Fault-tolerant delivery system

2025-09-04 02:54:49 +02:00
parent d47fba5cc9
commit 3057fdc927
31 changed files with 872 additions and 116 deletions
--- a/src/idempotency/key.rs
+++ b/src/idempotency/key.rs
@@ -0,0 +1,28 @@
+pub struct IdempotencyKey(String);
+
+impl TryFrom<String> for IdempotencyKey {
+    type Error = String;
+
+    fn try_from(value: String) -> Result<Self, Self::Error> {
+        if value.is_empty() {
+            return Err("The idempotency key cannot be empty.".into());
+        }
+        let max_length = 50;
+        if value.len() >= max_length {
+            return Err("The idempotency key must be shorter than {max_length} characters.".into());
+        }
+        Ok(Self(value))
+    }
+}
+
+impl From<IdempotencyKey> for String {
+    fn from(value: IdempotencyKey) -> Self {
+        value.0
+    }
+}
+
+impl AsRef<str> for IdempotencyKey {
+    fn as_ref(&self) -> &str {
+        &self.0
+    }
+}
--- a/src/idempotency/persistance.rs
+++ b/src/idempotency/persistance.rs
@@ -0,0 +1,128 @@
+use crate::idempotency::IdempotencyKey;
+use axum::{
+    body::{self, Body},
+    http::{HeaderName, HeaderValue},
+    response::{IntoResponse, Response},
+};
+use reqwest::StatusCode;
+use sqlx::{Executor, PgPool, Postgres, Transaction};
+use std::str::FromStr;
+use uuid::Uuid;
+
+#[derive(Debug, sqlx::Type)]
+#[sqlx(type_name = "header_pair")]
+struct HeaderPairRecord {
+    name: String,
+    value: Vec<u8>,
+}
+
+pub async fn get_saved_response(
+    connection_pool: &PgPool,
+    idempotency_key: &IdempotencyKey,
+    user_id: Uuid,
+) -> Result<Option<Response>, anyhow::Error> {
+    let saved_response = sqlx::query!(
+        r#"
+            SELECT
+                response_status_code as "response_status_code!",
+                response_headers as "response_headers!: Vec<HeaderPairRecord>",
+                response_body as "response_body!"
+            FROM idempotency
+            WHERE
+                user_id = $1
+                AND idempotency_key = $2
+        "#,
+        user_id,
+        idempotency_key.as_ref()
+    )
+    .fetch_optional(connection_pool)
+    .await?;
+    if let Some(r) = saved_response {
+        let status_code = StatusCode::from_u16(r.response_status_code.try_into()?)?;
+        let mut response = status_code.into_response();
+        for HeaderPairRecord { name, value } in r.response_headers {
+            response.headers_mut().insert(
+                HeaderName::from_str(&name).unwrap(),
+                HeaderValue::from_bytes(&value).unwrap(),
+            );
+        }
+        *response.body_mut() = r.response_body.into();
+        Ok(Some(response))
+    } else {
+        Ok(None)
+    }
+}
+
+pub async fn save_response(
+    mut transaction: Transaction<'static, Postgres>,
+    idempotency_key: &IdempotencyKey,
+    user_id: Uuid,
+    response: Response<Body>,
+) -> Result<Response<Body>, anyhow::Error> {
+    let status_code = response.status().as_u16() as i16;
+    let headers = response
+        .headers()
+        .into_iter()
+        .map(|(name, value)| HeaderPairRecord {
+            name: name.to_string(),
+            value: value.as_bytes().to_vec(),
+        })
+        .collect::<Vec<_>>();
+    let (response_head, body) = response.into_parts();
+    let body = body::to_bytes(body, usize::MAX).await?.to_vec();
+
+    let query = sqlx::query_unchecked!(
+        r#"
+            UPDATE idempotency
+            SET
+                response_status_code = $3,
+                response_headers = $4,
+                response_body = $5
+            WHERE
+                user_id = $1
+                AND idempotency_key = $2
+            "#,
+        user_id,
+        idempotency_key.as_ref(),
+        status_code,
+        headers,
+        &body,
+    );
+    transaction.execute(query).await?;
+    transaction.commit().await?;
+
+    let mut r = response_head.into_response();
+    *r.body_mut() = body.into();
+    Ok(r)
+}
+
+pub enum NextAction {
+    StartProcessing(Transaction<'static, Postgres>),
+    ReturnSavedResponse(Response),
+}
+
+pub async fn try_processing(
+    connection_pool: &PgPool,
+    idempotency_key: &IdempotencyKey,
+    user_id: Uuid,
+) -> Result<NextAction, anyhow::Error> {
+    let mut transaction = connection_pool.begin().await?;
+    let query = sqlx::query!(
+        r#"
+            INSERT INTO idempotency (user_id, idempotency_key, created_at)
+            VALUES ($1, $2, now())
+            ON CONFLICT DO NOTHING
+            "#,
+        user_id,
+        idempotency_key.as_ref()
+    );
+    let n_inserted_rows = transaction.execute(query).await?.rows_affected();
+    if n_inserted_rows > 0 {
+        Ok(NextAction::StartProcessing(transaction))
+    } else {
+        let saved_response = get_saved_response(connection_pool, idempotency_key, user_id)
+            .await?
+            .ok_or_else(|| anyhow::anyhow!("Could not find saved response."))?;
+        Ok(NextAction::ReturnSavedResponse(saved_response))
+    }
+}