### Configure Hystrix to use Servo Metrics Publisher and Publish to Graphite

Source: https://github.com/netflix/hystrix/blob/master/hystrix-contrib/hystrix-servo-metrics-publisher/README.md

This example shows how to register the HystrixServoMetricsPublisher with Hystrix plugins and configure minimal Servo settings to publish metrics to Graphite. Ensure Servo's PollScheduler is started and a Poller task is added.

```java
// Registry plugin with hystrix
HystrixPlugins.getInstance().registerMetricsPublisher(HystrixServoMetricsPublisher.getInstance());
        
   ........
        
// Minimal Servo configuration for publishing to Graphite
final List<MetricObserver> observers = new ArrayList<MetricObserver>();

observers.add(new GraphiteMetricObserver(getHostName(), "graphite-server.example.com:2003"));
PollScheduler.getInstance().start();
PollRunnable task = new PollRunnable(new MonitorRegistryMetricPoller(), BasicMetricFilter.MATCH_ALL, true, observers);
PollScheduler.getInstance().addPoller(task, 5, TimeUnit.SECONDS);
```

--------------------------------

### Run Hystrix Examples Web App via Gradle

Source: https://github.com/netflix/hystrix/blob/master/hystrix-examples-webapp/README.md

Clone the Hystrix repository, navigate to the examples web app directory, and run the application using Gradle. The application will be available at http://localhost:8989/hystrix-examples-webapp.

```bash
$ git clone git@github.com:Netflix/Hystrix.git
$ cd Hystrix/hystrix-examples-webapp
$ ../gradlew appRun
```

--------------------------------

### HystrixCommand Metrics Example

Source: https://github.com/netflix/hystrix/blob/master/hystrix-contrib/hystrix-metrics-event-stream/README.md

Example JSON payload for HystrixCommand metrics. This data is emitted continuously as long as a client connection is maintained.

```json
data: {
  "type": "HystrixCommand",
  "name": "PlaylistGet",
  "group": "PlaylistGet",
  "currentTime": 1355239617628,
  "isCircuitBreakerOpen": false,
  "errorPercentage": 0,
  "errorCount": 0,
  "requestCount": 121,
  "rollingCountCollapsedRequests": 0,
  "rollingCountExceptionsThrown": 0,
  "rollingCountFailure": 0,
  "rollingCountFallbackFailure": 0,
  "rollingCountFallbackRejection": 0,
  "rollingCountFallbackSuccess": 0,
  "rollingCountResponsesFromCache": 69,
  "rollingCountSemaphoreRejected": 0,
  "rollingCountShortCircuited": 0,
  "rollingCountSuccess": 121,
  "rollingCountThreadPoolRejected": 0,
  "rollingCountTimeout": 0,
  "currentConcurrentExecutionCount": 0,
  "latencyExecute_mean": 13,
  "latencyExecute": {
    "0": 3,
    "25": 6,
    "50": 8,
    "75": 14,
    "90": 26,
    "95": 37,
    "99": 75,
    "99.5": 92,
    "100": 252
  },
  "latencyTotal_mean": 15,
  "latencyTotal": {
    "0": 3,
    "25": 7,
    "50": 10,
    "75": 18,
    "90": 32,
    "95": 43,
    "99": 88,
    "99.5": 160,
    "100": 253
  },
  "propertyValue_circuitBreakerRequestVolumeThreshold": 20,
  "propertyValue_circuitBreakerSleepWindowInMilliseconds": 5000,
  "propertyValue_circuitBreakerErrorThresholdPercentage": 50,
  "propertyValue_circuitBreakerForceOpen": false,
  "propertyValue_circuitBreakerForceClosed": false,
  "propertyValue_circuitBreakerEnabled": true,
  "propertyValue_executionIsolationStrategy": "THREAD",
  "propertyValue_executionIsolationThreadTimeoutInMilliseconds": 800,
  "propertyValue_executionIsolationThreadInterruptOnTimeout": true,
  "propertyValue_executionIsolationThreadPoolKeyOverride": null,
  "propertyValue_executionIsolationSemaphoreMaxConcurrentRequests": 20,
  "propertyValue_fallbackIsolationSemaphoreMaxConcurrentRequests": 10,
  "propertyValue_metricsRollingStatisticalWindowInMilliseconds": 10000,
  "propertyValue_requestCacheEnabled": true,
  "propertyValue_requestLogEnabled": true,
  "reportingHosts": 1
}
```

--------------------------------

### Maven Dependency for Hystrix Examples

Source: https://github.com/netflix/hystrix/blob/master/hystrix-examples/README.md

Add this Maven dependency to include the Hystrix examples module in your project.

```xml
<dependency>
    <groupId>com.netflix.hystrix</groupId>
    <artifactId>hystrix-examples</artifactId>
    <version>1.0.2</version>
</dependency>
```

--------------------------------

### Hystrix Stream Data Example 2

Source: https://github.com/netflix/hystrix/blob/master/hystrix-contrib/hystrix-metrics-event-stream-jaxrs/README.md

This is another example of Hystrix stream data, showing metrics for the 'CryptexDecrypt' command, including updated reporting hosts and latency values.

```json
data: {"rollingCountFailure":0,"propertyValue_executionIsolationThreadInterruptOnTimeout":true,"rollingCountTimeout":0,"rollingCountExceptionsThrown":0,"rollingCountFallbackSuccess":0,"errorCount":0,"type":"HystrixCommand","propertyValue_circuitBreakerEnabled":true,"reportingHosts":3,"latencyTotal":{"0":1,"95":1,"99.5":1,"90":1,"25":1,"99":1,"75":1,"100":1,"50":1},"currentConcurrentExecutionCount":0,"rollingCountSemaphoreRejected":0,"rollingCountFallbackRejection":0,"rollingCountShortCircuited":0,"rollingCountResponsesFromCache":0,"propertyValue_circuitBreakerForceClosed":false,"name":"CryptexDecrypt","propertyValue_executionIsolationThreadPoolKeyOverride":"null","rollingCountSuccess":1,"propertyValue_requestLogEnabled":true,"requestCount":1,"rollingCountCollapsedRequests":0,"errorPercentage":0,"propertyValue_circuitBreakerSleepWindowInMilliseconds":15000,"latencyTotal_mean":1,"propertyValue_circuitBreakerForceOpen":false,"propertyValue_circuitBreakerRequestVolumeThreshold":60,"propertyValue_circuitBreakerErrorThresholdPercentage":150,"propertyValue_executionIsolationStrategy":"THREAD","rollingCountFallbackFailure":0,"isCircuitBreakerOpen":false,"propertyValue_executionIsolationSemaphoreMaxConcurrentRequests":60,"propertyValue_executionIsolationThreadTimeoutInMilliseconds":3000,"propertyValue_metricsRollingStatisticalWindowInMilliseconds":30000,"propertyValue_fallbackIsolationSemaphoreMaxConcurrentRequests":30,"latencyExecute":{"0":0,"95":0,"99.5":0,"90":0,"25":0,"99":0,"75":0,"100":0,"50":0},"group":"CRYPTEX","latencyExecute_mean":0,"propertyValue_requestCacheEnabled":true,"rollingCountThreadPoolRejected":0}
```

