Package org.apache.tomcat.util.threads
Class LimitLatch
java.lang.Object
org.apache.tomcat.util.threads.LimitLatch
Shared latch that allows the latch to be acquired a limited number of times
after which all subsequent requests to acquire the latch will be placed in a
FIFO queue until one of the shares is returned.
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Constructor Summary
ConstructorDescriptionLimitLatch
(long limit) Instantiates a LimitLatch object with an initial limit. -
Method Summary
Modifier and TypeMethodDescriptionlong
Releases a shared latch, making it available for another thread to use.void
Acquires a shared latch if one is available or waits for one if no shared latch is current available.long
getCount()
Returns the current count for the latchlong
getLimit()
Obtain the current limit.Provide access to the list of threads waiting to acquire this limited shared latch.boolean
Returnstrue
if there is at least one thread waiting to acquire the shared lock, otherwise returnsfalse
.boolean
Releases all waiting threads and causes thelimit
to be ignored untilreset()
is called.void
reset()
Resets the latch and initializes the shared acquisition counter to zero.void
setLimit
(long limit) Sets a new limit.
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Constructor Details
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LimitLatch
public LimitLatch(long limit) Instantiates a LimitLatch object with an initial limit.- Parameters:
limit
- - maximum number of concurrent acquisitions of this latch
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Method Details
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getCount
public long getCount()Returns the current count for the latch- Returns:
- the current count for latch
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getLimit
public long getLimit()Obtain the current limit.- Returns:
- the limit
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setLimit
public void setLimit(long limit) Sets a new limit. If the limit is decreased there may be a period where more shares of the latch are acquired than the limit. In this case no more shares of the latch will be issued until sufficient shares have been returned to reduce the number of acquired shares of the latch to below the new limit. If the limit is increased, threads currently in the queue may not be issued one of the newly available shares until the next request is made for a latch.- Parameters:
limit
- The new limit
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countUpOrAwait
Acquires a shared latch if one is available or waits for one if no shared latch is current available.- Throws:
InterruptedException
- If the current thread is interrupted
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countDown
public long countDown()Releases a shared latch, making it available for another thread to use.- Returns:
- the previous counter value
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releaseAll
public boolean releaseAll()Releases all waiting threads and causes thelimit
to be ignored untilreset()
is called.- Returns:
true
if release was done
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reset
public void reset()Resets the latch and initializes the shared acquisition counter to zero.- See Also:
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hasQueuedThreads
public boolean hasQueuedThreads()Returnstrue
if there is at least one thread waiting to acquire the shared lock, otherwise returnsfalse
.- Returns:
true
if threads are waiting
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getQueuedThreads
Provide access to the list of threads waiting to acquire this limited shared latch.- Returns:
- a collection of threads
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