Nginx what is upstream

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Google Cloud Platform. However, you can increase the number of requests to reduce this effect. Under high load requests are distributed among worker processes evenly, and the Least Connections method works as expected.

For servers in an upstream group that are identified with a domain name in the server directive, NGINX Plus can monitor changes to the list of IP addresses in the corresponding DNS record, and automatically apply the changes to load balancing for the upstream group, without requiring a restart.

This can be done by including the resolver directive in the http block along with the resolve parameter to the server directive:.

If a domain name resolves to several IP addresses, the addresses are saved to the upstream configuration and load balanced. Then specify the ntlm directive to allow the servers in the group to accept requests with NTLM authentication:. A configuration command can be used to view all servers or a particular server in a group, modify parameter for a particular server, and add or remove servers. Basic Functionality. Load Balancer. Content Cache. Web Server.

Security Controls. High Availability. Dynamic Modules. Mail Proxy. Deployment Guides. Amazon Web Services. Global Server Load Balancing. Google Cloud Platform. Load Balancing Third-Party Servers. Microsoft Azure. Migrate Hardware ADCs. Setting these headers correctly, depending on the sensitivity of the content, will help you take advantage of cache while keeping your private data safe and your dynamic data fresh.

If your backend also uses Nginx, you can set some of this using the expires directive, which will set the max-age for Cache-Control :. In the above example, the first block allows content to be cached for an hour. Nginx is first and foremost a reverse proxy, which also happens to have the ability to work as a web server. Because of this design decision, proxying requests to other servers is fairly straight forward.

Nginx is very flexible though, allowing for more complex control over your proxying configuration if desired. Where would you like to share this to? Twitter Reddit Hacker News Facebook. Share link Tutorial share link. Sign Up. DigitalOcean home. Community Control Panel. Hacktoberfest Contribute to Open Source. By Justin Ellingwood Published on November 25, General Proxying Information If you have only used web servers in the past for simple, single server configurations, you may be wondering why you would need to proxy requests.

Deconstructing a Basic HTTP Proxy Pass The most straight-forward type of proxy involves handing off a request to a single server that can communicate using http. Understanding How Nginx Processes Headers One thing that might not be immediately clear is that it is important to pass more than just the URI if you expect the upstream server handle the request properly. When Nginx proxies a request, it automatically makes some adjustments to the request headers it receives from the client: Nginx gets rid of any empty headers.

There is no point of passing along empty values to another server; it would only serve to bloat the request. Nginx, by default, will consider any header that contains underscores as invalid. It will remove these from the proxied request. This header is used to signal information about the particular connection established between two parties.

The upstream should not expect this connection to be persistent. The headers sent by the client are always available in Nginx as variables. Changing the Upstream Balancing Algorithm You can modify the balancing algorithm used by the upstream pool by including directives or flags within the upstream context: round robin : The default load balancing algorithm that is used if no other balancing directives are present. Each server defined in the upstream context is passed requests sequentially in turn.

This can be especially useful in situations where connections to the backend may persist for some time. The first three octets are used as a key to decide on the server to handle the request. The result is that clients tend to be served by the same server each time, which can assist in session consistency.

The servers are divided based on the value of an arbitrarily provided hash key. This can be text, variables, or a combination. This is the only balancing method that requires the user to provide data, which is the key that should be used for the hash. Using Buffers to Free Up Backend Servers One issue with proxying that concerns many users is the performance impact of adding an additional server to the process. The connection from the Nginx proxy to the backend server.

The default is to configure 8 buffers of a size equal to one memory page either 4k or 8k. Increasing the number of buffers can allow you to buffer more information. This directive sets the size of the buffer for this portion of the response. While a client can only read the data from one buffer at a time, buffers are placed in a queue to send to the client in bunches.

This directive controls the size of the buffer space allowed to be in this state. These are created when the upstream response is too large to fit into a buffer. Here is a diagram of a basic high availability setup: In this example, you have multiple load balancers one active and one or more passive behind a static IP address that can be remapped from one server to another.

Configuring Proxy Caching to Decrease Response Times While buffering can help free up the backend server to handle more requests, Nginx also provides a way to cache content from backend servers, eliminating the need to connect to the upstream at all for many requests. Now, we have configured the cache zone, but we still need to tell Nginx when to use the cache. Notes about Caching Results Caching can improve the performance of your proxy enormously.

This can be used if the data is dynamic and important. An ETag hashed metadata header is checked on each request and the previous value can be served if the backend returns the same hash value. This is the safest option for private data, as it means that the data must be retrieved from the server every time.

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