In Nginx, a distribution policy refers to how to allocate client requests to different backend servers according to certain rules or algorithms. Nginx's distribution strategy is very flexible and can be distributed according to load balancing, requested content, session retention and other methods. Here are several common distribution strategies for Nginx:
1. Round Robin
definition
Polling is the most commonly used load balancing algorithm that distributes requests in sequence to various servers on the backend.
How it works
- Requests are assigned to each server in sequence, regardless of the load conditions of each server.
- The default load balancing method is polling.
Pros and cons
- Advantages: Simple, easy to implement, and good load balancing effect.
- Disadvantages: Failure to take into account the actual load situation of the backend servers may cause some servers to be overloaded while others are idle.
Configuration example
http {
upstream backend {
server ;
server ;
server ;
}
server {
location / {
proxy_pass http://backend;
}
}
}
2. Weighted Round Robin
definition
Weighted polling is a variant of the polling algorithm that allows weighting to be set for each server, and servers with heavy weights allocated more requests to it.
How it works
- Each server allocates the corresponding number of requests based on the set weight. The higher the weight, the more requests assigned.
- This method is suitable for situations where server hardware configurations vary greatly, such as servers with different CPU, memory, and bandwidth.
Pros and cons
- Advantages: Load balancing is carried out according to the server's processing capacity, which can improve resource utilization.
- Disadvantages: Appropriate weights need to be set according to actual conditions.
Configuration example
http {
upstream backend {
server weight=3;
server weight=2;
server weight=1;
}
server {
location / {
proxy_pass http://backend;
}
}
}
3. Least Connections
definition
The minimum connection algorithm distributes requests to the backend server with the lowest number of connections currently. It determines the allocation of requests based on the server's load, and prefers the server with the lowest number of connections at present.
How it works
- Nginx monitors the number of connections per server in real time and sends requests to the server with the least number of connections, thus achieving load balancing.
Pros and cons
- Advantages: It better balances the server's load, especially suitable for long-term connection scenarios (such as database connections, WebSockets).
- Disadvantages: Not suitable for short connections, as each request may cause new connections to fluctuate.
Configuration example
http {
upstream backend {
least_conn;
server ;
server ;
server ;
}
server {
location / {
proxy_pass http://backend;
}
}
}
4. IP hash (IP hash)
definition
An IP hash is a hash value that calculates a hash value based on the IP address requested by the client and distributes the request to different backend servers based on this value. This way, requests for the same IP are always assigned to the same backend server.
How it works
- The hash value is calculated by the client's IP address, and the hash value determines which backend server the request should be sent to.
- Suitable for scenarios where session persistence is required.
Pros and cons
- Advantages: It can ensure that requests from the same IP are always routed to the same backend server, suitable for applications that require session retention.
- Disadvantages: If the backend server changes, it may affect the consistency of the session.
Configuration example
http {
upstream backend {
ip_hash;
server ;
server ;
server ;
}
server {
location / {
proxy_pass http://backend;
}
}
}
5. Weighted Least Connections
definition
The weighted minimum connection algorithm is an improved version of the minimum connection algorithm that combines the weights of the server and the number of connections. Servers with larger weights receive more requests, but the number of connections is taken into account when allocating.
How it works
- Each server has both weights and takes into account the minimum number of connections. The final load balancing decision is the result of the combined action of weights and connections.
Pros and cons
- Advantages: Combining weights and connection counts, it is more flexible and suitable for servers with different hardware configurations.
- Disadvantages: The configuration is relatively complex and requires precise setting of weights.
Configuration example
http {
upstream backend {
server weight=3;
server weight=2;
server weight=1;
least_conn;
}
server {
location / {
proxy_pass http://backend;
}
}
}
6. URL hashing (Hashing on URL)
definition
The URL hashing algorithm determines which server to assign the request to through the requested URL or other request parameters. The hash value for each URL request will determine the target server.
How it works
- Compute the hash value through the requested URL, and select the backend server based on this hash value. This way, the same URL request is always routed to the same backend server.
Pros and cons
- Advantages: Applicable to scenarios where distribution policy needs to be decided based on the request URL.
- Disadvantages: If the URL content changes a lot, it may cause uneven distribution of requests.
Configuration example
http {
upstream backend {
hash $request_uri;
server ;
server ;
server ;
}
server {
location / {
proxy_pass http://backend;
}
}
}
Summarize
Nginx provides a variety of load balancing strategies, each with its applicable scenarios and advantages and disadvantages:
- Polling: suitable for simple scenarios where load balancing does not depend on server load.
- Weighted polling: suitable for scenarios with different hardware performance.
- Minimum connection: Suitable for long connection scenarios.
- IP hash: Applicable to session retention requirements.
- Weighted minimum connections: a load balancing algorithm combining weights and connection counts.
- URL hash: Assign requests based on request URLs, suitable for scenarios where URLs are fixed and need to be assigned to the specified server.
Choosing the appropriate distribution strategy ensures the efficiency of Nginx load balancing and system stability.
This is the end of this article about the implementation of Nginx distribution strategy. For more related content of Nginx distribution strategy, please search for my previous articles or continue browsing the related articles below. I hope everyone will support me in the future!