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cache

Varnish 5.1 always online

Recently I posted about Varnish with secure AWS S3 bucket as backend and I wanted to have the “always online” enabled, meaning you can take the backend offline while serving from Varnish cache.

Varnish with secure AWS S3 bucket as backend

Serving static contents from S3 is common, but using Varnish in front is a bit tricky. Especially if you want to keep the bucket secure and only serve from Varnish, here is a simple Varnish file to solve this problem.

First secure your bucket via IP policy:

{
  "Version": "2012-10-17",
  "Id": "S3PolicyId1",
  "Statement": [
    {
      "Sid": "IPAllow",
      "Effect": "Allow",
      "Principal": "*",
      "Action": "s3:GetObject",
      "Resource": "arn:aws:s3:::example.bucket/*",
      "Condition": {
        "IpAddress": {
          "aws:SourceIp": [
            "5.6.7.8/32"  //varnish ip
          ]
        }
      }
    },
    {
      "Sid": "Explicit deny to ensure requests are allowed only from specific referer.",
      "Effect": "Deny",
      "Principal": "*",
      "Action": "s3:GetObject",
      "Resource": "arn:aws:s3:::example.bucket/*",
      "Condition": {
        "StringNotLike": {
          "aws:Referer": [
            "https://example.com/*"
          ]
        }
      }
    }
  ]
}

Setup postgreSQL RDS using Ansible

Setting up PostgreSQL on RDS using ansible is a bit tricky because the main user on RDS is not a SUPERUSER and roles membership is not automatically granted for ex: “ERROR: must be member of role ..” is quite common. Here is a working solution:

Fix W3 Total Cache W3_Plugin_TotalCache::ob_callback() expected to be a reference

Around a year ago I was playing with W3 Total Cache plugin on HHVM while I got an annoying warning

Warning: Parameter 1 to W3_Plugin_TotalCache::ob_callback() expected to be a reference, value given in /wp-includes/functions.php on line 3269

The funny part is that one of the functions was passing by reference which I still could not find the reason for it, maybe it was a limitation in PHP 4.3. Removing one character “&” fixed the issue so I submitted a pull request to the author although the repository currently does not accept pull request. Later on as PHP 7.0 was released, the issue started to show on PHP as well which brought more attention to this small fix. The users comments included anger such as user @kmob2 who said

this is becoming a running gag

Even more user @pratham2003 proposed a one line bash command to solve the problem

sed -i.bak 's/function ob_callback(&/function ob_callback(/g' /path/to/public_html/wp-content/plugins/w3-total-cache/lib/W3/Plugin/TotalCache.php

I hope that the developers will finally listen to the users and fix it soon!

Warming up WordPress cache, HHVM and testing blog pages

If you are minifying scripts and css files using a caching plugin or using FastCGI cache then you might need to warmup your blog after purging your cache. This is a simple warm up cli script for WordPress to initiate cache or HHVM HHBC and making sure all pages/posts do not have errors. Additionally the script creates a urllist.txt file that you can use with siege to test load your server.