How to proxy to multiple servers in WebSocket

user_12064310 0
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I have a proxy programmed in ballerina that receives a request from a user to a web socket and sends it through another web socket to a service that processes it. Currently when the service sends me a response, the ballerina script returns that response to the user. I would like to do that once I receive the response from the service, it is sent to another service to perform a second processing and when this service responds and return it to the user.

I have the following code:

import ballerina/http;
import ballerina/log;


final string ASSOCIATED_CONNECTION = "EXTRACTOR CONNECTION";
final string EXTRACTOR = "ws://192.168.10.248:8081";



@http:WebSocketServiceConfig {
    path: "/api/ws"
}

service RequestService on new http:Listener(9091) {

  resource function onOpen(http:WebSocketCaller caller) {

        http:WebSocketClient wsClientEp = new(
            EXTRACTOR,
            {callbackService: ClientService,
            readyOnConnect: false,
            maxFrameSize: 2147483648
        });

        wsClientEp.setAttribute(ASSOCIATED_CONNECTION, caller);
        caller.setAttribute(ASSOCIATED_CONNECTION, wsClientEp);

        var err = wsClientEp->ready();
        if (err is http:WebSocketError) {
            log:printError("Error calling ready on client", err);
        }
    }

    resource function onText(http:WebSocketCaller caller, string text, boolean finalFrame) {

        http:WebSocketClient clientEp = getAssociatedClientEndpoint(caller);
        var err = clientEp->pushText(text, finalFrame);
        if (err is http:WebSocketError) {
            log:printError("Error occurred when sending text message", err);
        }
    }


    resource function onError(http:WebSocketCaller caller, error err) {

       http:WebSocketClient clientEp = getAssociatedClientEndpoint(caller);
       var e = clientEp->close(statusCode = 1011, reason = "Unexpected condition");
       if (e is http:WebSocketError) {
           log:printError("Error occurred when closing the connection", e);
       }
       _ = caller.removeAttribute(ASSOCIATED_CONNECTION);
       log:printError("Unexpected error hence closing the connection", err);
   }

   resource function onClose(http:WebSocketCaller caller, int statusCode, string reason) {

       http:WebSocketClient clientEp = getAssociatedClientEndpoint(caller);
       var err = clientEp->close(statusCode = statusCode, reason = reason);
       if (err is http:WebSocketError) {
           log:printError("Error occurred when closing the connection", err);
       }
       _ = caller.removeAttribute(ASSOCIATED_CONNECTION);
   }
}

service ClientService = @http:WebSocketServiceConfig {} service {

    resource function onText(http:WebSocketClient caller, string text, boolean finalFrame) {
        http:WebSocketCaller serverEp = getAssociatedServerEndpoint(caller);
        var err = serverEp->pushText(text, finalFrame);
        if (err is http:WebSocketError) {
            log:printError("Error occurred when sending text message", err);
        }
    }

    resource function onError(http:WebSocketClient caller, error err) {
        http:WebSocketCaller serverEp = getAssociatedServerEndpoint(caller);
        var e = serverEp->close(statusCode = 1011, reason = "Unexpected condition");
        if (e is http:WebSocketError) {
            log:printError("Error occurred when closing the connection", err = e);
        }
        _ = caller.removeAttribute(ASSOCIATED_CONNECTION);
        log:printError("Unexpected error hense closing the connection", err);
    }

    resource function onClose(http:WebSocketClient caller, int statusCode, string reason) {
        http:WebSocketCaller serverEp = getAssociatedServerEndpoint(caller);
        var err = serverEp->close(statusCode = statusCode, reason = reason);
            if (err is http:WebSocketError) {
                log:printError("Error occurred when closing the connection", err);
            }
        _ = caller.removeAttribute(ASSOCIATED_CONNECTION);
    }
};

function getAssociatedClientEndpoint(http:WebSocketCaller ep) returns (http:WebSocketClient) {
    http:WebSocketClient wsClient = <http:WebSocketClient>ep.getAttribute(ASSOCIATED_CONNECTION);
    return wsClient;
}

function getAssociatedServerEndpoint(http:WebSocketClient ep) returns (http:WebSocketCaller) {
    http:WebSocketCaller wsEndpoint = <http:WebSocketCaller>ep.getAttribute(ASSOCIATED_CONNECTION);
    return wsEndpoint;
}

I have made the following pipeline: Client --> Ballerina Proxy --> Service1 --> Ballerina Proxy --> Client

I want: Client --> Ballerina Proxy --> Service1 --> Ballerina Proxy --> Service2 --> Ballerina Proxy --> Client

ballerina proxy websocket
1 Answers

We can chain the associated connections 

caller has wsClientEp
wsClientEp has wsClientEp2
wsClientEp2 has caller

I have written some rough code I think the following code should work. Make sure to change the variable names:

import ballerina/http;
import ballerina/log;


final string ASSOCIATED_CONNECTION = "EXTRACTOR CONNECTION";
final string EXTRACTOR = "ws://localhost:9090/basic";
final string EXTRACTOR2 = "ws://localhost:9091/basic";



