This article describes Ctrip's SRE team's journey in adopting chaos engineering, outlining the motivations, roadmap, concrete experiments, platform maturity, and future automation goals to improve system resilience and operational reliability in a large‑scale microservice environment.
This article explains why graceful shutdown is essential for Spring Boot and Spring Cloud applications, outlines key precautions, shows how Spring Boot 2.3 adds built‑in support, and provides configuration steps, code examples, and container‑specific behaviors to ensure clean service termination.
This article presents a step‑by‑step, enterprise‑wide roadmap for constructing a cloud‑native system, covering the five dimensions of architecture, a detailed evolution diagram, three maturity stages, common pitfalls, and practical solutions ranging from service‑oriented redesign to micro‑service governance and data‑driven personalization.
This tutorial walks through a complete Golang implementation of a food‑recommendation API using Domain‑Driven Design (DDD), covering the four DDD layers, entity and repository definitions, persistence setup with Gorm, application services, HTTP interfaces, middleware, and how to run the service.
This article walks through a practical, step‑by‑step transformation from a monolithic application to a cloud‑native, micro‑service architecture, covering planning, domain‑driven design, continuous integration, service registration, API gateways, databases, caching, logging, configuration management, containerization, performance monitoring, service governance, GitOps, traffic shading, service mesh, stress testing, and multi‑datacenter deployment.
This tutorial walks through building a Spring Boot application that uses Alibaba's Dubbo framework, covering the RPC workflow, project structure, Maven dependencies, Spring Boot and XML configurations, service interface definition, provider and consumer implementations, and a RESTful endpoint for testing.
This article explains the fundamentals of distributed transactions, compares five major solutions—including XA two‑phase commit, TCC, Saga, message‑based approaches, and maximum‑effort notification—covers their architectures, advantages, drawbacks, and provides guidance on selecting the right model for micro‑service systems.
This article walks through a complete Go implementation of a food recommendation API using Domain-Driven Design, covering project setup, layer separation, entity and repository definitions, infrastructure configuration, application services, HTTP interfaces, authentication, and how to run the application.
This article demonstrates how to consolidate exception handling in a Spring Cloud microservice using @RestControllerAdvice, @Slf4j, and @ExceptionHandler, defines a unified error code enum, and provides test scenarios with sample code and API requests.
The article examines the ongoing relevance of Spring Cloud and Dubbo, explaining how they have become complementary rather than competing frameworks, and argues that both are likely to coexist long‑term thanks to integration efforts and strong community support.
Apache Dubbo 2.7.7, the high‑performance lightweight Java RPC framework, introduces major features such as Nacos authentication integration, LFU cache support, network interface selection, memory‑optimized Hessian2 instances, new load‑balancing strategies, plus numerous enhancements and bug fixes to improve reliability and performance.
This article examines service discovery patterns, comparing client‑side and server‑side approaches, explores consistency trade‑offs, health‑check mechanisms, subscription models, graceful up/down procedures, and high‑availability designs to help engineers choose the right solution for microservice architectures.
This article explains the background, challenges, and architectural design of Tencent Cloud Task (TCT), a distributed scheduling platform that offers precise real‑time task execution, modular microservice architecture, stateless scaling, rich trigger rules, comprehensive monitoring, and advanced workflow orchestration for large‑scale cloud environments.
This article analyzes a real e‑commerce incident to explain how RPC timeouts work in microservice architectures, why proper timeout and retry configurations are essential, and provides step‑by‑step guidelines for setting sensible timeout values while avoiding common pitfalls such as duplicate requests and retry storms.
Meituan’s Naming Service 2.0 replaces the ZooKeeper‑based 1.0 design with a four‑layer, AP‑oriented architecture that leverages a service‑mesh sidecar, sharded KV storage, and a control service layer, delivering eight‑fold throughput gains, sub‑second latency, zero‑downtime migration for most services, and new business capabilities such as traffic isolation, elastic scaling, and data‑driven SLA monitoring.
The 2020 cloud‑native research report analyzes how 613 enterprises across finance, manufacturing, energy, telecom and other sectors adopted containers, Kubernetes, micro‑services and DevOps during the pandemic, revealing adoption rates, budget impacts, challenges and strategic priorities for digital transformation.
