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32 lines
1.5 KiB
Markdown
32 lines
1.5 KiB
Markdown
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@page arch_goals High level code design practices
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This page describes the high level design practices for Tor's code.
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This design is a long-term goal of what we want our code to look like,
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rather than a description of how it currently is.
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Overall, we want various parts of tor's code to interact with each
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other through a small number of interfaces.
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We want to avoid having "god objects" or "god modules". These are
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objects or modules that know far too much about other parts of the
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code. God objects/modules are generally recognized to be an
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antipattern of software design.
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Historically, there have been modules in tor that have tended toward
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becoming god modules. These include modules that help more
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specialized code communicate with the outside world: the configuration
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and control modules, for example. Others are modules that deal with
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global state, initialization, or shutdown.
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If a centralized module needs to invoke code in almost every other
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module in the system, it is better if it exports a small, general
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interface that other modules call. The centralized module should not
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explicitly call out to all the modules that interact with it.
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Instead, modules that interact with the centralized module should call
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registration interfaces. These interfaces allow modules to register
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handlers for things like configuration parsing and control command
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execution. (The config and control modules are examples of this.)
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Alternatively, registration can happen through statically initialized
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data structures. (The subsystem mechanism is an example of this.)
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