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Added CircuitBreaker post on failsafe
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4 files changed

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‎stubbornjava-examples/src/main/java/com/stubbornjava/examples/failsafe/FailsafeWebserver.java

Lines changed: 10 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -71,7 +71,7 @@ private static final void circuitClosed(HttpServerExchange exchange) {
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// {{end:handlers}}
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// {{start:request}}
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private static void request(boolean error, boolean exception) {
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private static void request(String message, boolean error, boolean exception) {
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HttpUrl url = HttpUrl.parse("http://localhost:8080")
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.newBuilder()
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.addQueryParameter("error", String.valueOf(error))
@@ -80,7 +80,7 @@ private static void request(boolean error, boolean exception) {
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Request request = new Request.Builder().get().url(url).build();
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try {
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log.info(HttpClient.globalClient().newCall(request).execute().body().string());
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log.info(message + " " + HttpClient.globalClient().newCall(request).execute().body().string());
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} catch (IOException e) {
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e.printStackTrace();
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}
@@ -101,28 +101,30 @@ public static void main(String[] args) {
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// Warm-up the circuit breaker it needs to hit at least max executions
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// Before it will reject anything. This will make that easier.
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for (int i = 0; i < 10; i++) {
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request(false, false);
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request("warmup", false, false);
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}
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ScheduledExecutorService schedExec = Executors.newScheduledThreadPool(1);
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// A simple request that should always succeed
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schedExec.scheduleAtFixedRate(() -> request(false, false), 0, 500, TimeUnit.MILLISECONDS);
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schedExec.scheduleAtFixedRate(() -> request("ping", false, false), 0, 500, TimeUnit.MILLISECONDS);
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// Send a batch of 15 bad requests to trigger the circuit breaker
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Runnable errors = () -> {
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log.info("Executing bad requests!");
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log.info("Start: Executing bad requests!");
114114
for (int i = 0; i < 15; i++) {
115-
request(true, false);
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request("bad request", true, false);
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}
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log.info("End: Executing bad requests!");
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};
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schedExec.schedule(errors, 1, TimeUnit.SECONDS);
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// Send a batch of 15 requests that throw exceptions
121122
Runnable exceptions = () -> {
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log.info("Executing requests that throw exceptions!");
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log.info("Start: Executing requests that throw exceptions!");
123124
for (int i = 0; i < 15; i++) {
124-
request(false, true);
125+
request("exception request", false, true);
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}
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log.info("End: Executing requests that throw exceptions!");
126128
};
127129
schedExec.schedule(exceptions, 5, TimeUnit.SECONDS);
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}

‎stubbornjava-webapp/src/main/java/com/stubbornjava/webapp/post/PostData.java

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Original file line numberDiff line numberDiff line change
@@ -760,6 +760,24 @@ public class PostData {
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))
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.build()
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);
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posts.add(PostRaw.builder()
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.postId(5L)
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.title("Increasing Resiliency with Circuit Breakers in your Undertow Webserver with Failsafe")
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.metaDesc("Utilize circuit breakers to fail fast and recover quickly with a CircuitBreakerHandler in Undertow. Shutoff misbehaving endpoints to allow other endpoints to proceede normally.")
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.dateCreated(LocalDateTime.parse("2018-02-05T01:15:30"))
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.dateUpdated(LocalDateTime.parse("2018-02-05T01:15:30"))
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.javaLibs(Lists.newArrayList(JavaLib.Undertow, JavaLib.Failsafe, JavaLib.OkHttp))
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.tags(Lists.newArrayList(Tags.WebServer, Tags.Resiliency))
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.gitFileReferences(Lists.newArrayList(
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FileReference.stubbornJava(
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"handler",
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"stubbornjava-common/src/main/java/com/stubbornjava/common/undertow/handlers/CircuitBreakerHandler.java")
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, FileReference.stubbornJava(
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"example",
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"stubbornjava-examples/src/main/java/com/stubbornjava/examples/failsafe/FailsafeWebserver.java")
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))
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.build()
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);
763781
}
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public static List<PostRaw> getPosts() {

