apps/labrinth/src/database/models/notifications_template_item.rs

@@ -1,14 +1,18 @@
 use crate::database::models::DatabaseError;
 use crate::database::redis::RedisPool;
 use crate::models::v3::notifications::{NotificationChannel, NotificationType};
+use crate::routes::ApiError;
 use serde::{Deserialize, Serialize};
 
 const TEMPLATES_NAMESPACE: &str = "notifications_templates";
 const TEMPLATES_HTML_DATA_NAMESPACE: &str = "notifications_templates_html_data";
+const TEMPLATES_DYNAMIC_HTML_NAMESPACE: &str =
+    "notifications_templates_dynamic_html";
+
 const HTML_DATA_CACHE_EXPIRY: i64 = 60 * 15; // 15 minutes
+const TEMPLATES_CACHE_EXPIRY: i64 = 60 * 30; // 30 minutes
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
-
 pub struct NotificationTemplate {
     pub id: i64,
     pub channel: NotificationChannel,
@@ -75,7 +79,7 @@ impl NotificationTemplate {
                 TEMPLATES_NAMESPACE,
                 channel.as_str(),
                 &templates,
-                None,
+                Some(TEMPLATES_CACHE_EXPIRY),
             )
             .await?;
 
@@ -111,3 +115,44 @@ impl NotificationTemplate {
             .await
     }
 }
+
+pub async fn get_or_set_cached_dynamic_html<F>(
+    redis: &RedisPool,
+    key: &str,
+    get: impl FnOnce() -> F,
+) -> Result<String, ApiError>
+where
+    F: Future<Output = Result<String, ApiError>>,
+{
+    #[derive(Debug, Clone, Serialize, Deserialize)]
+    struct HtmlBody {
+        html: String,
+    }
+
+    let mut redis_conn = redis.connect().await?;
+    if let Some(body) = redis_conn
+        .get_deserialized_from_json::<HtmlBody>(
+            TEMPLATES_DYNAMIC_HTML_NAMESPACE,
+            key,
+        )
+        .await?
+    {
+        return Ok(body.html);
+    }
+
+    drop(redis_conn);
+
+    let cached = HtmlBody { html: get().await? };
+    let mut redis_conn = redis.connect().await?;
+
+    redis_conn
+        .set_serialized_to_json(
+            TEMPLATES_DYNAMIC_HTML_NAMESPACE,
+            key,
+            &cached,
+            Some(HTML_DATA_CACHE_EXPIRY),
+        )
+        .await?;
+
+    Ok(cached.html)
+}

apps/labrinth/src/models/v2/notifications.rs

@@ -139,6 +139,11 @@ pub enum LegacyNotificationBody {
         amount: u64,
         date_available: DateTime<Utc>,
     },
+    Custom {
+        key: String,
+        title: String,
+        body_md: String,
+    },
     Unknown,
 }
 
@@ -217,6 +222,7 @@ impl LegacyNotification {
             NotificationBody::PayoutAvailable { .. } => {
                 Some("payout_available".to_string())
             }
+            NotificationBody::Custom { .. } => Some("custom".to_string()),
             NotificationBody::LegacyMarkdown {
                 notification_type, ..
             } => notification_type.clone(),
@@ -378,6 +384,15 @@ impl LegacyNotification {
                 service,
                 currency,
             },
+            NotificationBody::Custom {
+                title,
+                body_md,
+                key,
+            } => LegacyNotificationBody::Custom {
+                title,
+                body_md,
+                key,
+            },
             NotificationBody::PaymentFailed { amount, service } => {
                 LegacyNotificationBody::PaymentFailed { amount, service }
             }

apps/labrinth/src/models/v3/notifications.rs

@@ -56,6 +56,7 @@ pub enum NotificationType {
     ProjectStatusNeutral,
     ProjectTransferred,
     PayoutAvailable,
+    Custom,
     Unknown,
 }
 
