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Figure 4-1 XGVela Technical Architecture

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4.2.1PaaS Management

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XGVela, as PaaS platform for telecom scenarios, its functional framework is basically consistent with most of the commercial PaaS platforms. As shown in figure 4-1, PaaS platform contains two parts: PaaS Management and PaaS Service.

PaaS Management is responsible for managing PaaS services, which ensures PaaS platform to provide PaaS services to customers. PaaS Management complete the onboarding, orchestration, monitoring and maintenance of PaaS services in the background, make sure that applications and developer/operating stuff can select and use PaaS services, and help to manage operation status of PaaS services. Figure 4-1 shows the most basic functions that PaaS Management should have, which are service catalog, service lifecycle management, Image repository and package repository, API gateway, service & resource monitoring, service & resource log & event. For detailed description and requirements of each function, please refer to chapter 4.2.1

PaaS Service represents the capabilities/functions required by applications, developer and operation stuff, which achieves the core value of PaaS platform. It is managed and orchestrated by PaaS Management. The three types of PaaS capabilities concluded in chapter 2.2 belong to PaaS Service which are also separated as three categories (General PaaS, General PaaS + Adaptation Layer, Telco PaaS) based on using scenarios. The number of PaaS services keeps increasing with the diverse of use cases. And PaaS services keep upgrading based on customers’ needs. Currently, some functions/services have been summarized for different categories. For detailed description and requirements of each service, please refer to chapter 4.2.2 and 4.2.3.

If referring to existing commercial PaaS platform, PaaS Management and General PaaS usually together constitute the PaaS platform of IT industry. Therefore, blue block is used to represent these two together. Corresponding to chapter 3.2, what XGVela is doing is to pick required General PaaS capabilities (blue block) by telco use cases, then find the enhancement point of these General PaaS capabilities as adaptation layer, and explore Telco PaaS capabilities.

4.2 XGVela PaaS Functional Requirements

4.2.1PaaS Management

PaaS Management is responsible for the management of PaaS services. It is required to include at lease the following capabilities:

Service Catalog

Service Catalog is a directory of services, which lists all PaaS services provided by PaaS platform to customers. Specific requirements of service catalog includes:

• It is required that Service Catalog support adding new PaaS service to itself, and deleting, modifying, and querying existing PaaS services. The added PaaS services can exist in multiple forms, which can be local operator or helm package, as well as PaaS services on public cloud that adapted remotely through interfaces.
• It is required that Service Catalog support users/applications/external systems to order PaaS services on demand, and trigger the instantiation and configuration of selected PaaS services.
• It is recommended to achieve Service Catalog with well-designed UI.

Service Lifecycle Management

Service Lifecycle Management (Service LCM) is responsible for managing the lifecycle of PaaS services. Specific requirements include:

• It is required that Service LCM to select images and packages from Image & Package Repository based on user’s selection in Service Catalog, and complete instantiation of PaaS services, which are packaged as Operator or Helm Chart. It also requires Service LCM to start, stop, upgrade, delete PaaS services.
• Service LCM uses Kubernetes interface for resource application and orchestration of PaaS services.
• It is required that Service LCM manages scaling in/out of PaaS service instance based on monitoring KPIs and scaling policy set by customers.
• It is recommended to implement UI for service LCM.
• It is required that Service LCM supports access control, which provide unified user management and authentication mechanism, and support RBAC. Users can obtain management permission for PaaS services through role settings.

Image and Package Repository

Image & Package Repository is responsible for the storage and management of PaaS service images and deployment packages. The images and packages can be stored locally in PaaS platform repository, as well was remotely in cloud repositories (GitHub, docker hub, etc.). When user selects PaaS services in Service Catalog and triggers service instantiation process, Service LCM will ask Image & Package Repository for images and packages.

API Gateway

API Gateway is an PaaS service as well as an important PaaS Management function. When using as PaaS Management function, API Gateway is responsible for exposing the service API of PaaS services, and routing user traffic to target processing unit. Specific requirements include:

• It is required that API Gateway to support identity authentication and authorization of API calls, verifying the legitimacy and authority of API calling entity (user, other software, etc.), releasing secure access control, avoiding security threats on PaaS service.
• It is required that API Gateway to support forwarding user request to correct processing unit. The forwarding process supports load balancing, and traffic control actions based on pre-defined traffic management policies, which may include health check, rate limiting, time out & retry, circuit breaker, etc.
• It is recommended that API Gateway to support protocol processing, including HTTP, HTTP2, GRPC, web socket, etc.
• It is required that API Gateway support managing the service API of PaaS services, including API definition (path, parameters, etc.), APU publishing/ suspending/ online/ offline/ withdraw/ etc. This feature is mainly used by developers/operators to provide API-type PaaS services for external usage.
• It is required to support monitoring API usage and API data analysis, which cover performance, usage, alarm, log, etc.