--------------------------------

### Ivy Dependency for Hystrix Examples

Source: https://github.com/netflix/hystrix/blob/master/hystrix-examples/README.md

Add this Ivy dependency to include the Hystrix examples module in your project.

```xml
<dependency org="com.netflix.hystrix" name="hystrix-examples" rev="1.0.2" />
```

--------------------------------

### Build Hystrix Project with Gradle

Source: https://github.com/netflix/hystrix/blob/master/README.md

Commands to clone the Hystrix repository and build the project using Gradle. Requires Git and Gradle to be installed.

```bash
$ git clone git@github.com:Netflix/Hystrix.git
$ cd Hystrix/
$ ./gradlew build
```

--------------------------------

### HystrixObservableCommand Hello World Example

Source: https://github.com/netflix/hystrix/wiki/How-To-Use

An equivalent 'Hello World' implementation using HystrixObservableCommand. This is suitable for commands that may emit multiple values or need to be integrated with reactive streams.

```java
public class CommandHelloWorld extends HystrixObservableCommand<String> {

    private final String name;

    public CommandHelloWorld(String name) {
        super(HystrixCommandGroupKey.Factory.asKey("ExampleGroup"));
        this.name = name;
    }

    @Override
    protected Observable<String> construct() {
        return Observable.create(new Observable.OnSubscribe<String>() {
            @Override
            public void call(Subscriber<? super String> observer) {
                try {
                    if (!observer.isUnsubscribed()) {
                        // a real example would do work like a network call here
                        observer.onNext("Hello");
                        observer.onNext(name + "!");
                        observer.onCompleted();
                    }
                } catch (Exception e) {
                    observer.onError(e);
                }
            }
         } ).subscribeOn(Schedulers.io());
    }
}
```

--------------------------------

### Implement Request-Scoped HystrixCollapser

Source: https://github.com/netflix/hystrix/wiki/How-To-Use

Example of a request-scoped collapser that batches requests for a specific key. It defines how to get the request argument, create the batch command, and map the batch response back to individual requests. Requires Hystrix library.

```java
public class CommandCollapserGetValueForKey extends HystrixCollapser<List<String>, String, Integer> {

    private final Integer key;

    public CommandCollapserGetValueForKey(Integer key) {
        this.key = key;
    }

    @Override
    public Integer getRequestArgument() {
        return key;
    }

    @Override
    protected HystrixCommand<List<String>> createCommand(final Collection<CollapsedRequest<String, Integer>> requests) {
        return new BatchCommand(requests);
    }

    @Override
    protected void mapResponseToRequests(List<String> batchResponse, Collection<CollapsedRequest<String, Integer>> requests) {
        int count = 0;
        for (CollapsedRequest<String, Integer> request : requests) {
            request.setResponse(batchResponse.get(count++));
        }
    }

    private static final class BatchCommand extends HystrixCommand<List<String>> {
        private final Collection<CollapsedRequest<String, Integer>> requests;

        private BatchCommand(Collection<CollapsedRequest<String, Integer>> requests) {
                super(Setter.withGroupKey(HystrixCommandGroupKey.Factory.asKey("ExampleGroup"))
                    .andCommandKey(HystrixCommandKey.Factory.asKey("GetValueForKey")));
            this.requests = requests;
        }

        @Override
        protected List<String> run() {
            ArrayList<String> response = new ArrayList<String>();
            for (CollapsedRequest<String, Integer> request : requests) {
                // artificial response for each argument received in the batch
                response.add("ValueForKey: " + request.getArgument());
            }
            return response;
        }
    }
}
```

--------------------------------

### Hystrix Gradle Build Output

Source: https://github.com/netflix/hystrix/wiki/Getting-Started

Example output of a successful Gradle build for the Hystrix project, showing compilation, testing, and packaging steps.

```text
$ ./gradlew build
:hystrix-core:compileJava
:hystrix-core:processResources UP-TO-DATE
:hystrix-core:classes
:hystrix-core:jar
:hystrix-core:sourcesJar
:hystrix-core:signArchives SKIPPED
:hystrix-core:assemble
:hystrix-core:licenseMain UP-TO-DATE
:hystrix-core:licenseTest UP-TO-DATE
:hystrix-core:compileTestJava
:hystrix-core:processTestResources UP-TO-DATE
:hystrix-core:testClasses
:hystrix-core:test
:hystrix-core:check
:hystrix-core:build
:hystrix-examples:compileJava
:hystrix-examples:processResources UP-TO-DATE
:hystrix-examples:classes
:hystrix-examples:jar
:hystrix-examples:sourcesJar
:hystrix-examples:signArchives SKIPPED
:hystrix-examples:assemble
:hystrix-examples:licenseMain UP-TO-DATE
:hystrix-examples:licenseTest UP-TO-DATE
:hystrix-examples:compileTestJava
:hystrix-examples:processTestResources UP-TO-DATE
:hystrix-examples:testClasses
:hystrix-examples:test
:hystrix-examples:check
:hystrix-examples:build

BUILD SUCCESSFUL

Total time: 30.758 secs
```

--------------------------------

### Run Hystrix Demo Application

Source: https://github.com/netflix/hystrix/blob/master/README.md

Instructions to clone the Hystrix repository and run the demo application using Gradle. This will display example command execution outputs.

```bash
$ git clone git@github.com:Netflix/Hystrix.git
$ cd Hystrix/
./gradlew runDemo
```

