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Abstract

span> (c *calculator) Calculate(num... int) { ans := 0 for _, n := range num { ans += n } fmt.Println(ans) }

var Calculator calculator</pre></div>We exposed a struct which implements the method Calculate. This is required for the discovery and registration of the plugin. Now to compile this and make it a shared-object we need to build the library as a plugin.<div id="b6b4"><pre>go build -o -buildmode=plugin .</pre></div>After this, we will have a shared object file(in our case “add.so”) which we can dynamically load at runtime in our main application.<figure id="5129"><img src="https://cdn-images-1.readmedium.com/v2/resize:fit:800/1*HEBnzWVkvUP0JjhOsfOH7Q.png"><figcaption>updated file structure of the library</figcaption></figure>Now to dynamically load the library into our main application at run time we need use the plugin system of Golang.<div id="0960"><pre>import ( "fmt" "os" "plugin" )

type Calculator interface { Calculate(num... int) }

func main() { calculatorPlugin, err := plugin.Open("/abs/path/to/shared/object/file") if err != nil { fmt.Println("error while opening shared object file") os.Exit(1) }

symCalculator, err := calculatorPlugin.Lookup("Calculator") if err != nil { fmt.Println("error while lookup") os.Exit(1) }

var calculator Calculator calculator, ok := symCalculator.(Calculator) if !ok { fmt.Println("unexpected type from module symbol") os.Exit(1) }

calculator.Calculate(3,4) }</pre></div>In this case if we are making any changes to library, we don’t need to re-compile our main application. We only need to recompile the library’s shared object and rerun our main application.Due to the different characteristics, the advantages and disadvantages of static and dynamic libraries are also obvious; binaries that rely only on static libraries and are generated by static linking can be executed independently because they contain all the dependencies, but the compilation result is also larger. Dynamic libraries can be shared among multiple executables, which can reduce the memory footprint, and their linking process is often triggered during loading or running, so they can contain some modules that can be hot-plugged and reduce the memory footprint. Compiling binaries using static linking has very obvious deployment advantages, and the final compiled product will run directly on most machines. The deployment benefits of static linking are far more important than the lower memory footprint, that’s why Golang uses static linking as the default linking method.<h1 id="d290">Issues with Dynamic-linking (shared library plugins) in Go</h1>Plugins using shared libraries and the plugin package work well for Golang, as the previous section demonstrates. However, this approach also has some serious downsides. The most important downside is that Golang is very picky about keeping the main application and the shared libraries it loads compatible.As an experiment, try using different versions of a common d