‎stubbornjava-webapp/src/main/java/com/stubbornjava/webapp/post/Tags.java

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@@ -31,6 +31,7 @@ public class Tags {
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public static final Tag Ansible = addTag(new Tag(922794262770139008L, "Ansible"));
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public static final Tag Supervisord = addTag(new Tag(922794262770139008L, "Supervisord"));
3333
public static final Tag Security = addTag(new Tag(953801444178362856L, "Security"));
34+
public static final Tag Resiliency = addTag(new Tag(958330984838442254L, "Resiliency"));
3435

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private static Tag addTag(Tag tag) {
3637
TAGS.add(tag);

‎stubbornjava-webapp/ui/src/posts/increasing-resiliency-with-circuit-breakers-in-your-undertow-webserver-with-failsafe.hbs

Lines changed: 113 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,113 @@
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<div class="anchored-md">
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{{#assign "markdown"}}
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It's inevitable that your system will have failures whether they are caused by bugs, network partitions, load, etc. What is important is being able to recover and recovering quickly. There have been some great resiliency libraries released in Java over the past few years. We found Netflix's [Hystrix](https://github.com/Netflix/Hystrix) to have a higher learning curve and a bit more complicated to use. We opted for [Failsafe](https://github.com/jhalterman/failsafe) which has more of an opt in model to only use what you want. We will outline how to circuit break your web server to help fail fast and recover quicker.
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## What is a Circuit Breaker?
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The Wikipedia definition of a [circuit breaker](https://en.wikipedia.org/wiki/Circuit_breaker). "A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overcurrent, typically resulting from an overload or short circuit. Its basic function is to interrupt current flow after a fault is detected. Unlike a fuse, which operates once and then must be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation." In software we can think of this as a fail fast mechanism that will stop a code path once it notices a certain failure rate. This will hopefully give the system time to recover or at least allow other code paths to function while this one is down.
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### Example Failsafe Circuit Breaker
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{{> templates/src/widgets/code/code-snippet file=example section=example.sections.breaker}}
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## Circuit Breaker HttpHandler
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Let's utilize a `CircuitBreaker` to create a reusable `HttpHandler` that can circuit break based on a passed in `CircuitBreaker`. This could be useful if some resource pool is constrained and we want to help relieve some back-pressure by not sending any new requests. Another use case is potentially we have some bug such as forgetting to paginate a SQL query and just one specific endpoint is hanging non stop. Utilizing a `CircuitBreaker` we can automatically start shutting off individual endpoints or maybe an entire service as a whole using [middleware](/posts/logging-gzip-blocking-exception-handling-metrics-middleware-chaining-in-undertow). Keep in mind that techniques such as this can hurt you just as much as they help you if they are not configured well.
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{{> templates/src/widgets/code/code-snippet file=handler section=handler.sections.handler}}
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## Example Handlers
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Here we have a `HttpHandler` that we can easily mimic some errors in as well as a `HttpHander` that returns a 500 - server error.
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{{> templates/src/widgets/code/code-snippet file=example section=example.sections.handlers}}
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## Making some Requests
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Here is a quick little method to use [OkHttp](/posts/okhttp-example-rest-client) to send a HTTP request to our example server.
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{{> templates/src/widgets/code/code-snippet file=example section=example.sections.request}}
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## Example Server
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Finally we can start up a server and send some requests at it with a `ScheduledExecutorService`.
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{{> templates/src/widgets/code/code-snippet file=example section=example.sections.main}}
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### Output
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<pre class="line-numbers"><code class="language-bash">2018-02-05 23:43:16.168 [main] INFO c.s.common.undertow.SimpleServer - ListenerInfo{protcol='http', address=/0:0:0:0:0:0:0:0:8080, sslContext=null}
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2018-02-05 23:43:16.542 [main] INFO c.s.e.failsafe.FailsafeWebserver - warmup Circuit is open everything is functioning properly.
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2018-02-05 23:43:16.549 [main] INFO c.s.e.failsafe.FailsafeWebserver - warmup Circuit is open everything is functioning properly.
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2018-02-05 23:43:16.553 [main] INFO c.s.e.failsafe.FailsafeWebserver - warmup Circuit is open everything is functioning properly.
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2018-02-05 23:43:16.554 [main] INFO c.s.e.failsafe.FailsafeWebserver - warmup Circuit is open everything is functioning properly.
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2018-02-05 23:43:16.556 [main] INFO c.s.e.failsafe.FailsafeWebserver - warmup Circuit is open everything is functioning properly.
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2018-02-05 23:43:16.557 [main] INFO c.s.e.failsafe.FailsafeWebserver - warmup Circuit is open everything is functioning properly.
