ACP-Cloud1 Questions and Answers

Alibaba Cloud OSS is designed for scalable and secure object storage, allowing users to upload and download files through multiple interfaces, including the web console and APIs, offering flexibility and ease of use for developers and administrators.

=================

For optimal use of SLB with Auto Scaling, enabling Health Check is essential to determine which instances are healthy and ready to handle traffic. SLB doesn’t require all backend servers to have the same OS, be in the same scaling group, or have identical configurations, as it can manage heterogeneous server setups within the same load-balancing group.

=================

Alibaba Cloud ECS Open API supports both HTTP GET and POST requests. While GET requests are common, POST requests are often used for secure data transfer and handling complex request parameters. Therefore, you are not limited to using only GET requests when interacting with the ECS API.

Alibaba Cloud OSS does not charge for data ingress, meaning there are no traffic charges for uploading files to OSS, whether through the management console or Open API. However, traffic charges may apply for data egress, i.e., downloading files from OSS.

Alibaba Cloud CDN requires a domain name to function, as it uses DNS resolution to direct requests to the nearest edge nodes. CDN cannot directly accelerate an IP address without a domain name, so the statement is false.

 When the scheduled task is activated once, 4 ECS instances will be added in the scaling group. This is because the scaling rule “Add 6 ECS instances” will increase the number of instances in the scaling group to 9, which exceeds the maximum number of instances (7) that is set for the scaling group. Therefore, Auto Scaling will only add 4 ECS instances to reach the maximum number of instances. The remaining 2 ECS instances will not be added to avoid exceeding the quota. 

CloudMonitor allows users to create custom monitoring metrics and report data, which can then be analyzed and used for alerts. Customized monitoring is flexible, with no set limits on the number of metrics, and users can report data from Alibaba Cloud servers or other devices.

=================

 You can change the private IP address of an ECS instance after it is created, but you need to stop the instance first. The private IP address must be within the CIDR block of the VPC and the VSwitch that the instance belongs to. You can modify the private IP address of an instance by using the console or the API. References: 3, ACP Cloud Computing Certification - Alibaba Cloud Academy

After stopping an Alibaba Cloud Elastic Compute Service (ECS) instance, you will still be charged for some resources related to that ECS instance, such as disks, snapshots, and public IP addresses, until you release them. The charging policy depends on the billing method and network type of the ECS instance. For pay-as-you-go instances, you can choose whether to enable the No fees for stopped instances feature, which allows you to stop paying for vCPUs and memory when the instance is stopped. However, this feature is only available for VPC-connected instances in some regions1. For subscription instances, you will be charged for the entire subscription period regardless of whether the instance is running or stopped2. References:

1: Billing FAQ - Elastic Compute Service - Alibaba Cloud Documentation Center1

2: Billing overview - Elastic Compute Service - Alibaba Cloud Documentation Center2

 To execute a task at a specific time such as removing 1 ECS instance every night at 00:00, you need to perform two operations: create a scaling rule and create a scheduled task. A scaling rule is a set of instructions that defines how Auto Scaling scales computing resources in response to changes in business load. A scheduled task is a type of scaling task that can execute a specified scaling rule at a specified time. By creating a scaling rule that removes 1 ECS instance from the scaling group, and creating a scheduled task that executes this scaling rule every night at 00:00, you can achieve the desired result. You do not need to create a new scaling group, because you already have one scaling group created. You also do not need to create an event-triggered task, because this type of scaling task is triggered by events such as Cloud Monitor alarms or API calls, not by a specific time. References: 1, 2, and 3.

In Alibaba Cloud ECS, whenever an API request is made, a unique identifier called the RequestId is generated and returned. This ID is generated regardless of the request’s success or failure. RequestId serves as a unique identifier for tracking and debugging specific requests within the ECS environment, allowing users to trace and troubleshoot individual API calls. This practice ensures that issues can be resolved more efficiently by tracking the specific request, and it is a common practice across many Alibaba Cloud services.

