Implement short link redirect service (#180)

* Implement short link redirect service * Silence linter where imports needs to be below setup * Improve unknown link error * Provide session to worker to convert it to user id * Remove main entrypoint in favor of uvicorn command * Add base path for relative URLs * Add docs on launching redirect service to README.md * Fix wrong task argument name * Lint service code
2024-11-24 19:23:44 +03:00 · 2023-08-08 13:57:32 +03:00 · 2023-08-08 13:57:32 +03:00 · 21c02df7f0
commit 21c02df7f0
parent 223b5aba2d
13 changed files with 896 additions and 270 deletions
--- a/.env.example
+++ b/.env.example
@ -1,4 +1,4 @@
-DATABASE_URL=postgres://postgres:postgres@127.0.0.1:5432/akarpov
+DATABASE_URL=postgresql://postgres:postgres@127.0.0.1:5432/akarpov
 CELERY_BROKER_URL=redis://localhost:6379/0
 REDIS_URL=redis://localhost:6379/1
 REDIS_CACHE=rediscache://localhost:6379/1
--- a/README.md
+++ b/README.md
@ -16,6 +16,7 @@ $ python3 manage.py migrate
 ```shell
 $ python3 manage.py runserver
 $ celery -A config.celery_app worker --loglevel=info
+$ uvicorn redirect.app:app --reload
 ```


--- a/compose/production/django/entrypoint
+++ b/compose/production/django/entrypoint
@ -14,7 +14,7 @@ if [ -z "${POSTGRES_USER}" ]; then
    base_postgres_image_default_user='postgres'
    export POSTGRES_USER="${base_postgres_image_default_user}"
 fi
-export DATABASE_URL="postgres://${POSTGRES_USER}:${POSTGRES_PASSWORD}@${POSTGRES_HOST}:${POSTGRES_PORT}/${POSTGRES_DB}"
+export DATABASE_URL="postgresql://${POSTGRES_USER}:${POSTGRES_PASSWORD}@${POSTGRES_HOST}:${POSTGRES_PORT}/${POSTGRES_DB}"

 python << END
 import sys
--- a/poetry.lock
+++ b/poetry.lock
--- a/pyproject.toml
+++ b/pyproject.toml
@ -94,6 +94,9 @@ django-location-field = "^2.7.0"
 pydantic = "^2.0.2"
 channels-redis = "^4.1.0"
 django-ipware = "^5.0.0"
+fastapi = {extras = ["all"], version = "^0.101.0"}
+sqlalchemy = "^2.0.19"
+pydantic-settings = "^2.0.2"