@@ -89,6 +90,7 @@ impl NotificationType {
             NotificationType::ProjectStatusApproved => {
                 "project_status_approved"
             }
+            NotificationType::Custom => "custom",
             NotificationType::ProjectStatusNeutral => "project_status_neutral",
             NotificationType::ProjectTransferred => "project_transferred",
             NotificationType::Unknown => "unknown",
@@ -125,6 +127,7 @@ impl NotificationType {
             }
             "project_status_neutral" => NotificationType::ProjectStatusNeutral,
             "project_transferred" => NotificationType::ProjectTransferred,
+            "custom" => NotificationType::Custom,
             "unknown" => NotificationType::Unknown,
             _ => NotificationType::Unknown,
         }
@@ -236,6 +239,11 @@ pub enum NotificationBody {
         date_available: DateTime<Utc>,
         amount: u64,
     },
+    Custom {
+        key: String,
+        title: String,
+        body_md: String,
+    },
     Unknown,
 }
 
@@ -313,6 +321,7 @@ impl NotificationBody {
             NotificationBody::PayoutAvailable { .. } => {
                 NotificationType::PayoutAvailable
             }
+            NotificationBody::Custom { .. } => NotificationType::Custom,
             NotificationBody::Unknown => NotificationType::Unknown,
         }
     }
@@ -557,6 +566,12 @@ impl From<DBNotification> for Notification {
                     "#".to_string(),
                     vec![],
                 ),
+                NotificationBody::Custom { title, .. } => (
+                    "Notification".to_string(),
+                    title.clone(),
+                    "#".to_string(),
+                    vec![],
+                ),
                 NotificationBody::Unknown => {
                     ("".to_string(), "".to_string(), "#".to_string(), vec![])
                 }

apps/labrinth/src/queue/email.rs

@@ -4,7 +4,7 @@ use crate::database::models::notifications_deliveries_item::DBNotificationDelive
 use crate::database::models::notifications_template_item::NotificationTemplate;
 use crate::database::models::user_item::DBUser;
 use crate::database::redis::RedisPool;
-use crate::models::notifications::NotificationBody;
+use crate::models::notifications::{NotificationBody, NotificationType};
 use crate::models::v3::notifications::{
     NotificationChannel, NotificationDeliveryStatus,
 };
@@ -20,6 +20,7 @@ use sqlx::PgPool;
 use std::sync::Arc;
 use thiserror::Error;
 use tokio::sync::Mutex as TokioMutex;
+use tokio::sync::Semaphore;
 use tracing::{error, info, instrument, warn};
 
 const EMAIL_RETRY_DELAY_SECONDS: i64 = 10;
@@ -187,13 +188,19 @@ impl EmailQueue {
 
         // For all notifications we collected, fill out the template
         // and send it via SMTP in parallel.
-
         let mut futures = FuturesUnordered::new();
 
+        // Some email notifications should still be processed sequentially. This is to avoid cache stampede in the
+        // case that processing the email can be heavy. For example, custom emails always make a POST request to modrinth.com,
+        // which, while not necessarily slow, is subject to heavy rate limiting.
+        let sequential_processing = Arc::new(Semaphore::new(1));
+
         for notification in notifications {
             let this = self.clone();
             let transport = Arc::clone(&transport);
 
+            let seq = Arc::clone(&sequential_processing);
+
             futures.push(async move {
                 let mut txn = this.pg.begin().await?;
 
@@ -214,15 +221,35 @@ impl EmailQueue {
                     ));
                 };
 
-                this.send_one_with_transport(
-                    &mut txn,
-                    transport,
-                    notification.body,
-                    notification.user_id,
-                    mailbox,
-                )
-                .await
-                .map(|status| (notification.id, status))
+                // For the cache stampede reasons mentioned above, we process custom emails exclusively sequentially.
+                // This could cause unnecessary slowness if we're sending a lot of custom emails with the same key in one go,
+                // and the cache is already populated (thus the sequential processing would not be needed).
+                let maybe_permit = if notification.body.notification_type()
+                    == NotificationType::Custom
+                {
+                    Some(
+                        seq.acquire()
+                            .await
+                            .expect("Semaphore should never be closed"),
+                    )
+                } else {
+                    None
+                };
+
+                let result = this
+                    .send_one_with_transport(
+                        &mut txn,
+                        transport,
+                        notification.body,
+                        notification.user_id,
+                        mailbox,
+                    )
+                    .await
+                    .map(|status| (notification.id, status));
+
+                drop(maybe_permit);
+
+                result
             });
         }
 

