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Load Balancing Settings

Load Balancing Policy

Load Balancing Policy defines the load balancing strategy between multiple upstream servers.

See Envoy documentation for more details.

How to configure

Some policy types support additional configuration.

Config file keysTypeUsageDefault


- from:
- http://myapp-srv-1:8080
- http://myapp-srv-2:8080
- http://myapp-srv-3:8080
- http://myapp-srv-4:8080
- http://myapp-srv-5:8080
lb_policy: LEAST_REQUEST
choice_count: 2 # current envoy default

Load Balancing Policy options

Load Balancer Policy options
RING_HASH (may be further configured using ring_hash_lb_config option)
LEAST_REQUEST (may be further configured using least_request_lb_config)
MAGLEV (may be further configured using maglev_lb_config option)

Health Checks

When defined, Health Checks will issue periodic health check requests to upstream servers and unhealthy upstream servers won't serve traffic.

See Envoy's outlier_detection for automatic upstream server health detection. In the presence of multiple upstream servers, it is recommended to set up either health_checks, outlier_detection, or both.

Supported health checks parameters

Config file keysDefinitionTypeUsage
timeoutThe total time to wait for a health check response.Durationrequired
intervalThe interval between health checks.Durationrequired
unhealthy_thresholdThe number of unhealthy health checks required before a host is marked unhealthy.UInt32Valuerequired
healthy_thresholdThe number of healthy health checks required before a host is marked healthy.UInt32Valuerequired

See the Envoy documentation for a list of supported parameters.

How to configure

You may configure only one of the following options per health_check object definition:

  • http_health_check
  • tcp_health_check
  • grpc_health_check

HTTP health check

Config file keysDefinitionTypeUsage
hostThe Host header value in the HTTP health check request. If empty (default value), the name of the cluster this health check is associated with will be used.stringoptional
pathSpecifies the HTTP path requested during a health check. For example, /healthcheck.stringrequired
expected_statusesDefines a range of HTTP response statuses that are considered healthy.Int64Rangeoptional
codec_client_typeSpecifies which application protocol to use: HTTP1 or HTTP2.CodecClientTypeoptional

See the Envoy HTTP health checks documentation for more information.

TCP health check

Config file keysDefinitionTypeUsage
sendDefines the payload, which must be one of text or binary. An empty payload results in a connect-only health check.Payloadoptional
receiveChecks a response with 'fuzzy' matching to the extent that each payload block must be found, and in the specified order, but not necessarily contiguous.Payloadoptional

See the Envoy TCP health checks documentation for more information.

gRPC health check

Config file keysDefinitionTypeUsage
authorityThe :authority header value in a gRPC health check request.stringoptional
service_nameA service name parameter sent to the gRPC service. See gRPC health checking for more information.stringoptional

See the Envoy gRPC health checks documentation for more information.

Config file keysTypeUsage
health_checksarray of objectsoptional

HTTP example configuration

- from:
- http://myapp-srv-1:8080
- http://myapp-srv-2:8080
- timeout: 10s
interval: 60s
healthy_threshold: 1
unhealthy_threshold: 2
path: '/'

TCP example configuration

- from: tcp+
- tcp://tcp-1.local
- tcp://tcp-2.local
- timeout: 1s
interval: 5s
unhealthy_threshold: 3
healthy_threshold: 1
text: '50494E47' #PING
text: '504F4E47' #PONG