Explore the fundamentals of Envoy, the lightweight L7 proxy for modern SOA architectures, through a detailed walkthrough of its architecture, configuration structure, filter chain, and key components such as xDS, listeners, clusters, and runtime settings, illustrated with diagrams and practical examples.
This article details Toutiao’s rapid growth and its large‑scale data pipeline, covering article crawling, user modeling, recommendation engines, storage solutions, push notifications, micro‑service architecture, and the underlying virtualization PaaS platform that powers its personalized news service.
The article explains how traditional Java web projects that bundle JSP, static assets, and business logic into a single WAR cause performance and scalability issues, and advocates separating front‑end static resources from back‑end services to achieve true decoupling, better fault tolerance, and easier horizontal scaling.
This article presents PICC Insurance's digital strategy that leverages a DevOps model to support micro‑service architecture migration, detailing the company's unique DevOps standardization, end‑to‑end processes, quality safeguards, deployment solutions, and efficiency analysis as shared at the GNSEC 2020 summit.
This article examines the CQRS (Command Query Responsibility Segregation) pattern, outlining its objectives, three major complexity traps—over‑isolated commands, event sourcing coupling, and excessive tooling—and offers practical mitigation strategies, including relaxed isolation, alternative projection techniques, and careful service decomposition.
This article provides a comprehensive overview of Kubernetes, explaining its core concepts, advantages, key features, typical use cases, and the new capabilities introduced in version 1.18, while also linking to related tutorials and practical deployment guides for building scalable, resilient cloud‑native applications.
This article explains the concept of cloud native, tracing its origins from the CNCF foundation and early container technologies, and details key components such as containers, Docker, Kubernetes, microservices, service mesh, immutable infrastructure, and declarative APIs, highlighting how they together enable rapid iteration, automated deployment, and scalable, resilient applications.
This article explains what a service mesh is, outlines the operational challenges of microservice architectures, and details how Istio’s data‑plane and control‑plane components provide traffic control, security, and observability to simplify cloud‑native deployments.
This article traces the history of backend architecture from monolithic systems through distributed designs, Docker containers, microservices, Spring Cloud, and Kubernetes, culminating in a detailed overview of cloud‑native Service Mesh technologies such as Istio and their key capabilities.
This article explains the business scenarios that demand massive, precise, and reliable scheduled tasks, reviews the shortcomings of existing open‑source schedulers, and details the design, architecture, and key features of Tencent Cloud’s distributed task scheduling system TCT, highlighting its modular, stateless, and fully featured approach.
This tutorial walks through building a Spring Cloud micro‑service platform by preparing the development environment, adding backend menus, auto‑generating Vue pages, configuring Spring Cloud Gateway routing, registering services with Nacos, and solving CORS issues to enable seamless frontend‑backend interaction.
This article explains the fundamentals of microservice architecture, contrasts it with traditional three‑layer monolithic designs, outlines its characteristics, benefits, drawbacks, and implementation challenges, and compares it to SOA, providing a comprehensive overview for developers and architects.
This article introduces the limitations of traditional local and distributed transactions for microservices, explains the BASE theory, and details four major patterns—reliable event notification, max‑effort notification, business compensation, and TCC—to achieve eventual consistency in microservice architectures.
This article provides a comprehensive guide to Spring Cloud Gateway, covering its role as an API gateway, core features, underlying principles, step‑by‑step module creation, Maven dependency configuration, application annotations, YAML routing examples, and a runnable demo for building cloud‑native microservice architectures.
This tutorial demonstrates how to replace static Spring Boot property files with Spring Cloud Alibaba Nacos for real‑time, centralized configuration management across multiple microservices, covering dependency integration, bootstrap setup, namespace and group usage, multi‑config sets, and dynamic refresh with code examples.
This article recounts the four‑year journey of Ele.me's order platform, detailing the transition from a monolithic Zeus system to service‑oriented components, the challenges of sharding, message broadcasting, performance testing, Redis optimization, and the cultural practices that shaped a resilient backend architecture.
This article explains how to abstract business functions into middle‑platform models, outlines eight essential design principles for services, and describes key distributed mechanisms such as service registration, elastic scaling, rate limiting, gray‑release, message queues, and transaction handling to build robust, scalable backend systems.
This article demonstrates how to integrate Spring Cloud OpenFeign into a Java microservice project, covering dependency setup, Feign client definition, annotation usage, enabling remote calls, parameter passing, and testing with Postman, providing a complete step‑by‑step guide for distributed service communication.
