computer science

Funky caching

Funky caching is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Funky caching rather than just read about it. In short: Funky caching is the generation, display and storage of dynamic content when a requested static web page resource isn't available. The name is based on the idea of treating the web server, serving static pages, as a cache.

Key takeaways

Funky caching belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Funky caching to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Funky caching from memory before moving on to harder problems.

Reference excerpt

Funky caching is the generation, display and storage of dynamic content when a requested static web page resource isn't available. The name is based on the idea of treating the web server, serving static pages, as a cache. However, unlike common reverse caches, the funky cache is part of the web server software, and has the ability to dynamically generate this content. It assumes that all pages are potentially generatable on-demand. If they are not, the conventional HTTP 404 error is returned, as usual. The overall advantage is relatively small, compared to a conventional cache. Architecturally it is also a poor design. However it does allow small sites with no separate cache layer to achieve some of the advantages of caching (albeit a little inflexibly). This is why it became popular at one time for small, single-server dynamic web sites, particularly those built within the PHP community, where the technique originated. A drawback to the technique is that it requires the web server process to have write access to the web content space. For security reasons, this is not usually required or permitted.

Origin It is also known as the ErrorDocument trick, Smarter Caching and Rasmus' Trick, the latter name in honor of Rasmus Lerdorf, creator of the PHP programming language, who was allegedly the first to present this mechanism (though it is also attributed to Stig Bakken). One common usage is the replacement of the HTTP Error404 ErrorDocument with a dynamic script. Another way to look at it as a variation of the cache-aside pattern where, instead of reading the data from the data store, it is generated dynamically, and where the implementation spans an architecture (in this case the Web server and the Web app language) instead of being implemented in a single system.

References

Worked examples

Example 1 — a first encounter with Funky caching

Start with the simplest possible case. Write down what Funky caching claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Funky caching before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Funky caching ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Funky caching

In research: Funky caching appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Funky caching in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Funky caching is common in secondary-school and first-year university syllabi. It links to neighbouring topics Cache (computing), Computing stubs, so understanding it makes those chapters shorter.
In everyday life: Look for Funky caching outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Funky caching in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Funky caching means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Funky caching out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Funky caching in simple terms?

Why does Funky caching matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Funky caching?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Funky caching.