SLA and uptime tracking in Rest API - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Calculate uptime percentage from logs

Given a list of service status logs with timestamps and status ("up" or "down"), what is the output of the following code that calculates the uptime percentage?

Rest API

logs = [
    {"timestamp": "2024-06-01T00:00:00Z", "status": "up"},
    {"timestamp": "2024-06-01T01:00:00Z", "status": "down"},
    {"timestamp": "2024-06-01T02:00:00Z", "status": "up"},
    {"timestamp": "2024-06-01T03:00:00Z", "status": "up"}
]

up_count = sum(1 for log in logs if log["status"] == "up")
total = len(logs)
uptime_percentage = (up_count / total) * 100
print(f"Uptime: {uptime_percentage:.2f}%")

A Uptime: 75.00%

B Uptime: 25.00%

C Uptime: 50.00%

D Uptime: 100.00%

💡 Hint

Count how many logs have status 'up' and divide by total logs.

There are 3 logs with status 'up' out of 4 total logs, so uptime is (3/4)*100 = 75.00%.

🧠 Conceptual

intermediate

Understanding SLA breach conditions

Which of the following conditions correctly describes when an SLA breach occurs for a service with 99.9% uptime guarantee over a 30-day period?

A Service downtime exceeds 43.2 minutes in 30 days

B Service downtime exceeds 4.32 hours in 30 days

C Service downtime exceeds 432 minutes in 30 days

D Service downtime exceeds 0.432 minutes in 30 days

💡 Hint

Calculate allowed downtime as 0.1% of total minutes in 30 days.

30 days = 43200 minutes. 0.1% downtime allowed = 43.2 minutes. Exceeding this breaches SLA.

🔧 Debug

advanced

Identify the error in uptime calculation code

What error does the following code produce when calculating uptime percentage from a list of status logs?

Rest API

logs = [
    {"timestamp": "2024-06-01T00:00:00Z", "status": "up"},
    {"timestamp": "2024-06-01T01:00:00Z", "status": "down"}
]

up_count = sum(1 for log in logs if log.status == "up")
total = len(logs)
uptime_percentage = (up_count / total) * 100
print(f"Uptime: {uptime_percentage:.2f}%")

A ZeroDivisionError: division by zero

B AttributeError: 'dict' object has no attribute 'status'

C SyntaxError: invalid syntax

D No error, prints 'Uptime: 50.00%'

💡 Hint

Check how dictionary keys are accessed in Python.

Dictionaries use bracket notation with keys as strings, not dot notation.

📝 Syntax

advanced

Find the syntax error in SLA JSON response

Which option contains a syntax error in this JSON response representing SLA status?

Rest API

{
  "service": "API",
  "uptime": 99.95,
  "status": "up",
  "last_downtime": null
}

A

}
llun :"emitnwod_tsal"  
,"pu" :"sutats"  
,59.99 :"emitpu"  
,"IPA" :"ecivres"  
{

B

{
  "service": "API",
  "uptime": "99.95",
  "status": "up",
  "last_downtime": null
}

C

{
  "service": "API",
  "uptime": 99.95,
  "status": "up",
  "last_downtime": null
}

D

  "service": "API",
  "uptime": 99.95,
  "status": "up",
  "last_downtime": null
}

💡 Hint

Check for trailing commas in JSON objects.

JSON does not allow trailing commas after the last key-value pair.

🚀 Application

expert

Calculate monthly SLA uptime from daily logs

Given daily uptime percentages for a 30-day month, which option correctly calculates the overall monthly uptime percentage?

Rest API

daily_uptimes = [99.9, 100, 99.8, 99.7, 100, 99.9, 99.95, 100, 99.85, 99.9, 100, 99.9, 99.8, 99.7, 100, 99.9, 99.95, 100, 99.85, 99.9, 100, 99.9, 99.8, 99.7, 100, 99.9, 99.95, 100, 99.85]

# Calculate monthly uptime here

A sum(daily_uptimes) / len(daily_uptimes)

B min(daily_uptimes)

C max(daily_uptimes)

D

prod = 1
for d in daily_uptimes:
    prod *= d / 100
prod * 100

💡 Hint

Monthly uptime is the product of daily uptimes as fractions, not the average.

