com.sap.cloud.sdk.frameworks.hystrix

Class CachingCommand<T>

java.lang.Object

com.netflix.hystrix.HystrixCommand<T>

com.sap.cloud.sdk.frameworks.hystrix.Command<T>

com.sap.cloud.sdk.frameworks.hystrix.CachingCommand<T>

Type Parameters:

T - The return type of the function represented by this command.

All Implemented Interfaces:

com.netflix.hystrix.HystrixExecutable<T>, com.netflix.hystrix.HystrixInvokable<T>, com.netflix.hystrix.HystrixInvokableInfo<T>, com.netflix.hystrix.HystrixObservable<T>

Direct Known Subclasses:

CachingErpCommand

public abstract class CachingCommand<T>
extends Command<T>

Abstract class implementing a Hystrix protected command with the possibility to cache the result.

The implementing class needs to implement the runCacheable() and the getCache() methods. The key of the cache is, by default in getCommandCacheKey(), based on the current tenant and user, as well as the class name of the executed command.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected static class	com.netflix.hystrix.AbstractCommand.CommandState
protected static class	com.netflix.hystrix.AbstractCommand.ThreadState
protected static class	com.netflix.hystrix.AbstractCommand.TimedOutStatus

Nested classes/interfaces inherited from class com.netflix.hystrix.HystrixCommand

com.netflix.hystrix.HystrixCommand.Setter

Field Summary

Fields

Modifier and Type	Field and Description
protected com.netflix.hystrix.HystrixCircuitBreaker	circuitBreaker
protected static ConcurrentHashMap<com.netflix.hystrix.HystrixCommandKey,Boolean>	commandContainsFallback
protected com.netflix.hystrix.HystrixCommandGroupKey	commandGroup
protected com.netflix.hystrix.HystrixCommandKey	commandKey
protected long	commandStartTimestamp
protected AtomicReference<com.netflix.hystrix.AbstractCommand.CommandState>	commandState
protected com.netflix.hystrix.strategy.concurrency.HystrixConcurrencyStrategy	concurrencyStrategy
protected com.netflix.hystrix.HystrixRequestLog	currentRequestLog
protected rx.functions.Action0	endCurrentThreadExecutingCommand
protected com.netflix.hystrix.strategy.eventnotifier.HystrixEventNotifier	eventNotifier
protected com.netflix.hystrix.strategy.executionhook.HystrixCommandExecutionHook	executionHook
protected com.netflix.hystrix.ExecutionResult	executionResult
protected com.netflix.hystrix.ExecutionResult	executionResultAtTimeOfCancellation
protected com.netflix.hystrix.AbstractCommand.TryableSemaphore	executionSemaphoreOverride
protected static ConcurrentHashMap<String,com.netflix.hystrix.AbstractCommand.TryableSemaphore>	executionSemaphorePerCircuit
protected com.netflix.hystrix.AbstractCommand.TryableSemaphore	fallbackSemaphoreOverride
protected static ConcurrentHashMap<String,com.netflix.hystrix.AbstractCommand.TryableSemaphore>	fallbackSemaphorePerCircuit
protected AtomicReference<com.netflix.hystrix.AbstractCommand.TimedOutStatus>	isCommandTimedOut
protected boolean	isResponseFromCache
protected com.netflix.hystrix.HystrixCommandMetrics	metrics
protected com.netflix.hystrix.HystrixCommandProperties	properties
protected com.netflix.hystrix.HystrixRequestCache	requestCache
protected com.netflix.hystrix.HystrixThreadPool	threadPool
protected com.netflix.hystrix.HystrixThreadPoolKey	threadPoolKey
protected AtomicReference<com.netflix.hystrix.AbstractCommand.ThreadState>	threadState
protected AtomicReference<Reference<com.netflix.hystrix.util.HystrixTimer.TimerListener>>	timeoutTimer

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	CachingCommand(com.netflix.hystrix.HystrixCommand.Setter setter)
protected	CachingCommand(com.netflix.hystrix.HystrixCommand.Setter setter, boolean isCacheEnabled)
protected	CachingCommand(com.netflix.hystrix.HystrixCommandGroupKey group)
protected	CachingCommand(com.netflix.hystrix.HystrixCommandGroupKey group, boolean isCacheEnabled)
protected	CachingCommand(com.netflix.hystrix.HystrixCommandGroupKey group, com.netflix.hystrix.HystrixThreadPoolKey threadPool)
protected	CachingCommand(com.netflix.hystrix.HystrixCommandGroupKey group, com.netflix.hystrix.HystrixThreadPoolKey threadPool, boolean isCacheEnabled)
protected	CachingCommand(com.netflix.hystrix.HystrixCommandGroupKey group, com.netflix.hystrix.HystrixThreadPoolKey threadPool, int executionIsolationThreadTimeoutInMilliseconds)
protected	CachingCommand(com.netflix.hystrix.HystrixCommandGroupKey group, com.netflix.hystrix.HystrixThreadPoolKey threadPool, int executionIsolationThreadTimeoutInMilliseconds, boolean isCacheEnabled)
protected	CachingCommand(com.netflix.hystrix.HystrixCommandGroupKey group, int executionIsolationThreadTimeoutInMilliseconds)
protected	CachingCommand(com.netflix.hystrix.HystrixCommandGroupKey group, int executionIsolationThreadTimeoutInMilliseconds, boolean isCacheEnabled)

