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Use a spring based Aspect library that emits Markers automatically around function calls and retrofit your code to log via Luke's SLF4J for internal log messages.

LoggingWithAOP48534506

Logging Library Location and Use

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1. By selection of a logging provider such as Logback or Log4j, typically via the classpath. 
2. By way of a provider configuration document, typically logback.xml or log4j.xml. See Providers48534506.

SLF4J

SLF4J is a logging facade, and a humble masterpiece. It combines what's common to all major, modern Java logging providers into a single interface. This decouples the caller from the provider, and encourages the use of what's universal, familiar and proven. 

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Logback is the most commonly used provider. It is generally configured by an XML document named logback.xml. See Configuration 48534506.

See HELM template https://git.onap.org/logging-analytics/tree/reference/provider/helm/logback

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Log4j 2.X is somewhat less common than Logback, but equivalent. It is generally configured by an XML document named log4j.xml. See Configuration 48534506.

Log4j 1.X

Strongly discouraged from Beijing onwards, since 1.X is EOL, and since it does not support escaping, so its output may not be machine-readable. See https://logging.apache.org/log4j/1.2/.

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• Use a logging facade such as SLF4J or EELF. 
• Write log messages in English.
• Write meaningful messages. Consider what will be useful to consumers of logger output. 
• Log at the appropriate level. Be aware of the volume of logs that will be produced.
• Safeguard the information in exceptions, and ensure it is never lost.
• Use errorcodes error codes to characterise characterize exceptions. 
• Log in a machine-readable format. See Conventions.
• Log for analytics as well as troubleshooting.

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See https://www.slf4j.org/api/org/slf4j/Logger.html and https://logback.qos.ch/manual/layouts.html#ClassicPatternLayout for their origins and use.

Logger Name

This indicates the origin of a log name of the logger that logged the message.

It is confusingly named, and since in Java logging it is normally given as a class or package name, it's more often referred to as the logger "class" or "package"In Java it is convention to name the logger after the class or package using that logger.

• In Java, report the class or package name.
• In Python, the class or source filename.

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Think carefully about the information you report at each loglevellog level. The default log level is INFO.

Some loggers define non-standard levels, like FINE, FINER, WARNING, SEVERE, FATAL or CRITICAL. Use these judiciously, or avoid them.

Message

The freetext free text payload of a log event. 

This is the most important item of information in most log messages. See General 48534506 guidelines.

Internationalization

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if (logger.isDebugEnabled()) {
    logger.debug("But this WILL hurt: " + costlyToSerialize);
}

Parameterized logging is preferable.

Context

MDCs

A Mapped Diagnostic Context (MDC) allows an arbitrary string-valued attribute to be attached to a Java thread via a ThreadLocal variable. The MDC's value is then emitted with each message logged by that thread. The set of MDCs associated with a log message is serialized as unordered name-value pairs (see Text Output 48534506).

A good discussion of MDCs can be found at https://logback.qos.ch/manual/mdc.html. 

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Used as valuable URI - to annnote invoke marker

Review in terms of Marker 48534506 - INVOKE - possiblly add INVOKE-return - to filter reporting

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This should accompany INVOKE when the invocation is synchronous.

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SLF4J:

public static final Marker INVOKE_SYNCHRONOUS;
static {
    INVOKE_SYNCHRONOUS = MarkerFactory.getMarker("INVOKE");
    INVOKE_SYNCHRONOUS.add(MarkerFactory.getMarker("SYNCHRONOUS"));
}
// ...

// Generate and report invocation ID. 

final String invocationID = UUID.randomUUID().toString();
MDC.put(MDC_INVOCATION_ID, invocationID);
try {
    logger.debug(INVOKE_SYNCHRONOUS, "Invoking synchronously ... ");
}
finally {
    MDC.remove(MDC_INVOCATION_ID);
}

// Pass invocationID as HTTP X-InvocationID header.

callDownstreamSystem(invocationID, ... );

EELF example of SYNCHRONOUS reporting, without changing published APIs. 

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Error Codes

Errorcodes Error codes are reported as MDCs. 

TODO: add to table

Exceptions should be accompanied by an errrorcodeerror code. Typically this is achieved by incorporating errorcodes error codes into your exception hierarchy and error handling. ONAP components generally do not share this kind of code, though EELF defines a marker interface (meaning it has no methods) EELFResolvableErrorEnum.

A common convention is for errorcodes error codes to have two components:

1. A prefix, which identifies the origin of the error. 
2. A suffix, which identifies the kind of error.

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Logs on each filebeat docker container sidecar - /var/log/onap

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What's New

(Including what WILL be new in v1.2  / R2). 

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