From 118eb9c1fe938b5c2826c130b2cc7cc0383e2851 Mon Sep 17 00:00:00 2001 From: Eric Van Norman Date: Thu, 29 Aug 2019 09:25:32 -0500 Subject: [PATCH] Make sure user understands Outlier Detection is req'd for locality LB (#4854) * Make sure user understands Outlier Detection is req'd for locality LB * Code review comments * Fix lint issue * code review --- .../locality-load-balancing/index.md | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/content/en/docs/ops/traffic-management/locality-load-balancing/index.md b/content/en/docs/ops/traffic-management/locality-load-balancing/index.md index c7ff63e300..f329cdf578 100644 --- a/content/en/docs/ops/traffic-management/locality-load-balancing/index.md +++ b/content/en/docs/ops/traffic-management/locality-load-balancing/index.md @@ -35,6 +35,9 @@ As a result, this field does not need to be configured. In order for Istio to determine locality, a Service must be associated with the caller. +To determine when instances are unhealthy, the proxies require an [outlier detection](/docs/reference/config/networking/v1alpha3/destination-rule/#OutlierDetection) +configuration in a destination rule for each service. + ## Locality-prioritized load balancing _Locality-prioritized load balancing_ is the default behavior for _locality load balancing_. @@ -44,6 +47,11 @@ remains within the same locality. When instances become unhealthy, traffic spill instances in the next prioritized locality. This behavior continues until all localities are receiving traffic. You can find the exact percentages in the [Envoy documentation](https://www.envoyproxy.io/docs/envoy/latest/intro/arch_overview/upstream/load_balancing/priority). + {{< warning >}} + If no outlier detection configurations are defined in destination rules, the proxy can't determine if an instance is healthy, and it + routes traffic globally even if you enabled **locality-prioritized** load balancing. + {{< /warning >}} + A typical prioritization for an Envoy with a locality of `us-west/zone2` is as follows: - Priority 0: `us-west/zone2` @@ -58,9 +66,6 @@ The hierarchy of prioritization matches in the following order: Proxies in the same zone but different regions are not considered local to one another. -In order for Envoy to determine when instances are unhealthy, an [Outlier Detection](/docs/reference/config/networking/v1alpha3/destination-rule/#OutlierDetection) -rule must be defined for each service. - ### Overriding the Locality Fail-over Sometimes, you need to constrain the traffic fail-over to avoid sending traffic to