Virtual Service

The destination hosts to which traffic is being sent. Could be a DNS name with wildcard prefix or an IP address. Depending on the platform, short-names can also be used instead of a FQDN (i.e. has no dots in the name). In such a scenario, the FQDN of the host would be derived based on the underlying platform.

A single VirtualService can be used to describe all the traffic properties of the corresponding hosts, including those for multiple HTTP and TCP ports. Alternatively, the traffic properties of a host can be defined using more than one VirtualService, with certain caveats. Refer to the Operations Guide for details.

Note for Kubernetes users: When short names are used (e.g. “reviews” instead of “reviews.default.svc.cluster.local”), Istio will interpret the short name based on the namespace of the rule, not the service. A rule in the “default” namespace containing a host “reviews” will be interpreted as “reviews.default.svc.cluster.local”, irrespective of the actual namespace associated with the reviews service. To avoid potential misconfigurations, it is recommended to always use fully qualified domain names over short names.

The hosts field applies to both HTTP and TCP services. Service inside the mesh, i.e., those found in the service registry, must always be referred to using their alphanumeric names. IP addresses are allowed only for services defined via the Gateway.

Note: It must be empty for a delegate VirtualService.

The names of gateways and sidecars that should apply these routes. Gateways in other namespaces may be referred to by <gateway namespace>/<gateway name>; specifying a gateway with no namespace qualifier is the same as specifying the VirtualService’s namespace. A single VirtualService is used for sidecars inside the mesh as well as for one or more gateways. The selection condition imposed by this field can be overridden using the source field in the match conditions of protocol-specific routes. The reserved word mesh is used to imply all the sidecars in the mesh. When this field is omitted, the default gateway (mesh) will be used, which would apply the rule to all sidecars in the mesh. If a list of gateway names is provided, the rules will apply only to the gateways. To apply the rules to both gateways and sidecars, specify mesh as one of the gateway names.

An ordered list of route rules for HTTP traffic. HTTP routes will be applied to platform service ports using HTTP/HTTP2/GRPC protocols, gateway ports with protocol HTTP/HTTP2/GRPC/TLS-terminated-HTTPS and service entry ports using HTTP/HTTP2/GRPC protocols. The first rule matching an incoming request is used.

An ordered list of route rule for non-terminated TLS & HTTPS traffic. Routing is typically performed using the SNI value presented by the ClientHello message. TLS routes will be applied to platform service ports named ‘https-’, ’tls-’, unterminated gateway ports using HTTPS/TLS protocols (i.e. with “passthrough” TLS mode) and service entry ports using HTTPS/TLS protocols. The first rule matching an incoming request is used. NOTE: Traffic ‘https-’ or ’tls-’ ports without associated virtual service will be treated as opaque TCP traffic.

An ordered list of route rules for opaque TCP traffic. TCP routes will be applied to any port that is not a HTTP or TLS port. The first rule matching an incoming request is used.

A list of namespaces to which this virtual service is exported. Exporting a virtual service allows it to be used by sidecars and gateways defined in other namespaces. This feature provides a mechanism for service owners and mesh administrators to control the visibility of virtual services across namespace boundaries.

If no namespaces are specified then the virtual service is exported to all namespaces by default.

The value “.” is reserved and defines an export to the same namespace that the virtual service is declared in. Similarly the value “*” is reserved and defines an export to all namespaces.

The name of a service from the service registry. Service names are looked up from the platform’s service registry (e.g., Kubernetes services, Consul services, etc.) and from the hosts declared by ServiceEntry. Traffic forwarded to destinations 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 interpret the short name based on the namespace of the rule, not the service. A rule in the “default” namespace containing a host “reviews” will be interpreted as “reviews.default.svc.cluster.local”, irrespective of the actual namespace associated with the reviews service. To avoid potential misconfiguration, it is recommended to always use fully qualified domain names over short names.

The name of a subset within the service. Applicable only to services within the mesh. The subset must be defined in a corresponding DestinationRule.

Specifies the port on the host that is being addressed. If a service exposes only a single port it is not required to explicitly select the port.

The name assigned to the route for debugging purposes. The route’s name will be concatenated with the match’s name and will be logged in the access logs for requests matching this route/match.