apps/labrinth/src/queue/email/templates.rs

@@ -1,12 +1,15 @@
 use super::MailError;
 use crate::database::models::ids::*;
-use crate::database::models::notifications_template_item::NotificationTemplate;
+use crate::database::models::notifications_template_item::{
+    NotificationTemplate, get_or_set_cached_dynamic_html,
+};
 use crate::database::models::{
     DBOrganization, DBProject, DBUser, DatabaseError,
 };
 use crate::database::redis::RedisPool;
 use crate::models::v3::notifications::NotificationBody;
 use crate::routes::ApiError;
+use crate::util::error::Context;
 use ariadne::ids::base62_impl::to_base62;
 use futures::TryFutureExt;
 use lettre::Message;
@@ -138,12 +141,21 @@ pub async fn build_email(
         reply_address,
     } = from;
 
-    let (html_body_result, mut variables) = futures::try_join!(
-        get_html_body,
-        collect_template_variables(exec, redis, user_id, body)
-    )?;
+    let db_user = DBUser::get_id(user_id, &mut **exec, redis)
+        .await?
+        .ok_or(DatabaseError::Database(sqlx::Error::RowNotFound))?;
 
-    variables.insert(USER_EMAIL, to.email.to_string());
+    let map = [
+        (USER_NAME, db_user.username),
+        (USER_EMAIL, to.email.to_string()),
+    ]
+    .into_iter()
+    .collect();
+
+    let (html_body_result, either) = futures::try_join!(
+        get_html_body,
+        collect_template_variables(exec, redis, user_id, body, map)
+    )?;
 
     let mut message_builder = Message::builder().from(Mailbox::new(
         Some(from_name),
@@ -157,28 +169,79 @@ pub async fn build_email(
         ));
     }
 
-    let subject = fill_template(&template.subject_line, &variables);
-    message_builder = message_builder.to(to).subject(subject);
+    struct Body {
+        plaintext: Option<String>,
+        html: Option<String>,
+    }
 
-    let plaintext_filled_body =
-        fill_template(&template.plaintext_fallback, &variables);
+    let (body, subject) = match either {
+        EmailTemplate::Static(variables) => {
+            let plaintext_filled_body =
+                fill_template(&template.plaintext_fallback, &variables);
 
-    let email_message = match html_body_result {
-        Ok(html_body) => {
-            let html_filled_body = fill_template(&html_body, &variables);
-            message_builder
-                .multipart(MultiPart::alternative_plain_html(
-                    plaintext_filled_body,
-                    html_filled_body,
-                ))
-                .map_err(MailError::from)?
+            let email_body = Body {
+                plaintext: Some(plaintext_filled_body),
+                html: match html_body_result {
+                    Ok(html_body) => {
+                        Some(fill_template(&html_body, &variables))
+                    }
+                    Err(error) => {
+                        error!(%error, "Failed to fetch template body");
+                        None
+                    }
+                },
+            };
+
+            let subject = fill_template(&template.subject_line, &variables);
+
+            (email_body, subject)
         }
 
-        Err(error) => {
-            error!(%error, "Failed to fetch template body");
-            message_builder
-                .singlepart(SinglePart::plain(plaintext_filled_body))
-                .map_err(MailError::from)?
+        EmailTemplate::Dynamic {
+            variables,
+            body,
+            title,
+        } => {
+            let body = Body {
+                plaintext: None,
+                html: Some(fill_template(&body, &variables)),
+            };
+
+            (body, fill_template(&title, &variables))
+        }
+    };
+
+    message_builder = message_builder.to(to).subject(subject);
+
+    let email_message = match body {
+        Body {
+            plaintext: Some(plaintext),
+            html: Some(html),
+        } => message_builder
+            .multipart(MultiPart::alternative_plain_html(plaintext, html))
+            .map_err(MailError::from)?,
+
+        Body {
+            plaintext: Some(plaintext),
+            html: None,
+        } => message_builder
+            .singlepart(SinglePart::plain(plaintext))
+            .map_err(MailError::from)?,
+
+        Body {
+            plaintext: None,
+            html: Some(html),
+        } => message_builder
+            .singlepart(SinglePart::html(html))
+            .map_err(MailError::from)?,
+
+        Body {
+            plaintext: None,
+            html: None,
+        } => {
+            return Err(ApiError::Internal(eyre::eyre!(
+                "Neither HTML or plaintext could be generated"
+            )));
         }
     };
 