This guide walks through setting up Nacos as a service discovery platform for a Spring Cloud microservice architecture, covering dependency inclusion, server installation, configuration of each service’s address, enabling discovery annotations, naming services, and accessing the Nacos dashboard, with full code snippets and troubleshooting tips.
This article introduces Spring Cloud Alibaba as a one‑stop microservice solution, compares it with traditional Spring Cloud, outlines its advantages, presents a detailed component selection for the PassJava project, and provides version compatibility, Maven dependency snippets, and final technology choices.
This tutorial walks through setting up the development environment, configuring generator files, generating channel microservice code, updating Maven dependencies and application settings, testing service endpoints, and publishing the complete PassJava Spring Cloud project with code snippets and deployment instructions.
This article uses Taobao as a case study to illustrate the step‑by‑step evolution of server‑side architecture from a single‑machine setup to a cloud‑native, highly available system capable of handling tens of millions of concurrent requests, highlighting the technologies and design principles involved at each stage.
This tutorial walks through downloading the Renren‑Fast open‑source admin framework, integrating it into the PassJava project, configuring MySQL and Docker, adjusting application settings, launching the backend service, building the Vue front‑end, and performing end‑to‑end login verification, providing a complete step‑by‑step guide for developers.
This article outlines the critical backend components required for building robust Java services, covering API gateways, MVC/IOC/ORM frameworks, caching, databases, search engines, message queues, file storage, unified authentication, configuration, service governance, scheduling, logging, data pipelines, and monitoring strategies.
This article explains what microservices are, outlines their advantages and design considerations, and provides a practical Node.js/Express example that demonstrates a simple ticket‑query microservice along with deployment tips and best‑practice guidance.
This article explains how Dubbo's tag router feature can isolate parallel test environments by assigning tags to providers and consumers, outlines configuration methods, compares it with version/group routing, discusses known attachment bugs, and presents a practical SPI‑filter solution for reliable tag propagation.
This tutorial walks through creating the five microservice databases for the PassJava platform using PowerDesigner, detailing each service’s schema, showing screenshots, and providing the GitHub repository where the SQL files can be accessed.
This tutorial walks through creating a lightweight RPC system, illustrating how an order service can call a product service via dynamic proxies, socket communication, serialization, and service registration, while showing Maven module setup, API design, and concrete code examples for each component.
Even with thorough testing environments, bugs often surface in production due to missing continuous monitoring, rushed last‑minute releases, inadequate compatibility checks, data inconsistencies, outdated QA practices, lack of shared goals, and microservice deployment challenges, highlighting the need for robust, production‑mirroring QA processes.
This tutorial walks through creating an empty GitHub repository, importing it, adding a content service and additional microservices, configuring the Maven parent pom, setting up a root Maven configuration and .gitignore, and finally committing the code for the PassJava Java microservice suite.
This article introduces Spring Cloud, explains its key components such as service discovery, configuration management, messaging, security, and tracing, shows how they integrate to form a complete micro‑service architecture, and compares Spring Cloud with Dubbo, highlighting their different scopes and communication models.
This article introduces Spring Cloud as a Spring Boot‑based microservice framework, explains the fundamentals of service architecture through a company‑division analogy, details the essential components such as service registry, load‑balanced calls, circuit breakers, gateways, configuration centers, message bus and tracing, and provides concrete code examples for a Eureka server, a simple service, and a client using Ribbon and Feign.
Sentinel 1.7.2 introduces a Logger SPI extension, Zuul 2.x gateway flow‑control, SOFARPC adaptation, and numerous other enhancements, expanding its microservice, API gateway, and service‑mesh support across Java, C++, and Go ecosystems.
This article examines whether microservice architecture suits large organizations by outlining its cultural, technical, and operational impacts, the reasons to decompose monolithic systems, key considerations for architects, and practical guidance on avoiding deployment coupling while managing complexity.
This article compiles sixteen practical Spring Boot best‑practice recommendations—ranging from custom BOM management and auto‑configuration to test slicing and externalized configuration—drawn from years of professional experience and expert insights, to help developers build cleaner, more maintainable micro‑service applications.
