Push vs Pull

When Conquest! was first developed in 1993, it used a very simple model to exchange data between the server and players. A player would send a command and the server would reply with an appropriate response. If a player needed additional information, they would issue another command to retrieve it. This worked well for a text-based UI.

When the UI was developed in 2016, essentially the same model was used. However, it quickly became apparent that additional information was needed to update the UI. Therefore, after a player issued a command and the server sent the initial response, the client would send additional commands to the server to retrieve the rest of the information. For example, consider this sequence:

1. Player sends Buy
2. Server sends Response
3. Client Sends Person
4. Server sends Person
5. Client Sends Review
6. Server sends Review
7. Client Sends Market
8. Server Sends Market

This solved the issue of missing ancillary information but was inefficient and meant that any updates required a client deployment.

In January of 2021, I switch from a pull to a push model. With this model the server would decide what information to send after processing a command. The above example now looks like this:

1. Player sends Buy
2. Server sends Response
3. Server sends Person
4. Server sends Review
5. Server Sends Market

This reduced the amount of network traffic and server-side processing and meant that any fixes could be done quickly without a client update. This has worked well for 2.5 years, but I have recently become concerned that data was being sent multiple times as the web of what to send and when became difficult to trace (each individual command was responsible for deciding what data to send back to the client).

I have updated the pull model to use a centralized function to examine the player structures after a command is executed to dynamically determine the data required to send to the client. In this way, I do not have to worry about a command missing something (or sending too much data). The correct data is sent automatically each time.