@@ -218,23 +281,26 @@ fn fill_template(
     buffer
 }
 
+enum EmailTemplate {
+    Static(HashMap<&'static str, String>),
+    Dynamic {
+        variables: HashMap<&'static str, String>,
+        body: String,
+        title: String,
+    },
+}
+
 async fn collect_template_variables(
     exec: &mut sqlx::PgTransaction<'_>,
     redis: &RedisPool,
     user_id: DBUserId,
     n: &NotificationBody,
-) -> Result<HashMap<&'static str, String>, ApiError> {
-    let db_user = DBUser::get_id(user_id, &mut **exec, redis)
-        .await?
-        .ok_or_else(|| DatabaseError::Database(sqlx::Error::RowNotFound))?;
-
-    let mut map = HashMap::new();
-    map.insert(USER_NAME, db_user.username);
-
+    mut map: HashMap<&'static str, String>,
+) -> Result<EmailTemplate, ApiError> {
     match &n {
         NotificationBody::PatCreated { token_name } => {
             map.insert(NEWPAT_TOKEN_NAME, token_name.clone());
-            Ok(map)
+            Ok(EmailTemplate::Static(map))
         }
 
         NotificationBody::ModerationMessageReceived { project_id, .. } => {
@@ -250,7 +316,7 @@ async fn collect_template_variables(
             map.insert(PROJECT_ID, to_base62(project_id.0));
             map.insert(PROJECT_NAME, result.name);
             map.insert(PROJECT_ICON_URL, result.icon_url.unwrap_or_default());
-            Ok(map)
+            Ok(EmailTemplate::Static(map))
         }
 
         NotificationBody::ReportStatusUpdated { report_id } => {
@@ -273,7 +339,7 @@ async fn collect_template_variables(
             map.insert(REPORT_ID, to_base62(report_id.0));
             map.insert(REPORT_TITLE, result.title);
             map.insert(REPORT_DATE, date_human_readable(result.created));
-            Ok(map)
+            Ok(EmailTemplate::Static(map))
         }
 
         NotificationBody::ReportSubmitted { report_id } => {
@@ -294,7 +360,7 @@ async fn collect_template_variables(
 
             map.insert(REPORT_TITLE, result.title);
             map.insert(NEWREPORT_ID, to_base62(report_id.0));
-            Ok(map)
+            Ok(EmailTemplate::Static(map))
         }
 
         NotificationBody::ProjectStatusApproved { project_id } => {
@@ -310,7 +376,7 @@ async fn collect_template_variables(
             map.insert(PROJECT_ID, to_base62(project_id.0));
             map.insert(PROJECT_NAME, result.name);
             map.insert(PROJECT_ICON_URL, result.icon_url.unwrap_or_default());
-            Ok(map)
+            Ok(EmailTemplate::Static(map))
         }
 
         NotificationBody::ProjectStatusNeutral {
@@ -332,7 +398,7 @@ async fn collect_template_variables(
             map.insert(PROJECT_ICON_URL, result.icon_url.unwrap_or_default());
             map.insert(PROJECT_OLD_STATUS, old_status.as_str().to_string());
             map.insert(PROJECT_NEW_STATUS, new_status.as_str().to_string());
-            Ok(map)
+            Ok(EmailTemplate::Static(map))
         }
 
         NotificationBody::ProjectTransferred {
@@ -388,7 +454,7 @@ async fn collect_template_variables(
                 map.insert(NEWOWNER_NAME, org.name);
             }
 
