I'm trying to make a simple http request/response communication between two of my pages on App Engine. Here's the code:
class MainHandler(webapp.RequestHandler):
def get(self):
values = {'id' : '9',
'number' : '10001',
'age' : '15828',
'name' : 'Squeak' }
data = urllib.urlencode(values)
request = urllib2.Request("http://localhost:8082/post", data)
response = urllib2.urlopen(request)
content = response.read()
self.response.out.write(content)
class PostHandler(webapp.RequestHandler):
def post(self):
self.response.out.write(str(self.request.get('id')) + '<br>' + str(self.request.get('number')) + '<br>' + str(self.request.get('age')) + '<br>' + self.request.get('name'))
I assigned theses handlers to '/' and '/post' and what happens is that I get a DeadLineExceedError waiting for the HTTP Response, which, I guess was blocked because "the estabilished connection was aborted by the software in your host machine" [Errno 10053]. I tried disabling the firewall/antivirus and still it didn't work. Obviously I'm new to App Engine, but this stuff is supposed to be straightforward. Why is it happening? I've been struggling with this for some time already.
You don't get to choose the ports you want to use (serve data on) for app engine for a start, so forget about trying that.
Have you tried this on the deployed server then? As the comment notes, behaviour on local and deployed can be very different, especially where there are multiple requests.
Pages on app engine can't talk to each other, every time a request completes everything is forgotten about.
So what is probably happening with your code is this:
You make a post request.
That post request cannot be dealt with, as you are still dealing with the original get. So the post is queued until the get is complete.
The get never completes as it's waiting for the post to complete.
Or something like that anyway.
It would perhaps be better if you explained what you were trying to achieve with this code and re-ask that as a separate question. As there's no real way to "fix" this as is.
Related
I want to send a message to a websocket client when it connects to the server on AWS lambda and API gateway. Currently, I use wscat as a client. Since the response 'connected' is not shown on the wscat console when I connect to the server, I added post_to_connection to send a message 'hello world' to the client. However, it raises GoneException.
An error occurred (GoneException) when calling the PostToConnection
operation
How can I solve this problem and send some message to wscat when connecting to the server?
My python code is below. I use Python 3.8.5.
import os
import boto3
import botocore
dynamodb = boto3.resource('dynamodb')
connections = dynamodb.Table(os.environ['TABLE_NAME'])
def lambda_handler(event, context):
domain_name = event.get('requestContext',{}).get('domainName')
stage = event.get('requestContext',{}).get('stage')
connection_id = event.get('requestContext',{}).get('connectionId')
result = connections.put_item(Item={ 'id': connection_id })
apigw_management = boto3.client('apigatewaymanagementapi',
endpoint_url=F"https://{domain_name}/{stage}")
ret = "hello world";
try:
_ = apigw_management.post_to_connection(ConnectionId=connection_id,
Data=ret)
except botocore.exceptions.ClientError as e:
print(e);
return { 'statusCode': 500,
'body': 'something went wrong' }
return { 'statusCode': 200,
"body": 'connected'};
Self-answer: you cannot post_to_connection to the connection itself in onconnect.
I have found that the GoneException can occur when the client that initiated the websocket has disconnected from the socket and its connectionId can no longer be found. Is there something causing the originating client to disconnect from the socket before it can receive your return message?
My use case is different but I am basically using a DB to check the state of a connection before replying to it, and not using the request context to do that. This error's appearance was reduced by writing connectionIds to DynamoDB on connect, and deleting them from the table upon disconnect events. Messaging now writes to connectionIds in the table instead of the id in the request context. Most messages go through but some errors are still emitted when the client leaves the socket but does not emit a proper disconnect event which leaves orphans in the table. The next step is to enforce item deletes when irregular disconnections occur. Involving a DB may be overkill for your situation, just sharing what helped me make progress on the GoneException error.
We need to post to connection after connecting (i.e. when the routeKey is not $connect)
routeKey = event.get('requestContext', {}).get('routeKey')
print(routeKey) # for debugging
if routeKey != '$connect': # if we have defined multiple route keys we can choose the right one here
apigw_management.post_to_connection(ConnectionId=connection_id, Data=ret)
#nemy's answer is totally true but it doesn't explain the reason. So, I just want to explain...
