Debugging Tools & Techniques

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📖 Concept

Effective debugging in Salesforce requires mastering multiple tools — debug logs, Developer Console, VS Code debugging, and monitoring tools.

Debugging tools:

Debug Logs
- Configure via Setup → Debug Logs
- Set log levels per category (Database, Apex, Workflow, etc.)
- Each log has a size limit (5MB for Developer Console, 20MB total)
- Persist for 24 hours (or until overwritten)
- Critical sections: SOQL_EXECUTE, DML_BEGIN, USER_DEBUG, LIMIT_USAGE
Developer Console
- Execute anonymous Apex
- View and analyze debug logs
- Query Plan tool for SOQL optimization
- Test runner with code coverage
- Performance profiling via timeline
VS Code with Salesforce Extensions
- Replay Debugger — step through debug logs
- ISV Debugger — real-time debugging (ISV only)
- Apex Test Sidebar — run/debug tests
- SOQL Builder — visual query construction
Monitoring & Alerting
- Event Monitoring (Shield) — user activity tracking
- Apex Exception Emails — automatic error notifications
- Custom error logging — Error_Log__c custom object
- Health Check — security scanning
- Salesforce Optimizer — org health analysis

Debug log anatomy:

EXECUTION_STARTED         — Transaction begins
CODE_UNIT_STARTED         — Trigger/class entry
SOQL_EXECUTE_BEGIN/END    — Each SOQL query with timing
DML_BEGIN/END             — Each DML operation
USER_DEBUG                — System.debug() output
VARIABLE_SCOPE_BEGIN/END  — Variable values (FINER level)
LIMIT_USAGE_FOR_NS        — Governor limit consumption
CUMULATIVE_LIMIT_USAGE    — Total limits used in transaction
EXECUTION_FINISHED        — Transaction complete

