Logging for Unreal SDK

This page explains how to configure logging in the PubNub Unreal Software Development Kit (SDK) using log levels, custom loggers, and structured logging.

For general logging concepts and best practices applicable to all PubNub SDKs, see Logging.

Logging architecture

The SDK provides a flexible logging system that you can configure for different environments and use cases:

• Dual log sources: Logs originate from the UE SDK layer (C++) and the underlying C-Core library. You can filter each source independently.
• Default logger: A built-in logger (UPubnubDefaultLogger) routes all messages to Unreal's UE_LOG system, which outputs to the Output Log and log files.
• Custom loggers: You can add custom logger implementations via the IPubnubLoggerInterface interface to route logs to external systems.
• Structured logging: Every log entry is an FPubnubLogMessage struct that includes the log level, source, timestamp, callsite, and PubNub instance ID.

The SDK sends all log entries to every registered logger. Each logger independently filters messages based on its own minimum log level settings.

Log levels

The SDK uses six log levels, ordered from most verbose to least verbose:

Level	Enum value	Purpose
Trace	EPubnubLogLevel::PLL_Trace	Internal operations, detailed execution flow, and serialization steps
Debug	EPubnubLogLevel::PLL_Debug	User inputs, API parameters, HTTP requests and responses, and configuration properties
Info	EPubnubLogLevel::PLL_Info	Significant events like successful initialization and configuration changes
Warning	EPubnubLogLevel::PLL_Warning	Non-breaking issues, unusual conditions, and deprecation warnings
Error	EPubnubLogLevel::PLL_Error	Errors, failed operations, and exceptions
None	EPubnubLogLevel::PLL_None	Disables logging

Log sources

The SDK distinguishes between two log sources using EPubnubLogSource:

Source	Description
PLS_UE	Logs from the Unreal Engine SDK layer. These cover API call parameters, configuration, and SDK-level events.
PLS_CCore	Logs from the underlying C-Core library. These cover network requests, network responses, protocol-level errors, and internal state.

Each registered logger has separate minimum level settings for each source. This lets you, for example, capture detailed UE SDK logs at Debug while suppressing verbose C-Core output by setting it to None.

Enable logging

The SDK registers a default logger at startup which you don't have to configure.

Default logger

The SDK registers UPubnubDefaultLogger during client initialization. It routes messages to UE_LOG under the PubnubLog category with default minimum levels of PLL_Warning (UE SDK) and PLL_None (C-Core).

PubNub log level	UE_LOG verbosity
Trace, Debug, Info	Log
Warning	Warning
Error	Error

To capture more detail, lower the minimum levels at initialization or at runtime. To disable the default logger and use only custom loggers, set bEnableDefaultLogger = false in FPubnubLoggerConfig.

Configure logging at initialization

Use FPubnubLoggerConfig inside FPubnubConfig to configure logging when you create a PubNub client. The following table describes the available configuration fields:

Field	Default	Description
bEnableDefaultLogger	true	When true, the built-in default logger is registered during client initialization. Set to false to disable it entirely and rely only on your custom loggers.
DefaultLoggerMinLevel	PLL_Warning	Minimum log level for the default logger for UE SDK logs.
DefaultLoggerMinCCoreLevel	PLL_None	Minimum log level for the default logger for C-Core logs.
InitialLoggers	Empty	Additional custom logger objects to register during initialization. Each object must implement IPubnubLoggerInterface.

Reference code

Set up your Unreal project and follow the instructions in the lines marked with ACTION REQUIRED before running the code.

Actor.h

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Actor.cpp

1

Change log levels at runtime

You can retrieve registered loggers and adjust their minimum levels at any point after initialization.

Reference code

Set up your Unreal project and follow the instructions in the lines marked with ACTION REQUIRED before running the code.

Actor.h

1

Actor.cpp

1

Structured logging with FPubnubLogMessage

Every log entry the SDK dispatches to loggers is an FPubnubLogMessage struct. This provides structured information you can use to filter, format, or route log messages:

Field	Type	Description
LogLevel	EPubnubLogLevel	Severity level of the log message.
Source	EPubnubLogSource	Whether the log originated from the UE SDK (PLS_UE) or C-Core (PLS_CCore).
Message	FString	The log content. For C-Core logs, this includes formatted network request/response details and error information.
TimestampUtc	FDateTime	UTC timestamp of when the log message was created.
Callsite	FString	Optional source class or method that generated the log.
PubnubInstanceID	FString	PubNub client instance identifier, useful for distinguishing logs from multiple clients.

The default logger formats these fields into a single line:

2026-02-25T12:18:11.797Z [UE-SDK] PubNub-1 DEBUG [UPubnubClient::SubscribeToChannel_priv] Subscribing to channel...
2026-02-25T12:18:11.823Z [C-Core] PubNub-ee43324a DEBUG Network request: https://ps.pndsn.com/subscribe/...

Custom loggers

Beyond the built-in default logger, you can implement the IPubnubLoggerInterface to route logs to external monitoring services, files, or analytics platforms.

