has gone wrong with the client and closes the connection. If you need big queries (for example, if you are working with big BLOB columns), you can increase the query limit by setting the server's max_allowed_packet variable, which has a default value of 1MB. You may also need to increase the maximum packet size on the client end. More information on setting the packet size is given in Section B.5.2.10, “Packet Too Large”.
An INSERT or REPLACE statement that inserts a great many rows can also cause these sorts of errors. Either one of these statements sends a single request to the server irrespective of the number of rows to be inserted; thus, you can often avoid the error by reducing the number of rows sent per INSERT or REPLACE.
You also get a lost connection if you are sending a packet 16MB or larger if your client is older than 4.0.8 and your server is 4.0.8 and above, or the other way around.
It is also possible to see this error if host name lookups fail (for example, if the DNS server on which your server or network relies goes down). This is because MySQL is dependent on the host system for name resolution, but has no way of knowing whether it is working—from MySQL's point of view the problem is indistinguishable from any other network timeout.
You may also see the MySQL server has gone away error if MySQL is started with the --skip-networking option.
Another networking issue that can cause this error occurs if the MySQL port (default 3306) is blocked by your firewall, thus preventing any connections at all to the MySQL server.
You can also encounter this error with applications that fork child processes, all of which try to use the same connection to the MySQL server. This can be avoided by using a separate connection for each child process.
You have encountered a bug where the server died while executing the query.
You can check whether the MySQL server died and restarted by executing mysqladmin version and examining the server's uptime. If the client connection was broken because mysqld crashed and restarted, you should concentrate on finding the reason for the crash. Start by checking whether issuing the query again kills the server again. See Section B.5.4.2, “What to Do If MySQL Keeps Crashing”.
You can get more information about the lost connections by starting mysqld with the --log-warnings=2 option. This logs some of the disconnected errors in the hostname.err file. See Section 5.2.1, “The Error Log”.
If you want to create a bug report regarding this problem, be sure that you include the following information:
Indicate whether the MySQL server died. You can find information about this in the server error log. See Section B.5.4.2, “What to Do If MySQL Keeps Crashing”.
If a specific query kills mysqld and the tables involved were checked with CHECK TABLE before you ran the query, can you provide a reproducible test case? See Section 21.3, “Debugging and Porting MySQL”.
What is the value of the wait_timeout system variable in the MySQL server? (mysqladmin variables gives you the value of this variable.)
Have you tried to run mysqld with the general query log enabled to determine whether the problem query appears in the log? (See Section 5.2.2, “The General Query Log”.)