Reference documentation and code samples for the Compute Engine v1 API enum BackendService.Types.SessionAffinity.
Type of session affinity to use. The default is NONE. Only NONE and HEADER_FIELD are supported when the backend service is referenced by a URL map that is bound to target gRPC proxy that has validateForProxyless field set to true. For more details, see: Session Affinity.
2-tuple hash on packet's source and destination IP addresses. Connections from the same source IP address to the same destination IP address will be served by the same backend VM while that VM remains healthy.
ClientIpNoDestination
1-tuple hash only on packet's source IP address. Connections from the same source IP address will be served by the same backend VM while that VM remains healthy. This option can only be used for Internal TCP/UDP Load Balancing.
ClientIpPortProto
5-tuple hash on packet's source and destination IP addresses, IP protocol, and source and destination ports. Connections for the same IP protocol from the same source IP address and port to the same destination IP address and port will be served by the same backend VM while that VM remains healthy. This option cannot be used for HTTP(S) load balancing.
ClientIpProto
3-tuple hash on packet's source and destination IP addresses, and IP protocol. Connections for the same IP protocol from the same source IP address to the same destination IP address will be served by the same backend VM while that VM remains healthy. This option cannot be used for HTTP(S) load balancing.
GeneratedCookie
Hash based on a cookie generated by the L7 loadbalancer. Only valid for HTTP(S) load balancing.
HeaderField
The hash is based on a user specified header field.
HttpCookie
The hash is based on a user provided cookie.
None
No session affinity. Connections from the same client IP may go to any instance in the pool.
StrongCookieAffinity
Strong cookie-based affinity. Connections bearing the same cookie will be served by the same backend VM while that VM remains healthy, as long as the cookie has not expired.
UndefinedSessionAffinity
A value indicating that the enum field is not set.
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Missing the information I need","missingTheInformationINeed","thumb-down"],["Too complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-08 UTC."],[[["\u003cp\u003eThe \u003ccode\u003eBackendService.Types.SessionAffinity\u003c/code\u003e enum from the Compute Engine v1 API defines the type of session affinity used for backend services, with \u003ccode\u003eNONE\u003c/code\u003e as the default.\u003c/p\u003e\n"],["\u003cp\u003eVersion 3.6.0 is the latest version of the Compute Engine v1 API for \u003ccode\u003eBackendService.Types.SessionAffinity\u003c/code\u003e, and multiple previous versions are also listed and available, down to version 1.0.0.\u003c/p\u003e\n"],["\u003cp\u003eSession affinity types, such as \u003ccode\u003eClientIp\u003c/code\u003e, \u003ccode\u003eClientIpProto\u003c/code\u003e, \u003ccode\u003eHeaderField\u003c/code\u003e, \u003ccode\u003eHttpCookie\u003c/code\u003e and \u003ccode\u003eGeneratedCookie\u003c/code\u003e, determine how connections from the same client are directed to backend VMs.\u003c/p\u003e\n"],["\u003cp\u003eCertain session affinity types, such as \u003ccode\u003eClientIpNoDestination\u003c/code\u003e, \u003ccode\u003eClientIpPortProto\u003c/code\u003e and \u003ccode\u003eClientIpProto\u003c/code\u003e have restrictions on their use, like \u003ccode\u003eClientIpNoDestination\u003c/code\u003e being exclusive to Internal TCP/UDP Load Balancing, and \u003ccode\u003eClientIpPortProto\u003c/code\u003e and \u003ccode\u003eClientIpProto\u003c/code\u003e not being compatible with HTTP(S) load balancing.\u003c/p\u003e\n"],["\u003cp\u003e\u003ccode\u003eUndefinedSessionAffinity\u003c/code\u003e is an enum value that is used to denote that no value has been set for this field.\u003c/p\u003e\n"]]],[],null,[]]