 [build-system]
--- a/redirect/init.py
+++ b/redirect/init.py
@ -0,0 +1 @@
+"""Service to redirect users from short links."""
--- a/redirect/app.py
+++ b/redirect/app.py
@ -0,0 +1,77 @@
+import os
+from typing import Annotated
+
+import django
+from fastapi import Cookie, Depends, FastAPI, Header
+from fastapi.responses import HTMLResponse, RedirectResponse
+from sqlalchemy.orm import Session
+from starlette.requests import Request
+
+from redirect.db.curd import LinkNotFoundException, get_link_by_slug
+from redirect.db.dependency import get_db
+from redirect.settings import settings
+
+os.environ.setdefault("DJANGO_SETTINGS_MODULE", "config.settings.local")
+django.setup()
+app = FastAPI()
+
+
+from akarpov.tools.shortener.tasks import (  # noqa: This has to be imported strictly AFTER django setup
+    save_view_meta,
+)
+
+
+@app.exception_handler(LinkNotFoundException)
+async def unicorn_exception_handler(request: Request, exc: LinkNotFoundException):
+    return HTMLResponse(
+        status_code=404,
+        # language=HTML
+        content="""
+        <html lang="en">
+            <head>
+                <title>Unknown Link</title>
+                <style>
+                    h1 {
+                        font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", ui-system, sans-serif;
+                        font-weight: bold;
+                        font-size: medium;
+                        text-align: center;
+                    }
+                </style>
+            </head>
+        <body>
+            <h1>Such link doesn't exist or has been revoked</h1>
+        </body>
+        </html>
+        """,
+    )
+
+
+@app.get("/{slug}")
+def redirect(
+    slug: str,
+    request: Request,
+    db: Session = Depends(get_db),
+    user_agent: Annotated[str | None, Header()] = None,
+    sessionid: Annotated[str | None, Cookie()] = None,
+) -> RedirectResponse:
+    """Main route that redirects to a page based on the slug."""
+    if "+" in slug:
+        return RedirectResponse(url=f'/tools/shortener/p/{slug.replace("+", "")}')
+
+    link_id, link_target = get_link_by_slug(db, slug)
+
+    save_view_meta.apply_async(
+        kwargs={
+            "pk": link_id,
+            "ip": request.client.host,
+            "user_agent": user_agent,
+            "user_id": sessionid,
+        },
+    )
+
+    return RedirectResponse(
+        url=(settings.relative_base + link_target)
+        if link_target.startswith("/")
+        else link_target
+    )
--- a/redirect/db/init.py
+++ b/redirect/db/init.py
@ -0,0 +1,12 @@
+from sqlalchemy import create_engine, make_url
+from sqlalchemy.ext.declarative import declarative_base
+from sqlalchemy.orm import sessionmaker
+
+from redirect.settings import settings
+
+SQLALCHEMY_DATABASE_URL = make_url(settings.database_url)
+
+engine = create_engine(SQLALCHEMY_DATABASE_URL)
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+
+Base = declarative_base()
--- a/redirect/db/curd.py
+++ b/redirect/db/curd.py
@ -0,0 +1,41 @@
+from sqlalchemy.orm import Session
+
+from redirect.db import models
+from redirect.util import slug_to_link_id
+
+
+class LinkNotFoundException(Exception):
+    def __init__(self, slug: str):
+        self.slug = slug
+
+
+def get_link(db: Session, link_id: int):
+    """Gets short link metdata by its id.
+
+    :param db Open connection to a database
+    :param link_id id of the link
+
+    :return link metadata"""
+    return db.query(models.Link).filter(models.Link.id == link_id).first()
+
+
+_get_link_by_slug_cache = {}
+
+
+def get_link_by_slug(db: Session, slug: str) -> tuple[int, str]:
+    """Converts slug to id and gets related link target.
+
+    :param db Open connection to a database
+    :param slug of the link
+
+    :raise LinkNotFoundException if link is not found
+    :return target link id & url"""
+    if slug in _get_link_by_slug_cache:
+        return _get_link_by_slug_cache[slug]
+
+    link = get_link(db, slug_to_link_id(slug))
+    if link is None or not link.enabled:
+        raise LinkNotFoundException(slug)
+
+    _get_link_by_slug_cache[slug] = (link.id, link.source)
+    return link.id, link.source
--- a/redirect/db/dependency.py
+++ b/redirect/db/dependency.py
@ -0,0 +1,10 @@
+from redirect.db import SessionLocal
+
+
+def get_db():
+    """Route dependency that provides a database session."""
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()
--- a/redirect/db/models.py
+++ b/redirect/db/models.py
@ -0,0 +1,18 @@
+from sqlalchemy import Boolean, Column, DateTime, Integer, String
+
+from redirect.db import Base
+
+
+class Link(Base):
+    """Model of a short link that defines slug and target of a redirect."""
+
+    __tablename__ = "short_link"
+
+    id = Column(Integer, primary_key=True, index=True)
+    created = Column(DateTime)
+    modified = Column(DateTime)
+    source = Column(String)
+    slug = Column(String, index=True)
+    enabled = Column(Boolean)
+    viewed = Column(Integer)
+    creator_id = Column(Integer, index=True)
--- a/redirect/settings.py
+++ b/redirect/settings.py
@ -0,0 +1,19 @@
+from pydantic_settings import BaseSettings
+
+
+class AppSettings(BaseSettings):
+    """General configuration of the app."""
+
+    redirect_slug_cutoff: int = 3
+
+    relative_base: str = "http://127.0.0.1:8000"
+    database_url: str = "postgresql://postgres:postgres@127.0.0.1:5432/akarpov"
+
+    class Config:
+        env_prefix = ""
+        env_file = ".env"
+        env_file_encoding = "utf-8"
+        extra = "allow"
+
+
+settings = AppSettings()
--- a/redirect/util.py
+++ b/redirect/util.py
@ -0,0 +1,18 @@
+import string
+
+from redirect.settings import settings
+
+URL_CHARACTERS = list(string.ascii_letters + string.digits + ";,:@&-_.!~*'()#")
+SLUG_CUTOFF = settings.redirect_slug_cutoff
+
+
+def slug_to_link_id(slug: str) -> int:
+    """Converts given slug to an id of a link."""
+    link_id = 0
+    try:
+        for i, ch in enumerate(slug[:SLUG_CUTOFF - 1:-1]):  # fmt: skip
+            value = URL_CHARACTERS.index(ch)
+            link_id += value * len(URL_CHARACTERS) ** i
+    except ValueError:
+        pass
+    return link_id
				`@ -0,0 +1 @@`
				`"""Service to redirect users from short links."""`