is mdc thread safe

Full Answer

What is the difference between MDC.put and MDC.clear?

What is MDC in Log4J?

What does ThreadContext.put do?

What is mapped diagnostic context?

Is MDC available in SLF4J?

Does SLF4J support MDC?

Do you have to manually clean MDC?

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Is MDC thread-safe Java?

BTW, MDC is thread-safe. No worrying for concurrency. In multi-thread environment, if the child is create with the basic Thread + Runnable way, the child thread will automatically inherit parent's MDC.

Why do we use MDC?

MDC in Log4j allows us to fill a map-like structure with pieces of information that are accessible to the appender when the log message is actually written. The MDC structure is internally attached to the executing thread in the same way a ThreadLocal variable would be.

Is slf4j thread-safe?

In fact, it is not possible to guarantee that a Logger will always be thread-safe. Someone could implement their own slf4j compatible logging classes. Such an implementation could be non-thread-safe, by accident or by design. If it was, then the Logger exposed via the slf4j facade would also be non-thread-safe.

What is MDC in sl4j?

Logback leverages a variant of this technique included in the SLF4J API: Mapped Diagnostic Contexts (MDC). To uniquely stamp each request, the user puts contextual information into the MDC , the abbreviation of Mapped Diagnostic Context.

Is MDC ThreadLocal?

Internally, MDC uses ThreadLocal and it has some predefined functionalities like adding a prefix to every log.

Is MDC thread specific?

Yes, MDC is thread-local.

Is log4j and SLF4J same?

Unlike log4j, SLF4J (Simple Logging Facade for Java) is not an implementation of logging framework, it is an abstraction for all those logging frameworks in Java similar to log4J. Therefore, you cannot compare both.

Is log4j-over-SLF4J vulnerable?

The answer is "No" because log4j-over-slf4j only provides the log4j API but does not contain any implementation of log4j. But effectively by the presence of log4j-over-slf4j you can not derive any conclusion on the question is a the server vulnerable or not.

Is log4j multithreaded?

Yes, log4j is thread-safe. Log4j components are designed to be used in heavily multithreaded systems.

What is MDC and NDC?

MDC child thread automatically inherits a copy of the mapped diagnostic context of its parent. NDC operations such as push , pop , clear , getDepth and setMaxDepth affect the NDC of the current thread only.

What is thread context map MDC input data?

The Thread Context Map allows any number of items to be added and be identified using key/value pairs. The Thread Context Stack allows one or more items to be pushed on the Stack and then be identified by their order in the Stack or by the data itself.

What is MDC software?

The Crimestar Mobile Digital Communicator (MDC) is a powerful and secure digital dispatch/data communications system for field officers. The system allows field units to be silently dispatched to calls via Crimestar's Computer Aided Dispatch (CAD).

What MDC means?

Master of Development Communication (various locations) MDC. Media Development Centre (various locations) MDC. Millions of Dead Cops (1980s band)

What is MDC?

A Mapped Diagnostic Context, or MDC in short, is an instrument for distinguishing interleaved log output from different sources. Log output is typically interleaved when a server handles multiple clients near-simultaneously. The MDC is managed on a per thread basis.

What does MDC stand for in research?

Minimal detectable change (MDC) is defined as the minimal change that falls outside the measurement error in the score of an instrument used to measure a symptom.

What does MDC stand for in medical coding?

The Major Diagnostic Categories (MDC) are formed by dividing all possible principal diagnoses into 25 mutually exclusive diagnosis areas. The diagnoses in each MDC correspond to a single organ system or etiology and in general are associated with a particular medical specialty.

logging - How to use MDC of logback and SLF4J with spring boot to ...

You can use Logback's Mapped Diagnotic Context to propagate a unique tracking number to every log message.. There are two parts to this: Push your unique tracking number into MDC e.g. MDC.put("uniqueTrackingNumber", the_unique_tracking_number); Include the MDC entry in your log statements.

log4j - MDC logging in Core Java - Stack Overflow

This what is the significance of log4j rootlogger property in log4j properties file should help you out and add some insight as to what you're doing wrong (well not doing). Basically under log4j.rootLogger=DEBUG,consoleAppender you could add the line log4j.logger.org.apache.log4j.MDC=TRACE to get the most verbose logging. – JGlass

How to use Log4j and MDC in Java Spring Boot Application? - Sipios

How to log messages? What context information to add to our messages? Can this information be added when running asynchronous threads? This article will help you build a Spring Boot Java application to log messages with Log4j and use the MDC of this library (Mapping Diagnostic Context) to add contextualization data in addition to messages, especially for asynchronous tasks.