Even though the scaling rule is set to "Adjust to 10 ECS instances," the maximum instance limit set for the scaling group is 8. Thus, when the scheduled task is triggered, Auto Scaling will increase the number of instances up to the maximum allowed, which is 8. Therefore, the scaling group will contain 8 instances, not 10, as it adheres to the defined maximum limit.

Weighted Round Robin (WRR) is a load balancing mode that assigns requests to backend ECS instances based on their weights. The higher the weight of the backend ECS instance, the higher the chance that the instance will receive requests. This mode can exploit the different service capacities of backend ECS instances by setting higher weights to ECS instances with higher capacities. For example, if there are two ECS instances in the backend server pool, one with a weight of 10 and the other with a weight of 20, the ECS instance with a weight of 20 will receive twice as many requests as the ECS instance with a weight of 10.

References:

1: SLB overview - Server Load Balancer - Alibaba Cloud Documentation Center

4: Server Load Balancer - Alibaba Cloud

5: Alibaba Server Load Balancer (SLB) Course - Cloud Academy

Alibaba Cloud provides basic security services for ECS instances, which include protection against unexpected remote logins, DDoS attacks, brute-force password cracking, and alerts for potential sensitive information leakage. Key management services (KMS) are available but are not part of the free security services for ECS.

To enable Internet access for ECS instances in a VPC, Alibaba Cloud users can use a public SLB with an Internet IP address (Option B) or an SLB with an Elastic IP (EIP) attached (Option C). Both methods allow the SLB instance to receive external requests and forward them to ECS instances within the VPC. Option A is incorrect because it would require a more complex setup without direct Internet access. Option D is incorrect as SLB does not support directly mounting servers from an on-premises data center.

Alibaba Cloud OSS (Object Storage Service) is designed for storing large volumes of unstructured data, such as files, images, and videos, making it an optimal solution for network disk applications. By migrating storage from ECS data disks to OSS, the team can offload storage tasks, reduce the number of ECS instances required, and significantly lower O&M costs. OSS also provides high scalability, reliability, and cost-effectiveness for such use cases.

Alibaba Cloud Object Storage Service (OSS) is a cloud storage service that allows you to store, retrieve, and manage data in the cloud. OSS provides multiple file uploading modes for different scenarios, such as simple upload, multipart upload, append upload, resumable upload, and cross-region replication. These uploading modes can be implemented by using the API or the SDK provided by OSS. Therefore, options B and D are the correct answers. Option A is not correct because the OSS management console only supports simple upload for files that are smaller than 5 GB. Option C is not correct because OSS does not support directly copying to/from OSS using portable disks. References: Object Storage Service:Simple upload, Object Storage Service:Multipart upload, Object Storage Service:OSS tools

A route table is a set of rules that determine how network traffic is routed within a VPC or between different network instances1. A VRouter is a hub that connects all VSwitches in the same VPC and enables communication between them2. When you create a VPC, a VRouter and a default route table are automatically created for the VPC1. The default route table contains system routes that are automatically generated by the system based on the network topology1. The system routes cannot be modified or deleted1.

However, you can also create custom route tables for your VPC and add custom routes to them1. Custom routes are manually configured by users to route traffic to specific destinations, such as other VPCs, VBRs, VPN Gateways, or NAT Gateways1. Custom routes can be modified or deleted as needed1. You can also associate VSwitches with different route tables to implement fine-grained routing control1.

