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https://issues.apache.org/jira/browse/LOG4J2-1718?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Remko Popma updated LOG4J2-1718:
--------------------------------
Description:
Logging mutable objects asynchronously always has the risk that the object is
modified between the time the logger is called and the time the log message is
formatted and written to disk.
Log4j built-in Message implementation classes prevent this race condition in
one of two ways:
* Implement the {{ReusableMessage}} interface. Asynchronous logging components
in log4j cooperate with ReusableMessages by copying their _content_ (formatted
message, parameters) into the LogEvent rather than passing the Message instance
itself. This ensures the formatted message will not change when the mutable
object is modified.
* Cache the formatted message when the {{getFormattedMessage}} method is
called. Asynchronous logging components in log4j will call this method before
passing the Message object to another thread. (See LOG4J2-763.) For example,
FormattedMessage, LocalizedMessage, MessageFormatMessage, ObjectArrayMessage,
ObjectMessage, ParameterizedMessage, SimpleMessage and StringFormattedMessage
take this approach. Once initialized, {{getFormattedMessage}} returns the
cached String, so changes to the mutable object will not impact the formatted
message.
For performance reasons, users can choose to format _all_ messages in the
background by setting system property {{log4j.format.msg.async}} to true. (See
LOG4J2-898.)
Some messages do not capture mutable objects and are not at risk of the above
race condition.
This ticket proposes to introduce interface {{AsynchronouslyFormattable}} as a
marker interface to signal to asynchronous logging components that messages of
this type can safely be passed to a background thread without calling
{{getFormattedMessage}} first.
This benefits performance and avoids creating unnecessary (unused) objects.
Candidates for implementing this interface are message implementations which do
not cache anything in {{getFormattedMessage}}:
* flow messages (SimpleEntryMessage and SimpleExitMessage)
* MapMessage
* StructuredDataMessage
* ThreadDumpMessage (threads are cached in the constructor)
was:
Logging mutable objects asynchronously always has the risk that the object is
modified between the time the logger is called and the time the log message is
formatted and written to disk.
Log4j built-in Message implementation classes prevent this race condition in
one of two ways:
* Implement the {{ReusableMessage}} interface. Asynchronous logging components
in log4j cooperate with ReusableMessages by copying their _content_ (formatted
message, parameters) into the LogEvent rather than passing the Message instance
itself. This ensures the formatted message will not change when the mutable
object is modified.
* Cache the formatted message when the {{getFormattedMessage}} method is
called. Asynchronous logging components in log4j will call this method before
passing the Message object to another thread. (See LOG4J2-763.) For example,
FormattedMessage, LocalizedMessage, MessageFormatMessage, ObjectArrayMessage,
ObjectMessage, ParameterizedMessage, SimpleMessage and StringFormattedMessage
take this approach. Once initialized, {{getFormattedMessage}} returns the
cached String, so changes to the mutable object will not impact the formatted
message.
For performance reasons, users can choose to format _all_ messages in the
background by setting system property {{log4j.format.msg.async}} to true. (See
LOG4J2-898.)
Some messages do not capture mutable objects and are not at risk of the above
race condition.
This ticket proposes to introduce interface {{AsynchronouslyFormattable}} as a
marker interface to signal to asynchronous logging components that messages of
this type can safely be passed to a background thread without calling
{{getFormattedMessage}} first.
This benefits performance and avoids creating unnecessary (unused) objects.
Candidates for implementing this interface are message implementations which do
not cache anything in {{getFormattedMessage}}:
* flow messages (SimpleEntryMessage and SimpleExitMessage)
* MapMessage
* StructuredDataMessage
> Introduce marker interface AsynchronouslyFormattable
> ----------------------------------------------------
>
> Key: LOG4J2-1718
> URL: https://issues.apache.org/jira/browse/LOG4J2-1718
> Project: Log4j 2
> Issue Type: Improvement
> Components: API
> Affects Versions: 2.7
> Reporter: Remko Popma
> Assignee: Remko Popma
> Fix For: 2.8
>
>
> Logging mutable objects asynchronously always has the risk that the object is
> modified between the time the logger is called and the time the log message
> is formatted and written to disk.
> Log4j built-in Message implementation classes prevent this race condition in
> one of two ways:
> * Implement the {{ReusableMessage}} interface. Asynchronous logging
> components in log4j cooperate with ReusableMessages by copying their
> _content_ (formatted message, parameters) into the LogEvent rather than
> passing the Message instance itself. This ensures the formatted message will
> not change when the mutable object is modified.
> * Cache the formatted message when the {{getFormattedMessage}} method is
> called. Asynchronous logging components in log4j will call this method before
> passing the Message object to another thread. (See LOG4J2-763.) For example,
> FormattedMessage, LocalizedMessage, MessageFormatMessage, ObjectArrayMessage,
> ObjectMessage, ParameterizedMessage, SimpleMessage and StringFormattedMessage
> take this approach. Once initialized, {{getFormattedMessage}} returns the
> cached String, so changes to the mutable object will not impact the formatted
> message.
> For performance reasons, users can choose to format _all_ messages in the
> background by setting system property {{log4j.format.msg.async}} to true.
> (See LOG4J2-898.)
> Some messages do not capture mutable objects and are not at risk of the above
> race condition.
> This ticket proposes to introduce interface {{AsynchronouslyFormattable}} as
> a marker interface to signal to asynchronous logging components that messages
> of this type can safely be passed to a background thread without calling
> {{getFormattedMessage}} first.
> This benefits performance and avoids creating unnecessary (unused) objects.
> Candidates for implementing this interface are message implementations which
> do not cache anything in {{getFormattedMessage}}:
> * flow messages (SimpleEntryMessage and SimpleExitMessage)
> * MapMessage
> * StructuredDataMessage
> * ThreadDumpMessage (threads are cached in the constructor)
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