Match conditions to be satisfied for the rule to be activated. All conditions inside a single match block have AND semantics, while the list of match blocks have OR semantics. The rule is matched if any one of the match blocks succeed.

A HTTP rule can either return a direct_response, redirect or forward (default) traffic. The forwarding target can be one of several versions of a service (see glossary in beginning of document). Weights associated with the service version determine the proportion of traffic it receives.

A HTTP rule can either return a direct_response, redirect or forward (default) traffic. If traffic passthrough option is specified in the rule, route/redirect will be ignored. The redirect primitive can be used to send a HTTP 301 redirect to a different URI or Authority.

A HTTP rule can either return a direct_response, redirect or forward (default) traffic. Direct Response is used to specify a fixed response that should be sent to clients.

It can be set only when Route and Redirect are empty.

Delegate is used to specify the particular VirtualService which can be used to define delegate HTTPRoute.

It can be set only when Route and Redirect are empty, and the route rules of the delegate VirtualService will be merged with that in the current one.

NOTE:

1. Only one level delegation is supported.
2. The delegate’s HTTPMatchRequest must be a strict subset of the root’s, otherwise there is a conflict and the HTTPRoute will not take effect.

Rewrite HTTP URIs and Authority headers. Rewrite cannot be used with Redirect primitive. Rewrite will be performed before forwarding.

Timeout for HTTP requests, default is disabled.

Retry policy for HTTP requests.

Note: the default cluster-wide retry policy, if not specified, is:

attempts: 2
retryOn: "connect-failure,refused-stream,unavailable,cancelled,503"

This can be customized in Mesh Config defaultHttpRetryPolicy.

Fault injection policy to apply on HTTP traffic at the client side. Note that timeouts or retries will not be enabled when faults are enabled on the client side.

Mirror HTTP traffic to a another destination in addition to forwarding the requests to the intended destination. Mirrored traffic is on a best effort basis where the sidecar/gateway will not wait for the mirrored cluster to respond before returning the response from the original destination. Statistics will be generated for the mirrored destination.

Specifies the destinations to mirror HTTP traffic in addition to the original destination. Mirrored traffic is on a best effort basis where the sidecar/gateway will not wait for the mirrored destinations to respond before returning the response from the original destination. Statistics will be generated for the mirrored destination.

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.

Cross-Origin Resource Sharing policy (CORS). Refer to CORS for further details about cross origin resource sharing.

Header manipulation rules

Name specifies the name of the delegate VirtualService.

Namespace specifies the namespace where the delegate VirtualService resides. By default, it is same to the root’s.

Header manipulation rules to apply before forwarding a request to the destination service

Header manipulation rules to apply before returning a response to the caller

Overwrite the headers specified by key with the given values

Append the given values to the headers specified by keys (will create a comma-separated list of values)

Remove the specified headers

Match conditions to be satisfied for the rule to be activated. All conditions inside a single match block have AND semantics, while the list of match blocks have OR semantics. The rule is matched if any one of the match blocks succeed.

The destination to which the connection should be forwarded to.

Match conditions to be satisfied for the rule to be activated. All conditions inside a single match block have AND semantics, while the list of match blocks have OR semantics. The rule is matched if any one of the match blocks succeed.

The destination to which the connection should be forwarded to.

The name assigned to a match. The match’s name will be concatenated with the parent route’s name and will be logged in the access logs for requests matching this route.

URI to match values are case-sensitive and formatted as follows:

• exact: "value" for exact string match

• prefix: "value" for prefix-based match

• regex: "value" for RE2 style regex-based match.

Note: Case-insensitive matching could be enabled via the ignoreUriCase flag.

URI Scheme values are case-sensitive and formatted as follows:

• exact: "value" for exact string match

• prefix: "value" for prefix-based match

• regex: "value" for RE2 style regex-based match.

HTTP Method values are case-sensitive and formatted as follows:

• exact: "value" for exact string match

• prefix: "value" for prefix-based match

• regex: "value" for RE2 style regex-based match.

HTTP Authority values are case-sensitive and formatted as follows:

• exact: "value" for exact string match

• prefix: "value" for prefix-based match

• regex: "value" for RE2 style regex-based match.

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 RE2 style regex-based match.

If the value is empty and only the name of header is specified, presence of the header is checked. To provide an empty value, use {}, for example:

 - match:
   - headers:
       myheader: {}

Note: The keys uri, scheme, method, and authority will be ignored.