The article examines how Google, eBay, Twitter and Amazon evolved their massive systems into multi‑language microservice ecosystems, highlighting the organic growth of services, incentive‑driven design, standards emergence, service ownership, operational practices, and anti‑patterns for building and scaling cloud‑native architectures.
The Moonlight Box (JCASE) platform records production traffic and replays it in test environments to achieve fully automated, high‑coverage regression testing, reducing test data preparation effort and supporting online, offline, stress, and pre‑heat scenarios across large‑scale service architectures.
The article details FAW Group’s multi‑year cloud‑native digital transformation, describing how the automaker built a technology middle‑platform, adopted Tencent’s TSF microservice solution, containerized over half of its new projects with Kubernetes, and leveraged a self‑built DevOps toolchain to dramatically boost IT productivity and support emerging automotive services.
This article walks through the step‑by‑step evolution of a Java‑based e‑commerce platform, illustrating how a single‑machine deployment can be transformed into a scalable architecture using techniques such as server‑database separation, clustering, load‑balancing algorithms, read‑write splitting, caching, sharding, micro‑services and message queues.
This article explains the essence, purpose, and value of service‑oriented architecture, compares it with layered, microservice, and distributed architectures, defines services and their components, outlines design principles, granularity decisions, service roles, and provides a practical roadmap for successful service‑centric system design.
This article explains what Istio is, outlines the major updates in version 1.5—including the unified istiod control plane, WebAssembly extensibility, simplified installation, and improved observability—describes core control‑plane components, and provides step‑by‑step instructions for preparing a Kubernetes cluster and installing Istio.
The article explains why Spring Cloud is better suited than traditional Nginx or Dubbo solutions for building scalable, DevOps‑friendly microservices, detailing its REST‑based communication, comprehensive service‑governance components, and ongoing community support.
This article examines the origins, principles, advantages, and drawbacks of microservice architecture, outlines when it should be adopted, describes its evolution stages, presents design patterns, service‑splitting strategies, and reviews popular frameworks and tools to help teams decide if microservices fit their system complexity and organizational capabilities.
This article examines Taobao’s pivotal architectural transformation from a monolithic codebase to a large‑scale distributed system, detailing the challenges of personnel, business complexity, Oracle bottlenecks, and hardware limits, and describing the comprehensive solutions involving code and interface vertical splitting, custom middleware, database sharding, and new infrastructure.
The article details the design principles, modular architecture, and engineering optimizations of a backend algorithm platform that uses APIs, micro‑services, and asynchronous processing to enable fast, reliable, and scalable online algorithm services, including recall, ranking, metadata, feature reporting, and A/B testing.
The case study details how a major state‑owned real estate company, with nearly 40 years of experience, built a three‑stage cloud‑native middle‑platform strategy—business, data, and technology platforms—using microservices, containers, and Tencent Cloud TSF to achieve integrated operations, data‑driven decision making, and agile infrastructure across its nationwide projects.
This article introduces Istio as an open platform for connecting, securing, controlling, and observing services, explains the fundamentals of service mesh, outlines Istio’s architecture and components, and provides practical steps for adopting Istio in a Kubernetes environment.
This article explains the fundamental concepts of software architecture, distinguishes systems, subsystems, modules, components, and frameworks, outlines various architecture layers and classifications, describes architecture levels, tracks the evolution from monolithic to micro‑services, and discusses how to evaluate and avoid common architectural pitfalls.
This article explains the classic definition of patterns, introduces architecture patterns, and reviews five common software architecture styles—layered, microservices, microkernel, event‑driven, and cloud‑native—detailing their principles, advantages, drawbacks, and typical use cases, helping developers choose the right structure for complex systems.
This article outlines how to create solid software architectures by presenting a process for forming design principles, detailing fifteen universal architecture guidelines, and explaining service‑splitting and key design rules that together help build scalable, maintainable, and resilient systems.
This comprehensive guide covers essential Spring Boot concepts—including its definition, advantages, auto‑configuration, DevTools hot‑reloading, starter projects, embedded servers, Actuator monitoring, YAML configuration, MyBatis integration, WAR packaging, and common pitfalls—providing concise answers to 40+ interview‑style questions for backend developers.
This article explains the hierarchical architecture levels, contrasts strategic and tactical design, and walks through the evolution from monolithic applications to distributed services and micro‑services, highlighting benefits, drawbacks, and key metrics for evaluating a sound system architecture.
