Introduction
Remote Procedure Call (RPC) is a widely used communication protocol in distributed computing systems. The protocol enables two applications running on different machines to communicate with each other. In other words, RPC allows a client application to invoke a procedure on a remote server as if it were a local procedure.
The protocol provides a simple way to build distributed systems, where services or functions are distributed across multiple machines, but appear as a single system to the user. Let’s explore how RPC works and its applications in distributed computing.
What is RPC?
In technical terms, RPC is a protocol that enables the client application to call a procedure on a remote server, which executes the requested procedure and sends back the result to the client.
The client application and the server communicate through a network, using a communication protocol such as TCP or UDP. The process of calling a remote procedure is similar to calling a local procedure. The client passes the input parameters to the server, and the server returns the result.
To make the process of remote procedure call seamless, a middleware layer is used. The middleware layer provides an abstraction layer between the client and server, making it appear as if the client and server are communicating directly. The middleware layer is responsible for handling the low-level details of the communication, such as establishing and tearing down the connection, serialization and deserialization of data, and error handling.
How Does RPC Work?
The RPC process typically involves the following steps:
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Client Call: The client application makes a procedure call as if it were calling a local procedure. The client passes the input parameters to the server.
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Marshalling: The input parameters are serialized into a format that can be transmitted over the network. This process is known as marshalling.
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Network Communication: The marshalled data is sent over the network to the server.
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Unmarshalling: The server receives the data and deserializes it back into the original format. This process is known as unmarshalling.
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Server Execution: The server executes the requested procedure using the input parameters.
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Marshalling: The server serializes the result of the procedure into a format that can be transmitted over the network.
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Network Communication: The marshalled result is sent back to the client over the network.
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Unmarshalling: The client receives the result and deserializes it back into the original format.
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Client Response: The client receives the result of the procedure call and continues its execution.
The RPC process abstracts the details of network communication, serialization, and deserialization from the client and server, making it easy to build distributed systems.
Types of RPC
There are two main types of RPC:
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Synchronous RPC: In synchronous RPC, the client waits for the server to execute the procedure and return the result before continuing its execution. Synchronous RPC is simple to implement but can lead to performance issues if the server takes a long time to execute the procedure.
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Asynchronous RPC: In asynchronous RPC, the client does not wait for the server to return the result immediately. Instead, the client can continue its execution and handle the result when it is available. Asynchronous RPC can improve performance by allowing the client to continue its execution while waiting for the server to respond.
Examples of RPC
One of the most common examples of RPC is the use of Remote Method Invocation (RMI) in Java. RMI is a Java-specific implementation of RPC that allows objects in one Java Virtual Machine (JVM) to invoke methods on objects in another JVM. The RMI system provides a mechanism for distributed objects to communicate with each other, making it possible to build distributed applications in Java.
Another example of RPC is the use of gRPC ↗️, an open-source remote procedure call framework developed by Google. gRPC provides a high-performance, scalable, and language-independent RPC framework that can be used to build distributed systems in a wide range of programming languages.
Conclusion:
Remote Procedure Call (RPC) is a powerful tool for building distributed systems that can help make the interaction between different systems seamless. RPC provides an abstraction layer that enables developers to build distributed systems that appear as a single system to the end user.
It allows programs running on different machines to communicate with each other, making it possible to build distributed applications that can scale to handle large numbers of users.