Rails + Flutter App Server Health Check: 4 Issues Found and Fixed at Once

After uploading a test build of the app and running it myself, 4 things broke simultaneously. Google login failure, AI itinerary generation returning wrong results, app crash on tapping the notification button, and the popular destinations section completely empty. Here is the process of finding and fixing each cause.

1. Google SSO Fails While Apple Login Succeeds

Symptoms

Apple Sign-In works normally but Google Sign-In returns a 500 error. The client only shows a login failure toast.

Cause

The controller was fixed in a previous commit, but the Model’s from_omniauth method was left unchanged.

# User model — still references old column names after migration
def self.from_omniauth(auth)
  user = find_or_initialize_by(provider: auth.provider, uid: auth.uid)  # uid column doesn't exist
  user.image = auth.info.image  # image column doesn't exist either
end

In the DB schema, uid had been migrated to provider_uid and image to avatar_url. The controller queries were fixed but the model’s internal method was still referencing old columns.

Apple login was unaffected because it uses a separate path (verify_apple_identity_token! -> direct create_or_update_oauth_user!) that does not go through from_omniauth.

Fix

def self.from_omniauth(auth)
  user = find_or_initialize_by(provider: auth.provider, provider_uid: auth.uid)
  user.avatar_url = auth.info.image
  # ...
end

def set_uid_from_email
  self.provider_uid = email if self.provider_uid.blank?
end

Lessons Learned

When changing DB column names, fixing only the controller is not enough. Use grep -r "old_column_name" app/ to check models, services, and serializers as well. OAuth code is especially tricky because there are multiple login paths (Google, Apple, email), and testing only one path misses bugs in the others.

2. AI Itinerary Generation Returns Wrong Results

Symptoms

Requested AI itinerary generation with “Switzerland” keyword + “family trip” theme, but a domestic Korea trip itinerary appeared.

Cause

The route was defined but the controller file itself did not exist.

# routes.rb
post "ai/generate_itinerary", to: "ai_itinerary#generate"

app/controllers/api/v1/ai_itinerary_controller.rb -> does not exist (404)

The Flutter app had a silent catch that fell back to preset data on API call failure, and since there was no “Switzerland” preset, the default (Korea) was displayed.

try {
  final response = await apiClient.post('/ai/generate_itinerary', data: {...});
  // ...
} catch (e) {
  // silent — no error logs either
}

Fix

1. Create AI controller: OpenAI GPT-4o integration + preset fallback structure
2. Expand presets: 10 cities including Switzerland, Bangkok, London, Hawaii
3. Add Flutter-side presets too: Switzerland added to the app’s own fallback data

class AiItineraryController < BaseController
  skip_before_action :authenticate_user!

  def generate
    if ENV['OPENAI_API_KEY'].present?
      result = call_openai(params)
    else
      result = find_preset(params[:destination])
    end
    render_success(result)
  end
end

Lessons Learned

1. Defining a route does not equal completing the feature. You need to actually curl the endpoint to see if it returns 200 OK or 404
2. Flutter’s silent catch pattern is the enemy of debugging. At minimum, add debugPrint
3. Features depending on AI APIs must have a fallback strategy. Even when API keys are missing or the service is down, basic results should be provided

3. App Crashes When Tapping Notification Button

Symptoms

Top-right bell icon tap -> app crash (or blank screen)

Cause

The notification feature directory itself did not exist.

lib/features/notification/  -> directory does not exist

GoRouter tried to import a non-existent file for the /notifications route. Not caught at compile time (conditional import or lazy route), crashes at runtime.

Fix

Created a placeholder page:

class NotificationsPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Notifications')),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            Icon(Icons.notifications_none, size: 64, color: Colors.grey),
            SizedBox(height: 16),
            Text('No notifications yet'),
          ],
        ),
      ),
    );
  }
}

Lessons Learned

When defining navigation routes, the target page must exist as at least an empty Scaffold. Automating flutter analyze + route target file existence checks in CI can prevent this.