So, first of all What is GoneException or GoneError 410 ?
A 410 Gone error occurs when a user tries to access an asset which no longer exists on the requested server. In order for a request to return a 410 Gone status, the resource must also have no forwarding address and be considered to be gone permanently.
you can find more details about GoneException in this article.
In here, GoneException has occured; it means that the POST connection we are trying to make, doesn't exist - which fits perfectly in the scenario. Because we still haven't established the connection between Client and Server. The way APIGatewayWebsocketAPIs work is that you request an Endpoint(Route) and that Endpoint will invoke that Lambda Function (In our case it is ConnectionLambdaFunction for $connect Route).
Now, if The Lambda function resolves with statusCode: 200 then and only then the API Gateway will allow the connection to be established. So, basically untill we return statusCode: 200 from our Lambda Function we are not connected and untill then we are totally unknown to server and thats why the Post call that has been made before the return statement itself will throw an error.
I am building a BlogApp and I am stuck on a Problem.
What i am trying to do
I am trying to implement a feature that ,`If user is connected to internet then everything works fine BUT if user is not connected to internet then show a message like "You're not Connected to Internet".
What have i tried
I also tried channels but then i think internet connection are far away from Django-channels.
I also tried this :
url = "http://127.0.0.1:8000/"
timeout = 5
try:
request = requests.get(url, timeout=timeout)
print("Connected to the Internet")
except (requests.ConnectionError, requests.Timeout) as exception:
print("No INTERNET")
But it is keep showing me :
'Response' object has no attribute 'META'
I don't know what to do.
Any help would be Appreciated.
Thank You in Advance
It is not easy to know whether you're connected to the internet. In fact it is not even clear what this means. It depends a lot on the context.
In many practical cases it means, that your network setup is setup such, that you can access a DNS server and that you can access at least one machine on the internet.
You could just use one known url like for example "https://google.com" or "https://stackoverflow.com".
However this means that:
your test will fail if given service is for any reason down
you create requests to a server that isn't yours.
If you know, that the application should access your special web service, then you could use the url of your special web service:
url = "https://your_special_webservice.yourdomain"
Side information:
If you put the code in your question into a django view, that handles http requests, then you should probably write something like:
request = requests.get(url, timeout=timeout)
instead of
response = requests.get(url, timeout=timeout)
Otherwise you will overwrite the request object, of your django view
and this is probably what provoked your error message:
'Response' object has no attribute 'META'
I've struggled for two days to understand how REST API Gateways should return GET requests to browsers when the backend service runs on AMQP (without using Web Sockets or polling).
Have successfully RPC'ed betweeen AMQP service (with RabbitMqs reply_to & correlation_id), but with Flask HTTP request waiting I'm still lost.
gateway.py - Response Handler Inside The HTTP Handler, Times out
def products_get():
def handler(ch=None, method=None, properties=None, body=None):
if body:
return body
return False
return_queue = 'products.get.return'
broker.channel.queue_declare(return_queue)
broker.channel.basic_consume(handler, return_queue)
broker.publish(exchange='', routing_key='products.get', body='Request data', properties=pika.BasicProperties(reply_to=return_queue))
now = time.time() # for timeout. Not having this returns 'no content' immediately
while time.time() < now + 1:
if handler():
return handler()
return 'Time out'
POST/PUT can simply send the AMQP message, return 200/201/201 immediately and the service work at its own pace. A separate REST interface just for GET requests seems implausible, but don't know the other options.
Regards
I think what you're asking is "how to perform asynchronous GET requests". and I reckon that the answer is - you can't. and should not. its bad practice or bad design. and it does not scale.
Why are you trying to get your GET response payload from AMQP?
If the paylaod (the content of the response) can be pulled from some DB, just pull it from there. that's called a synchronous request.
If the payload must be processed in some backend, send it away and don't have the requester wait for a response. You could assign some ID and have the requester ask again later (or collect some callback URL from the requester and have your backend POST the response once its ready - less common design).
EDIT:
so, given that you have to work with AMQP-backed backend, I would do something a little more elaborate: spawn a thread or a process in your front end that would constantly consume from AMQP and store the results locally or in some db. and serve GET results based on data that you stored locally. if the data isn't yet available, just return 404. ideally you'll need to re-shape your API: split it into "post" requests (that would trigger work at the backend) and "get" requests (that would return the results if they're available).
