介紹
upstream 就是一個虛擬的服務。可用於配置多個target目標服務時實現負載均衡的效果。
注意：service的host指的就是upstream的name。
同時upstream提供了一個health check方法，用於檢查target目標服務是否健康。以此控制啟用或禁用target目標服務
和upstream關聯的kong模塊:service ,target
主要參數:algorithm 負載算法：round-robin（默認）, consistent-hashing, or least-connections
healthchecks.active.http_path 健康檢查路徑：默認/，該地址是指在目標服務器上，適用於目標服務器的所有請求
命令
1、add upstream
方法 post
api:/upstreams
2,list upstream ,retrieve upstream
方法：get
api：/upstreams
/upstreams/upstream id or name
/targets/{target host:port or id}/upstream 關聯指定target目標服務的upstream
3，update upstream
方法：patch
api:/upstreams/{upstream name or id}
/targets/{target host:port or id}/upstream
4,create or update upstream
方法：put
api:/upstreams/{upstream name or id}
/targets/{target host:port or id}/upstream
5,delete
方法：delete
api：/upstreams/{upstream name or id}
/targets/{target host:port or id}/upstream
健康檢查 health check
kong會發起對配置在upstream上的所有target進行健康檢查，若檢查失敗，將會暫時移除不健康的target服務。
恢復之后會再次加入。具體參數可在upstream參數中配置。
檢查結果主要為一下四大類（官網介紹）
- If a Target fails to be activated in the balancer due to DNS issues, its status displays as
DNS_ERROR. - When health checks are not enabled in the Upstream configuration, the health status for active Targets is displayed as
HEALTHCHECKS_OFF. - When health checks are enabled and the Target is determined to be healthy, either automatically or manually, its status is displayed as
HEALTHY. This means that this Target is currently included in this Upstream’s load balancer execution. - When a Target has been disabled by either active or passive health checks (circuit breakers) or manually, its status is displayed as
UNHEALTHY. The load balancer is not directing any traffic to this Target via this Upstream.
上述HEALTHY 、HEALTHCHECKS_OFF情況，target目標可以被轉發請求，其他兩類不被負載轉發。
查看：get方法。api:/upstreams/{name or id}/health/
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