Method Summary

Modifier and Type	Method and Description
protected Throwable	decomposeException(Exception arg0)
protected abstract com.google.common.cache.Cache<CacheKey,T>	getCache() Returns the instance of the command-specific cache.
protected String	getCacheKey() Deprecated. Use getCommandCacheKey() instead.
protected CacheKey	getCommandCacheKey() Returns the CacheKey that is used by this command.
protected Exception	getExceptionFromThrowable(Throwable arg0)
protected com.netflix.hystrix.AbstractCommand.TryableSemaphore	getExecutionSemaphore()
protected com.netflix.hystrix.AbstractCommand.TryableSemaphore	getFallbackSemaphore()
protected String	getLogMessagePrefix()
protected void	handleThreadEnd(com.netflix.hystrix.AbstractCommand<R> arg0)
protected boolean	isRequestCachingEnabled()
protected T	run()
protected abstract T	runCacheable() Implements the logic to be executed within the command.
protected boolean	shouldNotBeWrapped(Throwable arg0)
protected boolean	shouldOutputOnNextEvents()
protected boolean	useCache()

Methods inherited from class com.netflix.hystrix.HystrixCommand

commandIsScalar, execute, getExecutionObservable, getFallback, getFallbackMethodName, getFallbackObservable, isFallbackUserDefined, queue

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

circuitBreaker

protected final com.netflix.hystrix.HystrixCircuitBreaker circuitBreaker

threadPool

protected final com.netflix.hystrix.HystrixThreadPool threadPool

threadPoolKey

protected final com.netflix.hystrix.HystrixThreadPoolKey threadPoolKey

properties

protected final com.netflix.hystrix.HystrixCommandProperties properties

metrics

protected final com.netflix.hystrix.HystrixCommandMetrics metrics

commandKey

protected final com.netflix.hystrix.HystrixCommandKey commandKey

commandGroup

protected final com.netflix.hystrix.HystrixCommandGroupKey commandGroup

eventNotifier

protected final com.netflix.hystrix.strategy.eventnotifier.HystrixEventNotifier eventNotifier

concurrencyStrategy

protected final com.netflix.hystrix.strategy.concurrency.HystrixConcurrencyStrategy concurrencyStrategy

executionHook

protected final com.netflix.hystrix.strategy.executionhook.HystrixCommandExecutionHook executionHook

fallbackSemaphoreOverride

protected final com.netflix.hystrix.AbstractCommand.TryableSemaphore fallbackSemaphoreOverride

fallbackSemaphorePerCircuit

protected static final ConcurrentHashMap<String,com.netflix.hystrix.AbstractCommand.TryableSemaphore> fallbackSemaphorePerCircuit

executionSemaphoreOverride

protected final com.netflix.hystrix.AbstractCommand.TryableSemaphore executionSemaphoreOverride

executionSemaphorePerCircuit

protected static final ConcurrentHashMap<String,com.netflix.hystrix.AbstractCommand.TryableSemaphore> executionSemaphorePerCircuit

timeoutTimer

protected final AtomicReference<Reference<com.netflix.hystrix.util.HystrixTimer.TimerListener>> timeoutTimer

commandState

protected AtomicReference<com.netflix.hystrix.AbstractCommand.CommandState> commandState

threadState

protected AtomicReference<com.netflix.hystrix.AbstractCommand.ThreadState> threadState

executionResult

protected volatile com.netflix.hystrix.ExecutionResult executionResult

isResponseFromCache

protected volatile boolean isResponseFromCache

executionResultAtTimeOfCancellation

protected volatile com.netflix.hystrix.ExecutionResult executionResultAtTimeOfCancellation

commandStartTimestamp

protected volatile long commandStartTimestamp

isCommandTimedOut

protected final AtomicReference<com.netflix.hystrix.AbstractCommand.TimedOutStatus> isCommandTimedOut

endCurrentThreadExecutingCommand

protected volatile rx.functions.Action0 endCurrentThreadExecutingCommand

requestCache

protected final com.netflix.hystrix.HystrixRequestCache requestCache

currentRequestLog

protected final com.netflix.hystrix.HystrixRequestLog currentRequestLog

commandContainsFallback

protected static ConcurrentHashMap<com.netflix.hystrix.HystrixCommandKey,Boolean> commandContainsFallback

