Highest value of max_connections in AWS RDS micro instance

Question

Currently, the value for the max_connections parameter in a MySQL RDS t1.micro server model is {DBInstanceClassMemory/12582880} is 32.

Since my server does not allowing any more connections after 32, what is the Maximum safe value for max_connections I can use for a micro instance ?

For reference the AWS RDS product documentation is available at http://awsdocs.s3.amazonaws.com/RDS/latest/rds-ug.pdf — Damien Allison, Feb 06 '15 at 14:33

score 33 · Accepted Answer · edited Apr 13 '17 at 12:43

About 2 years ago, I was tasked with evaluating Amazon RDS for MySQL. I wrote some posts in the DBA StackExchange about my findings and observations:

Jul 25, 2012 : Scaling Percona datacenters: setup and replication
Aug 02, 2012 : Local database vs Amazon RDS
Sep 21, 2012 : MySQL 5.5 Runs Out of Memory, Drops All Connections When Creating Many Databases

In short, there are three options you cannot alter

max_connections (per Server Model)
innodb_buffer_pool_size (per Server Model)
innodb_log_file_size (all Server Models, 128M)

Here is the Chart I made telling you those per-Server Model limits

MODEL      max_connections innodb_buffer_pool_size
---------  --------------- -----------------------
t1.micro   34                326107136 (  311M)
m1-small   125              1179648000 ( 1125M,  1.097G)
m1-large   623              5882511360 ( 5610M,  5.479G)
m1-xlarge  1263            11922309120 (11370M, 11.103G)
m2-xlarge  1441            13605273600 (12975M, 12.671G)
m2-2xlarge 2900            27367833600 (26100M, 25.488G)
m2-4xlarge 5816            54892953600 (52350M, 51.123G)

As for your actual question, t1.micro has 34 as a max_connections setting. If you cannot surpass 32, that is quite understandable. Amazon AWS must be able to connect to and monitor things for the RDS Instance as a SUPER user. Not being able to go beyond 32 is reasonable for a t1.micro instance. In light of this, you will have no choice but to trust the management scheme administered by Amazon for apportioning max_connections and other options among all MySQL Instances in the AWS Cloud.

Nice answer. but I thought I can change it in custom Parameter group. So there is no other way than increasing Instance size? — Straw Hat, May 29 '14 at 13:30
Only those 3 options are immutable for the sake of the fair distribution CPU cycles, Memory, and Overall Performance to all running MySQL RDS instances. — RolandoMySQLDBA, May 29 '14 at 13:33
To check your max_connections, try this command: select @@max_connections; — stevendaniels, Apr 09 '16 at 23:43

advncd · Answer 2 · 2017-01-16T19:51:37.727

15

Here's what you can do to change max_connections or any other parameter in an AWS RDS (mysql) instance:

From RDS console go to Parameter Groups
Create a new parameter group based on the default group and name it my-param-group
Modify max_connections or other parameters in my-param-group
Go back to instance main page and click Modify in Instance Action button to modify the instance
Choose my-param-group as the DB Parameter Group
Reboot your instance
Done!

edited Jan 16 '17 at 19:51

answered Dec 02 '15 at 03:39

advncd

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I think this should be the accepted answer now – lucaConfa Oct 25 '17 at 04:51

score 9 · Answer 3 · answered Feb 14 '15 at 23:10

It appears that things have changed since the accepted answer. After seeing this thread I ran a test on a db.m3.medium RDS MySQL instance with max_connection manually set to 2000 using DB Parameter Groups. I was able to create 2000 connections and only then got the expected error of Too Many Connections.

Highest value of max_connections in AWS RDS micro instance

3 Answers3