Guillaume Quintard

Recent Posts

Understanding Varnish logging and log management

One aspect of Varnish that customers and enthusiasts most often ask questions about is how to make more effective use of Varnish’s powerful logging features. Logging and log management is important because your logs can be a real-time account of what is happening behind the scenes with your web traffic and transactions, resource performance, and much more. The detailed nature of logs lets you identify specific issues, anomalies or patterns and troubleshoot, sometimes getting to root causes of problems or seeing and stopping threats emerge before they can do any damage.

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2/11/21 3:39 PM
by Guillaume Quintard

The difference between Hit-for-Miss and Hit-for-Pass

A few weeks ago, I wrote and post introducing the concept of Hit-for-Miss and I received a few questions about it because "Hit-for-Pass" is much more common on the interwebz, and it looks like it could do something similar, and I completely omitted it last time. What's up with that?

Let's embark on a short chronological journey explaining how HfM and HfP (as the cool kids call them) came to be, how they are different and why you should care.

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12/4/20 11:15 AM
by Guillaume Quintard

Hit-for-Miss AND why a NULL TTL is bad for you

Varnish is a caching server, and a great one at that, that much we already know. But what about the content you don't want to cache? For example, those shopping cart requests and other completely uncacheable API calls?

We can of course handle it, but we've got to be wary of the sirens of the cargo cult because you will often see something like this on the internet:

sub vcl_backend_response {
# check if the backend response header named
# "cache-control" contains the word "private"
if (beresp.http.cache-control ~ "private") {
# if so, don't cache by limiting the Time-To-Live
# period to 0 second
set beresp.ttl = 0s;
}
}

This is both pretty intuitive, and also very wrong. In this post, we'll explore why it's a bad idea, how to do better, and along the way, we'll try to shine some light on a couple of lesser known features of Varnish.

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10/15/20 4:12 PM
by Guillaume Quintard

Request coalescing and other reasons to use Varnish as origin shield

The single most frequent question I get from people discovering Varnish is "Do you support request collapsing?". And I must admit, it always catches me off guard, because of course, it has been doing so for years, and it's a caching server, so that's a must-have, right? (Yes, yes it is.)

For this reason, in this post, we are going to review some of the little features we take for granted but that also make Varnish a great origin shield.

 

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7/29/20 11:14 AM
by Guillaume Quintard

Varnish Software Blog

The Varnish blog is where our team writes about all things related to Varnish Cache and Varnish Software...or simply vents.

 

 
 

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