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2018-02-05 23:43:16.559 [main] INFO c.s.e.failsafe.FailsafeWebserver - warmup Circuit is open everything is functioning properly.
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2018-02-05 23:43:16.561 [main] INFO c.s.e.failsafe.FailsafeWebserver - warmup Circuit is open everything is functioning properly.
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2018-02-05 23:43:16.562 [main] INFO c.s.e.failsafe.FailsafeWebserver - warmup Circuit is open everything is functioning properly.
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2018-02-05 23:43:16.564 [main] INFO c.s.e.failsafe.FailsafeWebserver - warmup Circuit is open everything is functioning properly.
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2018-02-05 23:43:16.568 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - ping Circuit is open everything is functioning properly.
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2018-02-05 23:43:17.068 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - ping Circuit is open everything is functioning properly.
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2018-02-05 23:43:17.568 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - ping Circuit is open everything is functioning properly.
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2018-02-05 23:43:17.568 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - Start: Executing bad requests!
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2018-02-05 23:43:17.569 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - bad request Bad Request
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2018-02-05 23:43:17.570 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - bad request Bad Request
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2018-02-05 23:43:17.572 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - bad request Bad Request
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2018-02-05 23:43:17.574 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - bad request Bad Request
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2018-02-05 23:43:17.575 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - bad request Bad Request
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2018-02-05 23:43:17.576 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - bad request Bad Request
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2018-02-05 23:43:17.577 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - bad request Bad Request
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2018-02-05 23:43:17.578 [XNIO-1 I/O-2] INFO c.s.e.failsafe.FailsafeWebserver - Circuit Opened
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2018-02-05 23:43:17.580 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - bad request 500 - Internal Server Error
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2018-02-05 23:43:17.581 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - bad request 500 - Internal Server Error
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2018-02-05 23:43:17.583 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - bad request 500 - Internal Server Error
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2018-02-05 23:43:17.584 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - bad request 500 - Internal Server Error
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2018-02-05 23:43:17.585 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - bad request 500 - Internal Server Error
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2018-02-05 23:43:17.587 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - bad request 500 - Internal Server Error
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2018-02-05 23:43:17.588 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - bad request 500 - Internal Server Error
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2018-02-05 23:43:17.589 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - bad request 500 - Internal Server Error
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2018-02-05 23:43:17.589 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - End: Executing bad requests!
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2018-02-05 23:43:18.070 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - ping 500 - Internal Server Error
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2018-02-05 23:43:18.568 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - ping 500 - Internal Server Error
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2018-02-05 23:43:19.068 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - ping 500 - Internal Server Error
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2018-02-05 23:43:19.570 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - ping 500 - Internal Server Error
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2018-02-05 23:43:20.070 [XNIO-1 I/O-2] INFO c.s.e.failsafe.FailsafeWebserver - Circuit Half-Open
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2018-02-05 23:43:20.071 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - ping Circuit is open everything is functioning properly.
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2018-02-05 23:43:20.573 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - ping Circuit is open everything is functioning properly.
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2018-02-05 23:43:21.068 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - ping Circuit is open everything is functioning properly.
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2018-02-05 23:43:21.569 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - ping Circuit is open everything is functioning properly.
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2018-02-05 23:43:21.570 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - Start: Executing requests that throw exceptions!
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2018-02-05 23:43:21.571 [XNIO-1 I/O-2] INFO c.s.e.failsafe.FailsafeWebserver - Circuit Closed
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2018-02-05 23:43:21.572 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - exception request 500 - Internal Server Error
