nym/nym-node/src/node/nym_apis_client.rs

// Copyright 2025 - Nym Technologies SA <contact@nymtech.net>
// SPDX-License-Identifier: GPL-3.0-only

use crate::error::NymNodeError;
use crate::node::NymNode;
use futures::{stream, StreamExt};
use nym_crypto::asymmetric::ed25519;
use nym_http_api_client::Client;
use nym_task::ShutdownToken;
use nym_validator_client::client::NymApiClientExt;
use nym_validator_client::models::{KeyRotationInfoResponse, NodeRefreshBody};
use nym_validator_client::nym_api::error::NymAPIError;
use rand::prelude::SliceRandom;
use rand::thread_rng;
use std::sync::Arc;
use std::time::Duration;
use tokio::sync::RwLock;
use tokio::time::sleep;
use tracing::{debug, warn};
use url::Url;

#[derive(Clone)]
pub struct NymApisClient {
    inner: Arc<RwLock<InnerClient>>,
}

struct InnerClient {
    // NOTE: this was implemented before the internal http client supported multiple URLs
    active_client: Client,
    available_urls: Vec<Url>,
    shutdown_token: ShutdownToken,
    currently_used_api: usize,
}

impl NymApisClient {
    pub(crate) fn new(
        nym_apis: &[Url],
        shutdown_token: ShutdownToken,
    ) -> Result<Self, NymNodeError> {
        if nym_apis.is_empty() {
            return Err(NymNodeError::NoNymApiUrls);
        }

        let mut urls = nym_apis.to_vec();
        urls.shuffle(&mut thread_rng());

        let active_client = Client::builder(urls[0].clone())?
            .no_hickory_dns()
            .with_user_agent(NymNode::user_agent())
            .with_timeout(Duration::from_secs(5))
            .build()?;

        Ok(NymApisClient {
            inner: Arc::new(RwLock::new(InnerClient {
                active_client: active_client.clone(),
                available_urls: urls,
                shutdown_token,
                currently_used_api: 0,
            })),
        })
    }

    // async fn use_next_endpoint(&self) {
    //     let mut guard = self.inner.write().await;
    //     if guard.available_urls.len() == 1 {
    //         return;
    //     }
    //
    //     let next_index = (guard.currently_used_api + 1) % guard.available_urls.len();
    //     let next = guard.available_urls[next_index].clone();
    //     guard.currently_used_api = next_index;
    //     guard.active_client.change_nym_api(next)
    // }

    pub(crate) async fn query_exhaustively<R, T>(
        &self,
        req: R,
        timeout_duration: Duration,
    ) -> Result<T, NymNodeError>
    where
        R: AsyncFn(Client) -> Result<T, NymAPIError>,
    {
        let guard = self.inner.read().await;
        let (res, last_working_endpoint) = guard.query_exhaustively(req, timeout_duration).await?;

        // if we had to use a different api, update our starting point for the future calls
        if guard.currently_used_api != last_working_endpoint {
            drop(guard);
            let mut guard = self.inner.write().await;
            guard.currently_used_api = last_working_endpoint;
            
            // Provide all URLs starting from the working endpoint for automatic failover
            let rotated_urls: Vec<_> = guard.available_urls
                .iter()
                .cycle()
                .skip(last_working_endpoint)
                .take(guard.available_urls.len())
                .map(|u| u.clone().into())
                .collect();
            
            guard.active_client.change_base_urls(rotated_urls);
        }

        Ok(res)
    }

    pub(crate) async fn broadcast_force_refresh(&self, private_key: &ed25519::PrivateKey) {
        self.inner
            .read()
            .await
            .broadcast_force_refresh(private_key)
            .await;
    }

    pub(crate) async fn get_key_rotation_info(
        &self,
    ) -> Result<KeyRotationInfoResponse, NymNodeError> {
        self.query_exhaustively(
            async |c| c.get_key_rotation_info().await,
            Duration::from_secs(5),
        )
        .await
    }
}

impl InnerClient {
    // currently there are no cases without json body, but for those we'd just need to slightly adjust the signature
    async fn broadcast<B, R>(&self, request_body: &B, req: R, timeout_duration: Duration)
    where
        R: AsyncFn(Client, &B) -> Result<(), NymAPIError>,
    {
        let broadcast_fut =
            stream::iter(self.available_urls.clone()).for_each_concurrent(None, |url| {
                let mut nym_api = self.active_client.clone();
                // For broadcast, we intentionally set a single URL per client
                // to ensure each endpoint receives the request
                nym_api.change_base_urls(vec![url.clone().into()]);
                let req_fut = req(nym_api, request_body);
                async move {
                    if let Err(err) = req_fut.await {
                        warn!("broadcast request to {url} failed: {err}")
                    }
                }
            });

        let timeout_fut = sleep(timeout_duration);

        tokio::select! {
            _ = broadcast_fut => {
                debug!("managed to broadcast data to all nym apis")
            }
            _ = timeout_fut => {
                warn!("timed out while attempting to broadcast data to known nym apis")

            }
            _ = self.shutdown_token.cancelled() => {
                debug!("received shutdown while attempting to broadcast data to known nym apis")
            }
        }
    }

    async fn query_exhaustively<R, T>(
        &self,
        req: R,
        timeout_duration: Duration,
    ) -> Result<(T, usize), NymNodeError>
    where
        R: AsyncFn(Client) -> Result<T, NymAPIError>,
    {
        let last_working = self.currently_used_api;

        // start from the last working api and progress from there
        // also, note this is DESIGNED to query sequentially (but exhaustively)
        // and not to try to send queries to ALL apis at once
        // and check which resolves first
        for (idx, url) in self
            .available_urls
            .iter()
            .enumerate()
            .skip(last_working)
            .chain(self.available_urls.iter().enumerate().take(last_working))
        {
            let mut nym_api = self.active_client.clone();
            // For exhaustive query, we test each endpoint individually in sequence
            // to find a working one - so single URL is correct here
            nym_api.change_base_urls(vec![url.clone().into()]);

            let timeout_fut = sleep(timeout_duration);
            let query_fut = req(nym_api);

            tokio::select! {
                res = query_fut => {
                    debug!("managed to broadcast data to all nym apis");
                    match res {
                        Ok(res) => return Ok((res, idx)),
                        Err(err) => {
                             warn!("failed to resolve query for {url}: {err}");
                        }
                    }
                }
                _ = timeout_fut => {
                    warn!("timed out while attempting to query {url}")

                }
                _ = self.shutdown_token.cancelled() => {
                    debug!("received shutdown while attempting to query {url}");
                    return Err(NymNodeError::ShutdownReceived)
                }
            }
        }

        Err(NymNodeError::NymApisExhausted)
    }

    async fn broadcast_force_refresh(&self, private_key: &ed25519::PrivateKey) {
        let request = NodeRefreshBody::new(private_key);

        self.broadcast(
            &request,
            async |client, request| client.force_refresh_describe_cache(request).await,
            Duration::from_secs(10),
        )
        .await;
    }
}

impl AsRef<Client> for InnerClient {
    fn as_ref(&self) -> &Client {
        &self.active_client
    }
}