title

Logging Troubleshooting Guide

Common logging issues and their solutions, plus guidance on using logs to debug AOT and runtime issues.

Common Logging Issues

No Logs Appearing

Issue: Logger configured but no logs appear

Symptoms:

Logger is passed to table constructor
No log output in console/file/sink
Application runs normally

Diagnosis:

// Check if logger is enabled
var logger = loggerFactory.CreateLogger<ProductsTable>().ToDynamoDbLogger();
Console.WriteLine($"Debug enabled: {logger.IsEnabled(LogLevel.Debug)}");
Console.WriteLine($"Info enabled: {logger.IsEnabled(LogLevel.Information)}");

Solutions:

Check minimum log level:

// Too high - won't see Debug/Trace logs
builder.Services.AddLogging(logging =>
{
    logging.SetMinimumLevel(LogLevel.Warning); // Change to Debug or Information
});

Check category filters:

// May be filtering out DynamoDB logs
builder.Services.AddLogging(logging =>
{
    logging.AddFilter("Microsoft", LogLevel.Warning); // Doesn't affect DynamoDB
    logging.AddFilter("ProductsTable", LogLevel.Debug); // Add this
});

Check sink configuration:

// Serilog - ensure sink is configured
Log.Logger = new LoggerConfiguration()
    .WriteTo.Console() // Add this
    .CreateLogger();

Verify logger is configured in options:

// Wrong - logger not configured
var table = new ProductsTable(client, "products");

// Correct - use FluentDynamoDbOptions
var options = new FluentDynamoDbOptions()
    .WithLogger(logger);
var table = new ProductsTable(client, "products", options);

Issue: Conditional compilation disabled logging

Symptoms:

Logs worked in Debug build
No logs in Release build
No errors or warnings

Diagnosis:

# Check if DISABLE_DYNAMODB_LOGGING is defined
dotnet build -c Release -v detailed | grep DISABLE_DYNAMODB_LOGGING

Solution:

<!-- Remove or comment out in .csproj -->
<PropertyGroup Condition="'$(Configuration)' == 'Release'">
  <!-- <DefineConstants>$(DefineConstants);DISABLE_DYNAMODB_LOGGING</DefineConstants> -->
</PropertyGroup>

See Conditional Compilation for details.

Too Many Logs

Issue: Log volume overwhelming

Symptoms:

Thousands of log entries per second
Performance degradation
Storage costs increasing
Difficult to find relevant logs

Solutions:

Increase minimum log level:

// Production - only Information and above
builder.Services.AddLogging(logging =>
{
    logging.SetMinimumLevel(LogLevel.Information);
});

Filter by event ID:

// Only log DynamoDB operations, not mapping details
builder.Services.AddLogging(logging =>
{
    logging.AddFilter((category, level, eventId) => 
        (eventId.Id >= 3000 && eventId.Id < 4000) || // Operations
        eventId.Id >= 9000); // Errors
});

Filter by category:

// Different levels for different tables
builder.Services.AddLogging(logging =>
{
    logging.AddFilter("ProductsTable", LogLevel.Debug);
    logging.AddFilter("OrdersTable", LogLevel.Information);
});

Sample high-volume logs:

// Sample 10% of Debug logs
builder.Services.AddLogging(logging =>
{
    logging.AddFilter((category, level, eventId) =>
    {
        if (level == LogLevel.Debug)
            return Random.Shared.Next(100) < 10;
        return true;
    });
});

Use conditional compilation:

<!-- Disable logging in production -->
<PropertyGroup Condition="'$(Configuration)' == 'Release'">
  <DefineConstants>$(DefineConstants);DISABLE_DYNAMODB_LOGGING</DefineConstants>
</PropertyGroup>

Logger Not Working with Custom Implementation

Issue: Custom IDynamoDbLogger not receiving calls

Symptoms:

Custom logger implemented
IsEnabled returns true
Log methods never called

Diagnosis:

public class TestLogger : IDynamoDbLogger
{
    public bool IsEnabled(LogLevel logLevel)
    {
        Console.WriteLine($"IsEnabled called: {logLevel}");
        return true;
    }
    
    public void LogDebug(int eventId, string message, params object[] args)
    {
        Console.WriteLine($"LogDebug called: {eventId}");
    }
    
