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- What's New
- Function Overview
- Service Overview
-
Getting Started
- Overview
- Getting Started with Clusters
- Getting Started with Replica Sets
- Getting Started with Single Nodes
- Logging In to the DDS Console
- Example: Buying and Connecting to a DDS Instance
- Change History (Getting Started) Europe Site
-
User Guide
- Migrating Data
- Performance Tuning
- Permissions Management
- Instance Lifecycle Management
- Instance Modifications
- Data Backups
- Data Restorations
-
Parameter Template Management
- Overview
- Creating a Parameter Template
- Modifying a Parameter Template
- Viewing Parameter Change History
- Exporting a Parameter Template
- Comparing Parameter Templates
- Replicating a Parameter Template
- Resetting a Parameter Template
- Applying a Parameter Template
- Viewing Application Records of a Parameter Template
- Modifying the Description of a Parameter Template
- Deleting a Parameter Template
- Connection Management
- Database Usage
- Data Security
- Monitoring and Alarm Reporting
- Auditing
- Logs
- Task Center
- Billing
- Tags
- Quotas
- DDS Usage Suggestions
- Change History
- Developer Guide
-
Best Practices
- Overview
- Common Methods for Connecting to a DDS Instance
- How Do Replica Sets Achieve High Availability and Read/Write Splitting?
- Sharding
- How Do I Improve DDS Performance by Optimizing SQL Statements?
- How Do I Prevent the Mongos Cache Problem?
- How Do I Solve the High CPU Usage Issue?
- Creating a User and Granting the Read-Only Permission to the User
- Security White Paper
- Performance White Paper
-
API Reference
- Before You Start
- API Overview
- Calling APIs
- Getting Started
-
APIs V3.0 (Recommended)
- Querying the API Version
- Querying Database Version Information
- Querying Database Specifications
- Querying the Database Disk Type
-
DB Instance Management
- Creating a DB Instance
- Restarting a DB Instance
- Deleting a DB Instance
- Querying Instances and Details
- Scaling Up Storage Space
- Adding Nodes for a Cluster Instance
- Modifying DB Instance Specifications
- Performing a Primary/Secondary Switchover in a Replica Set Instance
- Enabling or Disabling SSL
- Modifying a DB Instance Name
- Changing an Instance Description
- Changing a Database Port
- Changing a Security Group
- Binding an EIP
- Unbinding an EIP
- Changing a Private IP Address
- Creating Shard or Config IP Addresses of a Cluster Instance
- Configuring Cross-CIDR Access for a Replica Set
- Querying AZs to Which an Instance Can Be Migrated
- Migrating a DB Instance to Another AZ
- Adding Nodes to a Replica Set Instance
- Adding a Read Replica to an Instance
- Connection Management
-
Backup and Restoration
- Creating a Manual Backup
- Deleting a Manual Backup
- Querying the Backup List
- Querying an Automated Backup Policy
- Setting an Automated Backup Policy
- Restoring Data to a New DB Instance
- Obtaining the Link for Downloading a Backup File
- Querying the Restoration Time Ranges
- Obtaining the List of Databases That Can Be Restored
- Obtaining the List of Database Collections That Can Be Restored
- Restoring Data to the Original DB Instance
- Restoring Databases and Tables to a Point in Time
- Parameter Configuration
- Log Information Queries
- Tag Management
-
Managing Databases and Users
- Creating a Database User
- Creating a Database Role
- Querying Details About Database Users
- Querying the Database Role List
- Changing the Password of a Database User
- Checking the Password for Logging In to a Database
- Querying Cluster Balancing Settings
- Enabling or Disabling Cluster Balancing
- Setting the Activity Time Window for Cluster Balancing
- Deleting a Database User
- Deleting a Database Role
- Quota Management
- Task Management
- API V3 (Unavailable Soon)
- Examples
- Permissions Policies and Supported Actions
- Appendix
- Change History (European Sites)
- SDK Reference
-
FAQs
-
Product Consulting
- What Is the Relationship Between DDS and MongoDB Community Edition?
- What Are the Differences Between DDS and GaussDB(for Mongo)?
- What Precautions Should Be Taken When Using DDS?
- What Is the Availability of DDS DB Instances?
- Will My DDS DB Instances Be Affected by Other Users' DDS DB Instances?
- Does DDS Support Multi-AZ Deployment?
- Can I Change the VPC for a Created Instance?
- Can I Change the Region for a Created Instance?
- What Is Hidden Node?
- Database Versions
-
Resource and Disk Management
- Which Items Occupy the Storage Space of DDS Instances?
- Which Types of Logs and Files Occupy DDS DB Instance Storage Space?
- Why Is the Storage Space Usage Displayed on the GUI Smaller Than the Actual Usage?
- Why Does Available Disk Space Not Increase After Data Is Deleted?
- Why Is the Resident Memory of a 4 vCPUs/8 GB Memory Replica Set Instance Only 4 GB?
