Comment by akrymski

Logs should be studied in CS together with Turing Machines - they are a vital component of today's architecture. I applaud the effort of clearly describing the role of logs in today's distributed architectures in concise and easy to grasp way. Everyone studying database systems and distributed architectures should read this article. Thank's Jay!

We too have arrived at using logs at Post.fm, however with a slightly different application: syncing email clients that can go offline with remote servers (similar to Exchange). Instead of the traditional approach taken by most web apps - calling remote APIs directly (the new-age remote procedure calls in effect) I believe the new client-server architectures for web-apps will use logs to synchronise state. This is increasingly possible with the availability of local storage (web-sql, indexed-db, etc).

Another fascinating concept is Acid-State (http://acid-state.seize.it) which "keeps a history of all the functions (along with their arguments) that have modified the state. Thus, recreating the state after an unforeseen error is a simple as rerunning the functions in the history log." The idea of a log being transparently generated at application run-time is fascinating. Function calls elegantly map to 'transactions' when modifying multiple rows this way.

Another interesting outcome of thinking about database systems as logs, is that the tables are in effect read-only. You don't really "modify a row in a table", but add an entry to the log. At some point the database system updates the table to reflect the additions to the log (eventual consistency). If you make the database system wait for the log processing to complete before returning - you essentially get ACID.

Sometimes I wish there was a simpler, more transparent database system that made the log front and center, letting me specify if a SELECT requires the table to be updated with respect to the log or not. Current DBMSes seem to hide lots of functionality instead of providing a simple model that can be tweaked to a particular application.