Destination Rule

    Version specific policies can be specified by defining a namedsubset and overriding the settings specified at the service level. Thefollowing rule uses a round robin load balancing policy for all trafficgoing to a subset named testversion that is composed of endpoints (e.g.,pods) with labels (version:v3).

    1. apiVersion: networking.istio.io/v1alpha3
    2. kind: DestinationRule
    3. metadata:
    4.   name: bookinfo-ratings
    5. spec:
    6.   host: ratings.prod.svc.cluster.local
    7.   trafficPolicy:
    8.     loadBalancer:
    9.       simple: LEAST_CONN
    10.   subsets:
    11.   - name: testversion
    12.     labels:
    13.       version: v3
    14.     trafficPolicy:
    15.       loadBalancer:
    16.         simple: ROUND_ROBIN

    Note: Policies specified for subsets will not take effect untila route rule explicitly sends traffic to this subset.

    Traffic policies can be customized to specific ports as well. Thefollowing rule uses the least connection load balancing policy for alltraffic to port 80, while uses a round robin load balancing setting fortraffic to the port 9080.

    1. apiVersion: networking.istio.io/v1alpha3
    2. kind: DestinationRule
    3. metadata:
    4.   name: bookinfo-ratings-port
    5. spec:
    6.   host: ratings.prod.svc.cluster.local
    7.   trafficPolicy: # Apply to all ports
    8.     - port:
    9.         number: 80
    10.       loadBalancer:
    11.         simple: LEAST_CONN
    12.     - port:
    13.         number: 9080
    14.       loadBalancer:
    15.         simple: ROUND_ROBIN

    Connection pool settings for an upstream host. The settings apply toeach individual host in the upstream service. See Envoy’s circuitbreakerfor more details. Connection pool settings can be applied at the TCPlevel as well as at HTTP level.

    For example, the following rule sets a limit of 100 connections to redisservice called myredissrv with a connect timeout of 30ms

    1. apiVersion: networking.istio.io/v1alpha3
    2. kind: DestinationRule
    3. metadata:
    4.   name: bookinfo-redis
    5. spec:
    6.   host: myredissrv.prod.svc.cluster.local
    7.   trafficPolicy:
    8.     connectionPool:
    9.       tcp:
    10.         maxConnections: 100
    11.         connectTimeout: 30ms
    12.         tcpKeepalive:
    13.           time: 7200s
    14.           interval: 75s

    ConnectionPoolSettings.HTTPSettings

    Settings applicable to HTTP1.1/HTTP2/GRPC connections.

    FieldTypeDescriptionRequired
    http1MaxPendingRequestsint32Maximum number of pending HTTP requests to a destination. Default 2^32-1.No
    http2MaxRequestsint32Maximum number of requests to a backend. Default 2^32-1.No
    maxRequestsPerConnectionint32Maximum number of requests per connection to a backend. Setting thisparameter to 1 disables keep alive. Default 0, meaning “unlimited”,up to 2^29.No
    maxRetriesint32Maximum number of retries that can be outstanding to all hosts in acluster at a given time. Defaults to 2^32-1.No
    idleTimeoutDurationThe idle timeout for upstream connection pool connections. The idle timeout is defined as the period in which there are no active requests.If not set, the default is 1 hour. When the idle timeout is reached the connection will be closed.Note that request based timeouts mean that HTTP/2 PINGs will not keep the connection alive. Applies to both HTTP1.1 and HTTP2 connections.No
    h2UpgradePolicySpecify if http1.1 connection should be upgraded to http2 for the associated destination.No

    ConnectionPoolSettings.HTTPSettings.H2UpgradePolicy

    Policy for upgrading http1.1 connections to http2.

    NameDescription
    DEFAULTUse the global default.
    DO_NOT_UPGRADEDo not upgrade the connection to http2.This opt-out option overrides the default.
    UPGRADEUpgrade the connection to http2.This opt-in option overrides the default.

    ConnectionPoolSettings.TCPSettings

    Settings common to both HTTP and TCP upstream connections.

    FieldTypeDescriptionRequired
    maxConnectionsint32Maximum number of HTTP1 /TCP connections to a destination host. Default 2^32-1.No
    connectTimeoutDurationTCP connection timeout.No
    tcpKeepaliveIf set then set SO_KEEPALIVE on the socket to enable TCP Keepalives.No

    ConnectionPoolSettings.TCPSettings.TcpKeepalive

    TCP keepalive.

    FieldTypeDescriptionRequired
    probesuint32Maximum number of keepalive probes to send without response beforedeciding the connection is dead. Default is to use the OS level configuration(unless overridden, Linux defaults to 9.)No
    timeThe time duration a connection needs to be idle before keep-aliveprobes start being sent. Default is to use the OS level configuration(unless overridden, Linux defaults to 7200s (ie 2 hours.)No
    intervalDurationThe time duration between keep-alive probes.Default is to use the OS level configuration(unless overridden, Linux defaults to 75s.)No

    DestinationRule

    DestinationRule defines policies that apply to traffic intended for a serviceafter routing has occurred.

