Circuit breaker design pattern: Difference between revisions

Revision as of 22:34, 11 November 2022

Revision as of 21:20, 23 January 2023

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By how much depends on the storage layer used and generally available resources. The largest factors in this regard are the type of cache, for example, disk-based vs. memory-based and local vs. network.

== Different Statesstates of Circuitcircuit Breakerbreaker ==

* Closed

* Open

* Half Open-open

=== Closed State ===

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[[File:Circuit Breaker -Closed state.png|thumb|Circuit Breaker Closed State]]

=== Open Statestate ===

In this state circuit breaker returns an error immediately without even invoking the services. The Circuit breakers move into the half-open state after a timeout period elapses. Usually, it will have a monitoring system where the timeout will be specified.

[[File:Circuit Breaker -Openstate.png|thumb|Circuit Breaker Open State]]

=== Half-open Open Statestate ===

In this state, the circuit breaker allows a limited number of requests from the Microservice to passthrough and invoke the operation. If the requests are successful, then the circuit breaker will go to the closed state. However, if the requests continue to fail, then it goes back to Open state.

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<syntaxhighlight lang="php">

$mysqli = new mysqli('"localhost'", 'user'"username", 'pass'"password");

if ($mysqli->connect_error) {

apc_store('"dbStatus'", '"down'");

} else {

apc_store('"dbStatus'", '"up'");

$mysqli->close();

}

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<syntaxhighlight lang="php">

if (apc_fetch('"dbStatus'") === '"down'") {

echo '"The database server is currently not available. Please try again in a minute.'";

exit;

}

$mysqli = new mysqli('"localhost'", 'user'"username", 'pass'"password", '"database'");

$result = $mysqli->query('"SELECT * FROM table'");

</syntaxhighlight>