This class provides a mechanism for associating attributes with the current thread, and evaluating the logging rules associated with a category using those stored attributes. AttributeContext contains class data members that must be initialized (using the initialize class method) with a CategoryManager object containing a RuleSet that represents the currently installed logging rules for the process. Clients can obtain the context for the current thread by calling the getContext class method. The addAttributes and removeAttributes methods are used to add and remove collections of attributes from the (thread‐local) context object. Finally, AttributeContext provides methods (used primarily by other components in the ball package') to determine the effect of the current logging rules on the logging thresholds of a category. The hasRelevantActiveRules method returns true if there are any relevant and active rules that might modify the logging thresholds of the supplied category. A rule is "relevant" if the rule's pattern matches the category's name, and a rule is "active" if all the attributes defined for the rule are satisfied by the current thread's attributes (i.e., Rule::evaluate returns true for the collection of attributes maintained for the current thread by the thread's AttributeContext object). The determineThresholdLevels method returns the logging threshold levels for a category, factoring in any active rules that apply to the category that might override the category's thresholds. The behavior for the hasRelevantActiveRules and determineThresholdLevels methods is undefined unless initialize has been called. Note that, in practice, initialize is called internally when the logger manager singleton is initialized; clients ordinarily should not call initialize directly.

Synopsis

Declared in <ball_attributecontext.h>

class AttributeContext;

Type Aliases

Name

Description

iterator

Iterator over the attribute containers in an AttributeContext.

Member Functions

Name

Description

addAttributes

Add the specified attributes container to the list of attribute containers maintained by this object. The behavior is undefined unless attributes remains valid and unmodified until either attributes is removed from this context, clearCache is called, or this object is destroyed. Note that this method can be invoked safely even if the initialize class method has not yet been called.

clearCache

Clear this object's cache of evaluated rules. Note that this method must be called if an AttributeContainer object supplied to addAttributes is modified outside of this context.

containers

Return a const reference to the list of attribute containers maintained by this object. Note that this method can be invoked safely even if the initialize class method has not yet been called.

determineThresholdLevels

Populate the specified levels with the threshold levels for the specified category. This method compares the threshold levels defined by category with those of any active rules that apply to that category, and determines the minimum severity (i.e., the maximum numerical value) for each respective threshold amongst those values. A rule applies to category if the rule's pattern matches category‐>categoryName(), and a rule is active if all the attributes defined for that rule are satisfied by the current thread's attributes (i.e., Rule::evaluate returns true for the collection of attributes maintained by this object). This method operates on the set of rules maintained by the category manager supplied to the initialize class method (which, in practice, should be the global set of rules for the process). The behavior is undefined unless initialize has previously been invoked without a subsequent call to reset, and category is contained in the registry maintained by the category manager supplied to initialize.

hasAttribute

Return true if an attribute having the specified value exists in any of the attribute containers maintained by this object, and false otherwise. Note that this method can be invoked safely even if the initialize class method has not yet been called.

hasRelevantActiveRules

Return true if there is at least one rule defined for this process that is both "relevant" to the specified category and "active", and false otherwise. A rule is "relevant" to category if the rule's pattern matches category‐>categoryName(), and a rule is "active" if all the attributes defined for that rule are satisfied by the current thread's attributes (i.e., Rule::evaluate returns true for the collection of attributes maintained by this object). This method operates on the set of rules maintained by the category manager supplied to the initialize class method (which, in practice, should be the global set of rules for the process). The behavior is undefined unless initialize has previously been invoked without a subsequent call to reset, and category is contained in the registry maintained by the category manager supplied to initialize.

print

Format this object to the specified output stream at the (absolute value of) the optionally specified indentation level and return a reference to stream. If level is specified, optionally specify spacesPerLevel, the number of spaces per indentation level for this and all of its nested objects. If level is negative, suppress indentation of the first line. If spacesPerLevel is negative, format the entire output on one line, suppressing all but the initial indentation (as governed by level). If stream is not valid on entry, this operation has no effect.

removeAttributes

Remove the specified element from the list of attribute containers maintained by this object. Note that this method can be invoked safely even if the initialize class method has not yet been called.

Static Member Functions

Name

Description

getContext

Return the address of the current thread's attribute context, if such context exists; otherwise, create an attribute context, install it in thread‐local storage, and return the address of the newly created context. Note that this method can be invoked safely even if the initialize class method has not yet been called.

initialize

Initialize the static data members of AttributeContext using the specified categoryManager. Optionally specify a globalAllocator used to supply memory. If globalAllocator is 0, the currently installed global allocator is used. Unless reset is subsequently called, invoking this method more than once will log an error message using bsls::Log::platformDefaultMessageHandler, but will have no other effect. Note that in practice this method will be called automatically when the LoggerManager singleton is initialized ‐‐ i.e., it is not intended to be called directly by clients of the ball package.

lookupContext

Return the address of the modifiable AttributeContext object installed in local storage for the current thread, or 0 if no attribute context has been created for this thread. Note that this method can be invoked safely even if the initialize class method has not yet been called.

reset

Reset the static data members of AttributeContext to their initial state (0). Unless initialize is subsequently called, invoking this method more than once has no effect. Note that in practice this method will be called automatically when the LoggerManager singleton is destroyed ‐‐ i.e., it is not intended to be called directly by clients of the ball package.

visitAttributes

Invoke the specified visitor for all attributes in all attribute containers maintained by this object.

Friends

Name

Description

BloombergLP::ball::AttributeContextProctor

This class implements a proctor that, on its own destruction, will destroy the attribute context of the current thread. Attribute contexts are stored in thread‐local memory. On destruction, objects of this type will deallocate the current thread's attribute context (if one has been created), and set the thread‐local storage pointer to 0.

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