George Cristea

I implemented a directed acyclic graph used in a production system for entitlements where the read/write ratio is higher than 1,000. 此外，最常见的操作是获取节点的祖先. I extended the data structures from "using rational numbers to key nested sets" to implement a directed acyclic graph. 本文描述的数据结构是多路树. The node values in a sub-tree have an encoding in the interval defined by sub-tree root value and its right sibling node.

Work Done:
•引入根节点来处理原始论文未涵盖的情况(例如.g.，当某个节点在系统中不存在时).
• Transformed the data structure to allow representation of a directed acyclic graph and to detect and prevent cycles from being introduced. The code uses several multi-way trees to represent multiple paths from the root node to leaf nodes and each sub-tree is stored as a MongoDB document.
•为了确保数据的一致性，我使用Redis锁来更新文档. 使用Redis的原因与MongoDB的并发模型有关.
•使用连分式编码, I was able to ensure that read operations are executed in constant time in terms of the number of MongoDB queries.

我设计并实现了一个支持多个云提供商的云管理系统, both public and private. The private cloud was based on OpenStack while the public cloud providers were AWS, GCP, and Azure. 该系统提供审计云帐户的功能, 提供新的云帐户, 并与企业财务系统相结合.

It was implemented using AWS Simple Workflow Service and had several workflows for each provider. 后端是使用Node实现的.js and PostgreSQL.

Cassandra NoSQL存储系统试图使用一组硬编码的密码. However in situations when not all ciphers are present/installed on the host the server was failing to create SSL sockets so I created a fix for this.

I implemented a backup manager for a Cassandra cluster that comprised of approximately 20 nodes. The backup manager was using a distributed lock to restrict the number of nodes that were performing backups to only one at a time.

The distributed lock was implemented in Cassandra using a keyspace where the node performing a backup would write its identity. The value stored in the keyspace had a higher expiration period to ensure that the backup progresses in the presence of a node failure.

我实现了一个Erlang端口来与Berkeley DB High Availability C库进行接口. Berkeley DB HA提供从主节点到从节点的完整数据复制.

The Erlang port driver was running the same process as the Erlang VM and it kept track which node is was the master. All the reads were served from the local Berkeley DB storage while the write operations were forwarded to the master using Erlang's native remote procedure calls.

我设计并实现了一个计算订单总数的引擎, taxes, discounts, and shipping charges. 库的c++代码是由编译器根据字段依赖声明生成的. 编译器从输入中提取语义信息.g.，显示的价格应包括欧盟国家的税收).