With the rapid growth of cloud computing, efficient management of multi-tenant databases has become a vital challenge for cloud service providers. It is particularly important for Alibaba, which hosts a distributed multi-tenant database supporting one of the world's largest e-commerce platforms. It serves tens of millions of sellers as tenants, and supports transactions from hundreds of millions of buyers. The inherent imbalance of shopping preferences from the buyers essentially generates a drastically skewed workload on the database, which could create unpredictable hotspots and consequently large throughput decline and latency increase. In this paper, we present the architecture and implementation of ESDB (ElasticSearch Database), a cloud-native document-oriented database which has been running on Alibaba Cloud for 5 years as the main transaction database behind Alibaba's e-commerce platform. ESDB provides strong full-text search and retrieval capability, and proposes dynamic secondary hashing as the solution for processing extremely skewed workloads. We evaluate ESDB with both simulated workloads and real-world workloads, and demonstrate that ESDB significantly enhances write throughput and reduces the completion time of writes without sacrificing query throughput.

Cloud backup is becoming the preferred way for users to support disaster recovery. In addition to its convenience, users are deeply concerned about reducing storage costs in the face of large-scale backup data. Data deduplication is an effective method for backup storage. However, current deduplicate methods lack the utilization of cloud resources to provide scalable backup service for cloud backup users, and cannot meet the biased preference for different backup versions. For new backup versions, users want higher deduplicate and restore speed to reduce the waiting time. Conversely, reducing storage costs is more necessary for old backup versions.In this paper, we present SLIMSTORE, with a cloud-based deduplication architecture that disassembles the system into a storage layer and a computing layer to support elastic utilization of cloud resources. We propose two types of processing nodes with different design focuses to meet the needs of cloud-based backup. The L-node exploits locality and similarity, and adopts a history-aware strategy to provide fast online deduplication service. L-node also optimizes online restoration to realize high restore efficiency. Meanwhile, the G-node provides exact deduplication offline for the old versions, and helps the restore performance of the new versions by optimizing their physical storage. We compare SLIMSTORE with some state-of-art deduplicate and restore methods. Experimental results show that SLIMSTORE can achieve fast deduplication, efficient restoration, and effective space reduction. Furthermore, SLIMSTORE attains scalable deduplication and restoration.

With the growing market of cloud databases, careful detection and elimination of slow queries are of great importance to service stability. Previous studies focus on optimizing the slow queries that result from internal reasons (e.g., poorly-written SQLs). In this work, we discover a different set of slow queries which might be more hazardous to database users than other slow queries. We name such queries Intermittent Slow Queries (iSQs), because they usually result from intermittent performance issues that are external (e.g., at database or machine levels). Diagnosing root causes of iSQs is a tough but very valuable task. This paper presents iSQUAD, Intermittent Slow QUery Anomaly Diagnoser, a framework that can diagnose the root causes of iSQs with a loose requirement for human intervention. Due to the complexity of this issue, a machine learning approach comes to light naturally to draw the interconnection between iSQs and root causes, but it faces challenges in terms of versatility, labeling overhead and interpretability. To tackle these challenges, we design four components, i.e., Anomaly Extraction, Dependency Cleansing, Type-Oriented Pattern Integration Clustering (TOPIC) and Bayesian Case Model. iSQUAD consists of an offline clustering & explanation stage and an online root cause diagnosis & update stage. DBAs need to label each iSQ cluster only once at the offline stage unless a new type of iSQs emerges at the online stage. Our evaluations on real-world datasets from Alibaba OLTP Database show that iSQUAD achieves an iSQ root cause diagnosis average F1-score of 80.4%, and outperforms existing diagnostic tools in terms of accuracy and efficiency.