集群负载均衡应该在其节点上执行运行状况检查吗? [英] Should swarm loadbalancing perform healthchecks on its nodes?
问题描述
swarm文档中的负载平衡部分不要弄清楚内部负载均衡器是否也进行运行状况检查，以及是否删除不再运行该服务的节点(因为该节点已被杀死或节点已重新启动).
The Load Balancing section in the swarm docs don't make it clear if the internal loadbalancer also does health checks, and if it removes nodes that aren't running the service anymore (because it got killed or the node got rebooted).
在以下情况下，我有一个包含副本3的服务，在3个节点中的每个节点上运行1个实例.
In the following case I've got a service with replicas 3, 1 instance running on each of the 3 nodes.
经理:
[root@centosvm ~]# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
a593d485050a ddewaele/springboot.crud.sample:latest "sh -c 'java $JAVA_OP" 7 minutes ago Up 7 minutes springbootcrudsample.1.5syc6j4c8i3bnerdqq4e1yelm
节点1:
[root@node1 ~]# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
d3b3fbc0f2c5 ddewaele/springboot.crud.sample:latest "sh -c 'java $JAVA_OP" 4 minutes ago Up 4 minutes springbootcrudsample.3.7y1oyjyrifgkmxlr20oai5ppl
节点2:
[root@node2 ~]# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
ebca8f24ec3a ddewaele/springboot.crud.sample:latest "sh -c 'java $JAVA_OP" 7 minutes ago Up 7 minutes springbootcrudsample.2.4tqjad7od8ep047s55485na1t
现在，在node1上，我们杀死docker容器.此节点将不提供服务(群集将在几秒钟后在此处重新创建它，以使该服务上的Replication = 3保持不变)
Now, on node1, we kill the docker container. This node will be without a service (swarm will re-create it here after a couple of seconds to keep the replication=3 on the service)
[root@node1 ~]# docker kill d3b3fbc0f2c5
d3b3fbc0f2c5
容器不见了
[root@node1 ~]# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
新建容器
[root@node1 ~]# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
b8c9a7a5cf97 ddewaele/springboot.crud.sample:latest "sh -c 'java $JAVA_OP" 11 seconds ago Up 9 seconds springbootcrudsample.3.9v4cnhi8dvq7n8afb2kvp28sk
但是在下面的输出中，当容器d3b3fbc0f2c5被杀死时，入口负载均衡器未检测到此消息，并且它仍在向节点发送流量(导致连接被拒绝)?
In the output below however, when container d3b3fbc0f2c5 was killed, the ingress loadbalancer didn't detect this, and it was still sending traffic to the node (resulting in connection refused) ?
我们应该如何处理这种情况?在这种情况下，我们仍然需要外部负载均衡器吗?我们应该如何配置它?
How should we handle such a scenario ? Do we still need an external loadbalancer for this scenario and how should we configure it ?
[root@centosvm ~]# while :; do curl http://localhost:8080/env/hostname ; echo "" ; sleep 1; done
{"hostname":"d3b3fbc0f2c5"}
{"hostname":"a593d485050a"}
{"hostname":"ebca8f24ec3a"}
{"hostname":"d3b3fbc0f2c5"}
{"hostname":"a593d485050a"}
{"hostname":"ebca8f24ec3a"}
{"hostname":"d3b3fbc0f2c5"}
{"hostname":"a593d485050a"}
{"hostname":"ebca8f24ec3a"}
{"hostname":"a593d485050a"}
{"hostname":"ebca8f24ec3a"}
{"hostname":"a593d485050a"}
curl: (7) Failed connect to localhost:8080; Connection refused
{"hostname":"ebca8f24ec3a"}
{"hostname":"a593d485050a"}
curl: (7) Failed connect to localhost:8080; Connection refused
{"hostname":"ebca8f24ec3a"}
{"hostname":"a593d485050a"}
curl: (7) Failed connect to localhost:8080; Connection refused
{"hostname":"ebca8f24ec3a"}
{"hostname":"a593d485050a"}
curl: (7) Failed connect to localhost:8080; Connection refused
{"hostname":"ebca8f24ec3a"}
{"hostname":"a593d485050a"}
curl: (7) Failed connect to localhost:8080; Connection refused
{"hostname":"ebca8f24ec3a"}
{"hostname":"a593d485050a"}
curl: (7) Failed connect to localhost:8080; Connection refused
{"hostname":"ebca8f24ec3a"}
{"hostname":"a593d485050a"}
{"hostname":"b8c9a7a5cf97"}
{"hostname":"ebca8f24ec3a"}
{"hostname":"a593d485050a"}
{"hostname":"b8c9a7a5cf97"}
推荐答案
如FrançoisMaturel a>，通过适当的运行状况检查，Docker Swarm将考虑容器的运行状况，以决定是否将请求路由到该容器.
As indicated by François Maturel, with a proper healthcheck in place, Docker Swarm will take into account the health status of the container to decide if it will route requests to it.
对于已启用默认执行器的Spring Boot应用程序，将其添加到Dockerfile中足以进行基本的运行状况检查.当Spring Boot应用程序初始化并且其健康执行器已启用，以下http请求将返回有效的http 200响应，健康检查将通过.
For Spring Boot applications that have enabled the default actuators, adding this to the Dockerfile is sufficient for a basic healthcheck. When the Spring Boot app is initialized and its health actuator is enabled, the following http request will return a valid http 200 response and the healthcheck will pass.
HEALTHCHECK CMD wget -q http://localhost:8080/health -O /dev/null
这将导致您的Docker容器能够达到健康状态.启动Docker容器后，其中运行的服务可能仍在初始化中.为了进行适当的负载平衡并检测服务运行状况，Swarm需要知道何时能够将请求路由到特定的服务实例(节点上的容器).
This will result in your docker containers being anble to reach a healthy status. When your docker container is started, the service running within it might still be initializing. To do proper load balancing and detect service health, Swarm needs to know when it is able to route reqeusts to a particular service instance (container on a node).
因此，当Swarm启动服务副本时，它将启动容器，它将等待直到服务的运行状况为运行状况".在您的容器启动时，它将从开始"过渡:
So when Swarm starts a service replica, it fires up a container, it will wait until the health status of the service is "healthy". As your container is starting, it will transition from "starting" :
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
5001e1c46953 ddewaele/springboot.crud.sample@sha256:4ce69c3f50c69640c8240f9df68c8816605c6214b74e6581be44ce153c0f3b7a "/docker-entrypoin..." 5 seconds ago Up Less than a second (health: starting) springbootcrudsample.2.yt6d38zhhq2wxt1d6qfjz5974
健康".只有这样，Swarm负载均衡器才会将请求路由到此端点.
to 'healthy'. Only then will the Swarm load balancer route requests to this endpoint.
[root@centos-a ~]# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
5001e1c46953 ddewaele/springboot.crud.sample@sha256:4ce69c3f50c69640c8240f9df68c8816605c6214b74e6581be44ce153c0f3b7a "/docker-entrypoin..." About a minute ago Up About a minute (healthy) springbootcrudsample.2.yt6d38zhhq2wxt1d6qfjz5974
这篇关于集群负载均衡应该在其节点上执行运行状况检查吗?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
