at Object.generateQueryString (CanvasProxy.js:17)
at Function.request (CanvasProxy.js:21)
at Object.ajax (CanvasProxy.js:135)
at O (CanvasProxy.js:91)
at g (CanvasProxy.js:30)

Sfdc.canvas.client.refreshSignedRequest(function(data){
if(data.status === 200){
    var signedRequest = data.payload.response;
    var part = signedRequest.split('.')[1];
    var obj = JSON.parse(Sfdc.canvas.decode(part));
    Sfdc.canvas.client.subscribe(
        obj.client, {
            name: 'myapp1.testEvent' ,
            onData : function(inp){
                try{
                    console.log(inp);
                    Sfdc.canvas.client.ajax(
                        obj.context.links.restUrl + 'composite/tree/Attachment/',
                        {
                            client : obj.client,
                            method : 'POST',
                            headers : { "Authorization" : "OAuth " + obj.client.oauthToken, "Content-Type" : "application/json" },
                            data : { "records": [{"attributes" : {"type" : "Attachment", "referenceId" : "ref1"}, "name" : "test1234", "parentId" : "a040O00000Xd4rp" ,"Body" : "tset1"}]},
                            success : function(data) { alert("Status: " + data.status); }
                        }
                    );
                }
                catch(err){
                    alert(err);
                }
            }
        }
    );
}