--------------------------------

### Hystrix Demo Application Output Example

Source: https://github.com/netflix/hystrix/blob/master/README.md

Sample output from running the Hystrix demo application, illustrating successful and failed command executions, including cached responses and fallback successes.

```text
Request => GetUserAccountCommand[SUCCESS][8ms], GetPaymentInformationCommand[SUCCESS][20ms], GetUserAccountCommand[SUCCESS, RESPONSE_FROM_CACHE][0ms]x2, GetOrderCommand[SUCCESS][101ms], CreditCardCommand[SUCCESS][1075ms]
Request => GetUserAccountCommand[FAILURE, FALLBACK_SUCCESS][2ms], GetPaymentInformationCommand[SUCCESS][22ms], GetUserAccountCommand[FAILURE, FALLBACK_SUCCESS, RESPONSE_FROM_CACHE][0ms]x2, GetOrderCommand[SUCCESS][130ms], CreditCardCommand[SUCCESS][1050ms]
Request => GetUserAccountCommand[FAILURE, FALLBACK_SUCCESS][4ms], GetPaymentInformationCommand[SUCCESS][19ms], GetUserAccountCommand[FAILURE, FALLBACK_SUCCESS, RESPONSE_FROM_CACHE][0ms]x2, GetOrderCommand[SUCCESS][145ms], CreditCardCommand[SUCCESS][1301ms]
Request => GetUserAccountCommand[SUCCESS][4ms], GetPaymentInformationCommand[SUCCESS][11ms], GetUserAccountCommand[SUCCESS, RESPONSE_FROM_CACHE][0ms]x2, GetOrderCommand[SUCCESS][93ms], CreditCardCommand[SUCCESS][1409ms]

#####################################################################################
# CreditCardCommand: Requests: 17 Errors: 0 (0%)   Mean: 1171 75th: 1391 90th: 1470 99th: 1486 
# GetOrderCommand: Requests: 21 Errors: 0 (0%)   Mean: 100 75th: 144 90th: 207 99th: 230 
# GetUserAccountCommand: Requests: 21 Errors: 4 (19%)   Mean: 8 75th: 11 90th: 46 99th: 51 

```

--------------------------------

### Hystrix Demo Output Example

Source: https://github.com/netflix/hystrix/blob/master/hystrix-examples/README.md

Sample output from the Hystrix demo application, illustrating command execution results, success/failure states, response times, and cached responses.

```text
Request => GetUserAccountCommand[SUCCESS][8ms], GetPaymentInformationCommand[SUCCESS][20ms], GetUserAccountCommand[SUCCESS, RESPONSE_FROM_CACHE][0ms]x2, GetOrderCommand[SUCCESS][101ms], CreditCardCommand[SUCCESS][1075ms]
Request => GetUserAccountCommand[FAILURE, FALLBACK_SUCCESS][2ms], GetPaymentInformationCommand[SUCCESS][22ms], GetUserAccountCommand[FAILURE, FALLBACK_SUCCESS, RESPONSE_FROM_CACHE][0ms]x2, GetOrderCommand[SUCCESS][130ms], CreditCardCommand[SUCCESS][1050ms]
Request => GetUserAccountCommand[FAILURE, FALLBACK_SUCCESS][4ms], GetPaymentInformationCommand[SUCCESS][19ms], GetUserAccountCommand[FAILURE, FALLBACK_SUCCESS, RESPONSE_FROM_CACHE][0ms]x2, GetOrderCommand[SUCCESS][145ms], CreditCardCommand[SUCCESS][1301ms]
Request => GetUserAccountCommand[SUCCESS][4ms], GetPaymentInformationCommand[SUCCESS][11ms], GetUserAccountCommand[SUCCESS, RESPONSE_FROM_CACHE][0ms]x2, GetOrderCommand[SUCCESS][93ms], CreditCardCommand[SUCCESS][1409ms]

#####################################################################################
# CreditCardCommand: Requests: 17 Errors: 0 (0%)   Mean: 1171 75th: 1391 90th: 1470 99th: 1486 
# GetOrderCommand: Requests: 21 Errors: 0 (0%)   Mean: 100 75th: 144 90th: 207 99th: 230 
# GetUserAccountCommand: Requests: 21 Errors: 4 (19%)   Mean: 8 75th: 11 90th: 46 99th: 51 
# GetPaymentInformationCommand: Requests: 21 Errors: 0 (0%)   Mean: 18 75th: 21 90th: 24 99th: 25 
#####################################################################################

Request => GetUserAccountCommand[SUCCESS][10ms], GetPaymentInformationCommand[SUCCESS][16ms], GetUserAccountCommand[SUCCESS, RESPONSE_FROM_CACHE][0ms]x2, GetOrderCommand[SUCCESS][51ms], CreditCardCommand[SUCCESS][922ms]
Request => GetUserAccountCommand[SUCCESS][12ms], GetPaymentInformationCommand[SUCCESS][12ms], GetUserAccountCommand[SUCCESS, RESPONSE_FROM_CACHE][0ms]x2, GetOrderCommand[SUCCESS][68ms], CreditCardCommand[SUCCESS][1257ms]
Request => GetUserAccountCommand[SUCCESS][10ms], GetPaymentInformationCommand[SUCCESS][11ms], GetUserAccountCommand[SUCCESS, RESPONSE_FROM_CACHE][0ms]x2, GetOrderCommand[SUCCESS][78ms], CreditCardCommand[SUCCESS][1295ms]
Request => GetUserAccountCommand[FAILURE, FALLBACK_SUCCESS][6ms], GetPaymentInformationCommand[SUCCESS][11ms], GetUserAccountCommand[FAILURE, FALLBACK_SUCCESS, RESPONSE_FROM_CACHE][0ms]x2, GetOrderCommand[SUCCESS][153ms], CreditCardCommand[SUCCESS][1321ms]
```

--------------------------------

### Get User by ID with CacheKey

Source: https://github.com/netflix/hystrix/blob/master/hystrix-contrib/hystrix-javanica/README.md

Retrieves a user by ID, using the ID as the cache key. Requires no specific setup.

```java
public User getUserById(@CacheKey String id) {
            return storage.get(id);
        }
```

--------------------------------

### HystrixThreadPool Metrics Example

Source: https://github.com/netflix/hystrix/blob/master/hystrix-contrib/hystrix-metrics-event-stream/README.md