    FieldTypeDescriptionRequired
    hoststringThe 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 ServiceEntries. Rules defined forservices that do not exist in the service registry will be ignored.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.Note that the host field applies to both HTTP and TCP services.Yes
    Traffic policies to apply (load balancing policy, connection poolsizes, outlier detection).No
    subsetsSubset[]One or more named sets that represent individual versions of aservice. Traffic policies can be overridden at subset level.No
    exportTostring[]A list of namespaces to which this destination rule is exported.The resolution of a destination rule to apply to a service occurs in thecontext of a hierarchy of namespaces. Exporting a destination rule allowsit to be included in the resolution hierarchy for services inother namespaces. This feature provides a mechanism for service ownersand mesh administrators to control the visibility of destination rulesacross namespace boundaries.If no namespaces are specified then the destination rule is exported to allnamespaces by default.The value “.” is reserved and defines an export to the same namespace thatthe destination rule is declared in. Similarly, the value “” is reserved anddefines an export to all namespaces.NOTE: in the current release, the exportTo value is restricted to“.” or “” (i.e., the current namespace or all namespaces).No

    Load balancing policies to apply for a specific destination. See Envoy’sload balancingfor more details.

    The following example sets up sticky sessions for the ratings servicehashing-based load balancer for the same ratings service using thethe User cookie as the hash key.

    1.  apiVersion: networking.istio.io/v1alpha3
    2.  kind: DestinationRule
    3.  metadata:
    4.    name: bookinfo-ratings
    5.  spec:
    6.    host: ratings.prod.svc.cluster.local
    7.    trafficPolicy:
    8.      loadBalancer:
    9.        consistentHash:
    10.          httpCookie:
    11.            name: user
    12.            ttl: 0s

    LoadBalancerSettings.ConsistentHashLB

    Consistent Hash-based load balancing can be used to provide softsession affinity based on HTTP headers, cookies or otherproperties. This load balancing policy is applicable only for HTTPconnections. The affinity to a particular destination host will belost when one or more hosts are added/removed from the destinationservice.

    FieldTypeDescriptionRequired
    httpHeaderNamestring (oneof)Hash based on a specific HTTP header.Yes
    httpCookieHash based on HTTP cookie.Yes
    useSourceIpbool (oneof)Hash based on the source IP address.Yes
    minimumRingSizeuint64The minimum number of virtual nodes to use for the hashring. Defaults to 1024. Larger ring sizes result in more granularload distributions. If the number of hosts in the load balancingpool is larger than the ring size, each host will be assigned asingle virtual node.No

    LoadBalancerSettings.ConsistentHashLB.HTTPCookie

    Describes a HTTP cookie that will be used as the hash key for theConsistent Hash load balancer. If the cookie is not present, it willbe generated.

    FieldTypeDescriptionRequired
    namestringName of the cookie.Yes
    pathstringPath to set for the cookie.No
    ttlLifetime of the cookie.Yes

    LoadBalancerSettings.SimpleLB

    Standard load balancing algorithms that require no tuning.

    NameDescription
    ROUND_ROBINRound Robin policy. Default
    LEAST_CONNThe least request load balancer uses an O(1) algorithm which selectstwo random healthy hosts and picks the host which has fewer activerequests.
    RANDOMThe random load balancer selects a random healthy host. The randomload balancer generally performs better than round robin if no healthchecking policy is configured.
    PASSTHROUGHThis option will forward the connection to the original IP addressrequested by the caller without doing any form of loadbalancing. This option must be used with care. It is meant foradvanced use cases. Refer to Original Destination load balancer inEnvoy for further details.

    LocalityLoadBalancerSetting

    Locality-weighted load balancing allows administrators to control thedistribution of traffic to endpoints based on the localities of where thetraffic originates and where it will terminate. These localities arespecified using arbitrary labels that designate a hierarchy of localities in{region}/{zone}/{sub-zone} form. For additional detail refer toLocality WeightThe following example shows how to setup locality weights mesh-wide.

    Given a mesh with workloads and their service deployed to “us-west/zone1/”and “us-west/zone2/”. This example specifies that when traffic accessing aservice originates from workloads in “us-west/zone1/”, 80% of the trafficwill be sent to endpoints in “us-west/zone1/”, i.e the same zone, and theremaining 20% will go to endpoints in “us-west/zone2/”. This setup isintended to favor routing traffic to endpoints in the same locality.A similar setting is specified for traffic originating in “us-west/zone2/”.

