Virtual Service

a unit of application behavior bound to a unique name in aservice registry. Services consist of multiple network _endpoints_implemented by workload instances running on pods, containers, VMs etc.

Service versions (a.k.a. subsets) - In a continuous deploymentscenario, for a given service, there can be distinct subsets ofinstances running different variants of the application binary. Thesevariants are not necessarily different API versions. They could beiterative changes to the same service, deployed in differentenvironments (prod, staging, dev, etc.). Common scenarios where thisoccurs include A/B testing, canary rollouts, etc. The choice of aparticular version can be decided based on various criterion (headers,url, etc.) and/or by weights assigned to each version. Each service hasa default version consisting of all its instances.

Source - A downstream client calling a service.

Host - The address used by a client when attempting to connect to aservice.

Access model - Applications address only the destination service(Host) without knowledge of individual service versions (subsets). Theactual choice of the version is determined by the proxy/sidecar, enabling theapplication code to decouple itself from the evolution of dependentservices.

A VirtualService defines a set of traffic routing rules to apply when a host isaddressed. Each routing rule defines matching criteria for traffic of a specificprotocol. If the traffic is matched, then it is sent to a named destination service(or subset/version of it) defined in the registry.

The source of traffic can also be matched in a routing rule. This allows routingto be customized for specific client contexts.

The following example on Kubernetes, routes all HTTP traffic by default topods of the reviews service with label “version: v1”. In addition,HTTP requests with path starting with /wpcatalog/ or /consumercatalog/ willbe rewritten to /newcatalog and sent to pods with label “version: v2”.

A subset/version of a route destination is identified with a referenceto a named service subset which must be declared in a correspondingDestinationRule.

apiVersion: networking.istio.io/v1alpha3
kind: DestinationRule
metadata:
  name: reviews-destination
spec:
  host: reviews.prod.svc.cluster.local
  subsets:
  - name: v1
    labels:
      version: v1
  - name: v2
    labels:
      version: v2

Describes the Cross-Origin Resource Sharing (CORS) policy, for a givenservice. Refer to CORSfor further details about cross origin resource sharing. For example,the following rule restricts cross origin requests to those originatingfrom example.com domain using HTTP POST/GET, and sets theAccess-Control-Allow-Credentials header to false. In addition, it onlyexposes X-Foo-bar header and sets an expiry period of 1 day.

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: ratings-route
spec:
  hosts:
  - ratings.prod.svc.cluster.local
  http:
  - route:
    - destination:
        host: ratings.prod.svc.cluster.local
        subset: v1
    corsPolicy:
      allowOrigin:
      - example.com
      allowMethods:
      - POST
      - GET
      allowCredentials: false
      allowHeaders:
      - X-Foo-Bar
      maxAge: "24h"

Destination

Destination indicates the network addressable service to which therequest/connection will be sent after processing a routing rule. Thedestination.host should unambiguously refer to a service in the serviceregistry. Istio’s service registry is composed of all the services foundin the platform’s service registry (e.g., Kubernetes services, Consulservices), as well as services declared through theServiceEntry resource.

Note for Kubernetes users: When short names are used (e.g. “reviews”instead of “reviews.default.svc.cluster.local”), Istio will interpretthe short name based on the namespace of the rule, not the service. Arule in the “default” namespace containing a host “reviews will beinterpreted as “reviews.default.svc.cluster.local”, irrespective of theactual namespace associated with the reviews service. To avoid potentialmisconfigurations, it is recommended to always use fully qualifieddomain names over short names.

The following Kubernetes example routes all traffic by default to podsof the reviews service with label “version: v1” (i.e., subset v1), andsome to subset v2, in a Kubernetes environment.