    // Implement other methods...
}

Solutions:

Implement all methods:

// Must implement ALL interface methods
public class CustomLogger : IDynamoDbLogger
{
    public bool IsEnabled(LogLevel logLevel) => true;
    
    public void LogTrace(int eventId, string message, params object[] args) { }
    public void LogDebug(int eventId, string message, params object[] args) { }
    public void LogInformation(int eventId, string message, params object[] args) { }
    public void LogWarning(int eventId, string message, params object[] args) { }
    public void LogError(int eventId, string message, params object[] args) { }
    public void LogError(int eventId, Exception exception, string message, params object[] args) { }
    public void LogCritical(int eventId, Exception exception, string message, params object[] args) { }
}

Check IsEnabled implementation:

// Wrong - always returns false
public bool IsEnabled(LogLevel logLevel) => false;

// Correct
public bool IsEnabled(LogLevel logLevel) => logLevel >= LogLevel.Debug;

Verify logger is passed to operations:

// Generated methods need logger parameter
var item = Product.ToDynamoDb(entity, logger); // Pass logger
var product = Product.FromDynamoDb<Product>(item, logger); // Pass logger

Using Logs to Debug AOT Issues

Issue: AOT Compilation Fails

Symptom: Trimming warnings or AOT errors

Use logging to identify the issue:

Enable detailed logging:

builder.Services.AddLogging(logging =>
{
    logging.SetMinimumLevel(LogLevel.Trace);
});

Run the operation that fails:

try
{
    var product = Product.FromDynamoDb<Product>(item, logger);
}
catch (Exception ex)
{
    // Check logs for the last successful operation
}

Analyze logs:

[Trace] Starting FromDynamoDb mapping for Product with 8 attributes
[Debug] Mapping property Id from String
[Debug] Mapping property Name from String
[Error] Failed to map DynamoDB item to Product
Exception: System.InvalidCastException: Unable to cast object...

The error shows which property failed, helping identify AOT issues.

Issue: Reflection-Based Code in AOT

Symptoms:

Works in Debug
Fails in AOT-compiled build
Generic type errors

Debugging with logs:

[Debug] Mapping property Metadata from Map
[Error] Failed to convert Metadata to Map. PropertyType: Dictionary<string, string>
Exception: System.MissingMethodException: Cannot create instance...

Solution: Use source-generated code instead of reflection:

// Generated code is AOT-safe
[DynamoDbAttribute("metadata")]
public Dictionary<string, string> Metadata { get; set; }

Issue: JSON Serialization in AOT

Symptoms:

JsonBlob property fails in AOT
Works with Newtonsoft.Json in non-AOT

Debugging with logs:

[Debug] Converting JsonBlob property Data
[Error] JSON serialization failed for property Data
Exception: System.Text.Json.JsonException: The JSON value could not be converted...

Solution: Use System.Text.Json with source generation:

[JsonBlob(JsonSerializerType.SystemTextJson)]
[DynamoDbAttribute("data")]
public MyData Data { get; set; }

// Add JsonSerializerContext
[JsonSerializable(typeof(MyData))]
public partial class MyJsonContext : JsonSerializerContext { }

Debugging Mapping Issues

Issue: Property Not Mapped

Symptoms:

Property value is null after FromDynamoDb
No error thrown

Debugging:

Enable Debug logging:

logging.SetMinimumLevel(LogLevel.Debug);

Check logs:

[Trace] Starting FromDynamoDb mapping for Product with 8 attributes
[Debug] Mapping property Id from String
[Debug] Mapping property Name from String
[Debug] Skipping empty collection Tags
[Trace] Completed FromDynamoDb mapping for Product

Look for:
- Property not mentioned → Not in DynamoDB item
- "Skipping" message → Value is null/empty
- No error → Mapping succeeded but value is null

Solutions:

// Check if attribute exists in item
if (item.ContainsKey("tags"))
{
    // Attribute exists
}
else
{
    // Attribute missing - check DynamoDB table
}

// Check attribute type
if (item.TryGetValue("tags", out var value))
{
    Console.WriteLine($"Type: {value.SS != null ? "SS" : "Unknown"}");
}

Issue: Type Conversion Fails

Symptoms:

DynamoDbMappingException thrown
Property type mismatch

Debugging:

[Debug] Converting Tags from String Set with 3 elements
[Error] Failed to convert Tags to Set. PropertyType: HashSet<string>, ElementCount: 3
Exception: InvalidCastException...