Java Logging with Mapped Diagnostic Context (MDC) - HowToDoInJava

2. Printing MDC Values in Logs. To print the context information in the logs, we can use MDC keys in the log pattern string.. For referring to the MDC context keys, we use the %X specifier that is used to print the current thread’s Nested Diagnostic Context (NDC) and/or Mapped Diagnostic Context (MDC).. Use %X to include the full contents of the Map.; Use %X{key} to include the specified key.

When to invoke MDC.getCopyOfContextMap()?

In such cases, it is recommended that MDC.getCopyOfContextMap() is invoked on the original (master) thread before submitting a task to the executor. When the task runs, as its first action, it should invoke MDC.setContextMapValues() to associate the stored copy of the original MDC values with the new Executor managed thread.

Can a copy of a mapped diagnostic context be inherited by worker threads from the initiating thread?

A copy of the mapped diagnostic context can not always be inherited by worker threads from the initiating thread. This is the case when java.util.concurrent.Executors is used for thread management. For instance, newCachedThreadPool method creates a ThreadPoolExecutor and like other thread pooling code, it has intricate thread creation logic.

Is MDC.getCopyOfContextMap() thread safe?

Regarding your question about thread safety: MDC.getCopyOfContextMap() may be NOT thread safe, if used with outdated SLF4J, that just returns a mutable ThreadContext.getContext(). For newer SLF4J versions, new HashMap<>(ThreadContext.getContext()) is returned.

What is MDC in logging?

MDC is nothing but a Map, in which application stored the details as a key-value pair, which later can be used by different logging libraries while printing logs

What does logback look for in MDC?

then while printing logs logback will look for value of CLIENT_IP key in the MDC context, and what ever value will be stored against CLIENT_IP key that value will be printed instead of %X {CLIENT_IP} token.

When to use below wrapper class?

Below wrapper class can be used when we want to create new Callable implementation.

Can you use MDC in lambda?

Don’t use the MDC , it’s too unsafe. Every time you change threads, you will either get an empty MDC (best case scenario), or MDC values from an older request (worst case scenario). At every single point where you might hop threads, it will be necessary to copy the current MDC settings to a local variable, close over it in your next lambda, and set the new thread’s MDC to the correct value before logging on the new thread. If any new asynchronous step is introduced without doing the above work, the correct values are lost for the rest of the request resulting in malformed or incorrect logs. Considering that adding “Async” to the end of a method name is enough to hop threads, this is a lot of work.

Can a copy of a mapped diagnostic context be inherited by worker threads from the initiating thread?

A copy of the mapped diagnostic context can not always be inherited by worker threads from the initiating thread. This is the case when java.util.concurrent.Executors is used for thread management. For instance, newCachedThreadPool method creates a ThreadPoolExecutor and like other thread pooling code, it has intricate thread creation logic.

Is MDC documentation incorrect?

The MDC docs are incorrect, with sections of the documentation explicitly referencing out of date information. I draw your attention to the section titled “MDC and Managed Threads” which says the following:

What is the difference between MDC.put and MDC.clear?

Unsurprisingly MDC.put () is used to add a key and a corresponding value in the MDC while MDC.clear () empties the MDC.

What is MDC in Log4J?

MDC in Log4j allows us to fill a map-like structure with pieces of information that are accessible to the appender when the log message is actually written.

What does ThreadContext.put do?

Again, ThreadContext.put () adds an entry in the MDC and ThreadContext.clearAll () removes all the existing entries.

What is mapped diagnostic context?

The basic idea of Mapped Diagnostic Context is to provide a way to enrich log messages with pieces of information that could be not available in the scope where the logging actually occurs, but that can be indeed useful to better track the execution of the program.

Is MDC available in SLF4J?

MDC is available in SLF4J, too, under the condition that it is supported by the underlying logging library.

Does SLF4J support MDC?

It is worth noting that in case we set up the SLF4J back-end to a logging system that does not support MDC, all the related invocations will be simply skipped without side effects.

Do you have to manually clean MDC?

This way, the MDC cleanup would happen after each normal or exceptional execution automatically. So, there is no need to do it manually: