In a distributed system, microservices exchange information between one another, using predefined communication protocols. Some disruptions in data serialization might occur when software developers alter different microservices independently. In this article, I will revisit the most relevant practices for versioning serializers and spreading their changes throughout a system.

Communication Protocols

The OSI model establishes 7 abstraction layers for communication over the Internet. Microservices usually exchange information using the last, seventh layer, called the application layer, leveraging either preexisting protocols like HTTP or custom-made ones. I find it significant to note that the HTTP/2 protocol relies on the TCP protocol (the transport layer) which in turn relies on the IP protocol (the Internet layer) — this means that sharing information between two machines involves more work than meets the eye. I will not describe the fundamental differences between text and binary protocols here, but I want to stress that HTTP belongs to the family of the former, compared to both the TCP and the IP protocols, which belong to the family of the latter.

From this moment on I shall discuss serialization within the bounds of the HTTP protocol, mostly because of its popularity and applicability in distributed systems. Using the aforementioned protocol, a developer can transfer an information of a reasonable size in:

• the request line (including the query parameters),
• the headers of a request or a response (the protocol allows for custom ones),
• the message body of a the request or a response.

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