Therefore, the statement that the routing entries of the route table can not be modified manually is not correct, as it only applies to system routes, not custom routes. The other statements are correct, as each VRouter may have multiple route tables, one default and several custom1; when a VPC is deleted, the corresponding route table is also deleted3; and the default route table cannot be deleted1. References: Route table overview - Virtual Private Cloud - Alibaba Cloud Documentation Center, VRouter overview - Virtual Private Cloud - Alibaba Cloud Documentation Center, Delete a VPC - Virtual Private Cloud - Alibaba Cloud Documentation Center

This statement is not correct because it is not a good practice to store user access information on each ECS instance in the scaling group. This is because the ECS instances are dynamic and can be added or removed by the Auto Scaling service based on the load and demand. Therefore, the data stored on the ECS instances may be lost or inconsistent if the instances are terminated or replaced. Moreover, this approach does not provide a centralized and unified way to access and analyze the data, which may affect the accuracy and efficiency of the analysis. Therefore, it is better to use other services such as ApsaraDB for RDS, ApsaraDB for Memcache, or OSS to store the user access information in a persistent and scalable manner. References: Auto Scaling, ApsaraDB for RDS, ApsaraDB for Memcache, OSS

Alibaba Cloud SLB allows users to select between private and public SLB based on business needs. A public SLB provides a public IP address for Internet-facing applications, while a private SLB provides a private IP address for internal applications within a VPC. Alibaba Cloud assigns the appropriate IP type automatically based on the user’s selection of SLB type.

According to the Alibaba Cloud documentation1, Auto Scaling is a service that automatically adjusts the number of elastic computing resources based on your business demands and policies. When the demand for computing resources increases, Auto Scaling automatically adds ECS instances to ensure sufficient computing capabilities. When the demand decreases, Auto Scaling automatically removes ECS instances to reduce costs.

Auto Scaling supports adding an existing ECS instance into the scaling group, but the instance must meet some requirements1. One of the requirements is that the instance and the scaling group must be in the same region. However, they do not have to be in the same zone. A zone is a physical area within a region that has independent power grids and networks. A region is a geographic area where Alibaba Cloud deploys its resources. Therefore, the correct answer is B.

References:

1: Auto Scaling: Automatically Adjusts Computing Resources - Alibaba Cloud

2: Introduction to Auto Scaling - Alibaba Cloud Document Center

Data Transmission Service (DTS) is a real-time data streaming service that supports data transmission between data sources such as relational databases, NoSQL, and Big Data (OLAP). DTS supports data migration, data synchronization, and change data subscription scenarios. DTS can migrate your data to and from most of the widely used commercial and open source databases. It supports homogeneous migrations such as MySQL to MySQL, as well as heterogeneous migrations between different database platforms, such as Oracle to MySQL. Migrations can be from on-premises databases to RDS or ECS, databases running on ECS to RDS, or vice versa, as well as from one RDS database to another RDS database. DTS also supports database schema replication between instances, which means that DTS can automatically create the same schema as the source database in the target database. DTS also supports warning when source and destination has some unresolved conflict found, such as data type mismatch, primary key conflict, or foreign key constraint violation. DTS can help you resolve these conflicts by providing suggestions or allowing you to modify the data mapping rules. Therefore, the correct answer is C. Supports all of the above functions. References:

1: Data Transmission Service - Alibaba Cloud

2: What is Data Transmission Service? - Alibaba Cloud

3: Database Migration - AlibabaCloud

4: Cloud Migration without Stopping Services: Alibaba Cloud DTS

Intelligent DNS resolution is a feature of Alibaba Cloud DNS that allows users to configure different IP addresses for the same domain name based on the geographic locations or ISPs of the visitors. This way, visitors can access the nearest or optimal server for better performance and availability. Intelligent DNS resolution does not support web page content caching, which is a function of Alibaba Cloud CDN. Alibaba Cloud CDN is a distributed network that delivers content from the origin server to the edge nodes closest to the end users, reducing the network latency and bandwidth consumption. Alibaba Cloud CDN caches the static content of the web pages, such as images, CSS, and JavaScript files, on the edge nodes, so that the users can access them faster and reduce the load on the origin server. A user will receive data from the cache in the first-time access, and then will be updated from the origin site in subsequent requests based on the cache expiration time.

References:

1: Intelligent DNS resolution - Alibaba Cloud DNS - Alibaba Cloud Documentation Center

4: Alibaba Cloud Content Delivery Network (CDN) performs content acceleration with the support of intelligent DNS resolution The following function_________is NOT included in intelligent DNS resolution.