Service & Resource Monitoring

Service & Resource Monitoring is responsible for monitoring PaaS service instances and resources the service used, collecting and displaying monitoring data through well-designed dashboard, and alarm setting. The monitoring KPI and data are determined by PaaS services themselves. This function assists PaaS platform manager and PaaS service consumer to track the status of PaaS services and resources.

Monitoring contents usually include:

• Service-level: running status and performance of PaaS service instance.
• Resource-level: running status and performance of resource used by PaaS Service.

Service & Resource Log & Event

Service & Resource Log & Event is responsible for the log & event management of PaaS services and resource the services used. Log management includes log collection, log storage, log index, etc. Event management records all the changes of PaaS services and related resources. Event usually carries info of event content (what), event object (who), event time (how), event type, event status, etc. This function helps PaaS platform managers and PaaS service users efficiently find, locate, and solve problems.

To conclude, almost every PaaS platform would acquire the above management functions either in a manual way or in an automatic way. Mature representatives include open source implementation - OpenShift, public cloud - AWS, Azure, Alibaba cloud, Tencent cloud, and many other commercial products.

4.2.2 General PaaS Requirements

As described in Chapter 3.1, General PaaS represents all PaaS Services that have no industry differences. It can serve a variety of applications that have requirements on common PaaS services. It can also be used as the basis for other industrial PaaS services/platforms.

4.2.2.1 General Requirements on General PaaS

Before detailly analyzing the functions that General PaaS should provide, let’s take a look at the general requirements for all General PaaS services:

• General PaaS shall complete service lifecycle management through PaaS Management. There are usually two ways for users to use a PaaS service: call API of API-type PaaS service and create an instance-type PaaS service. API-type PaaS services (like AI service-facial recognition, image processing, etc.) are managed by API Gateway of PaaS Management. Instance-type PaaS Services (like DB/ LB, etc.) are managed by Service Lifecycle Management.
• General PaaS services shall be packaged as Operator or Helm Chart. Related image and package can be stored in local Image & Package Repository, as well as in remote repository while pre-configuring automatic access to the remote repo.
• All General PaaS service shall support to general monitoring data, logs, events, alarms, etc., and report to Service & Resource Monitoring function and Service & Resource Log & Event function in PaaS Management.
• General PaaS services shall support to be deployed on any Kubernetes cased CaaS (Container as a Service) layer.
• General PaaS shall support custom configuration. The configuration parameters are designed by developers, the configuration contents are provided by users according to application requirements following certain rules.
• It is recommended to select General PaaS software from commonly used CNCF projects.

4.2.2.2 Functional Requirements on General PaaS

The number and type of General PaaS services will keep increasing as more and more use cases and user requirements have been explored. In June 2020, XGVela and Anuket made a joint survey on commonly used General PaaS functions and software. Here we’ll provide requirements on mostly used General PaaS functions based on the statistical results.

Data Store/Databases

General PaaS shall provide mainstream relational databases and non-relational databases. The database shall support user management, configuration management and monitoring of itself. Detailed requirements are listed below.

• Data Store/ Database type & software:

• It is recommended database achieve the following monitoring KPIs: number of queries, response time, number of errors, throughput, number of query concurrency, number of tables.
• General PaaS shall support backup of data storage and database manually and automatically. The backup needs to support be downloaded and be used for data recovery.

Streaming & Messaging

General PaaS shall provide Streaming & Messaging functions and software, which can provide services through API or instantiation. Detailed requirements are listed below.

• Commonly used Streaming & Messaging software includes but not limited to AMQP， Apache Kafka, Apache Spark, Rabbit MQ, NATS.
• Streaming & Messaging functions provided by General PaaS should support message caching, transmission, replication, distribution, encryption and compression.
• It is recommended that Streaming & Messaging software achieve the following KPIs: total number of messages, message publish rate, message delivery rate, etc.

Service Proxy & Load Balancing

General PaaS shall provide Service Proxy & Load Balancing functions and software. The service can be provided through container instance or service APIs. The Service Proxy & Load Balancing functions should support customized configuration management, monitoring and operation. This function can be used to manage east-west traffic within a K8S cluster, as well as north-south traffic across multiple K8S clusters. Detailed requirements are listed below.

• This functions should dynamically update the status of service backend, including updating service IP address, traffic management like flow forwarding/ flow control/ ACL, etc.
• Commonly used Service Proxy & Load Balancing software includes but not limited to Istio, Contour, MetalLB, NGINX, Envoy, Linkerd.
• It is recommended that this function support statistic and analysis of flows, including number of messages (request/response/error/etc.). the number of sent/received data packets, delay, etc.

4.2.3 Telco PaaS Requirements

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