To get overall uptime, multiply daily uptime fractions, then convert back to percentage.

Practice

1. What does SLA stand for in the context of uptime tracking?

easy

A. Service Level Agreement

B. System Log Analysis

C. Server Load Average

D. Standard Latency Assessment

Solution

1. Step 1: Understand SLA meaning

   SLA is a contract that defines expected service performance and uptime.

2. Step 2: Match SLA to options

   Only "Service Level Agreement" correctly describes this contract.

3. Final Answer:

   Service Level Agreement -> Option A

4. Quick Check:

   SLA = Service Level Agreement [OK]

Hint: Remember SLA means agreement on service quality [OK]

Common Mistakes:

• Confusing SLA with system logs
• Thinking SLA measures latency
• Mixing SLA with server load

2. Which HTTP method is typically used to retrieve uptime data from a REST API?

easy

A. POST

B. DELETE

C. PUT

D. GET

Solution

1. Step 1: Identify REST API methods for data retrieval

   GET method is used to request data without changing server state.

2. Step 2: Match method to uptime data retrieval

   Since uptime data is fetched, GET is the correct method.

3. Final Answer:

   GET -> Option D

4. Quick Check:

   Retrieve data with GET [OK]

Hint: Use GET to fetch data from REST APIs [OK]

Common Mistakes:

• Using POST to fetch data
• Confusing DELETE with retrieval
• Using PUT for reading data

3. Given this JSON response from an uptime API:

{"uptime_percentage": 99.5, "downtime_minutes": 30}

What is the actual uptime in minutes if the total period is 1440 minutes (1 day)?

medium

A. 1440 minutes

B. 1395 minutes

C. 1410 minutes

D. 1430 minutes

Solution

1. Step 1: Calculate uptime from total and downtime

   Uptime = Total minutes - Downtime minutes = 1440 - 30 = 1410 minutes.

2. Step 2: Confirm with options

   1410 minutes matches 1410 minutes. The percentage is a separate metric.

3. Final Answer:

   1410 minutes -> Option C

4. Quick Check:

   Uptime = 1440 - 30 = 1410 [OK]

Hint: Subtract downtime from total time for uptime [OK]

Common Mistakes:

• Using downtime as uptime
• Ignoring total period
• Confusing percentage with minutes

4. You have this REST API call to get uptime:

import requests
response = requests.get('https://api.example.com/uptime')
data = response.json()
uptime = data['up_time_percentage']

What is the error in this code?

medium

A. Incorrect key name 'up_time_percentage' instead of 'uptime_percentage'

B. Missing import for requests module

C. Using GET instead of POST method

D. No error, code is correct

Solution

1. Step 1: Check JSON key names

   The API returns key 'uptime_percentage', but code uses 'up_time_percentage'.

2. Step 2: Identify key mismatch error

   This causes a KeyError because the key name is incorrect.

3. Final Answer:

   Incorrect key name 'up_time_percentage' instead of 'uptime_percentage' -> Option A

4. Quick Check:

   Key name must match JSON exactly [OK]

Hint: Match JSON keys exactly to avoid errors [OK]

Common Mistakes:

• Typos in key names
• Using wrong HTTP method
• Forgetting to import requests

5. You want to check if a service meets its SLA of 99.9% uptime over a month (43200 minutes). The API returns:

{"uptime_percentage": 99.85}

Which statement correctly describes the SLA status?

hard

A. Service meets SLA because uptime is above 99.8%.

B. Service fails SLA because uptime is below 99.9%.

C. Service meets SLA because downtime is less than 60 minutes.

D. Service fails SLA because uptime percentage is not provided.

Solution

1. Step 1: Compare reported uptime to SLA target

   The SLA requires at least 99.9%, but actual uptime is 99.85%, which is less.

2. Step 2: Determine SLA compliance

   Since 99.85% < 99.9%, the service fails the SLA.

3. Final Answer:

   Service fails SLA because uptime is below 99.9% -> Option B

4. Quick Check:

   Actual uptime < SLA target means failure [OK]

Hint: Compare actual uptime directly to SLA percentage [OK]

Common Mistakes:

• Assuming close enough meets SLA
• Ignoring SLA threshold
• Confusing downtime with uptime