Diagnostics and Logging

Describes how to control the Handler's log output and how to be notified about non-critical issues.

Controlling Logging in the Handler

The Handler logs all significant aspects of its execution. The log files are stored in the directory specified by the HandlerSettings::logDirectory member value. Logging includes network data received and processed by the Handler and, of course, errors occurred at the execution time.

Since the Handler outputs logging data into regular files, this affects its performance and sometimes requires significant system resources, like space on the hard drive. The Handler exposes several parameters which allow adjusting certain kinds of logging and thus reducing the system load and increasing general performance.

The following list describes logging-related parameters exposed by the HandlerSettings structure:

• Settings member: HandlerSettings::logLevel

  Default value: LogLevel::Info

  Specifies whether the Handler must output informational messages about its state as well as which kind of information must be put into the log. For more information, please, take a look at description of LogLevel enumeration entries.

• Settings member: HandlerSettings::logSettings

  Default value: LogSettings::Default

  If the logging is activated, this member specifies which additional data must be put into the log. For more information, please, take a look at description of LogSettings enumeration entries.

Activating Logging Example

The following example demonstrates how to set up the logging at maximum level :

    settings.logLevel = LogLevel::Debug;
 
    settings.logDirectory = "./logs";
 
    // Log messages will be stored in the file, as well as received binary
    // packets and full state of updated order books.
    settings.logSettings = LogSettings::TraceToFile
        | LogSettings::LogPackets
        | LogSettings::LogBooks;

Disabling Logging

Logging adds overhead on the processing path, so disabling it is a recommended low latency optimization. Use this code snippet to disable all logging operations:

    // Available only log messages for fatal errors.
    settings.logLevel = LogLevel::Fatal;
 
    // Available only logging to file.
    settings.logSettings = LogSettings::TraceToFile;

Warnings Concept

Miscellaneous non-critical issues may occur while the Handler's instance is being executed. The Handler processes such matters on its own; thus no special handling is required in that case. However, sometimes it is reasonable to be notified about such events. For this purpose, the Handler represents WarningListener class and invokes its WarningListener::onWarning member each time a non-critical issue occurs.