[#3] .Add added an example for connecting to cosmosdb

examples/README.md

@@ -0,0 +1,51 @@
+# Examples
+
+The provided exampled needs a germlin-server as counterpart. They can be either a local one or a cosmos db running on azure.
+
+## Against Local Gremlin-Server
+
+```bash
+# start a local gremlin server
+cd ..
+make infra.up
+
+# execute the example
+go run ./examples/local
+```
+
+## Against CosmosDB
+
+### Prerequisites
+
+1. Obtain the host/ endpoint of the CosmosDB
+
+   - Therefore one has to login into the Azure web console and navigate to the azure cosmos DB panel.
+   - Here just select the db you want to connect to, go to the overview tab and there copy the URL of the `Gremlin Endpoint`
+   - It should look like this `wss://xyz-my-db-abc.gremlin.cosmos.azure.com:443/`
+
+2. Obtain the username/ database name
+
+   - In our case the username is composed out of the name of the database and the name of the collection one want's to use
+   - Schema: `/dbs/<db-name>/colls/<name of the collection>`
+   - Example: `/dbs/mydatabase/colls/mygraph`
+
+3. Obtain the key of the CosmosDB
+
+   - Therefore one has to login into the Azure web console and navigate to the azure cosmos DB panel.
+   - Here just select the db you want to connect to, go to the keys tab and there copy the `PRIMARY KEY`
+   - It should look like this `Amx5obCQPF53Vf7WyqtXiu5qsZ89tS8envY9oON3KNRIGAjILWduRKbfwqvYZ2e8vtIUNNv1w0LlEoecfhNsk9w==`
+
+4. Set these parameters as environment variables
+
+   ```bash
+   export CDB_HOST=wss://xyz-my-db-abc.gremlin.cosmos.azure.com:443 && \
+   export  CDB_KEY=Amx5obCQPF53Vf7WyqtXiu5qsZ89tS8envY9oON3KNRIGAjILWduRKbfwqvYZ2e8vtIUNNv1w0Ll EoecfhNsk9w== && \
+   export CDB_USERNAME=/dbs/mydatabase/colls/mygraph
+   ```
+
+Then one can run the example via:
+
+```bash
+cd ..
+go run ./examples/cosmos
+```

examples/cosmos/main.go

@@ -0,0 +1,63 @@
+package main
+
+import (
+	"encoding/json"
+	"log"
+	"os"
+
+	"github.com/schwartzmx/gremtune"
+)
+
+var panicOnErrorOnChannel = func(errs chan error) {
+	err := <-errs
+	if err == nil {
+		return // ignore if the channel was closed
+	}
+	log.Fatalf("Lost connection to the database: %s", err)
+}
+
+func main() {
+
+	host := os.Getenv("CDB_HOST")
+	username := os.Getenv("CDB_USERNAME")
+	password := os.Getenv("CDB_KEY")
+
+	if len(host) == 0 {
+		log.Fatal("Host not set. Use export CDB_HOST=<CosmosDB Gremlin Endpoint> to specify it")
+	}
+
+	if len(username) == 0 {
+		log.Fatal("Username not set. Use export CDB_USERNAME=/dbs/<cosmosdb name>/colls/<graph name> to specify it")
+	}
+
+	if len(password) == 0 {
+		log.Fatal("Key not set. Use export CDB_KEY=<key> to specify it")
+	}
+
+	log.Println("Connecting using:")
+	log.Printf("\thost: %s\n", host)
+	log.Printf("\tusername: %s\n", username)
+	log.Printf("\tpassword: %s\n", password)
+
+	errs := make(chan error)
+	go panicOnErrorOnChannel(errs)
+
+	dialer := gremtune.NewDialer(host, gremtune.SetAuthentication(username, password))
+	gremlinClient, err := gremtune.Dial(dialer, errs) // Returns a gremtune client to interact with
+	if err != nil {
+		log.Fatalf("Failed to create the gremlin client: %s", err)
+	}
+
+	// Sends a query to Gremlin Server
+	res, err := gremlinClient.Execute("g.V()")
+	if err != nil {
+		log.Fatalf("Failed to execute a gremlin command: %s", err)
+	}
+
+	jsonEncodedResponse, err := json.MarshalIndent(res[0].Result.Data, "", "    ")
+	if err != nil {
+		log.Fatalf("Failed to encode the raw json into json: %s", err)
+	}
+
+	log.Printf("Received data: \n%s\n", jsonEncodedResponse)
+}