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Nesting too deep error while retrieving JSON using HTTParty

I am writing a very simple proxy for reddit api, so I can make JSONP requests with cross domains (reddit does not allow me to respond to JSONP).

I use the HTTParty stone to make a call and get a response, which I immediately endure as json.

I get subreddit json fine so far with this as my route:

match "r/:name" => "api#subreddit"

... and this is like my controller action:

 def subreddit render :json => HTTParty.get("http://www.reddit.com/r/" + params[:name] + "/.json"), :callback => params[:callback] end

As an example, the returned JSON is similar to this: http://www.reddit.com/r/pics/.json

My problem is that I am trying to capture comments for a specific thread.

My route is this:

 match "r/:name/comments/:id" => "api#comments"

... and my action with the controller is this:

  def comments render :json => HTTParty.get("http://www.reddit.com/r/" + params[:name] + "/comments/" + params[:id] + "/.json"), :callback => params[:callback] end

The JSON I want to return can be seen here: http://www.reddit.com/r/pics/comments/rhzgc/.json

When I call this action, I get the following error message:

 MultiJson::DecodeError in ApiController#comments Nesting of 20 is too deep

Full stack trace:

 json (1.6.6) lib/json/common.rb:148:in `parse' json (1.6.6) lib/json/common.rb:148:in `parse' multi_json (1.2.0) lib/multi_json/engines/json_common.rb:9:in `decode' multi_json (1.2.0) lib/multi_json.rb:81:in `decode' httparty (0.8.1) lib/httparty/parser.rb:116:in `json' httparty (0.8.1) lib/httparty/parser.rb:136:in `parse_supported_format' httparty (0.8.1) lib/httparty/parser.rb:103:in `parse' httparty (0.8.1) lib/httparty/parser.rb:66:in `call' httparty (0.8.1) lib/httparty/request.rb:222:in `parse_response' httparty (0.8.1) lib/httparty/request.rb:192:in `handle_response' httparty (0.8.1) lib/httparty/request.rb:75:in `perform' httparty (0.8.1) lib/httparty.rb:391:in `perform_request' httparty (0.8.1) lib/httparty.rb:343:in `get' httparty (0.8.1) lib/httparty.rb:423:in `get' app/controllers/api_controller.rb:12:in `comments' actionpack (3.1.1) lib/action_controller/metal/implicit_render.rb:4:in `send_action' actionpack (3.1.1) lib/abstract_controller/base.rb:167:in `process_action' actionpack (3.1.1) lib/action_controller/metal/rendering.rb:10:in `process_action' actionpack (3.1.1) lib/abstract_controller/callbacks.rb:18:in `block in process_action' activesupport (3.1.1) lib/active_support/callbacks.rb:416:in `_run__2872109728488784816__process_action__2261783022290592822__callbacks' activesupport (3.1.1) lib/active_support/callbacks.rb:386:in `_run_process_action_callbacks' activesupport (3.1.1) lib/active_support/callbacks.rb:81:in `run_callbacks' actionpack (3.1.1) lib/abstract_controller/callbacks.rb:17:in `process_action' actionpack (3.1.1) lib/action_controller/metal/rescue.rb:17:in `process_action' actionpack (3.1.1) lib/action_controller/metal/instrumentation.rb:30:in `block in process_action' activesupport (3.1.1) lib/active_support/notifications.rb:53:in `block in instrument' activesupport (3.1.1) lib/active_support/notifications/instrumenter.rb:21:in `instrument' activesupport (3.1.1) lib/active_support/notifications.rb:53:in `instrument' actionpack (3.1.1) lib/action_controller/metal/instrumentation.rb:29:in `process_action' actionpack (3.1.1) lib/action_controller/metal/params_wrapper.rb:201:in `process_action' activerecord (3.1.1) lib/active_record/railties/controller_runtime.rb:18:in `process_action' actionpack (3.1.1) lib/abstract_controller/base.rb:121:in `process' actionpack (3.1.1) lib/abstract_controller/rendering.rb:45:in `process' actionpack (3.1.1) lib/action_controller/metal.rb:193:in `dispatch' actionpack (3.1.1) lib/action_controller/metal/rack_delegation.rb:14:in `dispatch' actionpack (3.1.1) lib/action_controller/metal.rb:236:in `block in action' actionpack (3.1.1) lib/action_dispatch/routing/route_set.rb:65:in `call' actionpack (3.1.1) lib/action_dispatch/routing/route_set.rb:65:in `dispatch' actionpack (3.1.1) lib/action_dispatch/routing/route_set.rb:29:in `call' rack-mount (0.8.3) lib/rack/mount/route_set.rb:152:in `block in call' rack-mount (0.8.3) lib/rack/mount/code_generation.rb:96:in `block in recognize' rack-mount (0.8.3) lib/rack/mount/code_generation.rb:89:in `optimized_each' rack-mount (0.8.3) lib/rack/mount/code_generation.rb:95:in `recognize' rack-mount (0.8.3) lib/rack/mount/route_set.rb:141:in `call' actionpack (3.1.1) lib/action_dispatch/routing/route_set.rb:532:in `call' actionpack (3.1.1) lib/action_dispatch/middleware/best_standards_support.rb:17:in `call' rack (1.3.6) lib/rack/etag.rb:23:in `call' rack (1.3.6) lib/rack/conditionalget.rb:25:in `call' actionpack (3.1.1) lib/action_dispatch/middleware/head.rb:14:in `call' actionpack (3.1.1) lib/action_dispatch/middleware/params_parser.rb:21:in `call' actionpack (3.1.1) lib/action_dispatch/middleware/flash.rb:243:in `call' rack (1.3.6) lib/rack/session/abstract/id.rb:195:in `context' rack (1.3.6) lib/rack/session/abstract/id.rb:190:in `call' actionpack (3.1.1) lib/action_dispatch/middleware/cookies.rb:331:in `call' activerecord (3.1.1) lib/active_record/query_cache.rb:62:in `call' activerecord (3.1.1) lib/active_record/connection_adapters/abstract/connection_pool.rb:477:in `call' actionpack (3.1.1) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call' activesupport (3.1.1) lib/active_support/callbacks.rb:392:in `_run_call_callbacks' activesupport (3.1.1) lib/active_support/callbacks.rb:81:in `run_callbacks' actionpack (3.1.1) lib/action_dispatch/middleware/callbacks.rb:28:in `call' actionpack (3.1.1) lib/action_dispatch/middleware/reloader.rb:68:in `call' rack (1.3.6) lib/rack/sendfile.rb:101:in `call' actionpack (3.1.1) lib/action_dispatch/middleware/remote_ip.rb:48:in `call' actionpack (3.1.1) lib/action_dispatch/middleware/show_exceptions.rb:47:in `call' railties (3.1.1) lib/rails/rack/logger.rb:13:in `call' rack (1.3.6) lib/rack/methodoverride.rb:24:in `call' rack (1.3.6) lib/rack/runtime.rb:17:in `call' activesupport (3.1.1) lib/active_support/cache/strategy/local_cache.rb:72:in `call' rack (1.3.6) lib/rack/lock.rb:15:in `call' actionpack (3.1.1) lib/action_dispatch/middleware/static.rb:53:in `call' railties (3.1.1) lib/rails/engine.rb:456:in `call' railties (3.1.1) lib/rails/rack/content_length.rb:16:in `call' railties (3.1.1) lib/rails/rack/log_tailer.rb:14:in `call' rack (1.3.6) lib/rack/handler/webrick.rb:59:in `service' /Users/emcummings/.rvm/rubies/ruby-1.9.2-p290/lib/ruby/1.9.1/webrick/httpserver.rb:111:in `service' /Users/emcummings/.rvm/rubies/ruby-1.9.2-p290/lib/ruby/1.9.1/webrick/httpserver.rb:70:in `run' /Users/emcummings/.rvm/rubies/ruby-1.9.2-p290/lib/ruby/1.9.1/webrick/server.rb:183:in `block in start_thread'

What am I doing wrong here? If the JSON is too large for parsing (I find it hard to believe!), What can I do?

EDIT:

It seems that returning to the standard NET :: HTTP lib solved my problem:

 uri = URI.parse("http://www.reddit.com/r/pics/comments/rhzgc/.json") response = Net::HTTP.get_response(uri) render :json => response.body, :callback => params[:callback] #OK!

... but I'm still curious why I fail with the same call with HTTParty!

Thanks for the help!

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3 answers

Not too much JSON. He is too deeply embedded. HTTParty tries to decode the results that it receives automatically. After stack tracing and HTTParty dependencies HTTParty it relies on multi_json , which uses the json stone.

Inside json there is lib/json/pure/parser.rb . It sets the maximum default depth set, in particular, on line 79. Something in your returned JSON is at 20+ levels, causing an exception.

  if !opts.key?(:max_nesting) # defaults to 19 @max_nesting = 19
+3
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It seems like you can get around this by calling to_json with the max_nesting parameter.

 json = obj.to_json(max_nesting: 50)
+3
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Switch to OJ JSON parser by adding the following to my Gemfile:

 gem 'oj'

and this problem was resolved itself.

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Source: https://habr.com/ru/post/1404029/

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