Constructor Detail

CachingCommand

protected CachingCommand(@Nonnull
                         com.netflix.hystrix.HystrixCommandGroupKey group)

CachingCommand

protected CachingCommand(@Nonnull
                         com.netflix.hystrix.HystrixCommandGroupKey group,
                         boolean isCacheEnabled)

CachingCommand

protected CachingCommand(@Nonnull
                         com.netflix.hystrix.HystrixCommandGroupKey group,
                         @Nonnull
                         com.netflix.hystrix.HystrixThreadPoolKey threadPool)

CachingCommand

protected CachingCommand(@Nonnull
                         com.netflix.hystrix.HystrixCommandGroupKey group,
                         @Nonnull
                         com.netflix.hystrix.HystrixThreadPoolKey threadPool,
                         boolean isCacheEnabled)

CachingCommand

protected CachingCommand(@Nonnull
                         com.netflix.hystrix.HystrixCommandGroupKey group,
                         int executionIsolationThreadTimeoutInMilliseconds)

CachingCommand

protected CachingCommand(@Nonnull
                         com.netflix.hystrix.HystrixCommandGroupKey group,
                         int executionIsolationThreadTimeoutInMilliseconds,
                         boolean isCacheEnabled)

CachingCommand

protected CachingCommand(@Nonnull
                         com.netflix.hystrix.HystrixCommandGroupKey group,
                         @Nonnull
                         com.netflix.hystrix.HystrixThreadPoolKey threadPool,
                         int executionIsolationThreadTimeoutInMilliseconds)

CachingCommand

protected CachingCommand(@Nonnull
                         com.netflix.hystrix.HystrixCommandGroupKey group,
                         @Nonnull
                         com.netflix.hystrix.HystrixThreadPoolKey threadPool,
                         int executionIsolationThreadTimeoutInMilliseconds,
                         boolean isCacheEnabled)

CachingCommand

protected CachingCommand(@Nonnull
                         com.netflix.hystrix.HystrixCommand.Setter setter)

CachingCommand

protected CachingCommand(@Nonnull
                         com.netflix.hystrix.HystrixCommand.Setter setter,
                         boolean isCacheEnabled)

Method Detail

useCache

protected boolean useCache()

Returns:

true if the cache is actually used, false otherwise.

getCache

@Nonnull
protected abstract com.google.common.cache.Cache<CacheKey,T> getCache()

Returns the instance of the command-specific cache. Note that each command should have its own static cache.

Example usage:

 
 private static final Cache<CacheKey, T> cache = CacheManager.register(CacheBuilder.build(MyClass.class));
 
  @Override
 protected final Cache<CacheKey, T> getCache()
 {
     return cache;
 }
 

Returns:

The command-specific cache.

getCacheKey

@Deprecated
 @Nullable
protected final String getCacheKey()

Deprecated. Use getCommandCacheKey() instead.

Returns:

Always null since the internal Hystrix caching mechanism is obsolete when using a CachingCommand which introduces a cache across requests.

getCommandCacheKey

@Nullable
protected CacheKey getCommandCacheKey()
                                         throws TenantAccessException,
                                                UserAccessException

Returns the CacheKey that is used by this command. By default, this is a CacheKey.ofTenantAndUserIsolation() appended with the full class name of this command.

Returns:

The CacheKey for this command. If null is returned, the cache is not used.

Throws:

TenantAccessException - If there is an issue while accessing the tenant.

UserAccessException - If there is an issue while accessing the user.

run

@Nonnull
protected final T run()
                        throws Exception

Specified by:

run in class com.netflix.hystrix.HystrixCommand<T>

Throws:

Exception

runCacheable

@Nonnull
protected abstract T runCacheable()
                                    throws Exception

Implements the logic to be executed within the command.

Throws:

Exception

shouldNotBeWrapped

protected boolean shouldNotBeWrapped(Throwable arg0)

handleThreadEnd

protected void handleThreadEnd(com.netflix.hystrix.AbstractCommand<R> arg0)

shouldOutputOnNextEvents

protected boolean shouldOutputOnNextEvents()

getFallbackSemaphore

protected com.netflix.hystrix.AbstractCommand.TryableSemaphore getFallbackSemaphore()

getExecutionSemaphore

protected com.netflix.hystrix.AbstractCommand.TryableSemaphore getExecutionSemaphore()

decomposeException

protected Throwable decomposeException(Exception arg0)

isRequestCachingEnabled

protected boolean isRequestCachingEnabled()

getLogMessagePrefix

protected String getLogMessagePrefix()

getExceptionFromThrowable

protected Exception getExceptionFromThrowable(Throwable arg0)