5: Alibaba Cloud DNS:Alibaba Cloud line for intelligent DNS resolution (September 16, 2020) - Alibaba Cloud Documentation Center

Alibaba Cloud OSS ensures high reliability and availability by maintaining multiple copies of data across different physical locations, allowing it to recover within minutes in the event of hardware failures. This redundancy mechanism provides strong data durability and service continuity.

A low CDN cache hit rate can be due to low website traffic, poor cache configurations (such as a short Cache Expiry Time), or the presence of dynamic resources that require frequent retrieval from the origin. Proper configuration of "Cache-Control" and "Expires" headers is necessary to ensure caching.

=================

After stopping an Alibaba Cloud Elastic Compute Service (ECS) instance, you will not be charged for the instance usage fee or the public bandwidth fee (if applicable) until you start the instance again. However, you will still be charged for the disk usage fee and the snapshot usage fee (if applicable) regardless of which region the instance is located in. This is because the disks and snapshots are still occupying the storage space and need to be billed accordingly. Therefore, the statement is false. References: 1 - Billing FAQ - Alibaba Cloud Document Center - What fees do I need to pay after I stop a Pay-As-You-Go instance?

Applications deployed on ECS instances that are managed by Auto Scaling should be stateless and horizontally scalable. Stateless applications do not store session data or any critical information on a single instance, allowing them to be replicated or terminated without affecting the application's overall functionality. Horizontal scalability ensures that more instances can handle additional traffic as demand increases. This setup allows Auto Scaling to add or remove instances seamlessly without requiring reconfiguration.

According to the Alibaba Cloud ECS documentation1, the recommended instance type for Tomcat is ecs.c5.xlarge, which has 4 vCPUs and 4 GiB of memory. This instance type is suitable for web applications that require high performance and low latency. The recommended instance type for Memcache is ecs.r5.large, which has 2 vCPUs and 16 GiB of memory. This instance type is optimized for memory-intensive applications that require high memory bandwidth and low latency. Therefore, option D is the most recommended configuration for deploying Tomcat and Memcache on two ECS instances. References: Instance type families and Alibaba Cloud Elastic Compute Service Product Introduction

Alibaba Cloud RDS for MySQL supports cross-zone migration within the same region, allowing users to move their RDS instances to different availability zones if needed. This feature helps enhance disaster recovery and flexibility in resource allocation.

Data Transmission Service (DTS) is a real-time data streaming service that supports data transmission between data sources such as relational databases, NoSQL, and Big Data (OLAP). DTS supports data migration, data synchronization, and change data subscription scenarios. DTS can migrate your data to and from most of the widely used commercial and open source databases. It supports homogeneous migrations such as MySQL to MySQL, as well as heterogeneous migrations between different database platforms, such as Oracle to MySQL. Migrations can be from on-premises databases to RDS or ECS, databases running on ECS to RDS, or vice versa, as well as from one RDS database to another RDS database. DTS also supports migrating data between RDS instances of different Alibaba Cloud accounts, as long as they are in the same region1. Therefore, the statement B. The data cannot be migrated is NOT correct for migrating self-built MySQL databases (running on ECS) to RDS. The other statements are correct, as the data can be imported via the Intranet, the public network, or by running mysqldump234. References:

1: Migrate Self-built Database to RDS - Alibaba Cloud

2: Migrating a Self-built MySQL Database to Alibaba Cloud RDS for MySQL with Minimal Downtime - Alibaba Cloud Community

3: Migrating Data from a Self-Managed SQL Server Database on an ECS to an ApsaraDB RDS for SQL Server Database

4: Migrate data between RDS instances of different Alibaba Cloud accounts,Data Transmission Service

To isolate ECS instances within different VSwitches in a VPC while allowing them to access the internet and other intranet resources, each VSwitch's instances should be in separate Security Groups. By configuring each group to allow all VPC CIDR blocks first and then restricting access to other VSwitch CIDR blocks with a higher priority rule, instances in each VSwitch are isolated without affecting the VPC's external connections. This approach follows Alibaba Cloud's Security Group best practices and CIDR-based access control within VPC environments.