Options

ependency in the plugin application and the main application, rebuild the main application and run it. Most likely you’ll get this error:<div id="443c"><pre>"plugin was built with a different version of package XXX"</pre></div><figure id="d928"><img src="https://cdn-images-1.readmedium.com/v2/resize:fit:800/0*ow5zqQqWHmQoZqaC.gif"><figcaption></figcaption></figure>The reason for this is that Golang wants all the versions of all packages in the main application and plugins to match exactly. It’s clear what motivates this: safety.Consider C and C++ as counter-examples. In these languages, an application can load a shared library with dlopen and subsequently use dlsym to obtain symbols from it. dlsym is extremely weakly typed; it takes a symbol name and returns a void*. It’s up to the user to cast this to a concrete function type. If the function type changes because of a version update, the result can very likely be some sort of segmentation fault or even memory corruption.Since Golang relies on shared libraries from plugins, it has the same inherent safety issues. It tries to protect programmers from shooting themselves in the foot by ensuring that the application has been built with the same versions of packages as all its plugins. This helps avoid mismatch. In addition, the version of the Golang compiler used to build the application and plugins must match exactly.However, this protection comes with downsides — making developing plugins somewhat cumbersome. Having to rebuild all plugins whenever any common packages change — even in ways that don’t affect the plugin interface — is a heavy burden. Especially, considering that by their very nature plugins are typically developed separately from the main application; they may live in separate repositories, have separate release cadences etc.<h1 id="bfc1">Alternative approaches to shared library plugins in Golang</h1>Given that the plugin package was only added to Go in <a href="https://golang.org/doc/go1.8">version 1.8</a> and the limitation described previously, it’s not surprising that the Go ecosystem saw the emergence of alternative plugin approaches.One of the innovative approaches involves plugins via RPC. In this method instead of loading the plugins into the host process we load them in a separate process which then communicates to host via RPC or just TCP on localhost. It has several important upsides:<ul><li>Isolation: crash in a plugin does not bring the whole application down.</li><li>Interoperability between languages: if RPC is the interface, do you care what language the plugin is written in?</li><li>Distribution: if plugins interface via the network, we can easily distribute them to run on different machines for gains in performance, reliability, and so on.</li></ul>Moreover, Golang makes this particularly easy by having a fairly capable RPC package right in the standard library: net/rpc.One of the most widely used RPC-based plugin systems is <a href="https://github.com/hashicorp/go-plugin">hashicorp/go-plugin</a>. Hashicorp is well known for creating great Golang software, and apparently, they use go-plugin for many of their systems, so it’s battle-tested (though its documentation could be better 😛)Golang-plugin runs on top of net/rpc but also supports gRPC. Advanced RPC protocols like gRPC are well suitable for plugins because they include versioning out-of-the-box, tackling the difficult interoperability problem between different versions of plugins vs. the main application.However, this is also not a perfect solution as we talk about the fourth fundamental of plugin systems- “Extension APIs”. In a complex system, a plugin might make lot of Extension APIs calls which will end up increasing the latency if we are making network calls via RPC or TCP.<h1 id="1c76">Conclusion</h1>Golang still has a long way to go when it comes to Dynamic-linking (shared library plugins). No solution discussed in this blog can be considered perfect. One needs to consider the pros and cons of each solution available as per their specific requirements.</article></body>

Two Reasons Atheism Doesn’t Make Sense

Short philosophical reflections on the necessity of God’s existence

Atheism doesn’t make sense. Atheists are constantly ridiculing Christians, claiming they are foolish to believe something so senseless. For just a second, I want to flip the script. In this post I want to briefly identify two (of the many) reasons Atheism doesn’t make any sense.

The invisible longings of the human heart

There are so many things in existence that cannot exist without, at the very least, an eternal, intelligent designer. Among these things are the invisible attributes and longings of the human heart.

For example, humanity has always had a natural longing for purpose. We are born with it. No one has to explain it to us. We feel it. But how can we long for purpose in a universe in which purpose has never existed as a concept?

Somewhere, somehow, in the universe, purpose must be built in.

But this cannot happen with randomly exploding atoms and gases. It had to have been placed there. Even more specifically, it had to have been placed into the human heart.

It is ironic when the atheists mock us for believing God created the universe ex nihilo (out of nothing). They are asking us to believe in their own ex nihilo. They are asking us to believe that in a universe with no concept of purpose, and nowhere to even learn what such a thing is, the human heart suddenly began longing for purpose out of nowhere.

This longing for purpose is just one of many invisible realities that simply cannot be explained without some kind of design.

And wherever there is a design, there is a designer.

Hope

A poem

medium.com

Cause and effect

Everything that has a beginning has a cause. We would all agree with that. Here’s the thing. In order for that to happen there must be a cause that has no cause of its own. Otherwise, it is just a useless theory. This point was brilliantly made by Thomas Aquinas who referred to it as the “uncaused cause.”

In order for the process to even exist, there had to be something that never had a beginning to kick it all off. You cannot have a string of effects that stretches into eternity past. There must be a cause that, itself, stretches into eternity past. This is the cause of the first effect, and every effect after. Without the “uncaused cause" nothing could have ever began.

The laws of science themselves demand that we believe in eternity. They also demand that we believe there is something (or someone) that has eternally existed.

Once you reach that conclusion, you cannot escape the next logical step.

It is way more sensible to believe that the “uncaused cause” is an intelligent being with a will to create, not a mass of floating chemicals that randomly exploded. That explosion itself would be an effect which demanded a cause. Then we are right back down the rabbit hole of endless effects, looking for the original cause.

But that might be a post for another day.

If you enjoyed this post, feel free to check out my curated list of apologetics and theology articles: