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RavenDB 5.3 New Features: Incremental time series & implementing lambda based accounting

RavenDB 5.3 New Features: Incremental time series & implementing lambda based accounting

November 15, 2021

Everyone is on the cloud these days, and one of the things that I keep seeing pushed is the notion of usage based billing. Basically, the idea that you are paying for what you use. Let’s assume that we are building a software as a service where users can submit an image and you’ll do some computation on that. The actual details aren’t relevant.…

Blog
RavenDB 5.3 New Features: Incremental time series

RavenDB 5.3 New Features: Incremental time series

November 12, 2021

In RavenDB 5.0 we had a major new feature, native time series support. Using this feature, you can store values over time, query and aggregate them, store them efficiently, produce rollups, etc. The classic example for time series data in RavenDB is when you have data coming from sensors. For example a Fitbit monitoring heartrate, a stock exchange…

Blog
RavenDB 5.3 New Features: Concurrent Subscriptions & Serial operations

RavenDB 5.3 New Features: Concurrent Subscriptions & Serial operations

November 11, 2021

Almost as soon as we introduced concurrent subscriptions, we ran into a serious problem in their use. The desire was to do things in a serial fashion. That was quite infuriating, because we spent to much time working on making things concurrent, and now we had to deal with making them serial again? What the hell? Before I dive any further, it will…

Podcasts
Scalable architecture from the ground up

Scalable architecture from the ground up

November 11, 2021

In this talk, Oren Eini, founder of the RavenDB NoSQL database, speaks about how you can design and architect software systems that can easily scale to stupendous sizes, without causing either headache or pinching your wallet.

Blog
RavenDB 5.3 New Features: Concurrent subscriptions

RavenDB 5.3 New Features: Concurrent subscriptions

November 10, 2021

RavenDB supports a dedicated batch processing mode, using the notion of subscriptions. A subscription is simply a way to register a query with the database and have the database send the subscriber the documents that match the query. The previous sentence is taken directly from the Inside RavenDB book, and it is a good intro for the topic. A…

Blog
Finding and tracking a race condition in MemoryCache

Finding and tracking a race condition in MemoryCache

November 5, 2021

Following my previous posts, about the use after free bug that was found in a pull request, I put a lot of effort into testing the validity of the fix. As it turned out, my code was right and the fix worked properly. However, I uncovered a race condition in the .NET MemoryCache implementation. Here is what I got when I put the system under…

Blog
Caching hostility–usage patterns that breaks your system

Caching hostility–usage patterns that breaks your system

November 4, 2021

When you use a cache, you need to take into account several factors about the cache. There are several workload patterns that can cause the cache to turn into a liability, instead of an asset. One of the most common scenarios where you can pay heavily for the cache, but not benefit much, is when you have a sequential access pattern that exceed the…

Blog
Challenge: The code review bug that gives me nightmares–The fix

Challenge: The code review bug that gives me nightmares–The fix

November 3, 2021

After presenting the issue of how to return items to the array pool without creating a use after free bug, I asked you how you would fix that. There are several ways to try to do that, you can use reference counting scheme, or try to use locking, etc. All of those options are expensive, what is worse, they are expensive on a routine basis, not…

Blog
Challenge: The code review bug that gives me nightmares–the issue

Challenge: The code review bug that gives me nightmares–the issue

November 2, 2021

In my previous post, I discussed a bug that brought up in code review, that bug made me go into near panic mode. Here is the issue: In order to understand this bug, you have to take into account multiple concurrent threads at the same time. Look at the ComputeHashAndPutInCache() method, where we register an eviction callback for the item in the…