    1.   distribute:
    2.     - from: us-west/zone1/*
    3.       to:
    4.         "us-west/zone1/*": 80
    5.         "us-west/zone2/*": 20
    6.     - from: us-west/zone2/*
    7.       to:
    8.         "us-west/zone1/*": 20

    If the goal of the operator is not to distribute load across zones andregions but rather to restrict the regionality of failover to meet otheroperational requirements an operator can set a ‘failover’ policy instead ofa ‘distribute’ policy.

    The following example sets up a locality failover policy for regions.Assume a service resides in zones within us-east, us-west & eu-westthis example specifies that when endpoints within us-east become unhealthytraffic should failover to endpoints in any zone or sub-zone within eu-westand similarly us-west should failover to us-east.

    1.  failover:
    2.    - from: us-east
    3.      to: eu-west
    4.    - from: us-west
    5.      to: us-east

    Locality load balancing settings.

    FieldTypeDescriptionRequired
    distributeOptional: only one of distribute or failover can be set.Explicitly specify loadbalancing weight across different zones and geographical locations.Refer to Locality weighted load balancingIf empty, the locality weight is set according to the endpoints number within it.No
    failoverOptional: only failover or distribute can be set.Explicitly specify the region traffic will land on when endpoints in local region becomes unhealthy.Should be used together with OutlierDetection to detect unhealthy endpoints.Note: if no OutlierDetection specified, this will not take effect.No

    LocalityLoadBalancerSetting.Distribute

    Describes how traffic originating in the ‘from’ zone or sub-zone isdistributed over a set of ‘to’ zones. Syntax for specifying a zone is{region}/{zone}/{sub-zone} and terminal wildcards are allowed on anysegment of the specification. Examples: - matches all localitiesus-west/ - all zones and sub-zones within the us-west regionus-west/zone-1/* - all sub-zones within us-west/zone-1

    FieldTypeDescriptionRequired
    fromstringOriginating locality, ‘/’ separated, e.g. ‘region/zone/sub_zone’.No
    tomap<string, uint32>Map of upstream localities to traffic distribution weights. The sum ofall weights should be == 100. Any locality not assigned a weight willreceive no traffic.No

    Specify the traffic failover policy across regions. Since zone and sub-zonefailover is supported by default this only needs to be specified forregions when the operator needs to constrain traffic failover so thatthe default behavior of failing over to any endpoint globally does notapply. This is useful when failing over traffic across regions would notimprove service health or may need to be restricted for other reasonslike regulatory controls.

    OutlierDetection

    The following rule sets a connection pool size of 100 HTTP1 connectionswith no more than 10 req/connection to the “reviews” service. In addition,it sets a limit of 1000 concurrent HTTP2 requests and configures upstreamhosts to be scanned every 5 mins so that any host that fails 7 consecutivetimes with a 502, 503, or 504 error code will be ejected for 15 minutes.

    FieldTypeDescriptionRequired
    consecutiveErrorsint32Number of errors before a host is ejected from the connectionpool. Defaults to 5. When the upstream host is accessed over HTTP, a502, 503, or 504 return code qualifies as an error. When the upstream hostis accessed over an opaque TCP connection, connect timeouts andconnection error/failure events qualify as an error.No
    intervalDurationTime interval between ejection sweep analysis. format:1h/1m/1s/1ms. MUST BE >=1ms. Default is 10s.No
    baseEjectionTimeMinimum ejection duration. A host will remain ejected for a periodequal to the product of minimum ejection duration and the number oftimes the host has been ejected. This technique allows the system toautomatically increase the ejection period for unhealthy upstreamservers. format: 1h/1m/1s/1ms. MUST BE >=1ms. Default is 30s.No
    maxEjectionPercentint32Maximum % of hosts in the load balancing pool for the upstreamservice that can be ejected. Defaults to 10%.No
    minHealthPercentint32Outlier detection will be enabled as long as the associated load balancingpool has at least min_health_percent hosts in healthy mode. When thepercentage of healthy hosts in the load balancing pool drops below thisthreshold, outlier detection will be disabled and the proxy will load balanceacross all hosts in the pool (healthy and unhealthy). The threshold can bedisabled by setting it to 0%. The default is 0% as it’s not typicallyapplicable in k8s environments with few pods per service.No

    Subset

    A subset of endpoints of a service. Subsets can be used for scenarioslike A/B testing, or routing to a specific version of a service. Referto documentation for examples of usingsubsets in these scenarios. In addition, traffic policies defined at theservice-level can be overridden at a subset-level. The following ruleuses a round robin load balancing policy for all traffic going to asubset named testversion that is composed of endpoints (e.g., pods) withlabels (version:v3).

