I'm trying to use RestClient and Faraday to query an endpoint which returns multiple files in a multipart response. How do I parse the multipart envelopes in the response body? Rack::Utils::Multipart.parse_multipart would have done it, but in my case, this is outside of Rack. I'm open to using a different HTTP client if its helps.
Almost none of the popular HTTP clients, in almost any language, handle multipart responses from a server. In fact I'd be surprised if you can easily find HTTP servers with baked in multipart response capabilities. It's just not a common use case.
You'll find the converse true though, most HTTP servers handle multipart responses built from clients.
The good news is that "multipart" is just content type like XML or JSON, so you should be able to attach any old multipart parser to the response body after you've made the request with your favorite HTTP client.
Some parsers to consider:
https://github.com/danabr/multipart-parser
Rack::Multipart::Parser
Shoehorn your data into Rack::Utils.parse_multipart
Related
I was playing around with GZIP compression recently and the way I understand the following:
Client requests some files or data from a Web Server. Client also sends a header that says "Accept-Encoding,gzip"
Web Server retrieves the files or data, compresses them, and sends them back GZIP compressed to the client. The Web Server also sends a header saying "Content-Encoded,gzip" to note to the Client that the data is compressed.
The Client then de-compresses the data/files and loads them for the user.
I understand that this is common practice, and it makes a ton of sense when you need to load a page that requires a ton of HTML, CSS, and JavaScript, which can be relatively large, and add to your browser's loading time.
However, I was trying to look further into this and why is it not common to GZIP compress a request body when doing a POST call? Is it because usually request bodies are small so the time it takes to decompress the file on the web server is longer than it takes to simply send the request? Is there some sort of document or reference I can have about this?
Thanks!
It's uncommon because in a client - server relationship, the server sends all the data to the client, and as you mentioned, the data coming from the client tends to be small and so compression rarely brings any performance gains.
In a REST API, I would say that big request payloads were common, but apparently Spring Framework, known for their REST tools, disagree - they explicitly say in their docs here that you can set the servlet container to do response compression, with no mention of request compression. As Spring Framework's mode of operation is to provide functionality that they think lots of people will use, they obviously didn't feel it worthwhile to provide a ServletFilter implementation that we users could employ to read compressed request bodies.
It would be interesting to trawl the user mailing lists of tomcat, struts, jackson, gson etc for similar discussions.
If you want to write your own decompression filter, try reading this: How to decode Gzip compressed request body in Spring MVC
Alternatively, put your servlet container behind a web server that offers more functionality. People obviously do need request compression enough that web servers such as Apache offer it - this SO answer summarises it well already: HTTP request compression - you'll find the reference to the HTTP spec there too.
Very old question but I decided to resurrect it because it was my first google result and I feel the currently only answer is incomplete.
HTTP request compression is uncommon because the client can't be sure the server supports it.
When the server sends a response, it can use the Accept-Encoding header from the client's request to see if the client would understand a gzipped response.
When the client sends a request, it can be the first HTTP communication so there is nothing to tell the client that the server would understand a gzipped request. The client can still do so, but it's a gamble.
Although very few modern http servers would not know gzip, the configuration to apply it to request bodies is still very uncommon. At least on nginx, it looks like custom Lua scripting is required to get it working.
Don't do it, for no other reason than security. Firewalls have a hard or impossible time dealing with compressed input data.
I'm using Ruby on Rails. Here is the requirement: the client (a native mobile app developed by me) will send a http post request to my Ruby code, my code will add some extra http headers (based on some business logic), then I need to "forward" or "redirect" this post request to another backend server (which has a REST service) and return its response back to the client.
I have been able to write a rack middleware to intercept the post request and add the extra headers. Originally I thought I could just use http redirect (status code: 307 for post request). But the problem is that the extra headers could NOT be submitted, which is the whole point of my code. So this isn't http redirect or forwarding per se, it's more like transforming a request.
I'm able to make a separate post request from my code using net http. This works. But I have to COPY data from the incoming request to my outgoing request (eg form data, http headers). This copying seems a bit tedious.
I would prefer some kind of simple "repackaging" (which is akin to http redirect or forwarding), that is I copy the whole incoming request to the outgoing request, slap on the extra headers and send it to the destination URL and be done with. I am not sure how to do this, and if doing it this way is even a good idea. For example, HTTP_USER_AGENT shows the OS, browser type of the client, when I'm making a new request, I probably don't need to send this on.