-            Ok(map)
+            Ok(EmailTemplate::Static(map))
         }
         NotificationBody::TeamInvite {
             team_id: _,
@@ -419,7 +485,7 @@ async fn collect_template_variables(
             map.insert(TEAMINVITE_PROJECT_NAME, result.project_name);
             map.insert(TEAMINVITE_ROLE_NAME, role.clone());
 
-            Ok(map)
+            Ok(EmailTemplate::Static(map))
         }
 
         NotificationBody::OrganizationInvite {
@@ -451,7 +517,7 @@ async fn collect_template_variables(
             map.insert(ORGINVITE_ORG_NAME, result.organization_name);
             map.insert(ORGINVITE_ROLE_NAME, role.clone());
 
-            Ok(map)
+            Ok(EmailTemplate::Static(map))
         }
 
         NotificationBody::StatusChange {
@@ -479,7 +545,7 @@ async fn collect_template_variables(
             map.insert(STATUSCHANGE_OLD_STATUS, old_status.as_str().to_owned());
             map.insert(STATUSCHANGE_NEW_STATUS, new_status.as_str().to_owned());
 
-            Ok(map)
+            Ok(EmailTemplate::Static(map))
         }
 
         NotificationBody::ResetPassword { flow } => {
@@ -492,7 +558,7 @@ async fn collect_template_variables(
 
             map.insert(RESETPASSWORD_URL, url);
 
-            Ok(map)
+            Ok(EmailTemplate::Static(map))
         }
 
         NotificationBody::VerifyEmail { flow } => {
@@ -505,20 +571,20 @@ async fn collect_template_variables(
 
             map.insert(VERIFYEMAIL_URL, url);
 
-            Ok(map)
+            Ok(EmailTemplate::Static(map))
         }
 
         NotificationBody::AuthProviderAdded { provider }
         | NotificationBody::AuthProviderRemoved { provider } => {
             map.insert(AUTHPROVIDER_NAME, provider.clone());
 
-            Ok(map)
+            Ok(EmailTemplate::Static(map))
         }
 
         NotificationBody::TwoFactorEnabled
         | NotificationBody::TwoFactorRemoved
         | NotificationBody::PasswordChanged
-        | NotificationBody::PasswordRemoved => Ok(map),
+        | NotificationBody::PasswordRemoved => Ok(EmailTemplate::Static(map)),
 
         NotificationBody::EmailChanged {
             new_email,
@@ -526,7 +592,7 @@ async fn collect_template_variables(
         } => {
             map.insert(EMAILCHANGED_NEW_EMAIL, new_email.clone());
 
-            Ok(map)
+            Ok(EmailTemplate::Static(map))
         }
 
         NotificationBody::PaymentFailed { amount, service } => {
@@ -541,7 +607,7 @@ async fn collect_template_variables(
             map.insert(PAYMENTFAILED_SERVICE, service.clone());
             map.insert(BILLING_URL, url);
 
-            Ok(map)
+            Ok(EmailTemplate::Static(map))
         }
 
         NotificationBody::PayoutAvailable {
@@ -562,7 +628,7 @@ async fn collect_template_variables(
                 format!("USD${:.2}", *amount as f64 / 100.0),
             );
 
-            Ok(map)
+            Ok(EmailTemplate::Static(map))
         }
 
         NotificationBody::TaxNotification {
@@ -607,16 +673,59 @@ async fn collect_template_variables(
             map.insert(TAXNOTIFICATION_DUE, date_human_readable(*due));
             map.insert(TAXNOTIFICATION_SERVICE, service.clone());
             map.insert(SUBSCRIPTION_ID, to_base62(subscription_id.0));
-            Ok(map)
+            Ok(EmailTemplate::Static(map))
         }
 
+        NotificationBody::Custom {
+            title,
+            body_md,
+            key,
+        } => Ok(EmailTemplate::Dynamic {
+            variables: map,
+            body: dynamic_email_body(redis, title, body_md, key).await?,
+            title: title.to_string(),
+        }),
+
         NotificationBody::ProjectUpdate { .. }
         | NotificationBody::ModeratorMessage { .. }
         | NotificationBody::LegacyMarkdown { .. }
-        | NotificationBody::Unknown => Ok(map),
+        | NotificationBody::Unknown => Ok(EmailTemplate::Static(map)),
     }
 }
 