@http:WebSocketServiceConfig {
    path: "/api/ws"
}

service RequestService on new http:Listener(9092) {

  resource function onOpen(http:WebSocketCaller caller) {

        http:WebSocketClient wsClientEp = new(
            EXTRACTOR,
            {callbackService: ClientService1,
            readyOnConnect: false,
            maxFrameSize: 2147483648
        });
        http:WebSocketClient wsClientEp2 = new(
            EXTRACTOR2,
            {callbackService: ClientService2,
            readyOnConnect: false,
            maxFrameSize: 2147483648
        });

        caller.setAttribute(ASSOCIATED_CONNECTION, wsClientEp);
        wsClientEp.setAttribute(ASSOCIATED_CONNECTION, wsClientEp2);
        wsClientEp2.setAttribute(ASSOCIATED_CONNECTION, caller);

        var err = wsClientEp->ready();
        if (err is http:WebSocketError) {
            log:printError("Error calling ready on client 1", err);
        }

        err = wsClientEp2->ready();
        if (err is http:WebSocketError) {
            log:printError("Error calling ready on client 2", err);
        }
    }

    resource function onText(http:WebSocketCaller caller, string text, boolean finalFrame) {

        http:WebSocketClient clientEp = getAssociatedClientEndpoint(caller);
        var err = clientEp->pushText(text, finalFrame);
        if (err is http:WebSocketError) {
            log:printError("Error occurred when sending text message", err);
        }
    }


    resource function onError(http:WebSocketCaller caller, error err) {

       http:WebSocketClient clientEp = getAssociatedClientEndpoint(caller);
       var e = clientEp->close(statusCode = 1011, reason = "Unexpected condition");
       if (e is http:WebSocketError) {
           log:printError("Error occurred when closing the connection", e);
       }
       _ = caller.removeAttribute(ASSOCIATED_CONNECTION);
       log:printError("Unexpected error hence closing the connection", err);
   }

   resource function onClose(http:WebSocketCaller caller, int statusCode, string reason) {

       http:WebSocketClient clientEp = getAssociatedClientEndpoint(caller);
       var err = clientEp->close(statusCode = statusCode, reason = reason);
       if (err is http:WebSocketError) {
           log:printError("Error occurred when closing the connection", err);
       }
       _ = caller.removeAttribute(ASSOCIATED_CONNECTION);
   }
}

service ClientService1 = @http:WebSocketServiceConfig {} service {

    resource function onText(http:WebSocketClient caller, string text, boolean finalFrame) {
        http:WebSocketClient clientEp2 = getAssociatedClientEndpointFromClient(caller);
        var err = clientEp2->pushText(text, finalFrame);
        if (err is http:WebSocketError) {
            log:printError("Error occurred when sending text message", err);
        }
    }

    resource function onError(http:WebSocketClient caller, error err) {
        http:WebSocketClient clientEp2 = getAssociatedClientEndpointFromClient(caller);
        var e = clientEp2->close(statusCode = 1011, reason = "Unexpected condition");
        if (e is http:WebSocketError) {
            log:printError("Error occurred when closing the connection", err = e);
        }
        _ = caller.removeAttribute(ASSOCIATED_CONNECTION);
        log:printError("Unexpected error hense closing the connection", err);
    }

    resource function onClose(http:WebSocketClient caller, int statusCode, string reason) {
        http:WebSocketClient clientEp2 = getAssociatedClientEndpointFromClient(caller);
        var err = clientEp2->close(statusCode = statusCode, reason = reason);
            if (err is http:WebSocketError) {
                log:printError("Error occurred when closing the connection", err);
            }
        _ = caller.removeAttribute(ASSOCIATED_CONNECTION);
    }
};

service ClientService2 = @http:WebSocketServiceConfig {} service {

    resource function onText(http:WebSocketClient caller, string text, boolean finalFrame) {
        http:WebSocketCaller serverEp = getAssociatedServerEndpoint(caller);
        var err = serverEp->pushText(text, finalFrame);
        if (err is http:WebSocketError) {
            log:printError("Error occurred when sending text message", err);
        }
    }

    resource function onError(http:WebSocketClient caller, error err) {
        http:WebSocketCaller serverEp = getAssociatedServerEndpoint(caller);
        var e = serverEp->close(statusCode = 1011, reason = "Unexpected condition");
        if (e is http:WebSocketError) {
            log:printError("Error occurred when closing the connection", err = e);
        }
        _ = caller.removeAttribute(ASSOCIATED_CONNECTION);
        log:printError("Unexpected error hense closing the connection", err);
    }

    resource function onClose(http:WebSocketClient caller, int statusCode, string reason) {
        http:WebSocketCaller serverEp = getAssociatedServerEndpoint(caller);
        var err = serverEp->close(statusCode = statusCode, reason = reason);
            if (err is http:WebSocketError) {
                log:printError("Error occurred when closing the connection", err);
            }
        _ = caller.removeAttribute(ASSOCIATED_CONNECTION);
    }
};

function getAssociatedClientEndpoint(http:WebSocketCaller ep) returns (http:WebSocketClient) {
    http:WebSocketClient wsClient = <http:WebSocketClient>ep.getAttribute(ASSOCIATED_CONNECTION);
    return wsClient;
}

function getAssociatedServerEndpoint(http:WebSocketClient ep) returns (http:WebSocketCaller) {
    http:WebSocketCaller wsEndpoint = <http:WebSocketCaller>ep.getAttribute(ASSOCIATED_CONNECTION);
    return wsEndpoint;
}

function getAssociatedClientEndpointFromClient(http:WebSocketClient ep) returns (http:WebSocketClient) {
    http:WebSocketClient wsEndpoint = <http:WebSocketClient>ep.getAttribute(ASSOCIATED_CONNECTION);
    return wsEndpoint;
}

Note that I have change the urls a bit for testing.

user_35995350
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