The Cloud team at RavenDB has been working quite hard recently. The company at large is gearing up for the upcoming 6.2 release, but I can’t ignore the number of goodies that have dropped for RavenDB Cloud Customers.

Large Clusters & Sharding

RavenDB Cloud runs your production cluster with 3 nodes by default. Each one of them operates in a separate availability zone for maximum survivability. The new feature allows you to add additional nodes to your cluster. In the RavenDB Cloud Portal, you can see the “Add node” button and its impact:

Clicking this button allows you to add additional nodes to your cluster. The nodes will be deployed and attached to your cluster within a minute or two. The new nodes will be deployed in the same region (but not necessarily the same availability zone) where your cluster is already deployed.

There are plans in place to add support for deploying nodes in other regions and even in a multi-cloud environment. I would love to hear your feedback on this proposed feature.

You can see the new instances in the RavenDB Studio as well:

The key reason for adding additional nodes to a cluster is when you have very large datasets and you want to shard the data. Here is what this can look like:

In this case, we have sharded the data across 5 nodes, with a replication factor of 2.

Feature selection

There are certain Enterprise features that are only available in the higher-end instances in RavenDB Cloud (typically P30 or higher). We now allow you to selectively enable these features even on lower-tier instances.

This feature allows you to easily pick & choose (on an a-la-carte basis) the specific features you want, without having to upgrade to the more expensive tiers.

Metrics & monitoring

This feature isn’t actually new, but it absolutely deserves your attention. The RavenDB Cloud Portal has a metrics button that you should get familiar with:

Clicking it will provide a wealth of information about your cluster and its behavior. That can be really useful if you want to understand the system’s behavior. Take a peek:

Alerts & Warnings

In addition to just looking at the metrics, the RavenDB Cloud backend will give you some indication about things that you should pay attention to. For example, let’s assume that we had a node failure. You’ll typically not notice that since the RavenDB Cluster & client will work to ensure high availability.

You’ll be able to see that in the metrics, and the RavenDB Cloud Portal will bring it to your attention:

Summary

The major point we strive for in RavenDB and RavenDB Cloud is the notion that the entire experience will be seamless. From deployment and routine management to ensuring that you don’t have to concern yourself with the minutiae of data management, so you can focus on your application.

Being able to develop both the software and its execution environment greatly helps in providing solutions that Just Work. I’m really proud of what we have accomplished and I would love to get your feedback on it.

It has been almost a year since the release of RavenDB 6.0. The highlights of the 6.0 release were Corax (a new blazing-fast indexing engine) and Sharding (server-side and simple to operate at scale). We made 10 stable releases in the 6.0.x line since then, mostly focused on performance, stability, and minor features.

The new RavenDB 6.2 release is now out and it has a bunch of new features for you to play with and explore. The team has been working on a wide range of new features, from enabling serverless triggers to quality-of-life improvements for operations teams.

RavenDB 6.2 is a Long Term Support (LTS) release

RavenDB 6.2 is a Long Term Support release, replacing the current 5.4 LTS (released in 2022). That means that we’ll support RavenDB 5.4 until Oct 2025, and we strongly encourage all users to upgrade to RavenDB 6.2 at their earliest convenience.

You can get the new RavenDB 6.2 bits on the download page. If you are running in the cloud, you can open a support request and ask to be upgraded to the new release.

Data sovereignty and geo-distribution via Prefixed Sharding

In RavenDB 6.2 we introduced a seemingly simple change to the way RavenDB handles sharding, with profound implications for what you can do with it. Prefixed sharding allows you to define which shards a particular set of documents will go to.

Here is a simple example:

In this case, data for users in the US will reside in shards 0 & 1, while the EU data is limited to shards 2 & 3. The data from Asia is spread over shards 0, 2, & 4.  You can then assign those shards to specific nodes in a particular geographic region, and with that, you are done.

RavenDB will ensure that documents will stay only in their assigned location, handling data sovereignty issues for you. In the same manner, you get to geographically split the data so you can have a single world-spanning database while issuing mostly local queries.

You can read more about this feature and its impact in the documentation.

Actors architecture with Akka.NET

New in RavenDB 6.2 is the integration of RavenDB with Akka.NET. The idea is to allow you to easily manage state persistence of distributed actors in RavenDB. You’ll get both the benefit of the actor model via Akka.NET, simplifying parallelism and concurrency, while at the same time freeing yourself from persistence and high availability concerns thanks to RavenDB.

We have an article out discussing how you use RavenDB & Akka.NET, and if you are into that sort of thing, there is also a detailed set of notes covering the actual implementation and the challenges involved.

