Test, Debug, and Observe

Now let’s test the complete workflow. Upload a file, watch the function run, and verify the email is sent.

Testing Workflow

Here’s how to test everything:

Step 1: Upload a test file

# Create a test file
echo "This is a test file" > test-document.txt

# Upload to S3
aws s3 cp test-document.txt s3://my-notifications-bucket-2025/

# Verify upload
aws s3 ls s3://my-notifications-bucket-2025/

# Create a test file
echo "This is a test file" > test-document.txt

# Upload to Blob Storage
az storage blob upload \
--account-name mynotifications2025 \
--container-name uploads \
--name test-document.txt \
--file test-document.txt \
--auth-mode login

# Verify upload
az storage blob list \
--account-name mynotifications2025 \
--container-name uploads \
--auth-mode login

# Create a test file
echo "This is a test file" > test-document.txt

# Upload to Cloud Storage
gsutil cp test-document.txt gs://my-notifications-bucket-2025/

# Verify upload
gsutil ls gs://my-notifications-bucket-2025/

Step 2: Check function logs

The function should run automatically. Check the logs:

# View recent logs
aws logs tail /aws/lambda/notify-on-upload --follow

# Or in CloudWatch Console:
# 1. Go to CloudWatch → Log groups
# 2. Find /aws/lambda/notify-on-upload
# 3. Click latest log stream
# 4. View log entries

In Azure Portal:

1. Go to your Function App
2. Click "Functions" → your function
3. Click "Monitor" tab
4. View "Invocation log" for recent executions
5. Click on an execution to see details

Or use Azure CLI:
az functionapp log tail --name your-function-app --resource-group your-rg

# View recent logs
gcloud functions logs read notify-on-upload --limit 20

# Or in Cloud Console:
# 1. Go to Cloud Functions
# 2. Click your function
# 3. Click "Logs" tab
# 4. View recent executions

Step 3: Verify email received

• Check your recipient email inbox
• Look for email with subject “New file uploaded: test-document.txt”
• Verify email content includes file details

What to Look For in Logs

Successful execution:

Event received: {...}
File uploaded: test-document.txt in bucket my-notifications-bucket-2025
Message prepared: New file uploaded: test-document.txt
Email sent successfully
Notification sent for: test-document.txt

Error indicators:

ERROR: Email error: ...
ERROR: Missing environment variable: SENDGRID_API_KEY
ERROR: Permission denied

Common Errors and Solutions

Error: Function didn’t run

Symptoms:

• No logs appear
• File uploaded but nothing happens

Possible causes:

• Trigger not configured
• Function in wrong region
• Missing permissions

Solutions:

1. Verify trigger is enabled in console
2. Check function and bucket are in same region
3. Review IAM permissions
4. Check trigger configuration

Error: Permission denied

Symptoms:

• Function runs but fails with permission error
• “Access denied” in logs

Possible causes:

• Function lacks permission to access storage
• Email service API key invalid
• Missing IAM role permissions

Solutions:

1. Check function execution role has storage read permission
2. Verify email service API key is correct
3. Review IAM policies

Error: Email sending failed

Symptoms:

• Function runs but email not received
• “Email error” in logs

Possible causes:

• Invalid API key
• Sender email not verified
• Rate limit exceeded
• Invalid recipient email

Solutions:

1. Verify API key in environment variables
2. Verify sender email in email service dashboard
3. Check rate limits
4. Verify recipient email address

Error: Missing environment variable

Symptoms:

• “undefined” or “null” errors
• “Missing environment variable” in logs

Possible causes:

• Environment variable not set
• Wrong variable name
• Variable not saved

Solutions:

1. Check environment variables in function configuration
2. Verify variable names match code
3. Redeploy function after setting variables

Debugging Decision Tree

Use this flow to debug issues:

Did the function run?
├─ No → Check trigger configuration
│        ├─ Is trigger enabled?
│        ├─ Are function and bucket in same region?
│        └─ Are permissions correct?
│
└─ Yes → Are there errors in logs?
         ├─ Yes → Check error type
         │        ├─ Permission error → Check IAM roles
         │        ├─ Email error → Check API key and email service
         │        └─ Missing variable → Check environment variables
         │
         └─ No → Did email arrive?
                  ├─ No → Check email service logs
                  └─ Yes → Success! ✅

Common Error Messages

Monitoring Best Practices

Set up alerts:

• Function errors
• Email delivery failures
• High error rates

Track metrics:

• Function invocations
• Execution duration
• Error rates
• Email delivery rates

Regular checks:

• Review logs weekly
• Test workflow monthly
• Monitor costs

Testing Checklist

Before considering the system complete:

• File upload works - Can upload files to bucket
• Function triggers - Function runs when file uploaded
• Logs show execution - Can see function logs
• Email sent - Email arrives in inbox
• Email content correct - File details are accurate
• Error handling works - Errors are logged properly
• Multiple files work - System handles multiple uploads

What’s Next?

In the final page, we’ll cover security best practices, understand costs, and learn how to clean up resources when you’re done.