Send emails in a background thread

2 files changed, 59 insertions, 34 deletions

diff --git a/app.py b/app.py
index f8422a9..6b49760 100644
--- a/app.py
+++ b/app.py
@@ -6,6 +6,10 @@ import os
 import sys
 import traceback
 import uuid
+import threading
+import queue
+import time
+from typing import Callable
 from user_agents import parse as parse_user_agent
 from dataclasses import dataclass
 from flask import Flask, render_template, redirect, request, make_response
@@ -30,6 +34,9 @@ AUTHOR_NAME_MAX_LENGTH = 100
 AUTHOR_EMAIL_MAX_LENGTH = 100
 VOTER_NAME_MAX_LENGTH = 100
 
+Task = Callable[[], None]
+background_tasks_queue: queue.Queue[Task] = queue.Queue()
+
 def voter_selection_on_choice(voter_name: str, choice: db.Choice) -> int | None:
   for vote in choice.votes:
     if vote.voter_name == voter_name:
@@ -95,7 +102,11 @@ def create():
     choices,
   )
 
-  email_client.send_poll_created_email_if_enabled(poll_id=poll.id)
+  if email_client.email_enabled:
+    def task():
+      email_client.send_poll_created_email(poll_id=poll.id)
+
+    background_tasks_queue.put(task)
 
   resp = make_response(
     redirect(f"/manage/{poll.manage_code}")
@@ -190,7 +201,10 @@ def vote_poll(id):
 
   manage_code = db.vote_poll(id, voter_name, selections)
 
-  email_client.send_participation_email_if_enabled(poll_id=id, voter_name=voter_name)
+  if email_client.email_enabled:
+    def task():
+      email_client.send_participation_email(poll_id=id, voter_name=voter_name)
+    background_tasks_queue.put(task)
 
   response = make_response(
     redirect(f"/poll/{id}")
@@ -346,3 +360,14 @@ def toggle_display_mode():
   resp.set_cookie("diddle_display_mode", display_mode,
                   samesite="Lax", secure=False)
   return resp
+
+### Background thread
+
+def background_thread():
+  print("Background thread started")
+  while True:
+    task = background_tasks_queue.get()
+    task()
+    time.sleep(0.1)
+
+threading.Thread(target=background_thread, daemon=True).start()
diff --git a/email_client.py b/email_client.py
index acb6c9c..e06c901 100644
--- a/email_client.py
+++ b/email_client.py
@@ -67,38 +67,38 @@ if email_enabled:
 else:
   print("SMTP email client not enabled")
 
-def send_participation_email_if_enabled(poll_id: str, voter_name: str):
-  if email_enabled:
-    poll = db.get_poll(poll_id)
-    if not poll or poll.author_email is None:
-      return
+def send_participation_email(poll_id: str, voter_name: str):
+  poll = db.get_poll(poll_id)
+  if not poll or poll.author_email is None:
+    return
 
-    try:
-      send_email(
-        subject=f"{voter_name} participated in your poll \"{poll.title}\"",
-        body=f"{voter_name} participated in your diddle \"{poll.title}\".\n\n"
-             f"View the results at {BASE_URL}/poll/{poll.id}\n"
-             f"Manage your diddle at {BASE_URL}/manage/{poll.manage_code}\n"
-              "You will be notified by email when someone participates.",
-        recipient=poll.author_email,
-      )
-    except Exception as e:
-      traceback.print_exc(file=sys.stderr)
-      print(f"Failed to send participation email to {poll.author_email}", file=sys.stderr)
+  print(f"Sending participation email to {poll.author_email}")
+  try:
+    send_email(
+      subject=f"{voter_name} participated in your poll \"{poll.title}\"",
+      body=f"{voter_name} participated in your diddle \"{poll.title}\".\n\n"
+            f"View the results at {BASE_URL}/poll/{poll.id}\n"
+            f"Manage your diddle at {BASE_URL}/manage/{poll.manage_code}\n"
+            "You will be notified by email when someone participates.",
+      recipient=poll.author_email,
+    )
+  except Exception as e:
+    traceback.print_exc(file=sys.stderr)
+    print(f"Failed to send participation email to {poll.author_email}", file=sys.stderr)
 
-def send_poll_created_email_if_enabled(poll_id: str):
-  if email_enabled:
-    poll = db.get_poll(poll_id)
-    if not poll or poll.author_email is None:
-      return
+def send_poll_created_email(poll_id: str):
+  poll = db.get_poll(poll_id)
+  if not poll or poll.author_email is None:
+    return
 
-    try:
-      send_email(
-        subject=f"You created a new diddle \"{poll.title}\"",
-        body=f"Manage your diddle at {BASE_URL}/manage/{poll.manage_code}\n"
-              "You will be notified by email when someone participates.",
-        recipient=poll.author_email,
-      )
-    except Exception as e:
-      traceback.print_exc(file=sys.stderr)
-      print(f"Failed to send poll created email to {poll.author_email}", file=sys.stderr)
\ No newline at end of file
+  print(f"Sending poll created email to {poll.author_email}")
+  try:
+    send_email(
+      subject=f"You created a new diddle \"{poll.title}\"",
+      body=f"Manage your diddle at {BASE_URL}/manage/{poll.manage_code}\n"
+            "You will be notified by email when someone participates.",
+      recipient=poll.author_email,
+    )
+  except Exception as e:
+    traceback.print_exc(file=sys.stderr)
+    print(f"Failed to send poll created email to {poll.author_email}", file=sys.stderr)