=================

Active/standby server groups are a feature of Server Load Balancer (SLB) that allows you to configure a primary ECS instance and a secondary ECS instance for the backend of an SLB instance1. When the primary instance is working properly, the traffic is only forwarded to the primary ECS. When the primary instance is down, traffic is switched to the standby instance1. This feature is supported by TCP and HTTPS listeners, but not by HTTP and UDP listeners1. TCP and HTTPS listeners support session persistence, which ensures that requests from the same client are always forwarded to the same backend server2. HTTP and UDP listeners do not support session persistence, and they use round-robin or weighted round-robin algorithms to distribute traffic among the backend servers2. References: 1: Create an active/standby server group 2: [Configure a listener]

 A read-only RDS instance is a replica of the primary RDS instance that can handle read requests and increase the read capability of the database system. A read-only RDS instance inherits the network type (intranet or internet) of the primary RDS instance and cannot switch between them. Therefore, option D is the correct answer. References: Create a read-only ApsaraDB RDS for MySQL instance, Instance types for read-only ApsaraDB RDS instances

In cloud environments, Alibaba Cloud emphasizes that security responsibilities, data ownership (data attribution), and security standards remain with the user. However, O&M (Operations and Maintenance) methods often change due to the distinct management tools, automated processes, and distributed nature of cloud infrastructure. Cloud environments typically use different O&M approaches, so option D is not aligned with Alibaba Cloud's security principles.

The ossbrowser is a graphical tool provided by Alibaba Cloud for uploading and downloading files in OSS, offering an intuitive interface for managing objects. Other tools like ossutil and osscmd are command-line tools, while ossfs is used to mount OSS as a file system on Linux, not a graphical tool.

To handle high download traffic efficiently, Company F can use Object Storage Service (OSS) to store the installation package and Content Delivery Network (CDN) to distribute it. OSS provides scalable, low-cost storage, while CDN caches content at edge nodes, reducing the load on the ECS instance and improving download speeds for users. This combination helps control bandwidth costs on ECS and provides faster download speeds by serving content closer to end-users.

Alibaba Cloud ApsaraDB for RDS offers read/write splitting capabilities, allowing you to distribute read requests to read-only instances and write requests to the primary instance. This setup improves database performance under high traffic by optimizing read workloads, which is particularly useful for MySQL databases deployed in high-demand environments.

=================

Default VPCs do count toward your overall VPC quota in Alibaba Cloud, contrary to option D. Each region has a single default VPC that is automatically created by Alibaba Cloud, and users can create additional VPCs, which are then labeled as non-default VPCs. Default VPCs also have different constraints and operational characteristics compared to user-created VPCs, such as specific configurations for ease of use in basic setups.

Auto Scaling in Alibaba Cloud is designed to automatically adjust resources, such as ECS instances, based on the demand and scaling policies. This works best with applications that are stateless and horizontally scalable, as these applications do not rely on data stored locally on an instance, allowing them to scale in and out without affecting performance or user experience. Statelessness and horizontal scalability allow Auto Scaling to manage ECS instances efficiently without manual intervention.

When using Auto Scaling with Server Load Balancer (SLB), both the scaling group and the SLB instance must reside in the same region. This is because region-specific configurations enable low-latency connections and proper integration between the resources, ensuring the scaling group can register with the SLB instance effectively.

To confirm a previously unhealthy instance is now healthy, Alibaba Cloud SLB requires three consecutive successful health checks. With a health check interval of 2 seconds and a response timeout of 5 seconds, each check cycle takes up to 5 seconds. Therefore, three successive health checks would take a minimum of 5×3=155 \times 3 = 155×3=15 seconds in total. However, because the health checks are conducted at 2-second intervals, there’s overlap, reducing the actual time to at least 11 seconds for the SLB to mark the instance as healthy.

