MySQL 5.6 Reference Manual Including MySQL NDB Cluster 7.3-7.4 Reference Guide
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 increases 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
.