Telepresence Quick Start - Go

2. Try the Emojivoto application

The remote cluster is running the Emojivoto application, which consists of four services. Test out the application:

1. Go to the Emojivoto webapp and vote for some emojis.

   If the link to the remote demo cluster doesn't work, make sure you don't have an ad blocker preventing it from opening.

2. Now, click on the 🍩 emoji. You'll see that a bug is present, and voting 🍩 doesn't work.

3. Run the Docker container

The bug is present in the voting-svc service, you'll run that service locally. To save your time, we prepared a Docker container with this service running and all you'll need to fix the bug.

1. Run the Docker container locally, by running this command inside your local terminal:

   GNU/Linux

   Terminal

   copied
   $ docker run -p8083:8083 --name voting-demo --cap-add=NET_ADMIN --device /dev/net/tun:/dev/net/tun --pull always --rm -it -e AMBASSADOR_API_KEY=  -v $(if [[  "${XDG_CONFIG_HOME}" ]]; then echo "${XDG_CONFIG_HOME}"; else echo "$HOME/.config"; fi):/root/.host_config datawire/telepresence-emojivoto-go-demo
   	Connected to context telepresence-demo (https://$DEMO_CLUSTER_IP)
   	emoji             : ready to intercept (traffic-agent not yet installed)
   	web               : ready to intercept (traffic-agent not yet installed)
   	voting            : ready to intercept (traffic-agent not yet installed)
   	web-app-778477c59c: ready to intercept (traffic-agent not yet installed)
   	root@/opt/emojivoto#
   

   macOS

   Terminal

   copied
   $ docker run -p8083:8083 --name voting-demo --cap-add=NET_ADMIN --device /dev/net/tun:/dev/net/tun --pull always --rm -it -e AMBASSADOR_API_KEY=  -v ~/Library/Application\ Support:/root/.host_config datawire/telepresence-emojivoto-go-demo
   	Connected to context telepresence-demo (https://$DEMO_CLUSTER_IP)
   	emoji             : ready to intercept (traffic-agent not yet installed)
   	web               : ready to intercept (traffic-agent not yet installed)
   	voting            : ready to intercept (traffic-agent not yet installed)
   	web-app-778477c59c: ready to intercept (traffic-agent not yet installed)
   	root@/opt/emojivoto#
   

   Windows

   Terminal

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   $ IF %AppData%=="" (docker run -p8083:8083 --name voting-demo --cap-add=NET_ADMIN --device /dev/net/tun:/dev/net/tun --pull always --rm -it -e AMBASSADOR_API_KEY=  -v %userprofile%\AppData\Roaming:/root/.host_config datawire/telepresence-emojivoto-go-demo) ELSE (docker run -p8083:8083 --name voting-demo --cap-add=NET_ADMIN --device /dev/net/tun:/dev/net/tun --pull always --rm -it -e AMBASSADOR_API_KEY=  -v %AppData%:/root/.host_config datawire/telepresence-emojivoto-go-demo)
   	Connected to context telepresence-demo (https://$DEMO_CLUSTER_IP)
   	emoji             : ready to intercept (traffic-agent not yet installed)
   	web               : ready to intercept (traffic-agent not yet installed)
   	voting            : ready to intercept (traffic-agent not yet installed)
   	web-app-778477c59c: ready to intercept (traffic-agent not yet installed)
   	root@/opt/emojivoto#
   

2. The application is failing due to a little bug inside this service which uses gRPC to communicate with the others services. We can use grpcurl to test the gRPC endpoint and see the error by running:

   Terminal

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   $ grpcurl -v -plaintext -import-path ./proto -proto Voting.proto localhost:8081 emojivoto.v1.VotingService.VoteDoughnut
     Resolved method descriptor:
     rpc VoteDoughnut ( .emojivoto.v1.VoteRequest ) returns ( .emojivoto.v1.VoteResponse );
     Request metadata to send:
     (empty)
     Response headers received:
     (empty)
     Response trailers received:
     content-type: application/grpc
     Sent 0 requests and received 0 responses
     ERROR:
       Code: Unknown
       Message: ERROR
   