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: reviews-route
  namespace: foo
spec:
  hosts:
  - reviews # interpreted as reviews.foo.svc.cluster.local
  http:
  - match:
    - uri:
        prefix: "/wpcatalog"
    - uri:
        prefix: "/consumercatalog"
    rewrite:
      uri: "/newcatalog"
    route:
    - destination:
        host: reviews # interpreted as reviews.foo.svc.cluster.local
        subset: v2
  - route:
    - destination:
        host: reviews # interpreted as reviews.foo.svc.cluster.local
        subset: v1

And the associated DestinationRule

apiVersion: networking.istio.io/v1alpha3
kind: DestinationRule
metadata:
  name: reviews-destination
  namespace: foo
spec:
  host: reviews # interpreted as reviews.foo.svc.cluster.local
  subsets:
  - name: v1
    labels:
  - name: v2
    labels:
      version: v2

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: my-productpage-rule
  namespace: istio-system
spec:
  hosts:
  - productpage.prod.svc.cluster.local # ignores rule namespace
  http:
  - timeout: 5s
    route:
    - destination:
        host: productpage.prod.svc.cluster.local

To control routing for traffic bound to services outside the mesh, externalservices must first be added to Istio’s internal service registry using theServiceEntry resource. VirtualServices can then be defined to control trafficbound to these external services. For example, the following rules define aService for wikipedia.org and set a timeout of 5s for http requests.

Field	Type	Description	Required
`host`	`string`	The name of a service from the service registry. Servicenames are looked up from the platform’s service registry (e.g.,Kubernetes services, Consul services, etc.) and from the hostsdeclared by . Traffic forwarded todestinations that are not found in either of the two, will be dropped.Note for Kubernetes users: When short names are used (e.g. “reviews”instead of “reviews.default.svc.cluster.local”), Istio will interpretthe short name based on the namespace of the rule, not the service. Arule in the “default” namespace containing a host “reviews will beinterpreted as “reviews.default.svc.cluster.local”, irrespective ofthe actual namespace associated with the reviews service. To avoidpotential misconfigurations, it is recommended to always use fullyqualified domain names over short names.	Yes
`subset`	`string`	The name of a subset within the service. Applicable only to serviceswithin the mesh. The subset must be defined in a correspondingDestinationRule.	No
`port`	`PortSelector`	Specifies the port on the host that is being addressed. If a serviceexposes only a single port it is not required to explicitly select theport.	No

HTTPFaultInjection

HTTPFaultInjection can be used to specify one or more faults to injectwhile forwarding http requests to the destination specified in a route.Fault specification is part of a VirtualService rule. Faults includeaborting the Http request from downstream service, and/or delayingproxying of requests. A fault rule MUST HAVE delay or abort or both.

Note: Delay and abort faults are independent of one another, even ifboth are specified simultaneously.

Field	Type	Description	Required
`delay`	`Delay`	Delay requests before forwarding, emulating various failures such asnetwork issues, overloaded upstream service, etc.	No
`abort`		Abort Http request attempts and return error codes back to downstreamservice, giving the impression that the upstream service is faulty.	No

HTTPFaultInjection.Abort

Abort specification is used to prematurely abort a request with apre-specified error code. The following example will return an HTTP 400error code for 1 out of every 1000 requests to the “ratings” service “v1”.

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: ratings-route
spec:
  hosts:
  - ratings.prod.svc.cluster.local
  http:
  - route:
    - destination:
        host: ratings.prod.svc.cluster.local
        subset: v1
    fault:
      abort:
        percentage:
          value: 0.1
        httpStatus: 400

The httpStatus field is used to indicate the HTTP status code toreturn to the caller. The optional percentage field can be used to onlyabort a certain percentage of requests. If not specified, all requests areaborted.

Field	Type	Description	Required
`httpStatus`	`int32 (oneof)`	HTTP status code to use to abort the Http request.	Yes
`percentage`		Percentage of requests to be aborted with the error code provided.	No
`percent`	`int32`	Percentage of requests to be aborted with the error code provided (0-100).Use of integer `percent` value is deprecated. Use the double `percentage`field instead.	No

HTTPFaultInjection.Delay

Delay specification is used to inject latency into the requestforwarding path. The following example will introduce a 5 second delayin 1 out of every 1000 requests to the “v1” version of the “reviews”service from all pods with label env: prod

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: reviews-route
spec:
  hosts:
  - reviews.prod.svc.cluster.local
  http:
  - match:
    - sourceLabels:
        env: prod
    route:
    - destination:
        host: reviews.prod.svc.cluster.local
        subset: v1
    fault:
      delay:
        percentage:
          value: 0.1
        fixedDelay: 5s

The fixedDelay field is used to indicate the amount of delay in seconds.The optional percentage field can be used to only delay a certainpercentage of requests. If left unspecified, all request will be delayed.

