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"/docs/concepts/policy-and-control/mixer-config.html", title: "Mixer Configuration", order: 30, overview: "An overview of the key concepts used to configure Mixer."}); docs.push({path: [ "policy-and-control", "mixer.md", ], url: "/docs/concepts/policy-and-control/mixer.html", title: "Mixer", order: 20, overview: "Architectural deep-dive into the design of Mixer, which provides the policy and control mechanisms within the service mesh."}); docs.push({path: [ "traffic-management", "fault-injection.md", ], url: "/docs/concepts/traffic-management/fault-injection.html", title: "Fault Injection", order: 40, overview: "Introduces the idea of systematic fault injection that can be used to uncover conflicting failure recovery policies across services."}); docs.push({path: [ "traffic-management", "handling-failures.md", ], url: "/docs/concepts/traffic-management/handling-failures.html", title: "Handling Failures", order: 30, overview: "An overview of failure recovery capabilities in Envoy that can be leveraged by unmodified applications to improve robustness and prevent cascading failures."}); docs.push({path: [ "traffic-management", "index.md", ], url: "/docs/concepts/traffic-management/index.html", title: "Traffic Management", order: 20, overview: "Describes the various Istio features focused on traffic routing and control."}); docs.push({path: [ "traffic-management", "load-balancing.md", ], url: "/docs/concepts/traffic-management/load-balancing.html", title: "Discovery & Load Balancing", order: 25, overview: "Describes how traffic is load balanced across instances of a service in the mesh."}); docs.push({path: [ "traffic-management", "overview.md", ], url: "/docs/concepts/traffic-management/overview.html", title: "Overview", order: 0, overview: "Provides a conceptual overview of traffic management in Istio and the features it enables."}); docs.push({path: [ "traffic-management", "pilot.md", ], url: "/docs/concepts/traffic-management/pilot.html", title: "Pilot", order: 10, overview: "Introduces Pilot, the component responsible for managing a distributed deployment of Envoy proxies in the service mesh."}); docs.push({path: [ "traffic-management", "request-routing.md", ], url: "/docs/concepts/traffic-management/request-routing.html", title: "Request Routing", order: 20, overview: "Describes how requests are routed between services in an Istio service mesh."}); docs.push({path: [ "traffic-management", "rules-configuration.md", ], url: "/docs/concepts/traffic-management/rules-configuration.html", title: "Rules Configuration", order: 50, overview: "Provides a high-level overview of the domain-specific language used by Istio to configure traffic management rules in the service mesh."}); docs.push({path: [ "what-is-istio", "goals.md", ], url: "/docs/concepts/what-is-istio/goals.html", title: "Design Goals", order: 20, overview: "Describes the core principles that Istio's design adheres to."}); docs.push({path: [ "what-is-istio", "index.md", ], url: "/docs/concepts/what-is-istio/index.html", title: "What is Istio?", order: 10, overview: "A broad overview of the Istio system."}); docs.push({path: [ "what-is-istio", "overview.md", ], url: "/docs/concepts/what-is-istio/overview.html", title: "Overview", order: 15, overview: "Provides a conceptual introduction to Istio, including the problems it solves and its high-level architecture."}); genNavBarTree(docs) </script></ul></div><div id="tab-container" class="col-xs-1 tab-neg-margin pull-left"> <a id="sidebar-tab" class="glyphicon glyphicon-chevron-left" href="javascript:void 0;"></a></div><div id="content-container" class="thin-left-border col-sm-9 markdown"><div id="toc" class="toc"></div><div id="doc-content"><h1>Discovery & Load Balancing</h1><p>This page describes how Istio load balances traffic across instances of a service in a service mesh.</p><p><strong>Service registration:</strong> Istio assumes the presence of a service registry to keep track of the pods/VMs of a service in the application. It also assumes that new instances of a service are automatically registered with the service registry and unhealthy instances are automatically removed. Platforms such as Kubernetes, Mesos already provide such functionality for container-based applications. A plethora of solutions exist for VM-based applications.