💻 Code Example

codeTap to expand ⛶

1// Debugging Patterns & Techniques
2
3public class DebuggingService {
4    
5    // 1. Structured debug logging
6    public static void debugLog(String className, String methodName, String message) {
7        System.debug(LoggingLevel.INFO, 
8            '[' + className + '.' + methodName + '] ' + message);
9    }
10    
11    public static void debugLog(String className, String methodName, 
12        String message, Object data) {
13        System.debug(LoggingLevel.INFO, 
14            '[' + className + '.' + methodName + '] ' + message + 
15            ' | Data: ' + JSON.serialize(data));
16    }
17    
18    // 2. Transaction-level debugging
19    public static void debugTransaction(String context) {
20        System.debug(LoggingLevel.INFO, '=== Transaction Debug: ' + context + ' ===');
21        System.debug(LoggingLevel.INFO, 'User: ' + UserInfo.getUserId());
22        System.debug(LoggingLevel.INFO, 'SOQL: ' + Limits.getQueries() + '/' + Limits.getLimitQueries());
23        System.debug(LoggingLevel.INFO, 'DML: ' + Limits.getDmlStatements() + '/' + Limits.getLimitDmlStatements());
24        System.debug(LoggingLevel.INFO, 'CPU: ' + Limits.getCpuTime() + 'ms/' + Limits.getLimitCpuTime() + 'ms');
25        System.debug(LoggingLevel.INFO, 'Heap: ' + Limits.getHeapSize() + '/' + Limits.getLimitHeapSize());
26    }
27    
28    // 3. Conditional debugging (avoid heap in production)
29    private static Boolean isDebugEnabled = false;
30    
31    public static void enableDebug() { isDebugEnabled = true; }
32    
33    public static void conditionalDebug(String message, Object data) {
34        if (isDebugEnabled) {
35            System.debug(LoggingLevel.DEBUG, message + ': ' + JSON.serialize(data));
36        }
37    }
38    
39    // 4. Error tracking with custom object
40    public static void logError(Exception e, String context) {
41        try {
42            insert new Error_Log__c(
43                Class_Name__c = context,
44                Error_Message__c = e.getMessage()?.left(255),
45                Stack_Trace__c = e.getStackTraceString()?.left(32000),
46                Error_Type__c = e.getTypeName(),
47                Line_Number__c = e.getLineNumber(),
48                User__c = UserInfo.getUserId(),
49                Timestamp__c = Datetime.now(),
50                Transaction_Id__c = Request.getCurrent().getRequestId()
51            );
52        } catch (Exception logError) {
53            System.debug(LoggingLevel.ERROR, 'Failed to log error: ' + logError.getMessage());
54        }
55    }
56    
57    // 5. Trigger debugging — trace what triggered the execution
58    public static void debugTriggerContext() {
59        System.debug(LoggingLevel.INFO, '=== Trigger Context ===');
60        System.debug(LoggingLevel.INFO, 'isBefore: ' + Trigger.isBefore);
61        System.debug(LoggingLevel.INFO, 'isAfter: ' + Trigger.isAfter);
62        System.debug(LoggingLevel.INFO, 'isInsert: ' + Trigger.isInsert);
63        System.debug(LoggingLevel.INFO, 'isUpdate: ' + Trigger.isUpdate);
64        System.debug(LoggingLevel.INFO, 'isDelete: ' + Trigger.isDelete);
65        System.debug(LoggingLevel.INFO, 'size: ' + Trigger.size);
66        System.debug(LoggingLevel.INFO, 'new: ' + (Trigger.new != null ? Trigger.new.size() : 0));
67        System.debug(LoggingLevel.INFO, 'old: ' + (Trigger.old != null ? Trigger.old.size() : 0));
68    }
69    
70    // 6. Anonymous Apex debugging scripts
71    // Execute in Developer Console → Execute Anonymous
72    
73    // Quick data check
74    // List<Account> accs = [SELECT Id, Name, Industry FROM Account LIMIT 5];
75    // System.debug(JSON.serializePretty(accs));
76    
77    // Test a specific method
78    // try {
79    //     OpportunityService.closeDeals(new Set<Id>{'006xxxxxxxxxxxx'});
80    //     System.debug('SUCCESS');
81    // } catch (Exception e) {
82    //     System.debug('ERROR: ' + e.getMessage());
83    //     System.debug('STACK: ' + e.getStackTraceString());
84    // }
85    
86    // Check sharing visibility
87    // List<AccountShare> shares = [
88    //     SELECT AccountId, UserOrGroupId, AccountAccessLevel, RowCause
89    //     FROM AccountShare WHERE AccountId = '001xxxxxxxxxxxx'
90    // ];
91    // System.debug(JSON.serializePretty(shares));
92}

🏋️ Practice Exercise

Debugging Practice:

Set up debug logs for your user and analyze a complex transaction (trigger → flow → trigger)
Use the Developer Console Timeline to identify the slowest operation in a transaction
Write a structured logging utility that captures class, method, and context
Create an Error_Log__c object and build an error tracking system
Use Anonymous Apex to reproduce and debug a specific production issue
Set up the VS Code Replay Debugger to step through a captured debug log
Build a debugging dashboard that shows error trends over time
Implement conditional debugging that can be toggled per user via Custom Setting
Write a script that audits all sharing rules affecting a specific record
Create a production monitoring alert that fires when error rates exceed thresholds

⚠️ Common Mistakes

Leaving System.debug statements in production code — they consume CPU time and heap even if no one reads the logs. Use conditional debugging or remove before deploy
Debug log size truncation — logs over 5MB are truncated. Reduce log levels for categories you don't need (set to WARN or NONE)
Not using structured log format — random debug messages are impossible to search. Always include class name, method name, and context
Debugging production with FINEST level — this generates massive logs and can impact org performance. Use INFO/DEBUG for production
Not checking CUMULATIVE_LIMIT_USAGE — the section at the end of debug logs shows total limit consumption, including all triggers and automations

💼 Interview Questions

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