IPubnubLoggerInterface

The IPubnubLoggerInterface is a Blueprintable Unreal Interface that defines the logging contract. You can implement it in C++ or Blueprints:

1class IPubnubLoggerInterface
2{
3public:
4    // Common entry point called for all log messages
5    void Log(const FPubnubLogMessage& LogMessage);
6

7    // Level-specific entry points
8    void LogTrace(const FPubnubLogMessage& LogMessage);
9    void LogDebug(const FPubnubLogMessage& LogMessage);
10    void LogInfo(const FPubnubLogMessage& LogMessage);
11    void LogWarning(const FPubnubLogMessage& LogMessage);
12    void LogError(const FPubnubLogMessage& LogMessage);
13

14    // Log level control
15    void SetMinimumLogLevel(EPubnubLogLevel InLevel);
16    EPubnubLogLevel GetMinimumLogLevel() const;
17    void SetMinimumCCoreLogLevel(EPubnubLogLevel InLevel);
18    EPubnubLogLevel GetMinimumCCoreLogLevel() const;
19};

show all 19 lines

The SDK calls both the common Log() method and the level-specific method (for example, LogDebug()) for each message. The log manager checks each logger's minimum levels before dispatching. You only need to implement the methods you plan to use.

UPubnubBaseLogger

The SDK provides UPubnubBaseLogger, a UObject-based class that implements IPubnubLoggerInterface with default no-op behavior. Extend this class to create custom loggers without implementing every method:

1UCLASS(BlueprintType, Blueprintable)
2class UPubnubBaseLogger : public UObject, public IPubnubLoggerInterface
3{
4    // ...
5

6protected:
7    // Override these defaults in your subclass
8    EPubnubLogLevel MinimumLogLevel = EPubnubLogLevel::PLL_Warning;
9    EPubnubLogLevel MinimumCCoreLogLevel = EPubnubLogLevel::PLL_None;
10};

The built-in UPubnubDefaultLogger extends UPubnubBaseLogger and overrides the Log() method to format messages and route them to UE_LOG:

• Trace, Debug, and Info messages use UE_LOG(PubnubLog, Log, ...)
• Warning messages use UE_LOG(PubnubLog, Warning, ...)
• Error messages use UE_LOG(PubnubLog, Error, ...)

Register a custom logger

Create a logger object at runtime and register it with a PubNub client using AddLogger().

Reference code

Set up your Unreal project and follow the instructions in the lines marked with ACTION REQUIRED before running the code.

Actor.h

1

Actor.cpp

1

List registered loggers

Retrieve all currently registered loggers for a client:

Reference code

Set up your Unreal project and follow the instructions in the lines marked with ACTION REQUIRED before running the code.

Actor.h

1

Actor.cpp

1

Remove a logger

Remove a specific logger from a client:

Reference code

Set up your Unreal project and follow the instructions in the lines marked with ACTION REQUIRED before running the code.

Actor.h

1

Actor.cpp

1

Remove all loggers

Remove all registered loggers from a client:

Reference code

Set up your Unreal project and follow the instructions in the lines marked with ACTION REQUIRED before running the code.

Actor.h

1

Actor.cpp

1

Logged information

The SDK logs information at various stages of operation. This provides visibility into SDK behavior from both the UE SDK and C-Core layers.

UE SDK logs

The UE SDK layer logs the following at the Debug level:

• User-provided input data for each API call (channel names, messages, timetokens, filter expressions)
• Configuration property values at initialization
• Operation results and status codes

C-Core logs

The C-Core layer provides detailed protocol-level logging:

• Network requests: URL, query parameters, and request details
• Network responses: URL, HTTP status code, and response content
• Errors: Error code, error message, and optional details
• Structured objects: Internal state and complex data as formatted key-value pairs

C-Core logs are particularly useful for diagnosing connectivity issues and understanding the exact data flowing between your application and PubNub servers.

Viewing logs

Logs generated by the PubNub Unreal SDK can be viewed in:

• Unreal Editor's Output Log window during development (Window > Developer Tools > Output Log).
• Debug console when running a packaged game with the console enabled.
• Log files located in your project's Saved/Logs directory.

Filter the Output Log by the PubnubLog category to isolate PubNub SDK messages from other engine output.

Best practices

Choose the right log level

Environment	Recommended UE SDK level	Recommended C-Core level
Production	PLL_Warning or PLL_Error	PLL_None
Staging	PLL_Info	PLL_Warning
Development	PLL_Debug	PLL_Warning
Deep troubleshooting	PLL_Trace	PLL_Debug

Disable C-Core logging in production

C-Core logs at Debug and Trace levels generate significant output, especially for applications with many API calls. Keep DefaultLoggerMinCCoreLevel set to PLL_None in production to minimize performance impact and log noise.

Use custom loggers for monitoring

Implement IPubnubLoggerInterface to route critical errors to external monitoring services without affecting the default UE_LOG output. Extend UPubnubBaseLogger and override the Log() method to forward structured FPubnubLogMessage data to your monitoring backend. See Register a custom logger for a complete example of creating and registering a logger.

Provide complete logs to support

When reporting issues to PubNub support:

1. Set DefaultLoggerMinLevel to PLL_Debug or PLL_Trace.
2. Set DefaultLoggerMinCCoreLevel to PLL_Debug.
3. Reproduce the issue.
4. Collect logs from SDK initialization through the problem occurrence.
5. Include the PubNub SDK version and Unreal Engine version.