3. In order to fix the bug, use the Docker container's embedded IDE to fix this error. Go to http://localhost:8083 and open api/api.go. Remove the "fmt" package by deleting the line 5.

   go

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   3 import (
   4  "context"
   5  "fmt"     // DELETE THIS LINE
   6
   7  pb "github.com/buoyantio/emojivoto/emojivoto-voting-svc/gen/proto"
   
   

   and also replace the line 21:

   go

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   20 func (pS *PollServiceServer) VoteDoughnut(_ context.Context, _ *pb.VoteRequest) (*pb.VoteResponse, error) {
   21   return nil, fmt.Errorf("ERROR")
   22 }
   
   

   with

   go

   copied

   20 func (pS *PollServiceServer) VoteDoughnut(_ context.Context, _ *pb.VoteRequest) (*pb.VoteResponse, error) {
   21   return pS.vote(":doughnut:")
   22 }
   
   

   Then save the file (Ctrl+s for Windows, Cmd+s for Mac or Menu -> File -> Save) and verify that the error is fixed now:

   Terminal

   copied
   $ grpcurl -v -plaintext -import-path ./proto -proto Voting.proto localhost:8081 emojivoto.v1.VotingService.VoteDoughnut
     Resolved method descriptor:
     rpc VoteDoughnut ( .emojivoto.v1.VoteRequest ) returns ( .emojivoto.v1.VoteResponse );
     Request metadata to send:
     (empty)
     Response headers received:
     content-type: application/grpc
     Response contents:
     {
     }
     Response trailers received:
     (empty)
     Sent 0 requests and received 1 response
   

4. Telepresence intercept

1. Now the bug is fixed, you can use Telepresence to intercept all the traffic through our local service. Run the following command inside the container:

   Terminal

   copied
   $ telepresence intercept voting --port 8081:8080
     Using Deployment voting
     intercepted
       Intercept name         : voting
       State                  : ACTIVE
       Workload kind          : Deployment
       Destination            : 127.0.0.1:8081
       Service Port Identifier: 8080
       Volume Mount Point     : /tmp/telfs-XXXXXXXXX
       Intercepting           : all TCP connections
   

   Now you can go back to Emojivoto webapp and you'll see that voting for 🍩 woks as expected.

You have created an intercept to tell Telepresence where to send traffic. The voting-svc traffic is now destined to the local Dockerized version of the service. This intercepts all the traffic to the local voting-svc service, which has been fixed with the Telepresence intercept.

5. Telepresence intercept with a preview URL

Preview URLs allows you to safely share your development environment. With this approach, you can try and test your local service more accurately because you have a total control about which traffic is handled through your service, all of this thank to the preview URL.

1. First leave the current intercept:

   Terminal

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   $ telepresence leave voting
   

2. Then login to telepresence:

   Terminal

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   $ telepresence login --apikey $APIKEY
   

3. Create an intercept, which will tell Telepresence to send traffic to the service in our container instead of the service in the cluster. When prompted for ingress configuration, all default values should be correct as displayed below.

   Terminal

   copied
   $ telepresence intercept voting --port 8081:8080
   	To create a preview URL, telepresence needs to know how requests enter
   	your cluster. Please Confirm the ingress to use.
   	1/4: What's your ingress' IP address?
   	     You may use an IP address or a DNS name (this is usually a
   	     "service.namespace" DNS name).
   	     [default: ambassador.ambassador]:
   	2/4: What's your ingress' TCP port number?
   	     [default: 80]:
   	3/4: Does that TCP port on your ingress use TLS (as opposed to cleartext)?
   	     [default: n]:
   	4/4: If required by your ingress, specify a different hostname
   	     (TLS-SNI, HTTP "Host" header) to be used in requests.
   	     [default: ambassador.ambassador]:
   

4. If you access the Emojivoto webapp application on your remote cluster and vote for the 🍩 emoji, you'll see the bug is still present.

5. Vote for the 🍩 emoji using the Preview URL obtained in the previous step, and you will see that the bug is fixed, since traffic is being routed to the fixed version which is running locally.