NO.40 Company builds a music download website based on OSS and ECS, and users can download mp3 files after registering for the website. Recently, the public network traffic to the OSS has doubled but the increase of registered users is less than 10%. After in-depth analysis, engineers find that many user download requests are raised from search engine but not the website itself. In this case, which of the following measures is thought to be able to address this issue.
Explanation The issue that Company B faces is that their music files stored in OSS are being downloaded by unauthorized users who access them through search engines, rather than through their website. This is called leeching, which is a form of bandwidth theft that consumes the OSS traffic and increases the cost for Company B. To address this issue, Company B can limit the access sources by configuring the “Anti-leech settings” of OSS bucket attributes. Anti-leech settings allow the bucket owner to specify a referer whitelist, which is a list of domain names that are allowed to access the OSS resources. The referer is a part of the HTTP header that indicates the source URL of the request. By setting a referer whitelist, Company B can prevent leeches from accessing their music files directly from search engines or other websites, and only allow access from their own website domain name. This way, Company B can protect their OSS resources from unauthorized access and reduce their OSS traffic costs. The other options are not effective or relevant for addressing the issue. Migrating music files from OSS to data disks for ECS instances would increase the storage and computing costs for Company B, and also reduce the scalability and availability of their music files. Changing the website access mode to HTTPS would enhance the security and encryption of the website, but it would not prevent leeches from accessing the OSS resources through search engines. Introducing SLB for extra protection would improve the load balancing and high availability of the ECS instances, but it would not affect the access control of the OSS resources. References: OSS Anti-Leech Referer Configuration and Error Elimination
NO.48 A customer uses Alibaba Cloud Auto Scaling service and creates a scaling group. He/she sets the “Minimum number of instances” to 6 and “Maximum number of instances” to 8. After correctly configuring scaling settings, the customer adds a scaling rule “Adjust to 10 ECS instances”, and creates a scheduled task based on this rule. And then, the customer checks the scaling group and see it already contains 6 valid ECS instances, he/she then enables this scaling group immediately. How many ECS instances are left in the scaling group when the scheduled task is activated once?
Explanation Alibaba Cloud Auto Scaling service allows you to automatically adjust the number of ECS instances in a scaling group based on your business needs and scaling policies. You can set the minimum and maximum number of instances in a scaling group to limit the range of scaling actions1. When you create a scaling rule, you can specify the number of instances to be added or removed, or the expected number of instances after the scaling action2. You can also create a scheduled task to execute a scaling rule at a specified time or periodically3. In this question, the customer sets the minimum number of instances to 6 and the maximum number of instances to 8 in the scaling group. This means that the scaling group will always have at least 6 instances and at most 8 instances. The customer also adds a scaling rule to remove 5 instances, and creates a scheduled task based on this rule. However, this scaling rule will not be executed if it violates the minimum and maximum limits of the scaling group. Therefore, when the scheduled task is activated once, the scaling group will only remove 2 instances, which is the difference between the current number of instances (8) and the minimum number of instances (6). The remaining number of instances in the scaling group will be 6, which is the correct answer. References: 1: Create a scaling group – Auto Scaling – Alibaba Cloud Documentation Center2: Create a scaling rule – Auto Scaling – Alibaba Cloud Documentation Center3: Create a scheduled task – Auto Scaling – Alibaba Cloud Documentation Center.
NO.49 ECS is a highly flexible service. It can be used independently as a simple web server, or used with other Alibaba Cloud products, such as OSS and CDN, to provide advanced solutions. ECS can be used in applications such as:. (Choose four.)
Explanation A, B, C, and D are the correct answers according to the ACA Cloud Computing by Alibaba Cloud Academy Reference Materials and documents. Comprehensive and Detailed Explanation: = A, B, C, and D are the correct answers because ECS is a highly flexible service that can be used independently as a simple web server, or used with other Alibaba Cloud products, such as OSS and CDN, to provide advanced solutions. ECS can be used in applications such as: Official corporate websites: ECS can host official corporate websites that require high performance, stability, reliability, and scalability. ECS can also support various web frameworks and languages, such as PHP, Java, Node.js, Python, and Ruby. ECS can also be integrated with other Alibaba Cloud products, such as SLB, CDN, and WAF, to improve the security, availability, and performance of the websites1 Large-traffic apps: ECS can handle large-traffic apps that require high concurrency, low latency, and high throughput. ECS can also scale up or down based on the real-time traffic demands, and use Auto Scaling to automate the scaling process. ECS can also leverage the Alibaba Cloud network infrastructure, such as VPC, Express Connect, and Global Accelerator, to optimize the network connectivity and performance of the apps2 Databases: ECS can run various database systems, such as MySQL, PostgreSQL, MongoDB, and Redis, to provide data storage and processing capabilities for different applications. ECS can also use cloud disks or local disks as the storage media for the databases, and choose different disk types, such as SSD, ESSD, and Ultra Disk, based on the performance and cost requirements. ECS can also use RDS or PolarDB to replace the self-managed databases, and enjoy the benefits of managed database services, such as backup, recovery, monitoring, and maintenance3 Simple web applications: ECS can run simple web applications that do not require complex architectures or high availability. ECS can provide fast memory and the latest CPUs to power the web applications and achieve faster results with low latency. ECS can also use OSS to store static files, such as images, videos, and documents, and reduce the storage cost and load of the ECS instances. E is an incorrect answer because ECS is not a storage service that provides unlimited online storage. ECS is a compute service that provides virtual machines with limited storage capacity. ECS can use OSS or NAS to expand the storage capacity, but these are separate storage services that have their own pricing and billing methods. References: 1: Build a Corporate Website 2: Build a Large-Traffic App 3: Build a Database System : [Build a Simple Web Application] : [ECS Overview]