Specifies the ports on the host that is being addressed. Many services only expose a single port or label ports with the protocols they support, in these cases it is not required to explicitly select the port.

One or more labels that constrain the applicability of a rule to source (client) workloads with the given labels. If the VirtualService has a list of gateways specified in the top-level gateways field, it must include the reserved gateway mesh for this field to be applicable.

Names of gateways where the rule should be applied. Gateway names in the top-level gateways field of the VirtualService (if any) are overridden. The gateway match is independent of sourceLabels.

Query parameters for matching.

Ex:

• For a query parameter like “?key=true”, the map key would be “key” and the string match could be defined as exact: "true".

• For a query parameter like “?key”, the map key would be “key” and the string match could be defined as exact: "".

• For a query parameter like “?key=abc” or “?key=abx”, the map key would be “key” and the string match could be defined as prefix: "ab".

• For a query parameter like “?key=123”, the map key would be “key” and the string match could be defined as regex: "\d+$". Note that this configuration will only match values like “123” but not “a123” or “123a”.

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.

withoutHeader has the same syntax with the header, but has opposite meaning. If a header is matched with a matching rule among withoutHeader, the traffic becomes not matched one.

Source namespace constraining the applicability of a rule to workloads in that namespace. If the VirtualService has a list of gateways specified in the top-level gateways field, it must include the reserved gateway mesh for this field to be applicable.

The human readable prefix to use when emitting statistics for this route. The statistics are generated with prefix route.<stat_prefix>. This should be set for highly critical routes that one wishes to get “per-route” statistics on. This prefix is only for proxy-level statistics (envoy_) and not service-level (istio_) statistics. Refer to https://www.envoyproxy.io/docs/envoy/latest/api-v3/config/route/v3/route_components.proto#envoy-v3-api-field-config-route-v3-route-stat-prefix for statistics that are generated when this is configured.

Destination uniquely identifies the instances of a service to which the request/connection should be forwarded to.

Weight specifies the relative proportion of traffic to be forwarded to the destination. A destination will receive weight/(sum of all weights) requests. If there is only one destination in a rule, it will receive all traffic. Otherwise, if weight is 0, the destination will not receive any traffic.

Header manipulation rules

Destination uniquely identifies the instances of a service to which the request/connection should be forwarded to.

Weight specifies the relative proportion of traffic to be forwarded to the destination. A destination will receive weight/(sum of all weights) requests. If there is only one destination in a rule, it will receive all traffic. Otherwise, if weight is 0, the destination will not receive any traffic.

IPv4 or IPv6 ip addresses of destination with optional subnet. E.g., a.b.c.d/xx form or just a.b.c.d.

Specifies the port on the host that is being addressed. Many services only expose a single port or label ports with the protocols they support, in these cases it is not required to explicitly select the port.

One or more labels that constrain the applicability of a rule to workloads with the given labels. If the VirtualService has a list of gateways specified in the top-level gateways field, it should include the reserved gateway mesh in order for this field to be applicable.

Names of gateways where the rule should be applied. Gateway names in the top-level gateways field of the VirtualService (if any) are overridden. The gateway match is independent of sourceLabels.

Source namespace constraining the applicability of a rule to workloads in that namespace. If the VirtualService has a list of gateways specified in the top-level gateways field, it must include the reserved gateway mesh for this field to be applicable.

SNI (server name indicator) to match on. Wildcard prefixes can be used in the SNI value, e.g., *.com will match foo.example.com as well as example.com. An SNI value must be a subset (i.e., fall within the domain) of the corresponding virtual service’s hosts.

IPv4 or IPv6 ip addresses of destination with optional subnet. E.g., a.b.c.d/xx form or just a.b.c.d.

Specifies the port on the host that is being addressed. Many services only expose a single port or label ports with the protocols they support, in these cases it is not required to explicitly select the port.

One or more labels that constrain the applicability of a rule to workloads with the given labels. If the VirtualService has a list of gateways specified in the top-level gateways field, it should include the reserved gateway mesh in order for this field to be applicable.

Names of gateways where the rule should be applied. Gateway names in the top-level gateways field of the VirtualService (if any) are overridden. The gateway match is independent of sourceLabels.

