# GSThroughput class documentation

### Authors

Richard Frith-Macdonald (`rfm@gnu.org`)

Version: 33278

Date: 2011-06-11 15:41:59 +0100 (Sat, 11 Jun 2011)

Copyright: (C) 2005-2008 Free Software Foundation, Inc.

### Contents -

1. Software documentation for the GSThroughput class
2. GSThroughput constants

# Software documentation for the GSThroughput class

## GSThroughput : NSObject

> Declared in:
>   GSThroughput.h

The GSThroughput class is used maintain statistics about the number of events or the duration of operations in your software.

For performance reasons, the class avoids locking and you must ensure that an instance of the class is only ever used by a single thread (the one in which it was created). You are responsible for ensuring that a run loop runs in each thread in which you use an instance, so that stats can be updated for that thread every second.

You create an instance of the class for each event/operation that you are interested in monitoring, and you call the -add: or -addDuration: method to record events.
For duration logging, you may also use the -startDuration: and -endDuration methods to handle adding of the amount of time taken between the two calls.

To dump a record of the gathered statistics, you may call the -description method of an instance or the class +description method to dump statistics for all instances in the current thread.
If you need to gather a record for all the threads you use, you must generate a dump in each thread and combine the results.

To be notified of statistics at the end of each minute, you may call the -enableNotifications: method for an instance. The notifications are generated in the thread that instance belongs to.

Instance Variables
Method summary

- +allInstances
- +description
- +setTick:
- +tick
- -add:
- -add:duration:
- -addDuration:
- -description
- -enableNotifications:
- -endDuration
- -endDuration:
- -init
- -initWithDurations:forPeriods:ofLength:
- -name
- -setName:
- -startDuration:

### allInstances

+ (NSArray*) allInstances;
Return all the current throughput measuring objects in the current thread. NB. This does not return instances from other threads.

### description

+ (NSString*) description;
Return a report on all GSThroughput instances in the current thread...
This calls the [GSThroughput -description] method of the individual instances to get a report on each one.
The results are ordered alphabetically by name of the instances (an instance without a name is treated as having an empty string as a name).

### setTick:

+ (void) setTick: (BOOL)aFlag;
Instructs the monitoring system to use a timer at the start of each second for keeping its idea of the current time up to date. This timer is used to call the +tick method in the current thread.
Passing a value of `NO` for aFlag will turn off the timer for the current thread.
For the timer to work, the thread's runloop must be running.
Keeping the notion of the current time up to date is important for instances configured to record stats broken down over a number of periods, since the periodic breakdown must be adjusted each second.

### tick

+ (void) tick;
Updates the monitoring system's notion of the current time for all instances associated with the current thread.
This should be called at the start of each second (or more often) if you want an accurate breakdown of monitoring by the second.
If you don't want to call this yourself, you can call +setTick: to have it called automatically.
If you are not using any instances of the class configured to maintain a breakdown of stats by periods, you do not need to call this method.

### add:

- (void) add: (unsigned)count;
Add to the count of the number of transactions for the receiver.
You may use this method only if the receiver was initialised with duration logging turned off.

### add: duration:

- (void) add: (unsigned)count duration: (NSTimeInterval)length;
Adds a record for multiple events of the specified total duration.
This is useful where you know a lot of similar events have completed in a particular period of time, but can't afford to measure the duration of the individual events because the timing overheads would be too great.
You may use this method only if the receiver was initialised with duration logging turned on.

### addDuration:

- (void) addDuration: (NSTimeInterval)length;
Adds a record for a single event of the specified duration.
You may use this method only if the receiver was initialised with duration logging turned on.

### description

- (NSString*) description;
Returns a string describing the status of the receiver.
For an instance configured to maintain a periodic breakdown of stats, this reports information for the current second, all seconds in the current minute, all minutes in the current period, and all periods in the configured number of periods.
For an instance configured with no periodic breakdown, this produces a short summary of the total count of events and, where durations are used, the maximum, minimum and average duration of events.

### enableNotifications:

- (BOOL) enableNotifications: (BOOL)flag;
Sets a flag to say whether the receiver will send GSThroughputNotification at the end of each minute to provide information about statistics.
The method returnes the previous setting. The initial setting is `NO`.
The notification object is the reciever, and the user info dictionary contains some or all of the following keys depending on how the receiver was configured:

GSThroughputCountKey
  The number of events recorded ( unsigned integer number)
GSThroughputMaximumKey
  The maximum event duration (double floating point number)
GSThroughputMinimumKey
  The minimum event duration (double floating point number) or -1.0 if no events occurred during the minute.
GSThroughputTimeKey
  The time of the start of the minute (an NSDate)
GSThroughputTotalKey
  The sum of event durations (double floating point number)

### endDuration

- (void) endDuration;
Ends duration recording for the current event started by a matching call to the -startDuration: method.
Calls to this method without a matching call to -startDuration: are quietly ignored. This is useful if you wish to time a function or method by starting/ending timing before/after calling it, but also want the function/method to be able to end timing of itsself before it calls another function/method.

### endDuration:

- (void) endDuration: (unsigned)count;
Acts like -endDuration but records the duration as a total for count events (if count is zero then this ends the interval started by the corresponding -startDuration: call, but nothing is logged).
This can be used when recording multiple events where the overhead of timing each event individually would be too great.

### init

- (id) init;
Initialises the receiver for duration logging (in the current thread only) for fifteen minute periods over the last twentyfour hours.

### initWithDurations: forPeriods: ofLength:

- (id) initWithDurations: (BOOL)aFlag forPeriods: (unsigned)numberOfPeriods ofLength: (unsigned)minutesPerPeriod;
This is a designated initialiser for the class.

Initialises the receiver to maintain stats (for the current thread only) over a particular time range, specifying whether duration statistics are to be maintained, or just event/transaction counts.

If the specified numberOfPeriods or minutesPerPeriod is zero, only a running total is maintained rather than a per-second breakdown for the current minute and per minute breakdown for the current period and period breakdown for the number of periods.

If all instances in a thread are initialised with numberOfPeriods or minutesPerPeriod of zero, the +tick method does not need to be called and +setTick: should not be used.

### name

- (NSString*) name;
Return the name of this instance (as set using -setName:).
This is used in the -description method and for ordering instances in the +description method.

### setName:

- (void) setName: (NSString*)name;
Sets the name of this instance.

### startDuration:

- (void) startDuration: (NSString*)name;
Starts recording the duration of an event. This must be followed by a matching call to the -endDuration method.
The name argument is used to identify the location of the call for debugging/logging purposes, and you must ensure that the string continues to exist up to the point where -endDuration is called, as the receiver will not retain it.
You may use this method only if the receiver was initialised with duration logging turned on.
Use of this method if the reciever does not support duration logging or if the method has already been called without a matching call to -endDuration will cause an exception to be raised.

## Instance Variables for GSThroughput Class

### _data

@protected void* _data;
Warning the underscore at the start of the name of this instance variable indicates that, even though it is not technically private, it is intended for internal use within the package, and you should not use the variable in other code.

# GSThroughput constants

### GSThroughputCountKey

NSString* const GSThroughputCountKey;
Description forthcoming.

### GSThroughputMaximumKey

NSString* const GSThroughputMaximumKey;
Description forthcoming.

### GSThroughputMinimumKey

NSString* const GSThroughputMinimumKey;
Description forthcoming.

### GSThroughputNotification

NSString* const GSThroughputNotification;
Description forthcoming.

### GSThroughputTimeKey

NSString* const GSThroughputTimeKey;
Description forthcoming.

### GSThroughputTotalKey

NSString* const GSThroughputTotalKey;
Description forthcoming.