Example JSON payload for HystrixThreadPool metrics. This data provides insights into thread pool utilization and task counts.

```json
data:
{
  "currentPoolSize": 30,
  "rollingMaxActiveThreads": 13,
  "currentActiveCount": 0,
  "currentCompletedTaskCount": 4459519,
  "propertyValue_queueSizeRejectionThreshold": 30,
  "type": "HystrixThreadPool",
  "reportingHosts": 3,
  "propertyValue_metricsRollingStatisticalWindowInMilliseconds": 30000,
  "name": "ABClient",
  "currentLargestPoolSize": 30,
  "currentCorePoolSize": 30,
  "currentQueueSize": 0,
  "currentTaskCount": 4459519,
  "rollingCountThreadsExecuted": 919,
  "currentMaximumPoolSize": 30
}
```

--------------------------------

### Define a Hystrix Command

Source: https://github.com/netflix/hystrix/blob/master/README.md

Encapsulate code to be isolated within the run() method of a HystrixCommand. This example defines a simple 'Hello World' command.

```java
public class CommandHelloWorld extends HystrixCommand<String> {

    private final String name;

    public CommandHelloWorld(String name) {
        super(HystrixCommandGroupKey.Factory.asKey("ExampleGroup"));
        this.name = name;
    }

    @Override
    protected String run() {
        return "Hello " + name + "!";
    }
}
```

--------------------------------

### Hystrix Stream Data Example 1

Source: https://github.com/netflix/hystrix/blob/master/hystrix-contrib/hystrix-metrics-event-stream-jaxrs/README.md

This is an example of the JSON data received from the Hystrix stream endpoint, showing metrics for the 'IdentityCookieAuthSwitchProfile' command.

```json
data: {"rollingCountFailure":0,"propertyValue_executionIsolationThreadInterruptOnTimeout":true,"rollingCountTimeout":0,"rollingCountExceptionsThrown":0,"rollingCountFallbackSuccess":0,"errorCount":0,"type":"HystrixCommand","propertyValue_circuitBreakerEnabled":true,"reportingHosts":1,"latencyTotal":{"0":0,"95":0,"99.5":0,"90":0,"25":0,"99":0,"75":0,"100":0,"50":0},"currentConcurrentExecutionCount":0,"rollingCountSemaphoreRejected":0,"rollingCountFallbackRejection":0,"rollingCountShortCircuited":0,"rollingCountResponsesFromCache":0,"propertyValue_circuitBreakerForceClosed":false,"name":"IdentityCookieAuthSwitchProfile","propertyValue_executionIsolationThreadPoolKeyOverride":"null","rollingCountSuccess":0,"propertyValue_requestLogEnabled":true,"requestCount":0,"rollingCountCollapsedRequests":0,"errorPercentage":0,"propertyValue_circuitBreakerSleepWindowInMilliseconds":5000,"latencyTotal_mean":0,"propertyValue_circuitBreakerForceOpen":false,"propertyValue_circuitBreakerRequestVolumeThreshold":20,"propertyValue_circuitBreakerErrorThresholdPercentage":50,"propertyValue_executionIsolationStrategy":"THREAD","rollingCountFallbackFailure":0,"isCircuitBreakerOpen":false,"propertyValue_executionIsolationSemaphoreMaxConcurrentRequests":20,"propertyValue_executionIsolationThreadTimeoutInMilliseconds":1000,"propertyValue_metricsRollingStatisticalWindowInMilliseconds":10000,"propertyValue_fallbackIsolationSemaphoreMaxConcurrentRequests":10,"latencyExecute":{"0":0,"95":0,"99.5":0,"90":0,"25":0,"99":0,"75":0,"100":0,"50":0},"group":"IDENTITY","latencyExecute_mean":0,"propertyValue_requestCacheEnabled":true,"rollingCountThreadPoolRejected":0}
```

--------------------------------

### Unsupported: Sync Command, Async Fallback (No @HystrixCommand on Fallback)

Source: https://github.com/netflix/hystrix/blob/master/hystrix-contrib/hystrix-javanica/README.md

This case is unsupported for the same reasons as the previous example. The caller of a sync command expects a direct result, not a Future from an async fallback.

```java
        @HystrixCommand(fallbackMethod = "fallbackAsync")
        User getUserById(String id) {
            throw new RuntimeException("getUserById command failed");
        }

        Future<User> fallbackAsync(String id) {
            return new AsyncResult<User>() {
                @Override
                public User invoke() {
                    return new User("def", "def");
                }
            };
        }
```

--------------------------------

### Hystrix Command Metrics Streams

Source: https://github.com/netflix/hystrix/wiki/Metrics-and-Monitoring

Observes command execution start and completion events. Requires HystrixCommandKey.

```java
Observable<HystrixCommandExecutionStarted> observeCommandStartStream(HystrixCommandKey key)
Observable<HystrixCommandCompletion> observeCommandCompletionStream(HystrixCommandKey key)
```

--------------------------------

### Hystrix Fallback Exception Propagation Example

Source: https://github.com/netflix/hystrix/blob/master/hystrix-contrib/hystrix-javanica/README.md

Demonstrates how exceptions are propagated when a command has a fallback. Only the first exception that triggers the fallback logic is propagated to the caller.

```java
class Service {
    @HystrixCommand(fallbackMethod = "fallback")
    Object command(Object o) throws CommandException {
        throw new CommandException();
    }
    
    @HystrixCommand
    Object fallback(Object o) throws FallbackException {
        throw new FallbackException();
    }
}

// in client code
{
    try {
        service.command(null);
    } catch (Exception e) {
      assert CommandException.class.equals(e.getClass())
    }
}
```

--------------------------------

### Hystrix Static Fallback Example

Source: https://context7.com/netflix/hystrix/llms.txt

Use a static fallback to return a default safe value when the primary command fails. This is useful for simple, predictable defaults.

```java
public class GetFeatureFlagCommand extends HystrixCommand<Boolean> {

    private final String flagName;

    public GetFeatureFlagCommand(String flagName) {
        super(HystrixCommandGroupKey.Factory.asKey("FeatureFlags"));
        this.flagName = flagName;
    }

    @Override
    protected Boolean run() throws Exception {
        return featureFlagService.isEnabled(flagName);
    }

    @Override
    protected Boolean getFallback() {
        // Default to safe value
        return true;
    }
}
```