- Capacity Expansion and Specification Changes
-
Database Performance
- When Will a Primary/Standby Switchover Be Triggered for a Cluster or Replica Set?
- High Storage Usage
- What Is the Time Delay for Primary/Secondary Synchronization in a Replica Set?
- How Is Data Transferred Between the Primary and Secondary Nodes of a Replica Set?
- How Do I Clear an Alarm Saying the Shard Memory Usage Exceeds 90%?
- What Can I Do If a Query Error Is Reported After Data Is Written Into the DDS Cluster?
- Database Permissions
-
Creation and Deletion
- How Do I Select Instance Specifications and Nodes?
- Why Is an Instance Not Displayed on the Console After It Is Created?
- Can I Use a Template to Create DDS DB Instances?
- Why Is Data Missing from My Database?
- Will My Backups Be Deleted If I Delete My Cloud Account?
- What Are the Differences Between Instance Deletion and Unsubscription?
-
Database Connection
- What Should I Do If I Fail to Connect to a DDS Instance?
- What Can I Do If the Number of Connections of an Instance Reaches Its Maximum?
- How Do I Query and Limit the Number of Connections?
- What Should I Do If the ECS and DDS Are Deployed in Different VPCs and They Cannot Communicate with Each Other?
- Do Applications Need to Support Automatic Reconnecting to the DDS Database?
- How Do I Create and Log In to an ECS?
- Installing a Client
- Database Usage
- Database Migration
- Database Storage
- Database Parameters
- Backup and Restoration
- Network Security
- Monitoring and Alarm
- Change History (FAQs) Europe Site
-
Product Consulting
-
Troubleshooting
- DDS Instance Node Fault Handling Mechanism
- Connection Failure Message: network error while attempting to run command 'isMaster'
- Connection Failure Messages: No route to host and connection attempt failed
- Connection Failure Message: Authentication failed
- Connection Failure Message: couldn't connect to server
- Connection Failure Message: cannot list multiple servers in URL without 'replicaSet' option
- Connection Failure Message: Timeout while receiving message
- Connection Failure Message: exception: login failed and U_STRINGPREP_PROHIBITED_ERROR
- Change History (Troubleshooting) European Sites
- Videos
How Do Replica Sets Achieve High Availability and Read/Write Splitting?
DDS replica set instances can store multiple duplicates to ensure data high availability and support the automatic switch of private IP addresses to ensure service high availability. To enhance the read and write performance of your client for connecting to the instance, you can use your client to read different data copies. You are advised to use the recommended method to connect replica set instances. Otherwise, the high availability and high read performance of replica set instances cannot be guaranteed.
The primary node of a replica set instance is not fixed. If the instance settings are changed, or the primary node fails, or primary and secondary nodes are switched, a new primary node will be elected and the previous one becomes a secondary node. The following figure shows the process of a switchover.
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Connecting to a Replica Set Instance (HA)
A DDS replica set consists of the primary, secondary, and hidden nodes. The hidden node is invisible to users. Read/Write splitting and HA can be realized only when you connect to the IP addresses and ports of the primary and secondary nodes of the replica set at the same time (in HA mode).
The following describes how to use URL and Java to connect to an instance in HA mode.
Method 1: Using a URL
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Example: mongodb://rwuser:****@192.168.0.148:8635,192.168.0.96:8635/test?authSource=admin&replicaSet=replica
In the preceding URL, 192.168.0.148:8635 and 192.168.0.96:8635 are the IP addresses and ports of the primary and secondary nodes, respectively. If you use this address, the connection between your client and the instance can be ensured even when a primary/standby switchover occurs. In addition, using multiple IP addresses and port numbers can enhance the read and write performance of the entire database.
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Method 2: Using a Java Driver
Sample code:
MongoClientURI connectionString = new MongoClientURI("mongodb://rwuser:****@192.168.0.148:8635,192.168.0.96:8635/test?authSource=admin&replicaSet=replica"); MongoClient client = new MongoClient(connectionString); MongoDatabase database = client.getDatabase("test"); MongoCollection<Document> collection = database.getCollection("mycoll");
Parameter |
Description |
---|---|
rwuser:**** |
Username and password for starting authentication |
192.168.0.148:8635,192.168.0.96:8635 |
IP addresses and ports of the primary and secondary nodes in a replica set instance |
test |
Name of the database to be connected |
authSource=admin |
Database username for authentication |
replicaSet=replica |
Name of the replica set instance type |
(Not Recommended) Connecting to a Replica Set Instance
Using the Connection Address
mongodb://rwuser:****@192.168.0.148:8635/test?authSource=admin&replicaSet=replica
In the preceding URL, 192.168.0.148:8635 is the IP address and port number of the current primary node. If a switchover occurs or the primary node is changed, the client fails to connect to the replica set instance because the IP address and port of the newly elected primary node is unknown. As a result, the database service becomes unavailable. In addition, read and write operations can only be performed on a fixed primary node, so the read and write performance cannot be improved by adding nodes.
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Read/Write Splitting
For details about read/write splitting, see MongoDB official documents.
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