Certificates are mandatory when using the HTTPS protocol with Alibaba Cloud SLB to secure data transmission between clients and the SLB instance. HTTPS (HTTP Secure) requires an SSL/TLS certificate to encrypt the data, ensuring secure communication over the network. For protocols like HTTP or TCP, a certificate is not required, as they do not natively support encryption.

Alibaba Cloud ECS (Elastic Compute Service) is an Infrastructure as a Service (IaaS) offering, providing users with virtualized computing resources like virtual machines. IaaS services offer fundamental cloud infrastructure such as compute, storage, and networking resources.

By default, ECS instances in different zones within the same region are not interconnected via the Intranet. To enable communication between instances across zones, you would need to configure a VPC or use other network configurations. This setup provides isolation and flexibility in managing network traffic within different zones.

In Alibaba Cloud, a scaling group can be associated with multiple SLB instances as long as they are in the same region, allowing distributed load handling across multiple load balancers. However, there is no requirement for SLB instances or scaling configurations to be in the same zone, making it region-specific instead of zone-specific.

=================

 The Alibaba Cloud CDN can directly accelerate access to the files stored in OSS and reduce OSS traffic costs. Alibaba Cloud CDN is a global network of points of presence (POPs) that are distributed across the globe. Alibaba Cloud CDN serves to reduce back-to-origin traffic. This in turn prevents network congestion and ensures that content is delivered with minimal latency across regions in various use cases1. Alibaba Cloud CDN caches resources from your origin servers on POPs located across the globe. Whenever customers access your resources, the resources are served from the nearest POP instead of the origin server. This helps prevent lengthy back-to-origin requests and reduces loads on origin servers, delivering better experience to your customers and reducing back-to-origin costs1. Alibaba Cloud CDN also provides IPv6 support on some POPs1. You can use Alibaba Cloud CDN to accelerate access to Object Storage Service (OSS). If you directly access OSS resources, the access speed varies based on the region in which the buckets are located and is limited by the outbound bandwidth of OSS2. The Internet traffic cost of CDN is lower than that of OSS, and the back-to-source traffic cost from CDN to OSS is also lower than a user access to OSS directly2. Therefore, using CDN can reduce the traffic cost of OSS. References: Use Alibaba Cloud CDN to accelerate access to OSS, What is Alibaba Cloud CDN?

The X-Forwarded-For field in HTTP header is used to identify the originating IP address of a client connecting to a web server through an HTTP proxy or a load balancer. When the “Obtain the Visitor’s Real IP Address” function is enabled in Alibaba Cloud SLB, the SLB instance adds the X-Forwarded-For field to the HTTP header of each request and forwards the request to the backend server. The backend server can then obtain the real IP address of the visitor from the X-Forwarded-For field1. The format of the X-Forwarded-For field is as follows:

X-Forwarded-For: client, proxy1, proxy2

where the value is a comma+space separated list of IP addresses, the left-most being the original client, and each successive proxy that passed the request adding the IP address where it received the request from. In this example, the request passed through proxy1, proxy2, and then the SLB instance (proxy3).2

References: Obtain client IP addresses - Server Load Balancer - Alibaba Cloud, X-Forwarded-For - MDN Web Docs

According to the Alibaba Cloud Academy, a VPC is an isolated network environment that is completely isolated from each other. Each VPC has an independent tunnel ID, and a tunnel ID corresponds to a virtualized network. This means that different VPCs cannot communicate with each other through the tunnel ID. Subnets are not divided like the traditional network environment, but rather are logical divisions of the VPC. Different cloud servers within each subnet are connected by the same router, but different subnets are interconnected by route tables, not switches. ECS instances in a VPC use security group firewalls for Layer 4 network access control, not Layer 2. The internal networks of different VPCs are completely isolated and can be interconnected through IP addresses mapped to the outside, such as NAT Gateway or EIP. References: ACP Cloud Computing Certification Preparation Course - Internetworking with VPC, Alibaba Cloud VPC User Guide