--------------------------------

### HystrixRequestContextServletFilter Example

Source: https://github.com/netflix/hystrix/wiki/How-To-Use

A Servlet Filter implementation to manage the HystrixRequestContext lifecycle for all incoming web requests. It initializes the context before the request and shuts it down afterwards.

```java
public class HystrixRequestContextServletFilter implements Filter {

    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) 
     throws IOException, ServletException {
        HystrixRequestContext context = HystrixRequestContext.initializeContext();
        try {
            chain.doFilter(request, response);
        } finally {
            context.shutdown();
        }
    }
}
```

--------------------------------

### Get User by Profile Name with CacheKey and HystrixCommand

Source: https://github.com/netflix/hystrix/blob/master/hystrix-contrib/hystrix-javanica/README.md

Retrieves a user by profile name, using a specific key from the User object for caching. Requires @HystrixCommand.

```java
@CacheResult
        @HystrixCommand
        public void getUserByProfileName(@CacheKey("profile.email") User user) {
            storage.getUserByProfileName(user.getProfile().getName());
        }
```

--------------------------------

### DefaultProperties Annotation Example

Source: https://github.com/netflix/hystrix/blob/master/hystrix-contrib/hystrix-javanica/README.md

Demonstrates how @DefaultProperties sets default groupKey for Hystrix commands. An explicit groupKey in @HystrixCommand overrides the default.

```java
@DefaultProperties(groupKey = "DefaultGroupKey")
class Service {
    @HystrixCommand // hystrix command group key is 'DefaultGroupKey'
    public Object commandInheritsDefaultProperties() {
        return null;
    }
    @HystrixCommand(groupKey = "SpecificGroupKey") // command overrides default group key
    public Object commandOverridesGroupKey() {
        return null;
    }
}
```

--------------------------------

### Get User by Name with CacheResult and HystrixCommand

Source: https://github.com/netflix/hystrix/blob/master/hystrix-contrib/hystrix-javanica/README.md

Retrieves a user by name, caching the result using a method specified by getUserByNameCacheKey. Requires @HystrixCommand.

```java
@CacheResult(cacheKeyMethod = "getUserByNameCacheKey")
        @HystrixCommand
        public User getUserByName(String name) {
            return storage.getByName(name);
        }
        private Long getUserByNameCacheKey(String name) {
            return name;
        }
```

--------------------------------

### Unit Test Hystrix Request Cache With Hits

Source: https://github.com/netflix/hystrix/wiki/How-To-Use

Illustrates testing Hystrix command caching behavior within a request context. This example shows how to verify cache hits and misses, and how cache state resets across different request contexts.

```java
@Test
        public void testWithCacheHits() {
            HystrixRequestContext context = HystrixRequestContext.initializeContext();
            try {
                CommandUsingRequestCache command2a = new CommandUsingRequestCache(2);
                CommandUsingRequestCache command2b = new CommandUsingRequestCache(2);

                assertTrue(command2a.execute());
                // this is the first time we've executed this command with
                // the value of "2" so it should not be from cache
                assertFalse(command2a.isResponseFromCache());

                assertTrue(command2b.execute());
                // this is the second time we've executed this command with
                // the same value so it should return from cache
                assertTrue(command2b.isResponseFromCache());
            } finally {
                context.shutdown();
            }

            // start a new request context
            context = HystrixRequestContext.initializeContext();
            try {
                CommandUsingRequestCache command3b = new CommandUsingRequestCache(2);
                assertTrue(command3b.execute());
                // this is a new request context so this 
                // should not come from cache
                assertFalse(command3b.isResponseFromCache());
            } finally {
                context.shutdown();
            }
        }
```

--------------------------------

### Handle Network Events in Java

Source: https://github.com/netflix/hystrix/blob/master/hystrix-contrib/hystrix-network-auditor-agent/README.md

Example implementation for handling network events. It checks if the current thread is executing a Hystrix command, increments counters for non-isolated events, and captures stack traces for debugging.

```java
    @Override
    public void handleNetworkEvent() {
        if (Hystrix.getCurrentThreadExecutingCommand() == null) {
            // increment counter
            totalNonIsolatedEventsCounter.increment();
            // capture the stacktrace and record so network events can be debugged and tracked down
            StackTraceElement[] stack = Thread.currentThread().getStackTrace();
            HystrixNetworkEvent counter = counters.get(stack);
            if (counter == null) {
                counter = new HystrixNetworkEvent(stack);
                HystrixNetworkEvent c = counters.putIfAbsent(Arrays.toString(stack), counter);
                if (c != null) {
                    // another thread beat us
                    counter = c;
                }
            }
            counter.increment();
        }
    }
```

--------------------------------

### Setting Thread Pool Properties with @HystrixCommand

Source: https://github.com/netflix/hystrix/blob/master/hystrix-contrib/hystrix-javanica/README.md

Configures both command and thread pool properties using @HystrixCommand. This example sets execution timeout, core size, queue size, and other metrics properties.

```java
@HystrixCommand(commandProperties = {
            @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds", value = "500")
        },
                threadPoolProperties = {
                        @HystrixProperty(name = "coreSize", value = "30"),
                        @HystrixProperty(name = "maxQueueSize", value = "101"),
                        @HystrixProperty(name = "keepAliveTimeMinutes", value = "2"),
                        @HystrixProperty(name = "queueSizeRejectionThreshold", value = "15"),
                        @HystrixProperty(name = "metrics.rollingStats.numBuckets", value = "12"),
                        @HystrixProperty(name = "metrics.rollingStats.timeInMilliseconds", value = "1440")
        })
    public User getUserById(String id) {
        return userResource.getUserById(id);
    }
```

--------------------------------

### Construct HystrixCommandKey

Source: https://github.com/netflix/hystrix/wiki/How-To-Use

Constructs and interns HystrixCommandKey instances using the HystrixCommandKey.Factory.asKey() helper method. This is the recommended way to create command keys.

```java
HystrixCommandKey.Factory.asKey("HelloWorld")
```

