Public Cloud – Flexible Engine

Distributed Cache Service – A powerful caching solution for optimal application performance

[Features – Database]

DCS is an online, distributed, in-memory cache service

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It is reliable, scalable, usable out of the box, and easy to manage. Compatible with Redis, Memcached, and memory data grid (IMDG), DCS supports three instance types: single-node, master/standby, and cluster, ensuring high read/write performance and fast data access.

High Availability

  • DCS monitors instance status in real time. When a master cache node becomes faulty, the standby cache node will take over within seconds.
  • For DCS instances of master/standby type, the instance status is monitored in real time. DCS clients will not perceive the failover because the instance IP address exposed to them remains unchanged.
  • For DCS instances of cluster type, each shard is held on both master and standby cache nodes. DCS clients will not perceive the failover because the instance IP address exposed to them remains unchanged.

For DCS instances of cluster type, each shard is held on both master and standby cache nodes. DCS clients will not perceive the failover because the instance IP address exposed to them remains unchanged.

Various Capacity Specifications

Various capacity specifications are provided. Each DCS instance of single-node or master/standby type provides 2 GB to 64 GB, and each DCS instance of cluster type provides 64 GB to 1024 GB.

Scalability

Redis and Memcached DCS instances can quickly scale online as instance load increases, without affecting upper-layer services.

High Data Reliability

Redis and Memcached DCS instances support data persistence, backup, and restoration.

Security

Security measures include user identity authentication, VPCs, subnets, security groups, and audit logs.

Metric Monitoring

  • You can view over 30 metrics and customize alarm thresholds and policies.
  • Rich metrics :
    – External metrics include the number of commands, concurrent operations, connections, clients, and denied connections.
    – Resource usage metrics include CPU usage, physical memory usage, network input throughput, and network output throughput.
    – Internal metrics include instance capacity usage, as well as the number of keys, expired keys, PubSub channels, PubSub patterns, keyspace hits, and keyspace misses.
  • Custom alarm thresholds and policies
    – For example, if you suspect a service fault was caused by frequent keyspace misses, then you can set the keyspace miss threshold to 30 and specify the user that will receive the threshold crossing alert. When the number of keyspace misses reaches 30, the user will receive an alert.

Application scenarios

Web Pages

If the Redis or Memcached engine is used, caching the content of web pages improves page load times. The cached content can include static data such as Hypertext Markup Language (HTML) pages, Cascading Style Sheets (CSS), and images.

Status

If the Redis or Memcached engine is used, DCS provides quick and simple queries of session status and application-scaling status, enabling easy sharing of status information.

Application Objects

If the Redis, Memcached, or IMDG engine is used, DCS serves as a level-2 cache at the service layer and provides data storage and access for external entities. Storing frequently requested data in DCS instances can off load databases and reduce access latency.

Events

If the Redis engine is used, DCS provides continuous event querying, allowing streams of events to be processed as they occur.

Support for Standard SQL Interfaces

IMDG uses high-performance cache to store data and supports standard SQL interfaces for data access.

In-memory Data Collection and Computing

IMDG supports direct in-memory data collection and computing.

Cloud-based DCS has the following advantages

Usability Off the Shelf

You can create DCS instances with just a few clicks on the DCS console or by calling application programming interfaces (APIs). DCS responds to instance creation commands without requiring you to deal with complex underlying software and hardware.

Customizable Specifications

DCS Redis instance specifications range from 2 GB to 1024GB, DCS Memcached instance specifications range from 2 GB to 64 GB, and DCS IMDG instance specifications range from 2 GB to 16 GB, increasing the flexibility of the DCS.

Reliability

DCS supports master/standby and cluster modes to ensure data reliability, and supports automatic failover between cache nodes to ensure service availability.

Ease of Maintenance

You can create, start, stop, restart, and delete DCS instances with just a few clicks on the DCS console. DCS continuously monitors and maintains DCS instances so that you can focus on application development. Service monitoring metrics include keys, the number of client connections, and processed commands. System monitoring metrics include memory, CPU, and network usage.

Characteristics

For each single-node DCS instance, the available memory is less than the total memory because some memory is reserved for system overhead.

For each master/standby DCS Redis or Memcached instance, the available memory is less than the total memory because some memory is reserved for data persistence. If the DCS instances are deployed in master/standby mode, only the master cache node contributes to the available memory.

NOTE:

  • DCS Redis instances are classified into single-node, master/standby, and cluster. DCS Memcached instances are classified into single-node and master/standby.
  • In single-node and master/standby modes, there is no instance specification difference between Redis and Memcached.
  • The maximum intranet bandwidth is the sum of maximum inbound and outbound intranet bandwidths. Usually, DCS instances are read more frequently than they are written. Therefore, it is recommended that the maximum inbound intranet bandwidth be one third of the maximum intranet bandwidth and the maximum outbound intranet bandwidth be two thirds of the maximum intranet bandwidth
Memory (GB) Maximum Number of Connections Allowed Maximum Intranet Bandwidth (Mbit/s)
Total Available (Single Node) Available (Master/Standby)
2 1.5 1.5 10000 128
4 3.2 3.2 10000 192
8 6.8 6.4 10000 192
16 13.6 12.8 10000 256
32 27.2 25.6 10000 256
64 58.2 51.2 12000 384

Table 1 Specifications of single-node and master/standby DCS Redis and Memcache d instances 

The used memory of a cluster instance is the sum of used memory of each node. Therefore, the used memory of the instance may be slightly greater than the available memory of the instance.

Cluster DCS Redis instances in pay-per-user mode support 64 GB, 128 GB, and 256 GB; cluster DCS Redis instances in yearly/monthly subscription mode support 64 GB, 128 GB, 256 GB, 512 GB, and 1024 GB.

Total Memory (GB) Available Memory (GB) Maximum Number of Connections Allowed Maximum Intranet Bandwidth (Mbit/s)
64 64 20000 384
128 128 20000 384
256 256 20000 384
512 512 20000 384
1024 1024 20000 384

Table 2 Specifications of DCS Redis and Memcache d instances in the cluster mode

Limitations

Account

  • An account can create a DCS instance only after passing the real-name authentication.
  • An account can create a pay-per-use DCS instance only when the account balance is more than ¥ 100.
  • By default, you can create a maximum of 5 DCS instances with the total memory not exceeding 400 GB.
  • To create more DCS instances, submit a work order for application.
  • Currently, DCS instances cannot be transferred between pay-per-use and yearly/monthly subscription modes.

Region

Currently, DCS instances can be created in eu-west.

Specifications

Currently, DCS instances can Currently, you cannot create a DCS instance less than 2 GB.

Network

  • A public cloud uses VPCs to manage the network security of each service.
  • For a DCS Redis or Memcached instance, the client needs to be deployed on the elastic cloud server (ECS) for which the VPC is the same as that for the DCS instance.
  • For a DCS IMDG instance, the VPC and subnet for the ECS where the client is deployed must be the same as those for the DCS instance to ensure network connectivity between the ECS and the cache instance.
  • You are advised to select the same security group for a DCS instance and the ECS where the client is deployed. Otherwise, you need to add related inbound and outbound rules.

Scaling

You can scale up an instance only within the remaining quota scope. If the quota does not meet requirements, submit a work order for application of additional quota.

Compatibility with Redis Commands

The DCS Redis engine supports the majority of Redis commands. Any clients that support Redis can access DCS. For security purposes, certain Redis commands are disabled in DCS.

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