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2018-02-05 23:43:21.574 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - exception request 500 - Internal Server Error
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2018-02-05 23:43:21.575 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - exception request 500 - Internal Server Error
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2018-02-05 23:43:21.576 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - exception request 500 - Internal Server Error
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2018-02-05 23:43:21.578 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - exception request 500 - Internal Server Error
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2018-02-05 23:43:21.579 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - exception request 500 - Internal Server Error
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2018-02-05 23:43:21.581 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - exception request 500 - Internal Server Error
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2018-02-05 23:43:21.583 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - exception request 500 - Internal Server Error
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2018-02-05 23:43:21.584 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - exception request 500 - Internal Server Error
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2018-02-05 23:43:21.585 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - exception request 500 - Internal Server Error
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2018-02-05 23:43:21.586 [XNIO-1 I/O-2] INFO c.s.e.failsafe.FailsafeWebserver - Circuit Opened
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2018-02-05 23:43:21.587 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - exception request 500 - Internal Server Error
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2018-02-05 23:43:21.587 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - exception request 500 - Internal Server Error
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2018-02-05 23:43:21.589 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - exception request 500 - Internal Server Error
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2018-02-05 23:43:21.590 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - exception request 500 - Internal Server Error
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2018-02-05 23:43:21.591 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - exception request 500 - Internal Server Error
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2018-02-05 23:43:21.591 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - End: Executing requests that throw exceptions!
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2018-02-05 23:43:22.071 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - ping 500 - Internal Server Error
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2018-02-05 23:43:22.572 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - ping 500 - Internal Server Error
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2018-02-05 23:43:23.072 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - ping 500 - Internal Server Error
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2018-02-05 23:43:23.573 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - ping 500 - Internal Server Error
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2018-02-05 23:43:24.068 [XNIO-1 I/O-2] INFO c.s.e.failsafe.FailsafeWebserver - Circuit Half-Open
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2018-02-05 23:43:24.069 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - ping Circuit is open everything is functioning properly.
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2018-02-05 23:43:24.573 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - ping Circuit is open everything is functioning properly.
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2018-02-05 23:43:25.069 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - ping Circuit is open everything is functioning properly.
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2018-02-05 23:43:25.572 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - ping Circuit is open everything is functioning properly.
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2018-02-05 23:43:26.068 [XNIO-1 I/O-2] INFO c.s.e.failsafe.FailsafeWebserver - Circuit Closed
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2018-02-05 23:43:26.069 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - ping Circuit is open everything is functioning properly.
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2018-02-05 23:43:26.569 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - ping Circuit is open everything is functioning properly.
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2018-02-05 23:43:27.069 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - ping Circuit is open everything is functioning properly.
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2018-02-05 23:43:27.570 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - ping Circuit is open everything is functioning properly.
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2018-02-05 23:43:28.073 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - ping Circuit is open everything is functioning properly.
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2018-02-05 23:43:28.572 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - ping Circuit is open everything is functioning properly.
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2018-02-05 23:43:29.072 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - ping Circuit is open everything is functioning properly.
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2018-02-05 23:43:29.569 [pool-1-thread-1] INFO c.s.e.failsafe.FailsafeWebserver - ping Circuit is open everything is functioning properly.</code></pre>
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{{/assign}}
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{{md markdown}}
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</div>

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