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docs.push({path: [ "policy-and-control", "attributes.md", ], url: "/docs/concepts/policy-and-control/attributes.html", title: "Attributes", order: 10, overview: "Explains the important notion of attributes, which is a central mechanism for how policies and control are applied to services within the mesh."}); docs.push({path: [ "policy-and-control", "index.md", ], url: "/docs/concepts/policy-and-control/", title: "Policies and Control", order: 40, overview: "Introduces the policy control mechanisms."}); docs.push({path: [ "policy-and-control", "mixer-config.md", ], url: "/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: [ "security", "index.md", ], url: "/docs/concepts/security/", title: "Security", order: 30, overview: "Describes Istio's authorization and authentication functionality."}); docs.push({path: [ "security", "mutual-tls.md", ], url: "/docs/concepts/security/mutual-tls.html", title: "Mutual TLS Authentication", order: 10, overview: "Describes Istio's mutual TLS authentication architecture which provides a strong service identity and secure communication channels between services."}); 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/", 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/", 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."}); genSideBarTree(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>Request Routing</h1><p>This page describes how requests are routed between services in an Istio service mesh.</p><h2 id="service-model-and-service-versions">Service model and service versions</h2><p>As described in <a href="./pilot.html">Pilot</a>, the canonical representation of services in a particular mesh is maintained by Pilot. The Istio model of a service is independent of how it is represented in the underlying platform (Kubernetes, Mesos, Cloud Foundry, etc.). Platform-specific adapters are responsible for populating the internal model representation with various fields from the metadata found in the platform.</p><p>Istio introduces the concept of a service version, which is a finer-grained way to subdivide service instances by versions (<code>v1</code>, <code>v2</code>) or environment (<code>staging</code>, <code>prod</code>). These variants are not necessarily different API versions: they could be iterative changes to the same service, deployed in different environments (prod, staging, dev, etc.). Common scenarios where this is used include A/B testing or canary rollouts. Istio’s <a href="./rules-configuration.html">traffic routing rules</a> can refer to service versions to provide additional control over traffic between services.</p><h2 id="communication-between-services">Communication between services</h2><figure><img src="./img/pilot/ServiceModel_Versions.svg" alt="Showing how service versions are handled." title="Service Versions" /><figcaption>Service Versions</figcaption></figure><p>As illustrated in the figure above, clients of a service have no knowledge of different versions of the service. They can continue to access the services using the hostname/IP address of the service. The Envoy sidecar/proxy intercepts and forwards all requests/responses between the client and the service.</p><p>Envoy determines its actual choice of service version dynamically based on the routing rules specified by the operator using Pilot. This model enables the application code to decouple itself from the evolution of its dependent services, while providing other benefits as well (see <a href="/v0.4/docs/concepts/policy-and-control/mixer.html">Mixer</a>). Routing rules allow Envoy to select a version based on criteria such as headers, tags associated with source/destination, and/or by weights assigned to each version.</p><p>Istio also provides load balancing for traffic to multiple instances of the same service version. You can find out more about this in <a href="./load-balancing.html">Discovery and Load-Balancing</a>.</p><p>Istio does not provide a DNS. Applications can try to resolve the FQDN using the DNS service present in the underlying platform (kube-dns, mesos-dns, etc.).</p><h2 id="ingress-and-egress">Ingress and Egress</h2><p>Istio assumes that all traffic entering and leaving the service mesh transits through Envoy proxies. By deploying the Envoy proxy in front of services, operators can conduct A/B testing, deploy canary services, etc. for user-facing services. Similarly, by routing traffic to external web services (for instance, accessing the Maps API, or a video service API) via the sidecar Envoy, operators can add failure recovery features such as timeouts, retries, circuit breakers, etc., and obtain detailed metrics on the connections to these services.</p><figure><img src="./img/pilot/ServiceModel_RequestFlow.svg" alt="Ingress and Egress through Envoy." title="Request Flow" /><figcaption>Request Flow</figcaption></figure></div></div></div></div></div></div><script src="/v0.4/js/sidebar.min.js"></script><footer><div class="container"><div class="row"><div class="col-lg-2 col-md-2 col-sm-2"></div><div class="col-lg-3 col-md-3 col-sm-3 col-xs-12 center-block"><ul><li><a class="header" href="/v0.4/docs/welcome">Docs</a></li><li><a href="/v0.4/docs/concepts">Concepts</a></li><li><a href="/v0.4/docs/setup">Setup</a></li><li><a href="/v0.4/docs/tasks">Tasks</a></li><li><a href="/v0.4/docs/guides">Guides</a></li><li><a href="/v0.4/docs/reference">Reference</a></li></ul></div><div class="col-lg-3 col-md-3 col-sm-3 col-xs-12 center-block"><ul><li><a class="header" href="/v0.4/help">Help</a></li><li><a href="/v0.4/faq">FAQ</a></li><li><a href="/v0.4/glossary">Glossary</a></li><li><a href="/v0.4/troubleshooting">Troubleshooting</a></li><li><a href="/v0.4/bugs">Report Bugs</a></li><li><a href="https://github.com/istio/istio.github.io/issues/new?title=Issue with _docs/concepts/traffic-management/request-routing.md">Doc Bugs & Gaps</a></li><li><a href="https://github.com/istio/istio.github.io/edit/master/_docs/concepts/traffic-management/request-routing.md">Edit This Page</a></li></ul></div><div class="col-lg-3 col-md-3 col-sm-3 col-xs-12 center-block"><ul><li> <a class="header" href="/v0.4/community">Community</a></li><li> <a href="https://groups.google.com/forum/#!forum/istio-users" target="_blank" rel="noopener">User</a> | <a href="https://groups.google.com/forum/#!forum/istio-dev" target="_blank" rel="noopener">Dev Mailing Lists</a></li><li><a href="https://twitter.com/IstioMesh" target="_blank" rel="noopener">Twitter</a></li><li><a href="https://stackoverflow.com/questions/tagged/istio" target="_blank" rel="noopener">Stack Overflow</a></li><li><a href="https://github.com/istio/community" target="_blank" rel="noopener">GitHub</a></li><li><a href="https://github.com/istio/community/blob/master/WORKING-GROUPS.md" target="_blank" rel="noopener">Working Groups</a></li></ul></div><div class="col-lg-1 col-md-1 col-sm-1"></div></div><div class="row"><p class="description small text-center"> Istio 0.4, Copyright © 2017 Istio Authors<br> Archived on 20-Dec-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="https://cdnjs.cloudflare.com/ajax/libs/jquery.form/4.2.1/jquery.form.min.js"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery-visible/1.2.0/jquery.visible.min.js"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/jqueryui/1.12.1/jquery-ui.min.js"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/slick-carousel/1.6.0/slick.min.js"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/clipboard.js/1.7.1/clipboard.min.js"></script> <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script> <script src="/v0.4/js/common.min.js"></script> <script src="/v0.4/js/search.js"></script> <script src="/v0.4/js/prism.min.js"></script></body></html>
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