This article details a lightweight, low‑intrusion transactional message solution for microservices, covering design principles, database schema, Spring‑based implementation with RabbitMQ integration, compensation mechanisms, scheduling, and testing, illustrating how to achieve reliable asynchronous messaging while maintaining eventual consistency.
This article presents a comprehensive, English‑language overview of 27 Alibaba open‑source projects—including Spring Cloud Alibaba, Ant Design, Druid, fastjson, Dubbo, JStorm, Sentinel, Nacos, and many others—detailing their core purpose, key features, and GitHub URLs for developers building distributed, cloud‑native Java applications.
The article explores various microservice decomposition approaches—vertical vs. horizontal, business‑driven, stability‑based, reliability‑focused, and performance‑oriented—highlighting trade‑offs, team size considerations, and practical guidelines for achieving scalable, maintainable service architectures.
The article summarizes Xu Wenqi's 2019 Alibaba Cloud Summit talk on Ant Financial's distributed architecture, covering the shift from monolithic to microservices, modular development, load‑balancing, database sharding, the distributed TA system, task scheduling, gray‑release, full‑link stress testing, and OceanBase high‑availability solutions.
This article explains the concept of object serialization, compares generic formats like JSON/XML with binary approaches, discusses optimization principles, key performance metrics, and reviews major serialization frameworks such as Protobuf, Thrift, Hessian, Kryo, and Avro, while also covering TLV encoding, varint algorithms, and practical pitfalls.
This article provides a comprehensive, step‑by‑step tutorial for building, containerizing, and deploying a Spring Cloud microservice project on a Kubernetes cluster, covering environment preparation, Maven builds, Docker image creation, YAML orchestration, and verification of the frontend portal.
This article provides a comprehensive introduction to Spring Cloud, explaining how it builds on Spring Boot to simplify distributed system development with components for service discovery, configuration management, messaging, monitoring, security, and compares its approach to Dubbo's RPC framework.
This article describes how Ctrip's vacation product system was modernized by migrating from a legacy .NET/SQL Server architecture to a MySQL‑based, front‑end/back‑end separated platform, detailing the challenges, step‑by‑step storage reconstruction, replication elimination, data model splitting, messaging replacement, and overall architectural improvements.
This article analyzes the interference and latency problems caused by traditional service‑level Mock tools in a microservice environment and proposes a four‑component solution—servlet agent, local Mock proxy, Mock server, and configuration client—to isolate Mock functionality, eliminate cross‑application impact, and improve test stability.
This article introduces mall‑swarm, a Spring Cloud‑based microservice e‑commerce platform, outlines its architecture, backend technology stack, project structure, and provides a detailed learning roadmap with tutorials, deployment guides, and integration tips for both backend and frontend developers.
This article provides a comprehensive, illustrated introduction to Kubernetes, covering its definition, key advantages, practical scenarios such as logging, DevOps, and microservices, core features, architecture, and essential master and node components for beginners.
Segment’s engineering team recounts their evolution from a simple monolith to a sprawling micro‑service ecosystem and back again, detailing queue bottlenecks, repo fragmentation, shared‑library chaos, and how consolidating everything into a single codebase restored performance, scalability, and developer productivity.
Youzan’s full‑link tracing system combines a multi‑language SDK, Java Agent dynamic attachment, transparent upgrades, asynchronous context propagation, and a Spark‑based data pipeline that indexes traces in Elasticsearch and stores them in HBase, enabling real‑time diagnostics, log correlation, and future container‑level tracing expansion.
The article explains why achieving data consistency across multiple microservices is challenging, reviews the limitations of two‑phase commit, and presents practical techniques such as the Saga pattern, reconciliation, event logs, orchestration vs. choreography, and change‑data‑capture to keep distributed systems eventually consistent.
This article shares practical thinking frameworks such as OGSM and 5W1H, explains iterative internet mindset, demonstrates their application to software architecture design, defines architecture concepts, outlines common architectural goals, evaluation metrics like SLA, and presents a toolbox of techniques ranging from single‑machine performance to micro‑service high‑availability patterns.
This article examines microservice decomposition by presenting three expert‑derived splitting approaches—vertical/horizontal, business‑driven cost‑aware, and responsibility‑based—and discusses how factors such as team size, maintenance cost, scalability, stability, reliability and performance influence the optimal service boundaries.