Solutions:

Check property type matches DynamoDB type:

// DynamoDB: String Set (SS)
// C#: Must be HashSet<string> or ISet<string>
[DynamoDbAttribute("tags")]
public HashSet<string> Tags { get; set; }

Check for null values:

// DynamoDB doesn't support null in sets
// Ensure no null values in collection
public HashSet<string> Tags { get; set; } = new();

Issue: Large Collection Performance

Symptoms:

Slow mapping
High memory usage
Timeout errors

Debugging:

[Debug] Converting Tags from String Set with 10000 elements
[Warning] Large collection detected: Tags has 10000 elements

Solutions:

Use pagination:

// Don't load entire collection at once
await table.Query
    .Where("pk = :pk")
    .WithValue(":pk", "product-123")
    .Take(100) // Limit results
    .ExecuteAsync();

Use projection:

// Only load needed properties
await table.Query
    .Where("pk = :pk")
    .WithValue(":pk", "product-123")
    .WithProjection("pk, sk, name") // Exclude large collections
    .ExecuteAsync();

Store large data externally:

// Use blob storage for large collections
[BlobReference(BlobProvider.S3)]
[DynamoDbAttribute("tags_ref")]
public HashSet<string> Tags { get; set; }

Debugging DynamoDB Operation Issues

Issue: Query Returns No Results

Debugging:

[Information] Executing Query on table products. KeyCondition: pk = :pk
[Debug] Query parameters: 1 values
[Information] Query completed. ItemCount: 0, ConsumedCapacity: 1.0

Analysis:

Query executed successfully (no error)
Consumed capacity > 0 (query ran)
ItemCount: 0 (no matching items)

Solutions:

Check key condition:

// Log shows actual condition used
// Verify it matches your data

Check parameter values:

// Enable Trace logging to see parameter values
logging.SetMinimumLevel(LogLevel.Trace);

Verify data exists:

// Use AWS Console or CLI to verify data
aws dynamodb query --table-name products --key-condition-expression "pk = :pk" --expression-attribute-values '{":pk":{"S":"product-123"}}'

Issue: High Capacity Consumption

Debugging:

[Information] Query completed. ItemCount: 5, ConsumedCapacity: 25.0
[Warning] High capacity consumption detected

Analysis:

5 items returned
25 capacity units consumed
~5 units per item (very high)

Solutions:

Use projection:

await table.Query
    .Where("pk = :pk")
    .WithValue(":pk", "product-123")
    .WithProjection("pk, sk, name") // Only needed attributes
    .ExecuteAsync();

Check item sizes:

[Debug] Mapping property Data from Binary
[Warning] Large property detected: Data is 400KB

Use eventually consistent reads:

await table.Query
    .Where("pk = :pk")
    .WithValue(":pk", "product-123")
    .WithConsistentRead(false) // Halves capacity cost
    .ExecuteAsync();

Issue: Throttling Errors

Debugging:

[Error] Query failed on table products
Exception: ProvisionedThroughputExceededException: Rate exceeded

Solutions:

Implement exponential backoff:

var retryCount = 0;
while (retryCount < 3)
{
    try
    {
        return await table.Query().ToListAsync();
    }
    catch (ProvisionedThroughputExceededException)
    {
        await Task.Delay(TimeSpan.FromMilliseconds(Math.Pow(2, retryCount) * 100));
        retryCount++;
    }
}

Monitor capacity consumption:

// Track capacity in logs
logging.AddFilter((category, level, eventId) => 
    eventId.Id == 3110); // ConsumedCapacity event

Use batch operations:

// More efficient than individual operations
await table.BatchGet
    .WithKeys(keys)
    .ExecuteAsync();

