Cache problem running two consecutive HTTP GET requests from an APP1 to an APP2

问题

I use Ruby on Rails 3 and I have 2 applications (APP1 and APP2) working on two subdomains:

app1.domain.local
app2.domain.local

and I am tryng to run two consecutive HTTP GET requests from APP1 to APP2 like this:

Code in APP1 (request):

before_filter :run_request

def run_request
    response1 = Net::HTTP.get( URI.parse("http://app2.domain.local?test=first&id=1") )
    response2 = Net::HTTP.get( URI.parse("http://app2.domain.local/test=second&id=1") )
end

Code in APP2 (response):

before_filter :run_response

def run_response
    respond_to do |format|
      if <model_name>.find(params[:id]).<field_name> == "first"
        <model_name>.find(params[:id]).update_attribute ( <field_name>, <field_value> ) 
        format.xml { render :xml => <model_name>.find(params[:id]).<field_name> }
      elsif <model_name>.find(params[:id]).<field_name> == "second"
        format.xml { render :xml => <model_name>.find(params[:id]).<field_name> }
      end
    end
end

After the first request I get the correct XML (response1 is what I expect), but on the second it isn't (response2 isn't what I expect). Doing some tests I found that the second time that <model_name>.find(params[:id]).<field_name> run (for the elsif statements) it returns always a blank value so that the code in the elseif statement is never run.

Is it possible that the problem is related on caching <model_name>.find(params[:id]).<field_name>?

NOTICE

If I try this code

respond_to do |format|
  if <model_name>.find(params[:id]).<field_name> == "first"
    <model_name>.find(params[:id]).update_attribute ( <field_name>, <field_value> ) 
    format.xml { render :xml => <model_name>.find(params[:id]).<field_name> }
  else
    format.xml { render :xml => <model_name>.find(params[:id]) }
  end
end

the response2 is the whole <model_name>.find(params[:id] object. Note that I removed the "elsif" condition (in order to run the second request, so that I can get response2) and I changed the code from

format.xml { render :xml => <model_name>.find(params[:id]) }

format.xml { render :xml => <model_name>.find(params[:id]).<field_name> }

P.S.: I read about eTag and Conditional GET, but I am not sure that I must use that approach. I would like to keep all simple.

回答1:

It is possible the query is cached at the application controller level. Rails destroys query caches at the end of actions, but your queries are not in an action.

For what it's worth the code in APP2 most likely shouldn't be in the application controller, but in an action in the controller. That is much more RESTful, and will probably also take care of caching issues (as Rails will clear the query cache between APP1's requests).

来源：https://stackoverflow.com/questions/4636704/cache-problem-running-two-consecutive-http-get-requests-from-an-app1-to-an-app2

标签

ruby-on-rails

http

caching

get

request