Three points:

• I don't see the immediate connection between your "too many connections" and the table cache. There might be such connection, but you have not provided info which suggests the two relate.

• I disagree with the advice about "If Open_tables climbs above (Opened_tables / Uptime), I have a cause for concern.."

• You haven't listed the table_open_cache & table_definition_cache settings. The table_cache variable is an old one.

Some suggestions:

• With regard "too many connections", try the following: Set max_connections to some reasonable value, like 300, throwing around a number. Set open_files_limit to a very high values, like 8192. By default you are only allowed 1024 open files on linux. Sockets, threads, table descriptors -- all map to files. Do you have some connection pool which holds many open (idle) connections, with some keepalive? How many processes do you get on a typical SHOW PROCESSLIST?

• With regard table cache: I suggest set a high value. With 3,000 queries per hour you're not remotely near the problem of having a problem with that. Why don't you set: table_open_cache=2048 table_definition_cache=512 (even though you may only have a couple tables)

• With regard the advice about open tables, you should be more interested in the number of tables opened per second (or minute, whatever) in any given time period, rather than looking at the overall number of tables opened since the server started to run. So you should monitor your opened_tables status variable every few minutes, and do the math. You would typically want to see less than 1 table opened in a second. Again, I'm throwing numbers around, but just to give you proportion. The open_tables is nice to know, as well. On good usage it can be very high, and that means your server is actively reading from tables. Fine! As long as the number of opened_tables/sec does not rise too high, this is no worry.

• There could be other reasons for "too many connections". Are the queries very long? Such that they just accumulate? Are some background tasks failing to complete? (You do have a wait_timeout=300 which is good; however some PHP job might be issuing new queries every few seconds, failing to close properly?

• Noting again: watch over SHOW PROCESSLIST and see what comes up.

I am glad you said all your data is InnoDB so I can answer as follows: If max_allowed_packet is maxed out at 1G and you are still having issues, there is really only two places to look:

1. innodb_log_buffer_size : The size in bytes of the buffer that InnoDB uses to write to the log files on disk. The default value is 8MB. A large log buffer enables large transactions to run without a need to write the log to disk before the transactions commit. Thus, if you have big transactions, making the log buffer larger saves disk I/O.
2. innodb_log_file_size : The size in bytes of each log file in a log group. The combined size of log files must be less than 4GB. The default value is 5MB. Sensible values range from 1MB to 1/N-th of the size of the buffer pool, where N is the number of log files in the group. The larger the value, the less checkpoint flush activity is needed in the buffer pool, saving disk I/O. But larger log files also mean that recovery is slower in case of a crash.

I addressed something like about 2 years ago

• Aug 01, 2011 : How does max_allowed_packet affect the backup and restore of a database?
• Apr 20, 2011 : MySQL gives "Out of Memory" error when inserting a large file. From where is this filesize limitation arising?

SUGGESTIONS

You need to increase the InnoDB transaction logs. Here are the steps to safely increase innodb_log_buffer_size and innodb_log_file_size:

Step 01 : Add these to /etc/my.cnf

[mysqld]
innodb_log_buffer_size = 32M
innodb_log_file_size = 2047M

Step 02 : Run this in mysql

mysql> SET GLOBAL innodb_fast_shutdown = 0;

Step 03 : Shutdown mysql

service mysql stop

Step 04 : Move the old logs aside

mv ib_logfile0 ib_logfile0.bak
mv ib_logfile1 ib_logfile1.bak

Step 05 : Start mysql

service mysql start

That's it.

The InnoDB Infrastructure should now have enough logging space for different size BLOBs.

Give it a Try !!!