--------------------------------

### Test Request Cache Invalidation Behavior

Source: https://github.com/netflix/hystrix/wiki/How-To-Use

This unit test verifies the Get-Set-Get cache invalidation pattern. It asserts that the initial Get retrieves data, a subsequent Get from cache is confirmed, a Set operation invalidates the cache, and a final Get retrieves the updated data without using the cache.

```java
@Test
        public void getGetSetGet() {
            HystrixRequestContext context = HystrixRequestContext.initializeContext();
            try {
                assertEquals("ValueBeforeSet_1", new GetterCommand(1).execute());
                GetterCommand commandAgainstCache = new GetterCommand(1);
                assertEquals("ValueBeforeSet_1", commandAgainstCache.execute());
                // confirm it executed against cache the second time
                assertTrue(commandAgainstCache.isResponseFromCache());
                // set the new value
                new SetterCommand(1, "ValueAfterSet_").execute();
                // fetch it again
                GetterCommand commandAfterSet = new GetterCommand(1);
                // the getter should return with the new prefix, not the value from cache
                assertFalse(commandAfterSet.isResponseFromCache());
                assertEquals("ValueAfterSet_1", commandAfterSet.execute());
            } finally {
                context.shutdown();
            }
        }
    }
```

--------------------------------

### Building Hystrix with Gradle

Source: https://github.com/netflix/hystrix/wiki/Getting-Started

Builds the Hystrix project using Gradle. This command compiles the code, runs tests, and packages the artifacts.

```bash
./gradlew build
```

--------------------------------

### Executing a Hystrix Command

Source: https://github.com/netflix/hystrix/wiki/Getting-Started

Demonstrates different ways to execute a Hystrix command: synchronously with 'execute()', asynchronously with 'queue()' returning a Future, or as an Observable with 'observe()'.

```java
String s = new CommandHelloWorld("Bob").execute();
Future<String> s = new CommandHelloWorld("Bob").queue();
Observable<String> s = new CommandHelloWorld("Bob").observe();
```

--------------------------------

### Configure HystrixRequestContextServletFilter in web.xml

Source: https://github.com/netflix/hystrix/blob/master/hystrix-contrib/hystrix-request-servlet/README.md

Install the HystrixRequestContextServletFilter in your web.xml to initialize and clean up HystrixRequestContext for each HTTP request.

```xml
<filter>
    <display-name>HystrixRequestContextServletFilter</display-name>
    <filter-name>HystrixRequestContextServletFilter</filter-name>
    <filter-class>com.netflix.hystrix.contrib.requestservlet.HystrixRequestContextServletFilter</filter-class>
  </filter>
  <filter-mapping>
    <filter-name>HystrixRequestContextServletFilter</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>
```

--------------------------------

### Configure HystrixRequestLogViaLoggerServletFilter in web.xml

Source: https://github.com/netflix/hystrix/blob/master/hystrix-contrib/hystrix-request-servlet/README.md

Install the HystrixRequestLogViaLoggerServletFilter in your web.xml to log executed Hystrix commands at the end of each request.

```xml
<filter>
    <display-name>HystrixRequestLogViaLoggerServletFilter</display-name>
    <filter-name>HystrixRequestLogViaLoggerServletFilter</filter-name>
    <filter-class>com.netflix.hystrix.contrib.requestservlet.HystrixRequestLogViaLoggerServletFilter</filter-class>
  </filter>
  <filter-mapping>
    <filter-name>HystrixRequestLogViaLoggerServletFilter</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>
```

--------------------------------

### Apache 2.0 License Header for New Files

Source: https://github.com/netflix/hystrix/blob/master/CONTRIBUTING.md

When adding a new file to the Hystrix project, include this standard Apache 2.0 license header. Ensure all fields are accurate.

```java
/**
 * Copyright 2013 Netflix, Inc.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
 
```

--------------------------------

### JSR107 Cache Removal Example

Source: https://github.com/netflix/hystrix/blob/master/hystrix-contrib/hystrix-javanica/README.md

Demonstrates cache invalidation using JSR107 annotations with a custom cache key generator.

```java
    @CacheRemove(cacheName = "getUserById", cacheKeyGenerator = UserCacheKeyGenerator.class)
    @HystrixCommand
    public void update(@CacheKey User user) {
         storage.put(user.getId(), user);
    }
        
    public static class UserCacheKeyGenerator implements HystrixCacheKeyGenerator {
        @Override
        public HystrixGeneratedCacheKey generateCacheKey(CacheKeyInvocationContext<? extends Annotation>  cacheKeyInvocationContext) {
            CacheInvocationParameter cacheInvocationParameter = cacheKeyInvocationContext.getKeyParameters()[0];
            User user = (User) cacheInvocationParameter.getValue();
            return new DefaultHystrixGeneratedCacheKey(user.getId());
        }
    }
```

--------------------------------

### Construct HystrixCommand Object

Source: https://github.com/netflix/hystrix/wiki/How-it-Works

Instantiate a HystrixCommand for dependencies expected to return a single response. Pass necessary arguments to the constructor.

```java
HystrixCommand command = new HystrixCommand(arg1, arg2);
```

--------------------------------

### Hystrix Thread Pool Metrics Streams

Source: https://github.com/netflix/hystrix/wiki/Metrics-and-Monitoring

Observes thread pool execution start and completion events. Requires HystrixThreadPoolKey.

```java
Observable<HystrixCommandExecutionStarted> observeThreadPoolStartStream(HystrixThreadPoolKey key)
Observable<HystrixCommandCompletion> observeThreadPoolCompletionStream(HystrixThreadPoolKey key)
```

--------------------------------

### Reactive Execution with HystrixCommand

Source: https://context7.com/netflix/hystrix/llms.txt

Use `observe()` for hot observables that execute immediately, or `toObservable()` for cold observables that execute on subscription. Subscribe to handle results and combine multiple reactive commands using `Observable.merge()`.

```java
public class GetProductCommand extends HystrixCommand<Product> {

    private final String productId;

    public GetProductCommand(String productId) {
        super(HystrixCommandGroupKey.Factory.asKey("ProductCatalog"));
        this.productId = productId;
    }

    @Override
    protected Product run() throws Exception {
        return productCatalog.getProduct(productId);
    }

    @Override
    protected Product getFallback() {
        return Product.unavailable(productId);
    }
}

// Hot Observable - executes immediately
Observable<Product> hotObservable = new GetProductCommand("prod-123").observe();

// Cold Observable - executes only when subscribed
Observable<Product> coldObservable = new GetProductCommand("prod-456").toObservable();

// Subscribe to handle results
hotObservable.subscribe(
    product -> System.out.println("Received: " + product.getName()),
    error -> System.err.println("Error: " + error.getMessage()),
    () -> System.out.println("Completed")
);

// Combine multiple reactive commands
Observable.merge(
    new GetProductCommand("prod-1").observe(),
    new GetProductCommand("prod-2").observe(),
    new GetProductCommand("prod-3").observe()
).subscribe(product -> System.out.println("Product: " + product.getName()));
```