Log Analysis Examples

Find All Errors for an Entity

# Grep logs
grep "EntityType.*Product" logs.txt | grep "Error"

# Application Insights
traces
| where customDimensions.EntityType == "Product"
| where customDimensions.EventId >= 9000

Track Capacity Consumption

# Grep logs
grep "ConsumedCapacity" logs.txt

# Application Insights
traces
| where customDimensions.EventId == 3110
| summarize TotalCapacity = sum(todouble(customDimensions.ConsumedCapacity)) by bin(timestamp, 1h)

Identify Slow Operations

# Find operations taking > 1 second
grep "Operation completed" logs.txt | awk '{print $1, $NF}' | awk '$NF > 1000'

# Application Insights
traces
| where customDimensions.EventId == 3100
| extend Duration = datetime_diff('millisecond', timestamp, prev(timestamp))
| where Duration > 1000

Find Mapping Failures

# Grep logs
grep "EventId.*9000" logs.txt

# Application Insights
traces
| where customDimensions.EventId == 9000
| project timestamp, customDimensions.EntityType, customDimensions.PropertyName, message

Best Practices for Troubleshooting

Start with Information level - See high-level operations
Enable Debug for specific issues - Get property-level details
Use Trace sparingly - Only for deep debugging
Filter by event ID - Focus on specific operation types
Check structured properties - Query by EntityType, PropertyName, etc.
Compare Debug vs Release - Ensure consistent behavior
Test with logging disabled - Verify no dependencies on logging
Use log scopes - Add request/user context
Monitor capacity consumption - Track event ID 3110
Alert on errors - Event IDs >= 9000

Getting Help

If you're still stuck:

Collect logs - Enable Debug level and capture full logs
Identify pattern - When does it fail? Which entities?
Minimal reproduction - Create smallest example that fails
Check documentation - Review relevant guides
Search issues - Check GitHub issues for similar problems
Ask for help - Provide logs, code, and context

Next Steps

Logging Configuration - Configure loggers
Log Levels and Event IDs - Understand event IDs
Structured Logging - Query logs effectively
Error Handling - Handle exceptions properly

See Also:

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Logging Troubleshooting Guide

Common Logging Issues

No Logs Appearing

Issue: Logger configured but no logs appear

Issue: Conditional compilation disabled logging

Too Many Logs

Issue: Log volume overwhelming

Logger Not Working with Custom Implementation

Issue: Custom IDynamoDbLogger not receiving calls

Using Logs to Debug AOT Issues

Issue: AOT Compilation Fails

Symptom: Trimming warnings or AOT errors

Issue: Reflection-Based Code in AOT

Issue: JSON Serialization in AOT

Debugging Mapping Issues

Issue: Property Not Mapped

Issue: Type Conversion Fails

Issue: Large Collection Performance

Debugging DynamoDB Operation Issues

Issue: Query Returns No Results

Issue: High Capacity Consumption

Issue: Throttling Errors

Log Analysis Examples

Find All Errors for an Entity

Track Capacity Consumption

Identify Slow Operations

Find Mapping Failures

Best Practices for Troubleshooting

Getting Help

Next Steps

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Logging Troubleshooting Guide

Common Logging Issues

No Logs Appearing

Issue: Logger configured but no logs appear

Issue: Conditional compilation disabled logging

Too Many Logs

Issue: Log volume overwhelming

Logger Not Working with Custom Implementation

Issue: Custom IDynamoDbLogger not receiving calls

Using Logs to Debug AOT Issues

Issue: AOT Compilation Fails

Symptom: Trimming warnings or AOT errors

Issue: Reflection-Based Code in AOT

Issue: JSON Serialization in AOT

Debugging Mapping Issues

Issue: Property Not Mapped

Issue: Type Conversion Fails

Issue: Large Collection Performance

Debugging DynamoDB Operation Issues

Issue: Query Returns No Results

Issue: High Capacity Consumption

Issue: Throttling Errors

Log Analysis Examples

Find All Errors for an Entity

Track Capacity Consumption

Identify Slow Operations

Find Mapping Failures

Best Practices for Troubleshooting

Getting Help

Next Steps