| # Docker Swarm Service Driller(ssd) |
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| ssd is a troubleshooting utility for Docker swarm networks. |
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| ### control-plane and datapath consistency check on a node |
| ssd checks for the consistency between docker network control-plane (from the docker daemon in-memory state) and kernel data path programming. Currently the tool checks only for the consistency of the Load balancer (implemented using IPVS). |
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| In a three node swarm cluster ssd status for a overlay network `ov2` which has three services running, each replicated to 3 instances. |
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| ````bash |
| vagrant@net-1:~/code/go/src/github.com/docker/docker-e2e/tests$ docker run -v /var/run/docker.sock:/var/run/docker.sock -v /var/run/docker/netns:/var/run/docker/netns --privileged --net=host sanimej/ssd ov2 |
| Verifying LB programming for containers on network ov2 |
| Verifying container /s2.3.ltrdwef0iqf90rqauw3ehcs56... |
| service s2... OK |
| service s3... OK |
| service s1... OK |
| Verifying container /s3.3.nyhwvdvnocb4wftyhb8dr4fj8... |
| service s2... OK |
| service s3... OK |
| service s1... OK |
| Verifying container /s1.3.wwx5tuxhnvoz5vrb8ohphby0r... |
| service s2... OK |
| service s3... OK |
| service s1... OK |
| Verifying LB programming for containers on network ingress |
| Verifying container Ingress... |
| service web... OK |
| ```` |
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| ssd checks the required iptables programming to direct an incoming packet with the <host ip>:<published port> to the right <backend ip>:<target port> |
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| ### control-plane consistency check across nodes in a cluster |
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| Docker networking uses a gossip protocol to synchronize networking state across nodes in a cluster. ssd's `gossip-consistency` command verifies if the state maintained by all the nodes are consistent. |
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| ````bash |
| In a three node cluster with services running on an overlay network ov2 ssd consistency-checker shows |
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| vagrant@net-1:~/code/go/src/github.com/docker/docker-e2e/tests$ docker run -v /var/run/docker.sock:/var/run/docker.sock -v /var/run/docker/netns:/var/run/docker/netns --privileged sanimej/ssd ov2 gossip-consistency |
| Node id: sjfp0ca8f43rvnab6v7f21gq0 gossip hash c57d89094dbb574a37930393278dc282 |
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| Node id: bg228r3q9095grj4wxkqs80oe gossip hash c57d89094dbb574a37930393278dc282 |
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| Node id: 6jylcraipcv2pxdricqe77j5q gossip hash c57d89094dbb574a37930393278dc282 |
| ```` |
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| This is hash digest of the control-plane state for the network `ov2` from all the cluster nodes. If the values have a mismatch `docker network inspect --verbose` on the individual nodes can help in identifying what the specific difference is. |