--------------------------------

### Get Latest Synchronous Mean

Source: https://github.com/netflix/hystrix/wiki/Metrics-and-Monitoring

Fetch the latest calculated mean value from the bucketing distribution synchronously. Requires Hystrix core.

```java
int getLatestMean()
```

--------------------------------

### Initialize HystrixCommand with Instance Defaults

Source: https://github.com/netflix/hystrix/wiki/Configuration

Instantiate a HystrixCommand with a group key and a specific default execution timeout. This constructor simplifies setting common initial values.

```java
public HystrixCommandInstance(int id) {
    super(Setter.withGroupKey(HystrixCommandGroupKey.Factory.asKey("ExampleGroup"))
        .andCommandPropertiesDefaults(HystrixCommandProperties.Setter()
               .withExecutionTimeoutInMilliseconds(500)));
    this.id = id;
}
```

--------------------------------

### Enable Hystrix Network Auditor Agent

Source: https://github.com/netflix/hystrix/blob/master/hystrix-contrib/hystrix-network-auditor-agent/README.md

Add this to the JVM command-line to enable the agent. It instruments `java.net` and `java.io` classes.

```bash
-javaagent:/var/root/hystrix-network-auditor-agent-x.y.zjar
```

--------------------------------

### Register Hystrix Codahale Metrics Publisher

Source: https://github.com/netflix/hystrix/blob/master/hystrix-contrib/hystrix-codahale-metrics-publisher/README.md

Plug in the Hystrix Codahale Metrics Publisher by registering it with HystrixPlugins. Ensure you provide an initialized Coda Hale MetricRegistry.

```java
HystrixPlugins.getInstance().registerMetricsPublisher(new HystrixCodahaleMetricsPublisher(yourMetricRegistry));
```

--------------------------------

### Get Latest Synchronous Histogram Data

Source: https://github.com/netflix/hystrix/wiki/Metrics-and-Monitoring

Retrieve the most recent histogram data synchronously from bucketing distributions. Useful for immediate state checks.

```java
CachedValuesHistogram getLatest()
```

--------------------------------

### Construct HystrixCommandGroupKey

Source: https://github.com/netflix/hystrix/wiki/How-To-Use

Constructs and interns HystrixCommandGroupKey instances using the HystrixCommandGroupKey.Factory.asKey() helper method. This is used for grouping commands.

```java
HystrixCommandGroupKey.Factory.asKey("ExampleGroup")
```

--------------------------------

### Observe Bucketed Distributions as a Stream

Source: https://github.com/netflix/hystrix/wiki/Metrics-and-Monitoring

Treat bucketing distributions as a stream to get the latest aggregate histogram. Requires Hystrix core library.

```java
Observable<CachedValuesHistogram> observe()
```

--------------------------------

### Hystrix Primary-Secondary Command Execution

Source: https://github.com/netflix/hystrix/wiki/How-To-Use

Demonstrates a Hystrix command that can execute either a primary or secondary logic based on configuration. Includes unit tests for both scenarios.

```java
public static class CommandFacadeWithPrimarySecondary extends HystrixCommand<String> {

        private final int id;

        public CommandFacadeWithPrimarySecondary(int id) {
            // call primary or secondary based on configuration
            super(Setter.withGroupKey(HystrixCommandGroupKey.Factory.asKey("PrimarySecondaryGroup"))
                    .andCommandPropertiesDefaults(HystrixCommandProperties.Setter()
                            // we default to a 100ms timeout for secondary
                            .withExecutionTimeoutInMilliseconds(100)));
            this.id = id;
        }

        @Override
        protected String run() {
            // perform fast 'secondary' service call
            return "responseFromSecondary-" + id;
        }

    }

    public static class UnitTest {

        @Test
        public void testPrimary() {
            HystrixRequestContext context = HystrixRequestContext.initializeContext();
            try {
                ConfigurationManager.getConfigInstance().setProperty("primarySecondary.usePrimary", true);
                assertEquals("responseFromPrimary-20", new CommandFacadeWithPrimarySecondary(20).execute());
            } finally {
                context.shutdown();
                ConfigurationManager.getConfigInstance().clear();
            }
        }

        @Test
        public void testSecondary() {
            HystrixRequestContext context = HystrixRequestContext.initializeContext();
            try {
                ConfigurationManager.getConfigInstance().setProperty("primarySecondary.usePrimary", false);
                assertEquals("responseFromSecondary-20", new CommandFacadeWithPrimarySecondary(20).execute());
            } finally {
                context.shutdown();
                ConfigurationManager.getConfigInstance().clear();
            }
        }
    }
```

--------------------------------

### Execute HystrixCommand Asynchronously

Source: https://github.com/netflix/hystrix/wiki/How-To-Use

Execute a HystrixCommand asynchronously using the queue() method. Retrieve the result using the Future object's get() method.

```java
Future<String> fs = new CommandHelloWorld("World").queue();
```

```java
String s = fs.get();
```

```java
assertEquals("Hello World!", new CommandHelloWorld("World").queue().get());
assertEquals("Hello Bob!", new CommandHelloWorld("Bob").queue().get());
```

```java
Future<String> fWorld = new CommandHelloWorld("World").queue();
Future<String> fBob = new CommandHelloWorld("Bob").queue();

assertEquals("Hello World!", fWorld.get());
assertEquals("Hello Bob!", fBob.get());
```

```java
String s1 = new CommandHelloWorld("World").execute();
String s2 = new CommandHelloWorld("World").queue().get();
```

--------------------------------

### Execute Hystrix Commands

Source: https://github.com/netflix/hystrix/wiki/How-it-Works

Demonstrates various methods to execute Hystrix commands: execute() for blocking single response, queue() for a Future, observe() for a hot Observable, and toObservable() for a cold Observable. All commands are ultimately backed by an Observable.

```java
K             value   = command.execute();
Future<K>     fValue  = command.queue();
Observable<K> ohValue = command.observe();         //hot observable
Observable<K> ocValue = command.toObservable();    //cold observable
```

--------------------------------

### Define and Execute Hystrix Command in Clojure

Source: https://github.com/netflix/hystrix/blob/master/hystrix-contrib/hystrix-clj/README.md