Field	Type	Description	Required
`fixedDelay`		Add a fixed delay before forwarding the request. Format:1h/1m/1s/1ms. MUST be >=1ms.	Yes
`percentage`		Percentage of requests on which the delay will be injected.	No
`percent`	`int32`	Percentage of requests on which the delay will be injected (0-100).Use of integer `percent` value is deprecated. Use the double `percentage`field instead.	No

HTTPMatchRequest

HttpMatchRequest specifies a set of criterion to be met in order for therule to be applied to the HTTP request. For example, the followingrestricts the rule to match only requests where the URL pathstarts with /ratings/v2/ and the request contains a custom end-user headerwith value jason.

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: ratings-route
spec:
  hosts:
  - ratings.prod.svc.cluster.local
  http:
  - match:
    - headers:
        end-user:
          exact: jason
      uri:
        prefix: "/ratings/v2/"
      ignoreUriCase: true
    route:
    - destination:
        host: ratings.prod.svc.cluster.local

HTTPMatchRequest CANNOT be empty.

Field	Type	Description	Required
`name`	`string`	The name assigned to a match. The match’s name will beconcatenated with the parent route’s name and will be logged inthe access logs for requests matching this route.	No
`uri`		URI to matchvalues are case-sensitive and formatted as follows:-`exact: "value"` for exact string match-`prefix: "value"` for prefix-based match-`regex: "value"` for ECMAscript style regex-based matchNote: Case-insensitive matching could be enabled via the`ignoreuri_case` flag.	No
`scheme`	`StringMatch`	URI Schemevalues are case-sensitive and formatted as follows:-`exact: "value"` for exact string match-`prefix: "value"` for prefix-based match-`regex: "value"` for ECMAscript style regex-based match	No
`method`		HTTP Methodvalues are case-sensitive and formatted as follows:-`exact: "value"` for exact string match-`prefix: "value"` for prefix-based match-`regex: "value"` for ECMAscript style regex-based match	No
`authority`	`StringMatch`	HTTP Authorityvalues are case-sensitive and formatted as follows:-`exact: "value"` for exact string match-`prefix: "value"` for prefix-based match-`regex: "value"` for ECMAscript style regex-based match	No
`headers`	`map<string, >`	The header keys must be lowercase and use hyphen as the separator,e.g. _x-request-id.Header values are case-sensitive and formatted as follows:-`exact: "value"` for exact string match-`prefix: "value"` for prefix-based match-`regex: "value"` for ECMAscript style regex-based matchNote: The keys `uri`, `scheme`, `method`, and `authority` will be ignored.	No
`port`	`uint32`	Specifies the ports on the host that is being addressed. Many servicesonly expose a single port or label ports with the protocols they support,in these cases it is not required to explicitly select the port.	No
`sourceLabels`	`map<string, string>`	One or more labels that constrain the applicability of a rule toworkloads with the given labels. If the VirtualService has a list ofgateways specified at the top, it must include the reserved gateway`mesh` for this field to be applicable.	No
`queryParams`	`map<string, StringMatch>`	Query parameters for matching.Ex:- For a query parameter like “?key=true”, the map key would be “key” andthe string match could be defined as `exact: "true"`.- For a query parameter like “?key”, the map key would be “key” and thestring match could be defined as `exact: ""`.- For a query parameter like “?key=123”, the map key would be “key” and thestring match could be defined as `regex: "\d+$"`. Note that thisconfiguration will only match values like “123” but not “a123” or “123a”.Note: `prefix` matching is currently not supported.	No
`ignoreUriCase`	`bool`	Flag to specify whether the URI matching should be case-insensitive.Note: The case will be ignored only in the case of `exact` and `prefix`URI matches.	No

HTTPRedirect

HTTPRedirect can be used to send a 301 redirect response to the caller,where the Authority/Host and the URI in the response can be swapped withthe specified values. For example, the following rule redirectsrequests for /v1/getProductRatings API on the ratings service to/v1/bookRatings provided by the bookratings service.