Source namespace constraining the applicability of a rule to workloads in that namespace. If the VirtualService has a list of gateways specified in the top-level gateways field, it must include the reserved gateway mesh for this field to be applicable.

On a redirect, overwrite the Path portion of the URL with this value. Note that the entire path will be replaced, irrespective of the request URI being matched as an exact path or prefix.

On a redirect, overwrite the Authority/Host portion of the URL with this value.

On a redirect, overwrite the scheme portion of the URL with this value. For example, http or https. If unset, the original scheme will be used. If derivePort is set to FROM_PROTOCOL_DEFAULT, this will impact the port used as well

On a redirect, Specifies the HTTP status code to use in the redirect response. The default response code is MOVED_PERMANENTLY (301).

Specifies the HTTP response status to be returned.

Specifies the content of the response body. If this setting is omitted, no body is included in the generated response.

rewrite the path (or the prefix) portion of the URI with this value. If the original URI was matched based on prefix, the value provided in this field will replace the corresponding matched prefix.

rewrite the Authority/Host header with this value.

rewrite the path portion of the URI with the specified regex.

RE2 style regex-based match.

The string that should replace into matching portions of original URI. Capture groups in the pattern can be referenced in the new URI. Examples:

Example 1: rewrite with capture groups Path pattern “/service/update/v1/api” with match “^/service/([^/]+)(/.*)$” and rewrite string of “/customprefix/\2/\1” would transform into “/customprefix/v1/api/update”.

Example 2: case insensitive rewrite Path pattern “/aaa/XxX/bbb” with match “(?i)/xxx/” and a rewrite string of /yyy/ would do a case-insensitive match and transform the path to “/aaa/yyy/bbb”.

Number of retries to be allowed for a given request. The interval between retries will be determined automatically (25ms+). When request timeout of the HTTP route or per_try_timeout is configured, the actual number of retries attempted also depends on the specified request timeout and per_try_timeout values. MUST be >= 0. If 0, retries will be disabled. The maximum possible number of requests made will be 1 + attempts.

Timeout per attempt for a given request, including the initial call and any retries. Format: 1h/1m/1s/1ms. MUST be >=1ms. Default is same value as request timeout of the HTTP route, which means no timeout.

Specifies the conditions under which retry takes place. One or more policies can be specified using a ‘,’ delimited list. See the retry policies and gRPC retry policies for more details.

In addition to the policies specified above, a list of HTTP status codes can be passed, such as retryOn: "503,reset". Note these status codes refer to the actual responses received from the destination. For example, if a connection is reset, Istio will translate this to 503 for it’s response. However, the destination did not return a 503 error, so this would not match "503" (it would, however, match "reset").

If not specified, this defaults to connect-failure,refused-stream,unavailable,cancelled,503.

Flag to specify whether the retries should retry to other localities. See the retry plugin configuration for more details.

String patterns that match allowed origins. An origin is allowed if any of the string matchers match. If a match is found, then the outgoing Access-Control-Allow-Origin would be set to the origin as provided by the client.

List of HTTP methods allowed to access the resource. The content will be serialized into the Access-Control-Allow-Methods header.

List of HTTP headers that can be used when requesting the resource. Serialized to Access-Control-Allow-Headers header.

A list of HTTP headers that the browsers are allowed to access. Serialized into Access-Control-Expose-Headers header.

Specifies how long the results of a preflight request can be cached. Translates to the Access-Control-Max-Age header.

Indicates whether the caller is allowed to send the actual request (not the preflight) using credentials. Translates to Access-Control-Allow-Credentials header.

Indicates whether preflight requests not matching the configured allowed origin shouldn’t be forwarded to the upstream. Default is forward to upstream.

Delay requests before forwarding, emulating various failures such as network issues, overloaded upstream service, etc.

Abort Http request attempts and return error codes back to downstream service, giving the impression that the upstream service is faulty.

Percentage of requests on which the delay will be injected. If left unspecified, no request will be delayed.

Percentage of requests to be aborted with the error code provided. If not specified, no request will be aborted.

Destination specifies the target of the mirror operation.

Percentage of the traffic to be mirrored by the destination field. If this field is absent, all the traffic (100%) will be mirrored. Max value is 100.

Valid port number

The uint32 value.