+async fn dynamic_email_body(
+    redis: &RedisPool,
+    title: &str,
+    body_md: &str,
+    key: &str,
+) -> Result<String, ApiError> {
+    get_or_set_cached_dynamic_html(redis, key, || async {
+        let site_url = dotenvy::var("SITE_URL")
+            .wrap_internal_err("SITE_URL is not set")?;
+        let site_url = site_url.trim_end_matches('/');
+
+        let url = format!("{}/_internal/templates/email/dynamic", site_url);
+
+        std::str::from_utf8(
+            reqwest::Client::new()
+                .post(url)
+                .json(&serde_json::json!({
+                    "title": title,
+                    "body": body_md,
+                }))
+                .send()
+                .await
+                .and_then(|res| res.error_for_status())?
+                .bytes()
+                .await?
+                .as_ref(),
+        )
+        .wrap_internal_err("email body is not valid UTF-8")
+        .map(ToOwned::to_owned)
+    })
+    .await
+}
+
 fn date_human_readable(date: chrono::DateTime<chrono::Utc>) -> String {
     date.format("%B %d, %Y").to_string()
 }

apps/labrinth/src/routes/internal/external_notifications.rs

@@ -1,10 +1,15 @@
+use crate::auth::get_user_from_headers;
 use crate::database::models::ids::DBUserId;
 use crate::database::models::notification_item::NotificationBuilder;
 use crate::database::models::user_item::DBUser;
 use crate::database::redis::RedisPool;
+use crate::models::users::Role;
 use crate::models::v3::notifications::NotificationBody;
+use crate::models::v3::pats::Scopes;
+use crate::queue::session::AuthQueue;
 use crate::routes::ApiError;
 use crate::util::guards::external_notification_key_guard;
+use actix_web::HttpRequest;
 use actix_web::web;
 use actix_web::{HttpResponse, post};
 use ariadne::ids::UserId;
@@ -12,7 +17,7 @@ use serde::Deserialize;
 use sqlx::PgPool;
 
 pub fn config(cfg: &mut web::ServiceConfig) {
-    cfg.service(create);
+    cfg.service(create).service(send_custom_email);
 }
 
 #[derive(Deserialize)]
@@ -50,3 +55,64 @@ pub async fn create(
 
     Ok(HttpResponse::Accepted().finish())
 }
+
+#[derive(Deserialize)]
+struct SendEmail {
+    pub users: Vec<UserId>,
+    pub key: String,
+    pub body_md: String,
+    pub title: String,
+}
+
+#[post("external_notifications/send_custom_email")]
+pub async fn send_custom_email(
+    req: HttpRequest,
+    pool: web::Data<PgPool>,
+    redis: web::Data<RedisPool>,
+    session_queue: web::Data<AuthQueue>,
+    body: web::Json<SendEmail>,
+) -> Result<HttpResponse, ApiError> {
+    let user = get_user_from_headers(
+        &req,
+        &**pool,
+        &redis,
+        &session_queue,
+        Scopes::SESSION_ACCESS,
+    )
+    .await?
+    .1;
+
+    if user.role != Role::Admin {
+        return Err(ApiError::CustomAuthentication(
+            "You do not have permission to send custom emails!".to_string(),
+        ));
+    }
+
+    let SendEmail {
+        users,
+        body_md,
+        title,
+        key,
+    } = body.into_inner();
+
+    let users = users
+        .into_iter()
+        .map(|x| DBUserId(x.0 as i64))
+        .collect::<Vec<_>>();
+
+    let mut txn = pool.begin().await?;
+
+    NotificationBuilder {
+        body: NotificationBody::Custom {
+            title,
+            body_md,
+            key,
+        },
+    }
+    .insert_many(users, &mut txn, &redis)
+    .await?;
+
+    txn.commit().await?;
+
+    Ok(HttpResponse::Accepted().finish())
+}