Error classification in GraphQL - Mini Project: Build & Apply

Error classification

📖 Scenario: You work as a data analyst for a customer support team. They want to classify error messages from their system logs into categories to understand common problems.

🎯 Goal: Build a simple GraphQL query that returns error messages and their classification categories from a predefined dataset.

📋 What You'll Learn

Create a list of error messages with their types

Add a variable to filter errors by a specific type

Write a GraphQL query to select errors matching the filter

Display the filtered error messages and their categories

💡 Why This Matters

🌍 Real World

Classifying error messages helps support teams quickly identify and fix common problems in software systems.

💼 Career

Understanding how to filter and query data with GraphQL is useful for backend developers and data analysts working with APIs.

1

Create the error messages dataset

Create a list called errors with these exact entries: { id: 1, message: "Timeout error", category: "Network" }, { id: 2, message: "Null pointer exception", category: "Code" }, { id: 3, message: "Disk full", category: "Storage" }, { id: 4, message: "Timeout error", category: "Network" }.

GraphQL

# Your code here

Hint

Use an array of objects with id, message, and category keys.

2

Add a filter variable for category

Create a variable called filterCategory and set it to the string "Network".

GraphQL

const errors = [
  { id: 1, message: "Timeout error", category: "Network" },
  { id: 2, message: "Null pointer exception", category: "Code" },
  { id: 3, message: "Disk full", category: "Storage" },
  { id: 4, message: "Timeout error", category: "Network" }
];

# Your code here

Hint

Use a constant string variable to hold the category filter.

3

Write a GraphQL query to filter errors by category

Write a GraphQL query called getErrorsByCategory that takes a category argument of type String! and returns id, message, and category fields for errors matching the argument.

GraphQL

const errors = [
  { id: 1, message: "Timeout error", category: "Network" },
  { id: 2, message: "Null pointer exception", category: "Code" },
  { id: 3, message: "Disk full", category: "Storage" },
  { id: 4, message: "Timeout error", category: "Network" }
];

const filterCategory = "Network";

# Your code here

Hint

Define a GraphQL query type with a category argument and filter the errors array in the resolver.

4

Display the filtered error messages and categories

Write a console.log statement that prints the result of calling resolvers.Query.getErrorsByCategory with { category: filterCategory } as argument.

GraphQL

const errors = [
  { id: 1, message: "Timeout error", category: "Network" },
  { id: 2, message: "Null pointer exception", category: "Code" },
  { id: 3, message: "Disk full", category: "Storage" },
  { id: 4, message: "Timeout error", category: "Network" }
];

const filterCategory = "Network";

const typeDefs = `
  type Error {
    id: Int
    message: String
    category: String
  }

  type Query {
    getErrorsByCategory(category: String!): [Error]
  }
`;

const resolvers = {
  Query: {
    getErrorsByCategory: (_, { category }) => errors.filter(error => error.category === category)
  }
};

# Your code here

Hint

Call the resolver function with null as first argument and an object with category: filterCategory as second argument, then print the result.

Practice

1. What is the main purpose of error classification in data science models?

easy

A. To group model mistakes into clear categories for better understanding

B. To increase the speed of the model's predictions

C. To reduce the size of the dataset

D. To improve the model's user interface

Solution

1. Step 1: Understand error classification

   Error classification means sorting mistakes into groups to see patterns.

2. Step 2: Identify the goal of grouping errors

   Grouping helps find where the model works well or needs improvement.

3. Final Answer:

   To group model mistakes into clear categories for better understanding -> Option A

4. Quick Check:

   Error classification = Group mistakes [OK]

Hint: Error classification groups mistakes to spot issues fast [OK]

Common Mistakes:

• Thinking error classification speeds up predictions
• Confusing error classification with data size reduction
• Believing it improves user interface

2. Which GraphQL query structure correctly requests error counts grouped by error type?

easy

A. query { errorCountList { errorType, total } }

B. query { errors { count type } }

C. query { errorCounts(type, count) }

D. query { errorCounts { type count } }

Solution

1. Step 1: Identify correct GraphQL syntax

   GraphQL queries use curly braces with fields inside, like { errorCounts { type count } }.

2. Step 2: Check field names and order

   query { errorCounts { type count } } uses correct field names and structure matching typical GraphQL style.

3. Final Answer:

   query { errorCounts { type count } } -> Option D

4. Quick Check:

   Correct GraphQL query = query { errorCounts { type count } } [OK]

Hint: GraphQL queries list fields inside braces in correct order [OK]

Common Mistakes:

• Using parentheses instead of braces
• Swapping field names order incorrectly
• Using wrong field names not defined in schema

3. Given this GraphQL query:

query { errorCounts { type count } }

And this response:

{ "data": { "errorCounts": [ { "type": "False Positive", "count": 5 }, { "type": "False Negative", "count": 3 } ] } }

What is the total number of errors reported?

medium

A. 3

B. 8

C. 5

D. 15

Solution

1. Step 1: Extract counts from response

   The response shows 5 False Positives and 3 False Negatives.

2. Step 2: Add the counts together

   5 + 3 = 8 total errors.

3. Final Answer:

   8 -> Option B

4. Quick Check:

   5 + 3 = 8 total errors [OK]

Hint: Add all error counts from response to get total [OK]

Common Mistakes:

• Choosing only one error type count
• Multiplying counts instead of adding
• Ignoring one of the error types

4. This GraphQL query returns an error:

query { errorCounts { type, count } }

What is the likely cause?

medium

A. Incorrect field names

B. Missing query keyword

C. Using commas between fields inside braces

D. Using parentheses instead of braces

Solution

1. Step 1: Check GraphQL field syntax

   GraphQL fields inside braces should not have commas separating them.

2. Step 2: Identify the error cause

   The query uses commas between fields, causing syntax error.

3. Final Answer:

   Using commas between fields inside braces -> Option C

4. Quick Check:

   No commas between fields in GraphQL [OK]

Hint: Remove commas between fields in GraphQL queries [OK]

Common Mistakes:

• Adding commas between fields
• Omitting the query keyword (optional but valid)
• Using wrong field names without checking schema

5. You want to find which error type has the highest count using GraphQL. Which query and approach is best?

hard

A. query { errorCounts { type count } } and then find max count in client code

B. query { maxErrorCount } to get highest count directly

C. query { errorCounts(type: "max") { count } } to filter max error

D. query { errorCounts { count } } and assume first is max

Solution

1. Step 1: Understand GraphQL query capabilities

   GraphQL typically returns lists; aggregation like max often done client-side.

2. Step 2: Choose approach to find max error count

   Query all error counts and find max in client code is standard and flexible.

3. Final Answer:

   query { errorCounts { type count } } and then find max count in client code -> Option A

4. Quick Check:

   Get all counts, find max outside GraphQL [OK]

Hint: Fetch all counts, then find max in your code [OK]

Common Mistakes:

• Expecting GraphQL to do max aggregation automatically
• Filtering by 'max' as a type which is invalid
• Assuming first item is max without checking