MongoDB Adapter

1. Requirements

• MongoDB version 3.6 and higher.
• MongoDB must be in replica set or shard mode.

---

2. config.toml Explanation

2.1 Example of configs/config.toml

[gravity]
domain = "default"
host = "localhost"
port = 4222
pingInterval = 10
maxPingsOutstanding = 3
maxReconnects = -1
accessToken = ""
publishBatchSize = 1000
rateLimit = 0

[adapter]
adapterID = "mongodb_adapter"
adapterName = "Mongodb Adapter"

[source]
config = "./settings/sources.json"

[store]
enabled = true
path = "./statestore"

2.2 Parameters

Parameter	Description
gravity.domain	Sets the Gravity domain
gravity.host	Sets the Gravity NATS IP address
gravity.port	Sets the Gravity NATS port
gravity.pingInterval	Sets the Gravity ping interval
gravity.maxPingsOutstanding	Sets the maximum outstanding pings
gravity.maxReconnects	Sets the maximum number of reconnections
gravity.accessToken	Sets the Gravity access token (for authentication)
gravity.publishBatchSize	Sets the batch size for events sent to NATS
gravity.rateLimit	Sets the maximum rate (per second) for events sent to NATS (0 = no limit)
source.config	Path to the source configuration file
store.enabled	Enables persistent volume mounting (for state storage)
store.path	Path for mounting the persistent volume

INFO

The config.toml settings can also be provided via environment variables. The naming convention is as follows:

GRAVITY_ADAPTER_MONGODB_[SECTION]_[KEY]

All letters are uppercase, and underscores (_) separate the sections and keys.
Example for gravity.host:

env:
- name: GRAVITY_ADAPTER_MONGODB_GRAVITY_HOST
  value: 192.168.0.1

---

3. settings.json Explanation

3.1 Example of settings/sources.json

{
  "sources": {
    "my_mongo": {
      "disabled": false,
      "uri": "mongodb://mongodb-0:27017,mongodb-1:27017,mongodb-2:27017/?replicaSet=mongodb&tls=true",
      "ca_file": "rootCA.pem",
      "username": "admin",
      "password": "1qaz@WSX",
      "authSource": "admin",
      "dbname": "admin",
      "initialLoad": false,
      "tables": {
        "account": {
          "events": {
            "//comment": "snapshot events are not supported; initialLoad events are create, update, and delete",
            "create": "accountCreated",
            "update": "accountUpdated",
            "delete": "accountDeleted"
          }
        }
      }
    }
  }
}

3.2 Parameters

Parameter	Description
sources.SOURCE_NAME.disabled	Whether to disable this source
sources.SOURCE_NAME.uri	MongoDB connection URI. See Connection URI for details.
sources.SOURCE_NAME.ca_file	Path to the CA certificate when tls=true is enabled
sources.SOURCE_NAME.username	MongoDB login username
sources.SOURCE_NAME.password	MongoDB login password
sources.SOURCE_NAME.authSource	Database for user authentication
sources.SOURCE_NAME.dbname	MongoDB database name
sources.SOURCE_NAME.initialLoad	Whether to synchronize existing records during initialization
sources.SOURCE_NAME.tables.COLLECTION_NAME	Name of the MongoDB collection to capture events
sources.SOURCE_NAME.tables.COLLECTION_NAME.event.create	Event name for record creation
sources.SOURCE_NAME.tables.COLLECTION_NAME.event.update	Event name for record updates
sources.SOURCE_NAME.tables.COLLECTION_NAME.event.delete	Event name for record deletion

INFO

Database passwords can be provided via environment variables using AES encryption.
Example format:

[SOURCE_NAME]_PASSWORD

Kubernetes example using a secret:

env:
- name: MONGODB_SOURCE_PASSWORD
  valueFrom:
    secretKeyRef:
      name: mongodb-password
      key: db_source_mongodb_password

Secret definition:

apiVersion: v1
kind: Secret
metadata:
  name: mongodb-password
type: Opaque
stringData:
  db_source_mongodb_password: 8e5ca8439ddebbac9bf2b83caf4bef7a

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4. Build

To build the adapter image, use the following command:

podman buildx build --platform linux/amd64 --build-arg="AES_KEY=**********" -t hb.k8sbridge.com/gravity/gravity-adapter-mongodb:v2.0.0 -f build/docker/Dockerfile .

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5. Deploy MongoDB Replica Set Using Docker

5.1 Start MongoDB Instances

docker run -d --name mongo1 -p 27017:27017 mongo --replSet rs0 --bind_ip_all

5.2 Initiate the Replica Set

docker exec -it mongo1 mongosh --eval "rs.initiate({
 _id: \"rs0\",
 members: [
   {_id: 0, host: \"mongo1\"}
 ]
})"

5.3 Test and Verify the Replica Set

docker exec -it mongo1 mongosh --eval "rs.status()"

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6. Deploy gravity-adapter-mongodb on Kubernetes

6.1 Deploy the Adapter

1. Modify GRAVITY_ADAPTER_MONGODB_SOURCE_SETTINGS in samples/gravity-adapter-mongodb.yaml with the desired settings.
2. Apply the configuration:

   kubectl --namespace <my-namespace> apply -f samples/gravity-adapter-mongodb.yaml
3. Verify deployment:

   kubectl --namespace <my-namespace> get pods

6.2 Enable MongoDB TLS Connections

1. Create a config map for the CA certificate:

   kubectl --namespace <your-namespace> create configmap ca-config-map --from-file=ca.crt=<path-to-ca.crt>
2. Modify samples/gravity-adapter-mongodb_tls.yaml:
   • Add tls=true to the connection URI.
   • Set the ca_file parameter to the certificate path.
3. Deploy:

   kubectl --namespace <my-namespace> apply -f samples/gravity-adapter-mongodb_tls.yaml
4. Check logs for successful connection:

   kubectl --namespace <my-namespace> logs gravity-adapter-example-0