    1. apiVersion: networking.istio.io/v1alpha3
    2. kind: DestinationRule
    4.   name: bookinfo-ratings
    5. spec:
    6.   host: ratings.prod.svc.cluster.local
    7.   trafficPolicy:
    8.     loadBalancer:
    9.       simple: LEAST_CONN
    10.   subsets:
    11.   - name: testversion
    12.     labels:
    13.       version: v3
    14.     trafficPolicy:
    15.       loadBalancer:
    16.         simple: ROUND_ROBIN

    Note: Policies specified for subsets will not take effect untila route rule explicitly sends traffic to this subset.

    One or more labels are typically required to identify the subset destination,however, when the corresponding DestinationRule represents a host thatsupports multiple SNI hosts (e.g., an egress gateway), a subset without labelsmay be meaningful. In this case a traffic policy with TLSSettingscan be used to identify a specific SNI host corresponding to the named subset.

    FieldTypeDescriptionRequired
    namestringName of the subset. The service name and the subset name canbe used for traffic splitting in a route rule.Yes
    labelsmap<string, string>Labels apply a filter over the endpoints of a service in theservice registry. See route rules for examples of usage.No
    trafficPolicyTraffic policies that apply to this subset. Subsets inherit thetraffic policies specified at the DestinationRule level. Settingsspecified at the subset level will override the corresponding settingsspecified at the DestinationRule level.No

    TLSSettings

    SSL/TLS related settings for upstream connections. See Envoy’s for more details. These settings are common to both HTTP and TCP upstreams.

    For example, the following rule configures a client to use mutual TLSfor connections to upstream database cluster.

    1. apiVersion: networking.istio.io/v1alpha3
    2. kind: DestinationRule
    3. metadata:
    4.   name: db-mtls
    5. spec:
    6.   host: mydbserver.prod.svc.cluster.local
    7.   trafficPolicy:
    8.     tls:
    9.       mode: MUTUAL
    10.       clientCertificate: /etc/certs/myclientcert.pem
    11.       privateKey: /etc/certs/client_private_key.pem
    12.       caCertificates: /etc/certs/rootcacerts.pem

    The following rule configures a client to use TLS when talking to aforeign service whose domain matches *.foo.com.

    1. apiVersion: networking.istio.io/v1alpha3
    2. kind: DestinationRule
    3. metadata:
    4.   name: tls-foo
    5. spec:
    6.   host: "*.foo.com"
    7.   trafficPolicy:
    8.     tls:
    9.       mode: SIMPLE

    The following rule configures a client to use Istio mutual TLS when talkingto rating services.

    FieldTypeDescriptionRequired
    modeTLSmodeIndicates whether connections to this port should be securedusing TLS. The value of this field determines how TLS is enforced.Yes
    clientCertificatestringREQUIRED if mode is MUTUAL. The path to the file holding theclient-side TLS certificate to use.Should be empty if mode is ISTIO_MUTUAL.No
    privateKeystringREQUIRED if mode is MUTUAL. The path to the file holding theclient’s private key.Should be empty if mode is ISTIO_MUTUAL.No
    caCertificatesstringOPTIONAL: The path to the file containing certificate authoritycertificates to use in verifying a presented server certificate. Ifomitted, the proxy will not verify the server’s certificate.Should be empty if mode is ISTIO_MUTUAL.No
    subjectAltNamesstring[]A list of alternate names to verify the subject identity in thecertificate. If specified, the proxy will verify that the servercertificate’s subject alt name matches one of the specified values.If specified, this list overrides the value of subject_alt_namesfrom the ServiceEntry.No
    snistringSNI string to present to the server during TLS handshake.No

    TLSSettings.TLSmode

    TLS connection mode

    NameDescription
    DISABLEDo not setup a TLS connection to the upstream endpoint.
    SIMPLEOriginate a TLS connection to the upstream endpoint.
    MUTUALSecure connections to the upstream using mutual TLS by presentingclient certificates for authentication.
    ISTIO_MUTUALSecure connections to the upstream using mutual TLS by presentingclient certificates for authentication.Compared to Mutual mode, this mode uses certificates generatedautomatically by Istio for mTLS authentication. When this mode isused, all other fields in TLSSettings should be empty.

    TrafficPolicy

    Traffic policies to apply for a specific destination, across alldestination ports. See DestinationRule for examples.

    FieldTypeDescriptionRequired
    loadBalancerSettings controlling the load balancer algorithms.No
    connectionPoolConnectionPoolSettingsSettings controlling the volume of connections to an upstream serviceNo
    outlierDetectionSettings controlling eviction of unhealthy hosts from the load balancing poolNo
    tlsTLSSettingsTLS related settings for connections to the upstream service.No
    portLevelSettingsTraffic policies specific to individual ports. Note that port levelsettings will override the destination-level settings. Trafficsettings specified at the destination-level will not be inherited whenoverridden by port-level settings, i.e. default values will be appliedto fields omitted in port-level traffic policies.No

    Traffic policies that apply to specific ports of the service