### Issue:

You are setting up an OpenSearch cluster using LocalStack on a Kubernetes pod, exposing it via a Kubernetes service. When making a search request, you encounter the error:

exception during call chain: Unable to find operation for request to service es: POST /api-transactions/_search

### Possible Causes & Fixes:

#### 1. Verify OpenSearch Domain Exists

Run the following command to confirm that the domain was created successfully:

awslocal opensearch list-domain-names --endpoint-url http://localhost:4566

Ensure that api-transactions appears in the output. If not, try recreating it.

#### 2. Check the OpenSearch Endpoint

Get the domain details and check its Endpoint:

awslocal opensearch describe-domain --domain-name api-transactions --endpoint-url http://localhost:4566

Ensure you are making requests to the correct endpoint.

#### 3. Ensure LocalStack Recognizes OpenSearch

Since you have specified both opensearch and es in the LocalStack SERVICES environment variable:

name: SERVICES

value: "dynamodb,s3,sqs,opensearch,es"

Try setting only opensearch:

name: SERVICES

value: "dynamodb,s3,sqs,opensearch"

Then restart the LocalStack pod.

#### 4. Verify Your OpenSearch Request Format

Your Go code is signing the request with:

signer, err := requestsigner.NewSignerWithService(awsCfg, "es")

Try changing "es" to "opensearch":

signer, err := requestsigner.NewSignerWithService(awsCfg, "opensearch")

LocalStack may expect opensearch instead of es for signing requests.

#### 5. Manually Test OpenSearch API

Test OpenSearch directly to check if the issue is with LocalStack or your application:

curl -X POST "http://localhost:4566/api-transactions/_search" -H "Content-Type: application/json" -d '{ "query": { "match_all": {} } }'

If you get the same error, the issue is likely with LocalStack’s OpenSearch service.

#### 6. Check LocalStack Logs for Errors

Run:

kubectl logs <localstack-pod-name> | grep "opensearch"

Look for any errors indicating OpenSearch initialization issues.

#### 7. Specify the OpenSearch Endpoint Explicitly in Your Code

Instead of relying on auto-discovery, explicitly set the OpenSearch endpoint in your Go client:

osCfg, err := opensearchapi.Config{ Addresses: []string{"http://localhost:4566"}, Transport: signer, }

This ensures your application is hitting the right OpenSearch URL.

#### 8. Restart LocalStack if Necessary

If nothing works, restart the LocalStack pod:

kubectl delete pod <localstack-pod-name>

Then, redeploy with:

helm upgrade --install localstack localstack/localstack