Open Source DC/OS: The modern way to run a distributed database

00Architecture, General

The mission of ArangoDB is to simplify the complexity of data work. ArangoDB is a distributed native multi-model NoSQL database that supports JSON documents, graphs and key-value pairs in one database engine with one query language. The cluster management is based on Apache Mesos, a battle-hardened technology. With the launch of DC/OS by a community of more than 50 companies all ArangoDB users can easily scale. Read more

Improved Deadlock Detection

04Architecture

The upcoming ArangoDB version 2.8 (currently in devel) will provide a much better deadlock detection mechanism than its predecessors.

The new deadlock detection mechanism will kick in automatically when it detects operations that are mutually waiting for each other. In case it finds such deadlock, it will abort one of the operations so that the others can continue and overall progress can be made. Read more

Lockfree protection of data structures that are frequently read

04Architecture, Security

Motivation

In multi-threaded applications running on multi-core systems, it occurs often that there are certain data structures, which are frequently read but relatively seldom changed. An example of this would be a database server that has a list of databases that changes rarely, but needs to be consulted for every single query hitting the database. In such situations one needs to guarantee fast read access as well as protection against inconsistencies, use after free and memory leaks.

Therefore we seek a lock-free protection mechanism that scales to lots of threads on modern machines and uses only C++11 standard library methods. The mechanism should be easy to use and easy to understand and prove correct. This article presents a solution to this, which is probably not new, but which we still did not find anywhere else.

The concrete challenge at hand

Assume a global data structure on the heap and a single atomic pointer P to it. If (fast) readers access this completely unprotected, then a (slow) writer can create a completely new data structure and then change the pointer to the new structure with an atomic operation. Since writing is not time critical, one can easily use a mutex to ensure that there is only a single writer at any given time. The only problem is to decide, when it is safe to destruct the old value, because the writer cannot easily know that no reader is still accessing the old values. The challenge is aggravated by the fact that without thread synchronization it is unclear, when a reader actually sees the new pointer value, in particular on a multi-core machine with a complex system of caches.

If you want to see our solution directly, scroll down to “Source code links“. We first present a classical good approach and then try to improve on it. More info

Running V8 isolates in a multi-threaded ArangoDB database

00API, Architecture, C++, Documentation, nodejs

ArangoDB allows running user-defined JavaScript code in the database. This can be used for more complex, stored procedures-like database operations. Additionally, ArangoDB’s Foxx framework can be used to make any database functionality available via an HTTP REST API. It’s easy to build data-centric microservices with it, using the scripting functionality for tasks like access control, data validation, sanitation etc.

We often get asked how the scripting functionality is implemented under the hood. Additionally, several people have asked how ArangoDB’s JavaScript functionality relates to node.js.

This post tries to explain that in detail.

More info

Fulltext Index Enhancements

00API, Architecture

This post is about improvements for the fulltext index in ArangoDB 2.6. The improvements address the problem that non-string attributes were ignored when fulltext-indexing.

Effectively this prevented string values inside arrays or objects from being indexed. Though this behavior was documented, it was limited the usefulness of the fulltext index much. Several users requested the fulltext index to be able to index arrays and object attributes, too.

Finally this has been accomplished, so the fulltext index in 2.6 supports indexing arrays and objects!

Read on in Jan’s blog post about Fulltext Index Enhancements.

Agile development vs. schema enforcement – a paradox resolved

00Architecture

The fans of modern and agile software development usually propose to use schemaless database engines to allow for greater flexibility, in particular during the early rapid prototyping phase of IT projects. The more traditionally minded insist that having a strict schema that is enforced by the persistence layer throughout the lifetime of a project is necessary to ensure quality and security.
schema_enforcement
In this post I would like to explain briefly, why I believe that both groups are completely right and why this is not so paradoxical as it sounds at first glance. More info

Building Hypermedia APIs – a Design Approach using Statecharts

00API, Architecture, FoxxTags: , , ,

This is the second blog post on building hypermedia APIs with the focus on API design. In part 1 Lucas describes the concept of links in JSON.

Imagine we have an API where people can like books and other people can then see, who likes a certain book. We want this API to be highly connected: We don’t want to look up URLs in a documentation, we want to follow links as we know it from the world wide web. All we want to do as the author of the API is give our users a single URL from which they can then follow links to all other resources. This is similar to the way we would do this with a website. Leonard Richardson and Mike Amundsen refer to this as the billboard URL for this reason: If you put this URL on some billboard, people know everything to get started with your API. More info

Sign up for ArangoDB Newsletter

Enter your email and stay informed:


Subscribe to our Newsletter!

Sign up for ArangoDB Newsletter

Enter your email and stay informed:


Subscribe to our Newsletter!