I'm working on my first Flask app (version 0.10.1), and also my first Python (version 3.5) app. One of its pieces needs to work like this:
Submit a form
Run a Celery task (which makes some third-party API calls)
When the Celery task's API calls complete, send a JSON post to another URL in the app
Get that JSON data and update a database record with it
Here's the relevant part of the Celery task:
if not response['errors']: # response comes from the Salesforce API call
# do something to notify that the task was finished successfully
message = {'flask_id' : flask_id, 'sf_id' : response['id']}
message = json.dumps(message)
print('call endpoint now and update it')
res = requests.post('http://0.0.0.0:5000/transaction_result/', json=message)
And here's the endpoint it calls:
#app.route('/transaction_result/', methods=['POST'])
def transaction_result():
result = jsonify(request.get_json(force=True))
print(result.flask_id)
return result.flask_id
So far I'm just trying to get the data and print the ID, and I'll worry about the database after that.
The error I get though is this: requests.exceptions.ConnectionError: None: Max retries exceeded with url: /transaction_result/ (Caused by None)
My reading indicates that my data might not be coming over as JSON, hence the Force=True on the result, but even this doesn't seem to work. I've also tried doing the same request in CocoaRestClient, with a Content-Type header of application/json, and I get the same result.
Because both of these attempts break, I can't tell if my issue is in the request or in the attempt to parse the response.
First of all request.get_json(force=True) returns an object (or None if silent=True). jsonify converts objects to JSON strings. You're trying to access str_val.flask_id. It's impossible. However, even after removing redundant jsonify call, you'll have to change result.flask_id to result['flask_id'].
So, eventually the code should look like this:
#app.route('/transaction_result/', methods=['POST'])
def transaction_result():
result = request.get_json()
return result['flask_id']
And you are absolutely right when you're using REST client to test the route. It crucially simplifies testing process by reducing involved parts. One well-known problem during sending requests from a flask app to the same app is running this app under development server with only one thread. In such case a request will always be blocked by an internal request because the current thread is serving the outermost request and cannot handle the internal one. However, since you are sending a request from the Celery task, it's not likely your scenario.
UPD: Finally, the last one reason was an IP address 0.0.0.0. Changing it to the real one solved the problem.
I have created a web service in django and its hosted on a shared server.The django web service respond to request from a game made in unity. But whenever game tries to request a django Web service url the server send empty resonse.Response is always:
WWW Error: server return empty string
The Unity webplayer expects a http served policy file named "crossdomain.xml" to be available on the domain you want to access with the WWW class, (although this is not needed if it is the same domain that is hosting the unity3d file).So I placed a file "crossdomain.xml" at the root of my domain ,but still i am getting same empty reply.Help plz...
EDIT:
I tried it through browser my service works fine and reply with proper response.And you know what My game can communicate to django web service when both are running on local machine.But now the django project is hosted on actual server and when game tried accessing service it never get response :(
url.py
urlpatterns = patterns('',
url(r'^crossdomain.xml$',views.CrossDomain),
url(r'^ReadFile/$',views.ReadFile),
)
views.py
def CrossDomain(request):
f = open(settings.MEDIA_ROOT+'jsondata/crossdomain.xml', 'r')
data = f.read()
f.close()
return HttpResponse(data, mimetype="application/xml")
def ReadFile(request):
f = open(settings.MEDIA_ROOT+'jsondata/some_file.json', 'r')
data = f.read()
f.close()
return HttpResponse(data, mimetype="application/javascript")
def Test(request):
return HttpResponse("Hello", mimetype="text/plain")
As I said using django for this is slight overkill because you could just serve them. Point aside though. If your serving on a different server it could be
A) Connection problems mean that your response is lost
B) Firewall issues mean that the request mean something
C) The server isn't setup correctly and therefore it justs get an error.
You need to test the response on the server. so is you access the page on the server through your browser. If so then make the game make a request and check the server error and access logs. In the apache access log you should see something like
GET "/url" 200 each time a request is made.
If you don't see any request getting through then either the request isn't made or its been lost.
If you do then the problem is in the code somewhere.