Push vs Pull API Architecture
The number of internet users has increased massively in the past few years, and handling this enormous amount of traffic is a big challenge for application developers. Choosing an appropriate architecture for communication between the server and clients plays a significant role in ensuring that traffic is kept at a manageable level.
In this article, you’re going to learn about the push and pull architecture of network communications, and how push architecture can limit the load on your application server, increasing performance.
There are two primary approaches to network communications—push and pull.
Pull: Often referred to as polling, it’s especially common on the internet. A client, such as: a user, web browser, or application, etc. requests information and the server responds with the information requested. It’s like looking up the score of yesterday's football game: the information is static, and there's no need for frequent—or any—updates. The client requests the information, the server provides it, and the exchange is over.
Push: This is an architecture where data is pushed upstream over a connection as soon as it becomes available. One type of push-based transport is called a websocket, which is a persistent, bidirectional connection through which both the client and the server can push data. It's one of the foundations of the real-time web, and is the technology that underpins many popular chat and other real-time platforms. Other common places people encounter push-style communication is on their phones, where special offers, notifications, and score updates are often delivered directly to their devices.
It’s important to understand the difference between push and pull APIs so that you can select the right architecture for your service.
If your client app needs to find out if there is any new information on the server side, the easiest—if not always the best—way to accomplish this is to call and ask, which is basically how pull APIs work. They are a type of network communication where the client application initiates the communication by requesting updates. The server receives the request, verifies it, processes it, and sends an appropriate response back to the client.
This whole process of polling updates usually takes hundreds of milliseconds. If there are many requests, it can slow down or even overload your server layer, resulting in a poor user experience, customer complaints, and even economic losses. Therefore, to control traffic, many companies often use rate limits to limit how often a client can ask for the same information.
While some of the drawbacks of pull architecture can be mitigated by a system that can distribute processing, even this quickly becomes a very expensive, resource-intensive option. If you need the ability to communicate frequent updates, push architecture is likely a better choice.
The strongest use case for push APIs are for instances in which you have time-sensitive data that changes often, and clients need to be updated as soon as that data changes.
Push APIs allow the server to send updates to the client whenever new data becomes available, without a need for the client to explicitly request it. When the server receives new information, it pushes the data to the client application, no request needed. This makes it a more efficient communication standard for data that stays changes often.
- In a pull API, the client requests the information. In a push API, the server sends the information as it becomes available.
- Pull architecture is request driven: the client sends the request, and the server responds accordingly. Push architecture is event driven: the server pushes data to clients as updates become available.
- In a push API, the server needs to store client details to reach clients directly. With pull, the server doesn’t need to store these details, because they’re encoded in the request.
- Push APIs are significantly faster than pull APIs. In a pull API, the server must receive and verify the request, then process information to form a response that’s sent to the client. In a push API, the server immediately processes information and sends it to clients as soon as it's available.
Push APIs are widely used to minimize server load in apps with large user bases and frequent data exchanges or real-time data. Instead of users making frequent requests to stay updated with the newest information, servers instantly push data as new information is obtained. Push APIs are particularly useful for enhancing system efficiency by utilizing fewer resources, resulting in a more stable and cost-effective system.
Users receive around forty-five notifications every single day. Imagine the load that places on a system with thousands or even millions of users. Push APIs make this level of traffic much more manageable.
Push architecture also enables you to trigger parallel workflows in your application system. You can simply create a message with appropriate data for the workflow and push it to the parallel worker to process it or send it to the queue. A similar workflow can be performed using a pull architecture, but repeatedly requesting for messages to be placed in a queue can be time-consuming and difficult to implement.
Both architecture styles have use cases where they shine. Understanding these use cases will help you understand which API architecture is right for your application, and how it will affect your overall system.
Pull APIs can be an expensive and risky choice here. Let’s say you have a thousand users, and they request updates every five minutes. If that’s the case, you’re looking at around two hundred thousand requests a day, just for updates. This puts a huge, unnecessary burden on the system. This is especially true if your system isn’t updated frequently, since most of the time, the client will request information, and receive “updated” information in which nothing has changed.
Push APIs are an excellent option here, since they can eliminate the constant update requests to the server. This reduces the server load, and creates room for other processes in your application server.
If your application system requires complex routing across numerous servers, the communication architecture you choose can have a significant impact on both the system and the implementation process.
With push architecture, servers can simply push messages and client details to the queue together, making push architecture a viable option in a complex system. In a pull architecture, servers have to go through complex logic to check and pull a message out of another server and into a queue. Not only is this difficult to implement, but it’s also expensive and time-consuming.
There are many other common use cases where Push APIs are used as a standard approach.
- Event triggers: A new parallel workflow is initiated with an event trigger.
- Promotional marketing: Push notifications are sent to users to notify them about discounts, sales, and new offers.
- Geographic location tagging: Location and other geographic data are collected by remote devices, such as your cell phone, and sent to servers using push architecture.
- Notifications and reminders: Social media notifications, weather alerts, and top news articles that are sent to your device are made with push architectures.
Push APIs are a common feature of advanced network architectures, including the following.
Event-driven architecture is common in microservices-based systems. It utilises events to trigger communication and actions across different services.
Producers, brokers, and consumers are the three key components of this design. The publishers publish an event, which the brokers then filter and push to the consumer micro-services. This architecture uses push APIs to push events from publishers to brokers, and then from brokers to consumers, triggering appropriate services.
For asynchronous messaging, the pub/sub architecture is very popular. Pub/sub is a specific type of event-driven architecture that’s more scalable than other messaging architectures.
A publisher publishes information to a broker, and clients receive that information from the broker based on their subscriptions. Push APIs are used by the publisher to send information to the broker, who then sends the information to its subscribers.
WebSockets establishes a long-lived, socket-like connection between the server and the clients, enabling them to exchange data at any moment. There are no requests or responses; messages are just pushed from one end to the other, and push APIs are at the heart of the WebSockets architecture.
System architecture is rarely exclusively push or pull, but rather a combination of the two. All application services have different use cases, and you must choose an appropriate architecture for your expected use case to maximise your system’s potential.
Thanks for reading. Have coding.