</p><p><strong>Service Discovery:</strong> Pilot consumes information from the service registry and provides a platform-agnostic service discovery interface. Envoy instances in the mesh perform service discovery and dynamically update their load balancing pools accordingly.</p><figure><img src="./img/pilot/LoadBalancing.svg" alt="Discovery and Load Balancing" title="Discovery and Load Balancing" /><figcaption>Discovery and Load Balancing</figcaption></figure><p>As illustrated in the figure above, services in the mesh access each other using their DNS names. All HTTP traffic bound to a service is automatically re-routed through Envoy. Envoy distributes the traffic across instances in the load balancing pool. While Envoy supports several <a href="https://lyft.github.io/envoy/docs/intro/arch_overview/load_balancing.html">sophisticated load balancing algorithms</a>, Istio currently allows three load balancing modes: round robin, random, and weighted least request.</p><p>In addition to load balancing, Envoy periodically checks the health of each instance in the pool. Envoy follows a circuit breaker style pattern to classify instances as unhealthy or healthy based on their failure rates for the health check API call. In other words, when the number of health check failures for a given instance exceeds a pre-specified threshold, it will be ejected from the load balancing pool. Similarly, when the number of health checks that pass exceed a pre-specified threshold, the instance will be added back into the load balancing pool. You can find out more about Envoy’s failure-handling features in <a href="./handling-failures.html">Handling Failures</a>.</p><p>Services can actively shed load by responding with a HTTP 503 to a health check. In such an event, the service instance will be immediately removed from the caller’s load balancing pool.</p></div></div></div></div></div></div><script src="/v0.1/js/sidemenu.js"></script><footer><div class="container"><div class="row"><div class="col-md-2"></div><div class="col-md-3 col-sm-4 col-xs-12 center-block"><ul class="toggle"><p class="header">Docs</p><li><a href="/v0.1/docs/">Welcome</a></li><li><a href="/v0.1/docs/concepts">Concepts</a></li><li><a href="/v0.1/docs/tasks">Tasks</a></li><li><a href="/v0.1/docs/samples">Samples</a></li><li><a href="/v0.1/docs/reference">Reference</a></li></ul></div><hr class="footer-sections" /><div class="col-md-3 col-sm-4 col-xs-12 center-block"><ul class="toggle"><p class="header">Resources</p><li><a href="/v0.1/faq">Frequently Asked Questions</a></li><li><a href="/v0.1/troubleshooting">Troubleshooting Guide</a></li><li><a href="/v0.1/bugs">Report a Bug</a></li><li><a href="https://github.com/istio/istio.github.io/issues/new?title=Issue with _docs/concepts/traffic-management/load-balancing.md">Report a Doc Issue</a></li><li><a href="https://github.com/istio/istio.github.io/edit/master/_docs/concepts/traffic-management/load-balancing.md">Edit This Page on GitHub</a></li></ul></div><hr class="footer-sections" /><div class="col-md-3 col-sm-4 col-xs-12 center-block"><ul class="toggle"><p class="header">Community</p><li><a href="https://groups.google.com/forum/#!forum/istio-users" target="_blank"><span class="group">User</span></a> | <a href="https://groups.google.com/forum/#!forum/istio-dev" target="_blank">Dev Mailing Lists</a></li><li><a href="https://twitter.com/IstioMesh" target="_blank"><span class="twitter">Twitter</span></a></li><li><a href="https://github.com/istio/istio" target="_blank"><span class="github">GitHub</span></a></li></ul></div><div class="col-md-1"></div></div><div class="row"><p class="description small text-center"> Copyright © 2017 Istio Authors<br> Istio 0.1<br> Archived on 20-Jul-2017</p></div></div></footer><script src="https://cdnjs.cloudflare.com/ajax/libs/jquery-validate/1.15.0/jquery.validate.min.js"></script> <script src="/v0.1/js/jquery.form.min.js"></script> <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.1/js/bootstrap.min.js"></script> <script src="/v0.1/js/slick.min.js"></script> <script src="/v0.1/js/jquery.visible.min.js"></script> <script src="/v0.1/js/common.js" type="text/javascript" charset="utf-8"></script> <script src="/v0.1/js/buttons.js"></script> <script src="/v0.1/js/search.js"></script> <script src="/v0.1/js/prism.js"></script></body></html>
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