Monthly Archives: August 2018

AWS EC2 Elastic Beanstalk Going to Sleep – .Net/Windows/MSSQL Server Express

Hi everyone,

I’ve been having a bit of an issue with my AWS app going to sleep and taking a long time to handle initial requests.

I’m using .NET with Elastic Beanstalk on a T2 Micro Instance and MSSQL Server Express on RDS. My FrontEnd is a static ReactJS app that sits in S3 behind CloudFront. There’s also a load balancer across the backend.

My frontend was always instant but my initial Api calls were timing out. This ruled out S3 and CloudFront, leaving the following:

  • Load balancer
  • RDS/MSSQL
  • EC2/IIS

After a bit of Googling I came across something that looked fairly promising – MSSQL Server Express has a property called AutoClose set to ‘ON’ by default. AWS appears to correct this as mine was off however it’s worth checking:

-- If set to zero then auto close is off
SELECT DATABASEPROPERTY('mydatabasename','IsAutoShrink')
 
-- Check all instances at once
SELECT name,is_auto_close_on FROM sys.databases
 
-- Turn off if on
ALTER DATABASE myDB SET AUTO_CLOSE OFF

In my case the actual problem turned out to be IIS idle timeout. By default IIS automatically times out an application after 20 minutes. In order to disable this create the following ebextension:

commands:
    setIdleTimeoutToZero:
        cwd: "C:\\windows\\system32\\inetsrv"
        command: "appcmd set apppool /apppool.name:DefaultAppPool /.processModel.idleTimeout:0.00:00:00"

If you haven’t done this before, all you need to do is create a folder called .ebextensions under your project directory. Then create a new file called iis-idle-timeout.config and add the yaml to it. If you need more information on iis timing out check out this great blog post: https://notebookheavy.com/2017/06/21/set-iis-idle-timeout-elastic-beanstalk/

Thanks to these sources for the solutions:
Disable auto_close: https://stackoverflow.com/a/1750400/522859
IIS Timeout: https://notebookheavy.com/2017/06/21/set-iis-idle-timeout-elastic-beanstalk/
EBExtension Info: http://notebookheavy.com/2017/05/01/auto-install-newrelic-agent-elastic-beanstalk/

NavLink ListItems not Applying activeClassName class when Clicked On – ReactJS React-Router MaterialUI

Hi everyone,

A bit of a hairy issue I ran into today that took a while to track down. I’m using React Router with Material UI to render a Drawer as a sidebar:

The issue was that some links were not applying the expected activeclass:

<ListItem button component={NavLink} to="/about" onClick={this.handleItemClick} className={classes.sidebarContentListItem} activeClassName={classes.active}>
	<ListItemIcon className={classes.sidebarText}>
		<Info />
	</ListItemIcon>
	<ListItemText primary={
		<Typography type="body2" className={classes.sidebarText}>
			About
		</Typography>
	} />
</ListItem>

After trawling through react-router I eventually found a post on github that mentioned a similar issue: https://github.com/ReactTraining/react-router/issues/4638

The solution turned out to be wrapping all relevant components with withrouter.

Uncaught SyntaxError: Unexpected token < - ReactJS Build

Hi everyone,

A ReactJS issue I ran into after running npm run build:

Uncaught SyntaxError: Unexpected token <

This one took a while to track down but it essentially boils down to the built index.html file referencing paths relatively:

Issue: index.html was referencing
"<script ... src="./static/js/main.e7b5bb28.js"></script></body></html".
 
Instead of:
"<script ... src="/static/js/main.e7b5bb28.js"></script></body></html".

This meant that anytime a page was accessed directly it attempted to load the static files from the wrong directory. To fix it, I had to update the homepage node in package.json

Original:
...
"version": "0.1.0",
  "homepage": "./",
  "private": true,
...
 
Instead use:
"version": "0.1.0",
  "homepage": "/",
  "private": true,

Hopefully that’s able to help someone else out, took a while to track down!