HTTP Request to a docker container

[Soockee]

Hi folks,

i wonder how to properly do a http request to a docker container. My current libraries, which might matter are tokio and reqwest

Reqwest tells me, that URLs such as are not valid.
"http://mycontainer:8080"

In fact here is the error, which describes the situation pretty well.

Blockquote
app_1 | 2021-05-27 15:59:38,908 WARN [user_service::repository] BaseURL: "http://auth-app:8000/"
app_1 | 2021-05-27 15:59:38,908 WARN [user_service::repository] Endpoint: "api/v1/login"
app_1 | 2021-05-27 15:59:38,908 TRACE [mio::poll] deregistering handle with poller
app_1 | thread 'tokio-runtime-worker' panicked at 'called Result::unwrap() on an Err value: RelativeUrlWithoutBase', src/repository.rs:52:72
app_1 | note: run with RUST_BACKTRACE=1 environment variable to display a backtrace

What is a good way to communicate between docker container in e.g. a docker swam environment. Besides using message broker such as rabbitmq.

[alice]

I would double-check that the domain is actually part of the url you are using. If you pass "api/v1/login" as the url to reqwest, you get that error.

[Soockee]

I did double-check the url string:

Blockquote
log::warn!("BaseURL: {}",auth_service_base_url); // output: [user_service::repository] BaseURL: "http://auth-app:8000/api/v1/login"
let request_url_test = reqwest::Url::parse(&auth_service_base_url).unwrap(); // error here
log::warn!("Parsed URL: {}", request_url_test.into_string())

Results in following error:

Blockquote
user_app | 2021-06-15 11:53:22,818 WARN [user_service::repository] BaseURL: "http://auth-app:8000/api/v1/login"
user_app | thread 'tokio-runtime-worker' panicked at 'called Result::unwrap() on an Err value: RelativeUrlWithoutBase', src/repository.rs:46:72

What i did try is extending the hostname e.g. auth-app with a domain e.g. auth-app .com
and naming the container explicitly. Parsing did work. Since i want to address an Service this '.com' is really unnecessary and i was wondering why the parse function does not like the described url.

[Fabio]

Communication with a docker container over http is no different than communicating with anything else over http. During development, I will often use the command-line curl as a sanity check to make sure I have my docker port mappings, environment variables, etc. set up properly before I assume the error is with my code: Something like

$ curl --header "Content-Type: application/json" \
  --request POST \
  --data '{"username":"xyz","password":"xyz"}' \
  http://mycontainer:8000/api/login

Specific to your instance, if your code is running inside a container that is part of the same swarm/deployment, you should be able to access your service simply via http:://containername:default_port. If it is not running inside the same deployment, you will have to use the ip address/port. Typically I check these with something like

sudo docker container ls | grep "auth-app"

You should see something like 127.0.0.1:ephemeral_port->8080

[Soockee]

Hi Fabio, thanks for the response.

I did manage to track down the problem. tldr: wrong url string, because it was enclosed in "" since i read it from env.

Stuff i did, which led me to the problem:

i just tried to do this, because of your suggestion.

1. entered my rust container
2. curled following:

Blockquote
curl -X POST -H "Content-Type: application/json" -d '{"username":"mario", "guid":"123123"}' http://auth_app:8000/api
/v1/login

and got following correct response:

Blockquote
{"jwt-token":"eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJleHAiOjE1MDAwLCJpc3MiOiJhdXRoZW50aWZpY2F0aW9uX3NlcnZpY2UiLCJ1c2Vyb
mFtZSI6Im1hcmlvIiwiZ3VpZCI6IjEyMzEyMyJ9.9dnz1LrISnZrrBDG3fDYEGjMzfRGS2o3seTjhop7k1k","success":"Created","userlogin":"4f
b5c87c-cdd4-11eb-9e81-0242ac120003"}

i would say this proves, that the communication channel between the two containers is working as indended. ( you gave me a hint tho. the url base name was auth-app instead of auth_app )

nonetheless: this didn't change the situation that my URL-String ist not parsed into a URL Object by the Reqwest library via the parse function.

i tried to setup a minimal example:

Blockquote
fn main() {
println!("Hello, world!");
let url = "http://auth_app:8000/api/v1/login";
let parsed_url = reqwest::Url::parse(&url).unwrap();
println!("{}", parsed_url);
}

this did work as expected. And i was wondering why. This led me to inspecting the types. In my appliation i was using 'String' but the parse function expects '&str'. Furthermore i was reading url from an env var.
The env var was enclosed by "" and therefore an invalid url