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: ratings-route
spec:
  hosts:
  - ratings.prod.svc.cluster.local
  http:
  - match:
    - uri:
        exact: /v1/getProductRatings
    redirect:
      uri: /v1/bookRatings
      authority: newratings.default.svc.cluster.local
  ...

Field	Type	Description	Required
`uri`	`string`	On a redirect, overwrite the Path portion of the URL with thisvalue. Note that the entire path will be replaced, irrespective of therequest URI being matched as an exact path or prefix.	No
`authority`	`string`	On a redirect, overwrite the Authority/Host portion of the URL withthis value.	No
`redirectCode`	`uint32`	On a redirect, Specifies the HTTP status code to use in the redirectresponse. The default response code is MOVED_PERMANENTLY (301).	No

Describes the retry policy to use when a HTTP request fails. Forexample, the following rule sets the maximum number of retries to 3 whencalling ratings:v1 service, with a 2s timeout per retry attempt.

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: ratings-route
spec:
  hosts:
  http:
  - route:
    - destination:
        host: ratings.prod.svc.cluster.local
        subset: v1
    retries:
      attempts: 3
      perTryTimeout: 2s
      retryOn: gateway-error,connect-failure,refused-stream

HTTPRewrite

HTTPRewrite can be used to rewrite specific parts of a HTTP requestbefore forwarding the request to the destination. Rewrite primitive canbe used only with HTTPRouteDestination. The following exampledemonstrates how to rewrite the URL prefix for api call (/ratings) toratings service before making the actual API call.

Field	Type	Description	Required
`uri`	`string`	rewrite the path (or the prefix) portion of the URI with thisvalue. If the original URI was matched based on prefix, the valueprovided in this field will replace the corresponding matched prefix.	No
`authority`	`string`	rewrite the Authority/Host header with this value.	No

HTTPRoute

Describes match conditions and actions for routing HTTP/1.1, HTTP2, andgRPC traffic. See VirtualService for usage examples.

Field	Type	Description	Required
`name`	`string`	The name assigned to the route for debugging purposes. Theroute’s name will be concatenated with the match’s name and willbe logged in the access logs for requests matching thisroute/match.	No
`match`	`HTTPMatchRequest[]`	Match conditions to be satisfied for the rule to beactivated. All conditions inside a single match block have ANDsemantics, while the list of match blocks have OR semantics. The ruleis matched if any one of the match blocks succeed.	No
`route`		A http rule can either redirect or forward (default) traffic. Theforwarding target can be one of several versions of a service (seeglossary in beginning of document). Weights associated with theservice version determine the proportion of traffic it receives.	No
`redirect`	`HTTPRedirect`	A http rule can either redirect or forward (default) traffic. Iftraffic passthrough option is specified in the rule,route/redirect will be ignored. The redirect primitive can be used tosend a HTTP 301 redirect to a different URI or Authority.	No
`rewrite`		Rewrite HTTP URIs and Authority headers. Rewrite cannot be used withRedirect primitive. Rewrite will be performed before forwarding.	No
`timeout`	`Duration`	Timeout for HTTP requests.	No
`retries`		Retry policy for HTTP requests.	No
`fault`	`HTTPFaultInjection`	Fault injection policy to apply on HTTP traffic at the client side.Note that timeouts or retries will not be enabled when faults areenabled on the client side.	No
`mirror`		Mirror HTTP traffic to a another destination in addition to forwardingthe requests to the intended destination. Mirrored traffic is on abest effort basis where the sidecar/gateway will not wait for themirrored cluster to respond before returning the response from theoriginal destination. Statistics will be generated for the mirroreddestination.	No
`mirrorPercent`	`UInt32Value`	Percentage of the traffic to be mirrored by the `mirror` field.If this field is absent, all the traffic (100%) will be mirrored.Max value is 100.	No
`corsPolicy`		Cross-Origin Resource Sharing policy (CORS). Refer toCORSfor further details about cross origin resource sharing.	No
`headers`		Header manipulation rules	No

HTTPRouteDestination

Each routing rule is associated with one or more service versions (seeglossary in beginning of document). Weights associated with the versiondetermine the proportion of traffic it receives. For example, thefollowing rule will route 25% of traffic for the “reviews” service toinstances with the “v2” tag and the remaining traffic (i.e., 75%) to“v1”.

