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Over the last lectures,

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we learned that Docker has some pretty nice features,

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when it comes to requests leaving one container

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and going to the host machine

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or going to another container.

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Specifically, we can use host docker internal

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as an address to target the host machine,

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in case some services running there.

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And you just learned about container networks

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and that when you use them

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and multiple containers are in the same network,

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you can actually use the name of a container as a domain,

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as an address, and Docker will automatically resolve

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the IP addresses.

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That's a cool feature.

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I just want to ensure that we all understand it correctly.

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Docker will not, important, not go ahead

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and start replacing your source code under the hood.

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That is not what it's doing.

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It's not replacing your source code.

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So it will not read your source code,

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see a container name and plug in the IP address

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of that container into your code.

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That would be way too complex

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and it's not what it's doing.

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Instead Docker owns the environment

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in which your application runs.

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And if your application sends an HTTP request

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or a MongoDB request or any other kind

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of request that leaves the container,

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then Docker is aware of that.

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And it's that point of time where Docker

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then is able to resolve the address,

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or the container name or host Docker internal

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and replace it with the actual IP address,

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since it is aware of the surrounding containers

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and the host machine.

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So it's only when a request leaves the container.

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If a request does not leave a container,

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or if a request is generated somewhere else,

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for example, in the browser.

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If users are visiting your web app and JavaScript code

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is running in their browser

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and a request is sent from there,

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then Docker is not doing anything

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because it's not replacing the source code.

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That's just important that we all understand

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how that auto IP resolving feature

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actually works under the hood.