[GitHub] [couchdb] sergey-safarov opened a new issue #2142: docker/kubrenetes nodes discovery

[GitBox <gi...@apache.org>]

sergey-safarov opened a new issue #2142: docker/kubrenetes nodes discovery
URL: https://github.com/apache/couchdb/issues/2142
 
 
   ## Summary
   
   I can create docker stack using this file
   ```yaml
   version: "3.7"
   
   networks:
     main:
   
   services:
     couchdb:
       image: couchdb:2.3.1
       environment:
       - NODENAME=couchdb-{{.Task.Slot}}
       - COUCHDB_SECRET=monster
       - ERL_FLAGS="-setcookie monster"
       ports:
       - "5984"
       - "5986"
       networks:
       - main
       deploy:
         replicas: 5
   ```
   
   And command
   ```sh
   docker stack deploy --compose-file docker-compose.yaml kazoo
   ```
   This will create
   1. `kazoo_main` network
   1. `couchdb` service
   1. five couchdb containers with unique names
   
   Could you implement following logic for couchdb node discovery and automatic cluster formation.
   
   **resolv ${SEED_DNS_NAME}**
   ```sh
   root@dbef6f82ce5f:/# nslookup ${SEED_DNS_NAME}
   Server:		127.0.0.11
   Address:	127.0.0.11#53
   
   Non-authoritative answer:
   Name:	tasks.couchdb
   Address: 10.0.52.7
   Name:	tasks.couchdb
   Address: 10.0.52.6
   Name:	tasks.couchdb
   Address: 10.0.52.5
   Name:	tasks.couchdb
   Address: 10.0.52.4
   Name:	tasks.couchdb
   Address: 10.0.52.3
   ```
   
   Now we can couchdb nodes names
   ```sh
   root@dbef6f82ce5f:/# curl http://10.0.52.3:5984/_membership
   {"all_nodes":["couchdb@couchdb-5"],"cluster_nodes":["couchdb@couchdb-5"]}
   root@dbef6f82ce5f:/# curl http://10.0.52.4:5984/_membership
   {"all_nodes":["couchdb@couchdb-1"],"cluster_nodes":["couchdb@couchdb-1"]}
   root@dbef6f82ce5f:/# curl http://10.0.52.5:5984/_membership
   {"all_nodes":["couchdb@couchdb-2"],"cluster_nodes":["couchdb@couchdb-2"]}
   root@dbef6f82ce5f:/# curl http://10.0.52.6:5984/_membership
   {"all_nodes":["couchdb@couchdb-3"],"cluster_nodes":["couchdb@couchdb-3"]}
   root@dbef6f82ce5f:/# curl http://10.0.52.7:5984/_membership
   {"all_nodes":["couchdb@couchdb-4"],"cluster_nodes":["couchdb@couchdb-4"]}
   ```
   
   Now we can join cluster nodes into cluster using commands
   ```
   curl -X PUT "http://localhost:5986/_nodes/couchdb@couchdb-1/10.0.52.4" -d {}
   curl -X PUT "http://localhost:5986/_nodes/couchdb@couchdb-2/10.0.52.5" -d {}
   curl -X PUT "http://localhost:5986/_nodes/couchdb@couchdb-3/10.0.52.6" -d {}
   curl -X PUT "http://localhost:5986/_nodes/couchdb@couchdb-4/10.0.52.7" -d {}
   curl -X PUT "http://localhost:5986/_nodes/couchdb@couchdb-5/10.0.52.3" -d {}
   ```
   
   Here I suggest extended command join syntax to use `runtime` containers IP address.
   
   If couchdb node is restarted, then
   1. node again resolve `${SEED_DNS_NAME}` and gets current couchdb nodes IP addresses;
   1. request `/_node/_local/_system` resource from each IP and gets couchdb node
   name behind each IP
   1. update own map of couchdb nodes and their IP addresses
   
   ## Additional context
   
   This feature may be used in `docker swarm` and `kubernetes` clouds.
   In kubernetes need use statefulset + service like
   ```yaml
   # file contains database headless service
   # creates kubernetes dns records for database daemons
   # required for database nodes discovery
   apiVersion: v1
   kind: Service
   metadata:
     name: db
   spec:
     type: ClusterIP
     clusterIP: None
     publishNotReadyAddresses: true
     selector:
       app: db
   ```
   Kubernetes service yaml file must contain `publishNotReadyAddresses: true`

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