This article traces the evolution of Service Mesh from early microservice communication challenges through multiple generations of architectures, explains its role as a transparent infrastructure layer for service-to-service traffic, and discusses its benefits, language-agnostic nature, and current performance and operational trade‑offs.
This article presents a comprehensive collection of Alibaba’s open‑source projects—including Spring Cloud Alibaba, Ant Design, Druid, Dubbo, JStorm, Sentinel, and many others—detailing their core features and providing repository links to help developers build scalable, high‑performance backend and cloud‑native applications.
This article chronicles the evolution of the BeLiao kindergarten parent platform, detailing its three‑stage architectural transformation—from an initial simple LNMP monolith, through a Java‑based distributed V2.0 redesign, to a full microservice V3.0 system—highlighting the challenges, decisions, and technologies that enabled rapid growth and high availability.
This article reflects on the redesign of a high‑traffic transaction system, discussing the decision‑making process, programming paradigms, SOLID principles, domain‑driven design, component decomposition, and the evolution from simple state machines to flexible, maintainable backend architectures.
This article walks through the step‑by‑step evolution of a high‑traffic e‑commerce backend—from a single‑machine setup to distributed caching, load‑balancing, database sharding, microservices, and finally cloud‑native deployment—highlighting the key technologies and design principles at each stage.
The article examines the architectural differences between microservices and Service‑Oriented Architecture, covering component sharing, service orchestration versus choreography, middleware roles, API layers, and remote service access, highlighting how each style impacts coupling, performance, and deployment complexity.
Transitioning from a monolithic architecture to microservices can be fraught with hidden complexities, but by following twelve proven best‑practice guidelines—such as independent data stores, dedicated teams, automated deployments, RESTful APIs, cultural shifts, and incremental migration steps—organizations can avoid costly pitfalls and achieve a smoother, scalable transformation.
This article explains cloud‑native fundamentals, the evolving role of DevOps in the cloud‑native era, and presents a detailed GitOps secure release model with architecture diagrams, branch‑to‑environment mappings, Jenkins pipelines, and supporting tools for efficient, safe application delivery.
This article examines the long‑standing technical and operational challenges of Alibaba's DataWorks platform—such as heavy legacy baggage, complex environments, tight coupling, and frequent releases—and explains how adopting a cloud‑native microservice architecture, service mesh, and DevOps practices can transform the platform into a flexible, scalable, and future‑proof data development ecosystem.
This article introduces Kong, a cloud‑native API gateway, outlines its key features such as high performance, plugin architecture, and traffic control, explains why it solves common microservice challenges, and provides detailed deployment, clustering, plugin development, and troubleshooting guidance with practical code examples.
This article introduces Kong, a cloud‑native API gateway, outlines its key features such as high performance, plugin architecture, and built‑in security, explains why it solves common microservice challenges like unified entry, scalability and CI/CD, and provides step‑by‑step guidance for deployment, clustering, custom plugin development, and troubleshooting.
This article explains how to construct a full‑stack microservice system using Spring Boot, Spring Cloud, Docker, and Netflix OSS tools, covering functional services, infrastructure components such as configuration, authentication, API gateway, service discovery, load balancing, circuit breaking, monitoring, logging, security, and continuous delivery pipelines.
The 2019 cloud‑native survey of over 400 enterprises across finance, energy, manufacturing and automotive sectors showed that 70.7% planned container, DevOps and micro‑service initiatives, 70% saw modest IT budget growth, and 11.4% had piloted benchmark cloud‑native practices, prompting a 2020 follow‑up study to assess current adoption and challenges.
The article introduces the MockRpc platform, which uses Spring‑based extensions and a mock server to fully decouple front‑end services from middle‑end services in a micro‑service architecture, enabling zero‑intrusion testing, configurable mock data, and improved development efficiency for JD Retail.
This article explains the technical differences between RPC and HTTP services, covering the OSI model, RPC architecture, synchronous versus asynchronous calls, and compares popular frameworks like gRPC, Thrift, and Dubbo to help developers choose the right approach for large‑scale systems.
The article explains how to use feature flags in a three‑tier microservice architecture, describing the need for both high‑level end‑to‑end tests and low‑level unit tests within CI/CD pipelines to ensure correct behavior when flags are on or off, while avoiding excessive test combinatorial explosion.
