Custom Error pages for Linux Apache2 and the Rackspace Load Balancer

This article describes how to configure custom error pages for Apache2 and Zeus Load Balancer thru Rackspace API.

I have noticed that every now and then this question comes up. For instance, for most people there will define the errorpage within apache2, but if your not able to do that, and want a more helpful error page to be custom set, perhaps in the same xhtml layout as on your website, then custom error page for Load Balancer may be useful to you.

In apache2 this is traditionally set using the ErrorDocument directive.

The most common error pages are:

400 — Bad Request
The server did not understand the request due to bad syntax.

401 — Unauthorized
The visitor must by authorized (e.g., have a password) to access the page.

403 — Forbidden
The server understood the request but was unable to execute it. This could be due to an incorrect username and/or password or the server requires different input.

404 — Not Found
The server cannot find a matching URL.

500 — Internal Server Error
The server encountered an unexpected condition which prevented it from fulfilling the request.

In your apache2 httpd.conf you will need to add some directives to configure custom error pages. These custom error-pages will be forwarded to the Load Balancer in the case you have servers behind the Load Balancer, and the cloud server behind it encounters an error, it will be sent to the LB and then relayed to the customer, obviously. Instead of being sent directly to the customer as with a traditional apache2 webserver. To form your error page directive edit your httpd conf file either in sites-enabled or httpd.conf or similar, and merely add the following:

ErrorDocument 404 /my404page.html
ErrorDocument 500 /myphppage.php

ErrorDocument 403 /my-custom-forbidden-error-page.html
ErrorDocument 400 /my-bad-request-error-page.html

Then ensure that the error page defined (i.e. my404page.html my-custom-forbidden-error-page.html is placed in the correct directory i.e. the websites root /).

I.e. if your Documentroot is /var/www/html then your my404page.html should go in there.

For some people, for example who are using Load Balancer ACL, the blocked customer/client/visitor won’t be able to see/contact your server when it’s added to the LB DENY list. Therefore you might want to setup another error page on the LB to help customers that are accidentally/wrongly blocked on what process to carry out to remove the block, i.e. contact admin email, etc, etc.

To set custom error page on the load balancer you can use the API like so. You will need two files to achieve this, which will be detailed below:

errorpage.json (file)

{"errorpage":
{"content":"\n\n   Warning- Your IP has been blocked by the Load Balancer ACL, or there is an error contacting the servers behind the load balancer. Please contact [email protected] if you believe you have been blocked in error. \n\n"}
}

customerror.sh (file)

#!/bin/bash
# Make sure to set your customer account number, if you don't know what it is, it's the number that appears in the URL
# after logging in to mycloud.rackspace.com
# ALSO set your username and apikey, visible from the 'account settings' part of rackspace mycloud control panel

USERNAME='mycloudusernamehere'
APIKEY='mycloudapikeygoeshere'
ACCOUNTNUMBER='1001100'

# The load balancer ID, shown in the load balancer details page in mycloud contrl panel
LOADBALANCERID='157089'


API_ENDPOINT="https://lon.loadbalancers.api.rackspacecloud.com/v1.0/$ACCOUNTNUMBER"


# Store the API auth password response in the variable TOKEN

TOKEN=`curl https://identity.api.rackspacecloud.com/v2.0/tokens -X POST -d '{ "auth":{"RAX-KSKEY:apiKeyCredentials": { "username":"'$USERNAME'", "apiKey": "'$APIKEY'" }} }' -H "Content-type: application/json" |  python -mjson.tool | grep -A5 token | grep id | cut -d '"' -f4`

# Execute the API call to update the load balancer error page, submitting as a file the errorpage.json to be used

curl -s -v  \
-H "X-Auth-Token: $TOKEN"  \
-H "X-Project-Id: $ACCOUNTNUMBER" \
-H "Accept: application/json"  \
-d @errorpage.json -X PUT -H "content-type: application/json" \
"$API_ENDPOINT/loadbalancers/$LOADBALANCERID/errorpage"

That it, this concludes the discussion/tutorial on how to set basic error pages both in apache2 (without load balancer) , and with the load balancer only as described above. Please note, it appears you can only set a single error page for the load balancer, as opposed to one error page for each HTTP code.

If anyone see’s any differences or errors though, please let me know!

Best wishes,
Adam

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