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: reviews-route
spec:
  hosts:
  - reviews.prod.svc.cluster.local
  http:
  - route:
    - destination:
        host: reviews.prod.svc.cluster.local
        subset: v2
      weight: 25
    - destination:
        host: reviews.prod.svc.cluster.local
        subset: v1
      weight: 75

apiVersion: networking.istio.io/v1alpha3
kind: DestinationRule
  name: reviews-destination
spec:
  host: reviews.prod.svc.cluster.local
  subsets:
  - name: v1
    labels:
      version: v1
  - name: v2
    labels:
      version: v2

Traffic can also be split across two entirely different services withouthaving to define new subsets. For example, the following rule forwards 25% oftraffic to reviews.com to dev.reviews.com

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: reviews-route-two-domains
spec:
  hosts:
  - reviews.com
  http:
  - route:
    - destination:
        host: dev.reviews.com
      weight: 25
    - destination:
        host: reviews.com
      weight: 75

Field	Type	Description	Required
`destination`		Destination uniquely identifies the instances of a serviceto which the request/connection should be forwarded to.	Yes
`weight`	`int32`	The proportion of traffic to be forwarded to the serviceversion. (0-100). Sum of weights across destinations SHOULD BE == 100.If there is only one destination in a rule, the weight value is assumed tobe 100.	No
`headers`	`Headers`	Header manipulation rules	No
`removeResponseHeaders`	`string[]`	Use of `remove_response_header` is deprecated. Use the `headers`field instead.	No
`appendResponseHeaders`	`map<string, string>`	Use of `append_response_headers` is deprecated. Use the `headers`field instead.	No
`removeRequestHeaders`	`string[]`	Use of `remove_request_headers` is deprecated. Use the `headers`field instead.	No
`appendRequestHeaders`	`map<string, string>`	Use of `append_request_headers` is deprecated. Use the `headers`field instead.	No

Headers

Message headers can be manipulated when Envoy forwards requests to,or responses from, a destination service. Header manipulation rules canbe specified for a specific route destination or for all destinations.The following VirtualService adds a test header with the value trueto requests that are routed to any reviews service destination.It also romoves the foo response header, but only from responsescoming from the v1 subset (version) of the reviews service.

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: reviews-route
spec:
  hosts:
  - reviews.prod.svc.cluster.local
  http:
  - headers:
      request:
        set:
          test: true
    route:
    - destination:
        host: reviews.prod.svc.cluster.local
        subset: v2
      weight: 25
    - destination:
        host: reviews.prod.svc.cluster.local
        subset: v1
      headers:
        response:
          remove:
          - foo
      weight: 75

Field	Type	Description	Required
`request`	`HeaderOperations`	Header manipulation rules to apply before forwarding a requestto the destination service	No
`response`		Header manipulation rules to apply before returning a responseto the caller	No

Headers.HeaderOperations

HeaderOperations Describes the header manipulations to apply

Field	Type	Description	Required
`set`	`map<string, string>`	Overwrite the headers specified by key with the given values	No
`add`	`map<string, string>`	Append the given values to the headers specified by keys(will create a comma-separated list of values)	No
`remove`	`string[]`	Remove a the specified headers	No

L4MatchAttributes

L4 connection match attributes. Note that L4 connection matching supportis incomplete.