Wrap a function with `defcommand` to make it a Hystrix dependency. Execute it directly or queue for asynchronous processing.

```clojure
(defn make-request
  [arg]
  ... make the request ...)

; execute the request
(make-request "baz")
```

```clojure
(defcommand make-request
  [arg]
  ... make the request ...)

; execute the request
(make-request "baz")

; or queue for async execution
(queue #'make-request "baz")
```

--------------------------------

### Hystrix Request Stream JSON Output

Source: https://github.com/netflix/hystrix/wiki/Metrics-and-Monitoring

Example JSON output from the Hystrix request events SSE stream, detailing command names, events, and latencies.

```json
data: [[{"name":"GetOrderCommand","events":["SUCCESS"],"latencies":[111]},{"name":"GetPaymentInformationCommand","events":["SUCCESS"],"latencies":[15]},{"name":"GetUserAccountCommand","events":["TIMEOUT","FALLBACK_SUCCESS"],"latencies":[59],"cached":2},{"name":"CreditCardCommand","events":["SUCCESS"],"latencies":[957]}],[{"name":"GetUserAccountCommand","events":["SUCCESS"],"latencies":[3],"cached":2},{"name":"GetOrderCommand","events":["SUCCESS"],"latencies":[77]},{"name":"GetPaymentInformationCommand","events":["SUCCESS"],"latencies":[21]},{"name":"CreditCardCommand","events":["SUCCESS"],"latencies":[1199]}]])
```

--------------------------------

### Hystrix Utilization Stream JSON Output

Source: https://github.com/netflix/hystrix/wiki/Metrics-and-Monitoring

Example JSON output from the Hystrix utilization SSE stream, showing active counts for commands and thread pools.

```json
data: {"type":"HystrixUtilization","commands":{"CreditCardCommand":{"activeCount":0},"GetUserAccountCommand":{"activeCount":0},"GetOrderCommand":{"activeCount":1},"GetPaymentInformationCommand":{"activeCount":0}},"threadpools":{"User":{"activeCount":0,"queueSize":0,"corePoolSize":8,"poolSize":2},"CreditCard":{"activeCount":0,"queueSize":0,"corePoolSize":8,"poolSize":1},"Order":{"activeCount":1,"queueSize":0,"corePoolSize":8,"poolSize":2},"PaymentInformation":{"activeCount":0,"queueSize":0,"corePoolSize":8,"poolSize":2}}}
```

--------------------------------

### Download Hystrix Dependencies using Maven

Source: https://github.com/netflix/hystrix/blob/master/README.md

Command to execute a Maven build using a specific POM file to download Hystrix core and its dependencies. The JARs will be placed in the './target/dependency/' directory.

```bash
mvn -f download-hystrix-pom.xml dependency:copy-dependencies
```

--------------------------------

### Get Default Command Name

Source: https://github.com/netflix/hystrix/wiki/How-To-Use

Retrieves the default command name using the class's simple name. This is the default behavior if no explicit name is provided.

```java
getClass().getSimpleName();
```

--------------------------------

### Primary-Secondary Facade with Hystrix

Source: https://context7.com/netflix/hystrix/llms.txt

This command routes requests to either a primary or secondary service based on a dynamic configuration property. It uses semaphore isolation and defines distinct thread pools for primary and secondary commands, each with its own timeout.

```java
public class PrimarySecondaryFacade extends HystrixCommand<String> {

    private static final DynamicBooleanProperty usePrimary = 
        DynamicPropertyFactory.getInstance()
            .getBooleanProperty("service.usePrimary", true);

    private final String requestId;

    public PrimarySecondaryFacade(String requestId) {
        super(Setter
            .withGroupKey(HystrixCommandGroupKey.Factory.asKey("ServiceFacade"))
            .andCommandKey(HystrixCommandKey.Factory.asKey("PrimarySecondaryFacade"))
            .andCommandPropertiesDefaults(HystrixCommandProperties.Setter()
                // Use semaphore since we're delegating to other commands
                .withExecutionIsolationStrategy(
                    HystrixCommandProperties.ExecutionIsolationStrategy.SEMAPHORE)));
        this.requestId = requestId;
    }

    @Override
    protected String run() throws Exception {
        if (usePrimary.get()) {
            return new PrimaryServiceCommand(requestId).execute();
        } else {
            return new SecondaryServiceCommand(requestId).execute();
        }
    }

    @Override
    protected String getFallback() {
        return "static-fallback-" + requestId;
    }

    // Primary service command with its own thread pool
    private static class PrimaryServiceCommand extends HystrixCommand<String> {
        private final String requestId;

        PrimaryServiceCommand(String requestId) {
            super(Setter
                .withGroupKey(HystrixCommandGroupKey.Factory.asKey("ServiceFacade"))
                .andCommandKey(HystrixCommandKey.Factory.asKey("PrimaryService"))
                .andThreadPoolKey(HystrixThreadPoolKey.Factory.asKey("PrimaryServicePool"))
                .andCommandPropertiesDefaults(HystrixCommandProperties.Setter()
                    .withExecutionTimeoutInMilliseconds(1000)));
            this.requestId = requestId;
        }

        @Override
        protected String run() throws Exception {
            return primaryService.execute(requestId);
        }
    }

    // Secondary service command with its own thread pool
    private static class SecondaryServiceCommand extends HystrixCommand<String> {
        private final String requestId;

        SecondaryServiceCommand(String requestId) {
            super(Setter
                .withGroupKey(HystrixCommandGroupKey.Factory.asKey("ServiceFacade"))
                .andCommandKey(HystrixCommandKey.Factory.asKey("SecondaryService"))
                .andThreadPoolKey(HystrixThreadPoolKey.Factory.asKey("SecondaryServicePool"))
                .andCommandPropertiesDefaults(HystrixCommandProperties.Setter()
                    .withExecutionTimeoutInMilliseconds(500))); // Faster timeout for cache
            this.requestId = requestId;
        }

        @Override
        protected String run() throws Exception {
            return secondaryService.execute(requestId);
        }
    }
}
```

```java
// Usage - automatically routes based on configuration
String result = new PrimarySecondaryFacade("request-123").execute();
```

```java
// Switch to secondary at runtime
ConfigurationManager.getConfigInstance()
    .setProperty("service.usePrimary", false);
```