4. Popular Destinations Section Is Completely Empty

Symptoms

“Popular Destinations” section at the bottom of the home screen has no data or only shows 5 hardcoded entries.

Cause

• No DB table (migration not run)
• No model
• No API endpoint
• Flutter app only has 5 hardcoded data entries

Fix

Built the full stack at once:

1) Migration

create_table :popular_destinations, id: :uuid do |t|
  t.string :name, null: false
  t.string :name_en
  t.string :country_code, null: false
  t.text :description
  t.string :image_url
  t.decimal :rating, precision: 2, scale: 1
  t.integer :trip_count, default: 0
  t.string :tags, array: true, default: []
  t.string :keywords, array: true, default: []
  t.string :season
  t.integer :position
  t.boolean :featured, default: false
  t.boolean :active, default: true
  t.timestamps
end

2) Model + Scopes

class PopularDestination < ApplicationRecord
  scope :active, -> { where(active: true) }
  scope :featured, -> { where(featured: true) }
  scope :ordered, -> { order(:position) }
end

3) Public API Endpoint

class PopularDestinationsController < BaseController
  skip_before_action :authenticate_user!

  def index
    destinations = PopularDestination.active.ordered
    destinations = destinations.featured if params[:featured].present?
    render_success(destinations)
  end
end

4) Seed data – 12 cities including Kyoto, Bali, New York, Santorini, Paris, Switzerland

Bonus: Verifying E2E Flow with Seed Data

Just fixing bugs and moving on means the same problems will recur. Reproducing the entire trip lifecycle with seed data makes development and QA much easier.

Flow 1: Complete Trip Planning Flow

Connecting all related data to a single completed trip:

Trip (completed, is_public: true)
├── Flights (2 round-trip, ICN<->JFK)
├── Schedules (7-day itinerary + ScheduleFeedbacks)
├── Expenses (14 entries + ExpenseParticipants 2-person split)
├── Accommodation (1 hotel)
├── TransportationBookings (airport transfer, Uber)
├── LocalTransports (MetroCard 7-day pass)
├── ShoppingItems (souvenirs, fashion, beauty - 5 items)
├── ScrapedLinks (wishlist 4 items)
├── Recommendations (restaurants, attractions - 4 items)
├── ChecklistItems (trip prep checklist - 8 items)
├── TripAlbum + TripPhotos (1 album + 5 photos, with GPS)
└── Settlement (settlement complete, share_token issued)

Flow 2: Community Viewer Flow

User C (viewer)
├── Follows: User A, User B
├── Browses: completed public trips
├── Posts: 5 trip reviews (A: 2, B: 2, C: 1)
├── Comments: 9 entries (mutual comments)
└── Likes: 8 entries (mutual likes)

Seed Execution Results

Users: 3
Trips: 11 (completed 7, active 2, planning 2)
Flights: 4 | Schedules: 44 | Expenses: 68
Posts: 5 | Comments: 9 | Likes: 8 | Follows: 4
ScheduleFeedbacks: 7 | TripPhotos: 8 | Settlements: 1

Additional Bugs Found (Schema-Model Mismatch)

Problems discovered while inserting seed data:

Post/Comment Model Missing user_id FK

# Model
class Post < ApplicationRecord
  belongs_to :user  # expects user_id column
end

# Actual schema — no user_id, only a text-type user field
create_table "posts" do |t|
  t.text "user"     # For storing user info as JSON (not an FK)
  t.text "body"
end

belongs_to :user expects a user_id FK but the actual table did not have one. Resolved by adding a migration.

Post Model validates :content – Actual Column Is body

validates :content, presence: true  # content column doesn't exist, body is correct

This kind of mismatch frequently occurs when migrations and models are written at different times. Writing seed data that touches every model helps discover these mismatches early.

Summary

Common lesson: When adding a feature, the entire chain of “route definition -> controller -> model -> migration -> seed -> client” must be verified at once. Reproducing E2E flows with seed data helps find these gaps quickly.