Field	Type	Description	Required
`destinationSubnets`	`string[]`	IPv4 or IPv6 ip addresses of destination with optional subnet. E.g.,a.b.c.d/xx form or just a.b.c.d.	No
`port`	`uint32`	Specifies the port on the host that is being addressed. Many servicesonly expose a single port or label ports with the protocols they support,in these cases it is not required to explicitly select the port.	No
`sourceLabels`	`map<string, string>`	One or more labels that constrain the applicability of a rule toworkloads with the given labels. If the VirtualService has a list ofgateways specified at the top, it should include the reserved gateway`mesh` in order for this field to be applicable.	No
`gateways`	`string[]`	Names of gateways where the rule should be applied to. Gateway namesat the top of the VirtualService (if any) are overridden. The gatewaymatch is independent of sourceLabels.	No

Percent specifies a percentage in the range of [0.0, 100.0].

PortSelector

PortSelector specifies the number of a port to be used formatching or selection for final routing.

Field	Type	Description	Required
`number`	`uint32`	Valid port number	No

RouteDestination

L4 routing rule weighted destination.

Field	Type	Description	Required
`destination`	`Destination`	Destination uniquely identifies the instances of a serviceto which the request/connection should be forwarded to.	Yes
`weight`	`int32`	The proportion of traffic to be forwarded to the serviceversion. If there is only one destination in a rule, all traffic will berouted to it irrespective of the weight.	No

StringMatch

Describes how to match a given string in HTTP headers. Match iscase-sensitive.

Field	Type	Description	Required
`exact`	`string (oneof)`	exact string match	Yes
`prefix`	`string (oneof)`	prefix-based match	Yes
`regex`	`string (oneof)`	ECMAscript style regex-based match	Yes

TCPRoute

Describes match conditions and actions for routing TCP traffic. Thefollowing routing rule forwards traffic arriving at port 27017 formongo.prod.svc.cluster.local to another Mongo server on port 5555.

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: bookinfo-Mongo
spec:
  hosts:
  - mongo.prod.svc.cluster.local
  tcp:
  - match:
    - port: 27017
    route:
    - destination:
        host: mongo.backup.svc.cluster.local
          number: 5555

Field	Type	Description	Required
`match`		Match conditions to be satisfied for the rule to beactivated. All conditions inside a single match block have ANDsemantics, while the list of match blocks have OR semantics. The ruleis matched if any one of the match blocks succeed.	No
`route`	`RouteDestination[]`	The destination to which the connection should be forwarded to.	No

TLSMatchAttributes

TLS connection match attributes.

Field	Type	Description	Required
`sniHosts`	`string[]`	SNI (server name indicator) to match on. Wildcard prefixescan be used in the SNI value, e.g., *.com will match foo.example.comas well as example.com. An SNI value must be a subset (i.e., fallwithin the domain) of the corresponding virtual serivce’s hosts.	Yes
`destinationSubnets`	`string[]`	IPv4 or IPv6 ip addresses of destination with optional subnet. E.g.,a.b.c.d/xx form or just a.b.c.d.	No
`port`	`uint32`	Specifies the port on the host that is being addressed. Many servicesonly expose a single port or label ports with the protocols theysupport, in these cases it is not required to explicitly select theport.	No
`sourceLabels`	`map<string, string>`	One or more labels that constrain the applicability of a rule toworkloads with the given labels. If the VirtualService has a list ofgateways specified at the top, it should include the reserved gateway`mesh` in order for this field to be applicable.	No
`gateways`	`string[]`	Names of gateways where the rule should be applied to. Gateway namesat the top of the VirtualService (if any) are overridden. The gatewaymatch is independent of sourceLabels.	No

TLSRoute

Describes match conditions and actions for routing unterminated TLStraffic (TLS/HTTPS) The following routing rule forwards unterminated TLStraffic arriving at port 443 of gateway called “mygateway” to internalservices in the mesh based on the SNI value.

Field	Type	Description	Required
`match`		Match conditions to be satisfied for the rule to beactivated. All conditions inside a single match block have ANDsemantics, while the list of match blocks have OR semantics. The ruleis matched if any one of the match blocks succeed.	Yes
`route`	`RouteDestination[]`	The destination to which the connection should be forwarded to.	No

Configuration affecting traffic routing.

google.protobuf.UInt32Value

Wrapper message for uint32.

The JSON representation for UInt32Value is JSON number.

Field	Type	Description	Required
`value`		The uint32 value.	No