Improve Performance - Case Study :: Article - 2eNetWorX

Part 1 - Key Features and Design
Part 2 - Cache Storage and Implementation
Part 3 - GetRecordset Function
Part 4 - Cache Expiration and Removal
Part 5 - Using the Cache Engine in your Projects
Part 6 - Case Study and Final Words

Step #2 (knowing when to call expiration methods) actually depends on your application design.

For example, if your Customers table gets updated a few times a day; it would be wise to call ExpireTable "Customers" whenever you update your table.

'...
'You would have code above to initialize

rs.AddNew
rs("FirstName") = Request("txtFirstName")
rs("LastName") = Request("txtLastName")
'...
rs.Update

'Now it's a good time to expire your
'Customers table:

Dim MyCache
Set MyCache = New DataCache

MyCache.ExpireTable "Customers"

There is a tradeoff between performance and freshness when we talk about caches. Our implementation is no different.

If you don't expire your cache items when appropriate, you will come up with pages that display old data.

If you expire your cache items too often (once in a few minutes for example), the performance may not satisfy you.

It all depends on a few factors to know how often the cache should be expired:

Daily number of pageviews on database-bound pages
Complexity of the database queries
Frequency of database updates
Ability to know when a database gets updated

Let's analyze the 2eNetWorX/dev forums case;

Thousands of pageviews on forum pages
Forum queries are complex and recursive (very slow)
Forum database is not updated very often
We know when the forum database is updated, it's when a visitor submits a new entry.

For such a scenario, it would be very effective to expire the cache items only when a visitor submits a new entry to the forum. 99% of the time, forum data will be served from the cache.

You can also put up a button somewhere in your administration pages to call RemoveAll() method on a periodic basis to make sure your all cache items get expired regularly.

This caching technique is being used on 2eNetWorX/dev for a long time and provides impressive performance gain. Of course, the internal cache engine is more complex and have more features, but it's based on the ideas presented in this article.

I have performed a few tests with a large database that contains hundreds of thousands of records (actually it's an old 2eNetWorX StatCounteX database).

Here are the results:

	Time to get from DB	Time to get from Cache	Performance Improvement
Query 1	406 ms	47 ms	800% (8x faster)
Query 2	3,602 ms	62 ms	4,900% (42x faster)
Query 3	8,062 ms	47 ms	17,200% (172x faster)

Query 1: SELECT AVG(StatID) FROM Stats
Query 2: SELECT * FROM TopPageViewsPerDay
Query 3: SELECT * FROM TopIpsPerDay

For a sneak preview of the internal 2eNetWorX cache engine, take a look at the cache reports.

Feel free to contact us if you have questions, comments or new ideas related to the material presented here, or about purchasing the advanced version of the cache engine. Remember that we developers need feedback.

Until the next article, take care.

Download the source code for this article.

< Previous Part: Using the Cache Engine in your Projects

Hakan Eskici
2eNetWorX OpenSource Projects
http://www.2enetworx.com/dev

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