Golang gocql cannot connect to Cassandra (using Docker) - database

Question

I am trying to setup and connect to a Cassandra single node instance using docker and Golang and it is not working.
The closest information I could find to addressing connection issues between the golang gocql package and Cassandra is available here: Cassandra cqlsh - connection refused, however there are many different upvote answers with no clear indication of which is preferred. It is also a protected question (no "me toos"), so a lot of community members seem to be having trouble with this.
This problem should be slightly different, as it is using Docker and I have tried most (if not all of the solutions linked to above).
version: "3"
services:
cassandra00:
restart: always
image: cassandra:latest
volumes:
- ./db/casdata:/var/lib/cassandra
ports:
- 7000:7000
- 7001:7001
- 7199:7199
- 9042:9042
- 9160:9160
environment:
- CASSANDRA_RPC_ADDRESS=127.0.0.1
- CASSANDRA_BROADCAST_ADDRESS=127.0.0.1
- CASSANDRA_LISTEN_ADDRESS=127.0.0.1
- CASSANDRA_START_RPC=true
db:
restart: always
build: ./db
environment:
POSTGRES_USER: patientplatypus
POSTGRES_PASSWORD: SUPERSECRETFAKEPASSD00T
POSTGRES_DB: zennify
expose:
- "5432"
ports:
- 5432:5432
volumes:
- ./db/pgdata:/var/lib/postgresql/data
app:
restart: always
build:
context: .
dockerfile: Dockerfile
command: bash -c 'while !</dev/tcp/db/5432; do sleep 10; done; realize start --run'
# command: bash -c 'while !</dev/tcp/db/5432; do sleep 10; done; go run main.go'
ports:
- 8000:8000
depends_on:
- db
- cassandra00
links:
- db
- cassandra00
volumes:
- ./:/go/src/github.com/patientplatypus/webserver/
Admittedly, I am a little shaky on what listening addresses I should pass to Cassandra in the environment section, so I just passed 'home':
- CASSANDRA_RPC_ADDRESS=127.0.0.1
- CASSANDRA_BROADCAST_ADDRESS=127.0.0.1
- CASSANDRA_LISTEN_ADDRESS=127.0.0.1
If you try and pass 0.0.0.0 you get the following error:
cassandra00_1 | Exception (org.apache.cassandra.exceptions.ConfigurationException) encountered during startup: listen_address cannot be a wildcard address (0.0.0.0)!
cassandra00_1 | listen_address cannot be a wildcard address (0.0.0.0)!
cassandra00_1 | ERROR [main] 2018-09-10 21:50:44,530 CassandraDaemon.java:708 - Exception encountered during startup: listen_address cannot be a wildcard address (0.0.0.0)!
Overall, however I think that I am getting the correct start up procedure for Cassandra (afaict) because my terminal outputs that Cassandra started up as normal and is listening on the appropriate ports:
cassandra00_1 | INFO [main] 2018-09-10 22:06:28,920 StorageService.java:1446 - JOINING: Finish joining ring
cassandra00_1 | INFO [main] 2018-09-10 22:06:29,179 StorageService.java:2289 - Node /127.0.0.1 state jump to NORMAL
cassandra00_1 | INFO [main] 2018-09-10 22:06:29,607 NativeTransportService.java:70 - Netty using native Epoll event loop
cassandra00_1 | INFO [main] 2018-09-10 22:06:29,750 Server.java:155 - Using Netty Version: [netty-buffer=netty-buffer-4.0.44.Final.452812a, netty-codec=netty-codec-4.0.44.Final.452812a, netty-codec-haproxy=netty-codec-haproxy-4.0.44.Final.452812a, netty-codec-http=netty-codec-http-4.0.44.Final.452812a, netty-codec-socks=netty-codec-socks-4.0.44.Final.452812a, netty-common=netty-common-4.0.44.Final.452812a, netty-handler=netty-handler-4.0.44.Final.452812a, netty-tcnative=netty-tcnative-1.1.33.Fork26.142ecbb, netty-transport=netty-transport-4.0.44.Final.452812a, netty-transport-native-epoll=netty-transport-native-epoll-4.0.44.Final.452812a, netty-transport-rxtx=netty-transport-rxtx-4.0.44.Final.452812a, netty-transport-sctp=netty-transport-sctp-4.0.44.Final.452812a, netty-transport-udt=netty-transport-udt-4.0.44.Final.452812a]
cassandra00_1 | INFO [main] 2018-09-10 22:06:29,754 Server.java:156 - Starting listening for CQL clients on /127.0.0.1:9042 (unencrypted)...
cassandra00_1 | INFO [main] 2018-09-10 22:06:29,990 ThriftServer.java:116 - Binding thrift service to /127.0.0.1:9160
In my golang code I have the following package that is being called (simplified to show relevant section):
package data
import(
"fmt"
"github.com/gocql/gocql"
)
func create_userinfo_table() {
<...>
fmt.Println("replicating table in cassandra")
cluster := gocql.NewCluster("localhost") //<---error here!
cluster.ProtoVersion = 4
<...>
}
Which results in the following error in my terminal:
app_1 | [21:52:38][WEBSERVER] : 2018/09/10
21:52:38 gocql: unable to dial control conn 127.0.0.1:
dial tcp 127.0.0.1:9042: connect: connection refused
app_1 | [21:52:38][WEBSERVER] : 2018/09/10
21:52:38 gocql: unable to dial control conn ::1:
dial tcp [::1]:9042: connect: cannot assign requested address
app_1 | [21:52:38][WEBSERVER] : 2018/09/10
21:52:38 Could not connect to cassandra cluster: gocql:
unable to create session: control: unable to connect to initial hosts:
dial tcp [::1]:9042: connect: cannot assign requested address
I have tried several variations on the connection address
cluster := gocql.NewCluster("localhost")
cluster := gocql.NewCluster("127.0.0.1")
cluster := gocql.NewCluster("127.0.0.1:9042")
cluster := gocql.NewCluster("127.0.0.1:9160")
These seemed likely candidates for example, but no luck.
Does anyone have any idea what I am doing wrong?

Answer 1

Use the service name cassandra00 for the hostname per the docker-compose documentation https://docs.docker.com/compose/compose-file/#links
Containers for the linked service are reachable at a hostname identical to the alias, or the service name if no alias was specified.
Leave the CASSANDRA_LISTEN_ADDRESS envvar unset (or pass auto) per https://docs.docker.com/samples/library/cassandra/
The default value is auto, which will set the listen_address option in cassandra.yaml to the IP address of the container as it starts. This default should work in most use cases.