Azure Functions integration with ETL to Azure Queues

This is the sort of feature with hidden depths. ETL to Azure Queue Storage is fairly simple on the surface, it allows you to push data using RavenDB’s usual ETL mechanisms to Azure Queues. At a glance, this looks like a simple extension of our already existing capabilities with queues (ETL to Kafka or RabbitMQ).

The reason that this is a top-line feature is that it also enables a very interesting scenario. You can now seamlessly integrate Azure Functions into your RavenDB data pipeline using this feature. We have an article out that walks you through setting up Azure Functions to process data from RavenDB.

OpenTelemetry integration

In RavenDB 6.2 we have added support for the OpenTelemetry framework. This allows your operations team to more easily integrate RavenDB into your infrastructure. You can read more about how to set up OpenTelemetry for your RavenDB cluster in the documentation.

OpenTelemetry integration is in addition to Prometheus, Telegraf, and SNMP telemetry solutions that are already in RavenDB. You can pick any of them to monitor and inspect the state of RavenDB.

Studio Omni-Search

We made some nice improvements to RavenDB Studio as well, and probably the most visible of those is the Omni-Search feature.  You can now hit Ctrl+K in the Studio and just search across everything:

• Commands in the Studio
• Documents
• Indexes

This feature greatly enhances the discoverability of features in RavenDB as well as makes it a joy for those of us (myself included) who love to keep our hands on the keyboard.

Summary

I’m really happy about this release. It follows a predictable and stable release cadence since the release of 6.0 a year ago. The new release adds a whole bunch of new features and capabilities, and it can be upgraded in place (including cross-version clusters) and deployed to production with no hassles.

Looking forward, we have already started work on the next version of RavenDB, tentatively meant to be 7.0. We have some cool ideas about what will go into that release (check the roadmap), but the key feature is likely to make RavenDB a more intelligent database, one might even say, artificially so.

I wanted to test low-level file-system behavior in preparation for a new feature for RavenDB. Specifically, I wanted to look into hole punching - where you can give low-level instructions to the file system to indicate that you’re giving up disk space, but without actually reducing the size of the file.

This can be very helpful in space management. If I have a section in the file that is full of zeroes, I can just tell the file system that, and it can skip storing that range of zeros on the disk entirely. This is an advanced feature for file systems. I haven't actually used that in the past, so I needed to gain some expertise with it.

I wrote the following code for Linux:

int fd = open("test.file", O_CREAT | O_WRONLY, 0644);
lseek(fd, 128 * 1024 * 1024 - 1, SEEK_SET); // 128MB file
write(fd, "", 1);
fallocate(fd, // 32 MB hole from the 16MB..48MB range
    FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, 
    16 * 1024 * 1024, 32 * 1024 * 1024); 
close(fd);

The code for Windows is here if you want to see it. I tested the feature on both Windows & Linux, and it worked. I could see that while the file size was 128MB, I was able to give back 16MB to the operating system without any issues. I turned the code above into a test and called it a day.

And then the CI build broke. But that wasn’t possible since I tested that. And there had been CI runs that did work on Linux. So I did the obvious thing and started running the code above in a loop.

I found something really annoying. This code worked, sometimes. And sometimes it just didn’t.

In order to get the size, I need to run this code:

struct stat st;
fstat(fd, &st);
printf("Total size: %lld bytes\n",
    (long long)st.st_size);
printf("Actual size on disk: %lld bytes\n", 
    (long long)st.st_blocks * 512);

I’m used to weirdness from file systems at this point, but this is really simple. All the data is 4KB aligned (in fact, all the data is 16MB aligned). There shouldn’t be any weirdness here.

As you can see, I’m already working at the level of Linux syscalls, but I used strace to check if there is something funky going on. Nope, there was a 1:1 mapping between the code and the actual system calls issued.

That means that I have to debug deeper if I want to understand what is going on. This involves debugging the Linux Kernel, which is a Big Task. Take a look at the code in the relevant link. I’m fairly certain that the issue is in those lines. The problem is that this cannot be, since both offset & length are aligned to 4KB.

I got out my crystal ball and thinking hat and meditated on this. If you’ll note, the difference between the expected and actual values is exactly 4KB. It almost looks like the file itself is not aligned on a 4KB boundary, but the holes must be.

Given that I just want to release this space to the operating system and 4KB is really small, I can adjust that as a fudge factor for the test. I would love to understand exactly what is going on, but so far the “file itself is not 4KB aligned, but holes are” is a good working hypothesis (even though my gut tells me it might be wrong).

If you know the actual reason for this, I would love to hear it.

And don't get me started on what happened with sparse files in macOS. There, the OS will randomly decide to mark some parts of your file as holes, making any deterministic testing really hard.