Alternatively, I can copy only the application specific data, because they're all the backend server (the destination of this "redirect") cares about. But I'm averse to hardcoding attributes in my code, causing close-coupling with the client (our native mobile app). Ideally I only copy application-specific data without hardcoding their attribute names. Is this possible? If so, how?
Any advice would be appreciated.
Thank you.
HTTP does not allow redirects for anything other than GET request.
(This is not technically correct but using HTTP 307 is kind of sketchy - see https://softwareengineering.stackexchange.com/questions/99894/why-doesnt-http-have-post-redirect)
If you need too send a POST request to another server for processing then using a proxy as you already seem to be doing is the correct solution.
Recreating the request in the proxy may seem tedious but it actually serves as a guarantee that you are calling the other servers "API" correctly.
While you can simply loop through the request headers:
uri = URI('http://www.example.com/todo.cgi')
req = Net::HTTP::Post.new(uri)
request.headers.each do |key, value|
req[key] = value
end
And pass the request form data:
req.set_form_data = request.request_parameters
You should ask yourself if it really is prudent to proxy everything.
See http://api.rubyonrails.org/classes/ActionDispatch/Request.html
I have a Delphi 6 application that uses an Indy TIdTCPClient instance to communicate with a web server. The reason I am not using an HTTP client directly is because the the server is an image streaming server that uses the same socket connection for receiving the command to start streaming as it does to start "pushing" images back to you. In other words, after you send it a typical HTTP POST request, it replies with an HTTP response, and immediately after that it starts sending out a stream of JPEG images.
I already know how to craft a proper POST request and send it using the TIdTCPClient WriteBuffer() method and then use the ReadBuffer() method to receive reply data. What I'd like to do instead is to send a POST request and then ask Indy to wait for a typical HTTP response including retrieving all the bytes in the response body if there is a Content-Length header variable. I of course want it to leave the JPEG frames intact that may have piled in after the HTTP response in the receive queue until I start requesting them (that is, I don't want it including any of the JPEG frames in the HTTP response to my streaming request command until I ask for them using a successive read call).
Is there a method that I can call on a TIdTCPClient that will retrieve completely a typical HTTP response with body content, and nothing else? I thought about using SendCmd() and checking the LastCmdResult property (type: TIdRFCReply) for the response, but I can't tell from the Indy documentation if it retrieves the response body content too if there is a Content-Length header variable as part of the response it returns, nor can I tell if it leaves the rest of the receive queue after the response intact.
What is the best way to accomplish this mixed mode interaction with an HTTP web server that pushes out a stream of JPEG frames right after you make the HTTP request to start streaming?
Also, if there is a clever way to have Indy split the frames using the JPEG frame WINBONDBOUDARY delimiting string, rather than accumulating blocks of data and parsing them out myself, please share that technique.
The correct way to read an HTTP response is to first read the CRLF-delimited response headers line-by-line until a blank line is encountered, aka a CRLF+CRLF sequence, then you can use those headers to decide how to read the remaining response data. The headers will tell you not only what kind of stream is being sent (via the Content-Type header), but also how the data is being framed (Content-Length, Transfer-Encoding: chunked, something specific to the particular Content-Type, etc).
To receive the headers, you can use the connection's Capture() method, setting its ADelim parameter to a blank string.
How you read the remaining data afterwards depends on the actual formatting/framing of the stream. Without knowing exactly what kind of stream you are receiving, there is no way to advise you how best to read it, as there are several different types of streaming protocols used by HTTP servers, and most of them are not standardized. Provide that information, then I/we can show you how to implement it with Indy.
You cannot use SendCmd() as the HTTP protocol does not format its responses in a way that is compatible with that method.
Is it possible to POST "url encoded" parameters to a remote web service instead of JSON or XML ?
My rails application consumes a web service which takes URL encoded parameters (content-type: application/x-www-form-urlencoded) in POST requests and give JSON answers.
Is this kind of RESTful services common ?
When you make a hit to a JSON or XML web service using Ajax then the parameters are just getting encoded as either GET or POST, and is typically sent using the application/x-www-form-urlencoded content type anyway (see http://api.jquery.com/jQuery.ajax/ for an example specific to jQuery).
So, basically, yes, it is possible to send data in any format (JSON, XML, BSON etc.) in this manner.
I am dealing with a third-party api here and I need to send HTTP Post request represented in XML. How should I go about doing this in Rails? Which library/method if any will allow me to do this?
Try net/http package, in particular post method. There're examples too.
As to xml part, you can send any data you want as long as it's string.
A good starting point would be Net::HTTP library: http://stdlib.rubyonrails.org/libdoc/net/http/rdoc/index.html