private long handleResponse(SimpleHttpResponse response) throws UncheckedIOException {
        try {
            int statusCode = response.getCode();
            if (statusCode != HttpStatus.SC_OK) throw new IOException("Expected status code 200, got " + statusCode);
            if (response.getBody() == null) throw new IOException("Response has no content");
            return generationFromContainerState(Jackson.mapper().readTree(response.getBodyText()));
        } catch (IOException e) {
            throw new UncheckedIOException(e);
        }
    }
Get service generation of service at given URL
configserver/src/main/java/com/yahoo/vespa/config/server/application/ConfigConvergenceChecker.java