135 lines
3.9 KiB
Markdown
135 lines
3.9 KiB
Markdown
# gex = gajumaru exchange
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Currently there is only one thing, which is the Gajumaru HTTP Daemon.
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## How to run `gex_httpd`
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Last updated: September 23, 2025 (PRH).
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1. **Install Erlang and zx/zomp**
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Source: [*Building Erlang 26.2.5 on Ubuntu 24.04*](https://zxq9.com/archives/2905)
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Adapt this to your Linux distribution.
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1.a. **Install necessary build tools**
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```bash
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sudo apt update
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sudo apt upgrade
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sudo apt install \
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gcc curl g++ dpkg-dev build-essential automake autoconf \
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libncurses-dev libssl-dev flex xsltproc libwxgtk3.2-dev \
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wget vim git
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```
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1.b. **Put [Kerl](https://github.com/kerl/kerl) somewhere in your
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`$PATH`**. This is a tool to build Erlang releases.
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```bash
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wget -O ~/bin/kerl https://raw.githubusercontent.com/kerl/kerl/master/kerl
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chmod u+x ~/bin/kerl
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```
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1.c. **Build Erlang from source using Kerl**
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```bash
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kerl update releases
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## use the most recent one that looks stable
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## you do need to type the number twice, that's not a typo
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kerl build 28.1 28.1
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kerl install 28.1 ~/.erts/28.1
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```
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1.d. **Put Erlang in your `$PATH`**
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Update .bashrc or .zshrc or whatever with the following line:
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```bash
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. $HOME/.erts/28.1/activate
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```
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1.e. **Install zx**
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```bash
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wget -q https://zxq9.com/projects/zomp/get_zx && bash get_zx
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```
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1.f. **Test zx works**
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zx installs itself to `~/bin`, so make sure that's in your
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`$PATH`.
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```bash
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zx run erltris
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```
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## Notes
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### Big Picture: telnet chat server -> HTTP server
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- The default project (see initial commit) is a telnet echo server. It's like
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the most ghetto low-budget chat server imaginable.
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Lefty and middley can chat just like normal.
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However, righty (`curl`) foolishly thinks he is talking to an HTTP server.
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His request is echoed to lefty and middley.
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Curl crashed because instead of a valid HTTP response back, he got something
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like
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```
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MESSAGE from YOU: GET / HTTP/1.1
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```
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- We make this into an HTTP server by replacing the "echo my message to
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everyone else" logic with "parse this message as an HTTP request and send
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back an HTTP response" logic.
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- Our "application logic" or "business logic" or whatever is contained in that
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process of how the request is mapped to a response.
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- It really is not more complicated than that.
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### Basics of Erlang Processes
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These are heuristics that are good starting points
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- each module ~= 1 process
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- it helps to think of erlang as an operating system, and erlang modules as
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shell scripts that run in that operating system.
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- some modules correspond to fungible processes, some are non-fungible
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- in Observer (`observer:start()`)
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- named processes are non-fungible (e.g. `gh_client_sup`)
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- the name can be anything, but conventionally it's the module name
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- fungible processes have numbers (PIDs) (e.g. the `gh_client` code)
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- named processes also have PIDs, they just also have names
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### Following the call chain of `gex_httpd:listen(8080)`
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- Reference commit: `49a09d192c6f2380c5186ec7d81e98785d667214`
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- By default, the telnet server doesn't occupy a port
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- `gex_httpd:listen(8080)` tells it to listen on port 8080
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```
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%% gex_httpd.erl
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-spec listen(PortNum) -> Result
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when PortNum :: inet:port_num(),
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Result :: ok
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| {error, {listening, inet:port_num()}}.
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%% @doc
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%% Make the server start listening on a port.
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%% Returns an {error, Reason} tuple if it is already listening.
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listen(PortNum) ->
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gh_client_man:listen(PortNum).
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%%
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