TomTom::Matrix: Handle error responses from TomTom

Occasionally, the following error would appear in our logs:

    NoMethodError
    RouteWayCostWorker/perform

    Error message
    NoMethodError: undefined method `each_with_index' for nil:NilClass

    Stack trace (show Rails)
                                 /app/lib/tom_tom/matrix.rb:  83:in `extract_costs_to_way_costs!'
                                 /app/lib/tom_tom/matrix.rb:  23:in `matrix'
                                        /app/lib/tom_tom.rb:  24:in `matrix'
             /app/app/services/route_way_cost_calculator.rb:   8:in `calculate!'
                  /app/app/workers/route_way_cost_worker.rb:  12:in `perform'
    …ems/2.3.0/gems/sidekiq-4.2.10/lib/sidekiq/processor.rb: 167:in `execute_job'
    …ems/2.3.0/gems/sidekiq-4.2.10/lib/sidekiq/processor.rb: 139:in `block (5 levels) in process'
     /var/lib/gems/2.3.0/gems/sidekiq-4.2.10/lib/sidekiq.rb:  36:in `block in <module:Sidekiq>'
    …ems/2.3.0/gems/sidekiq-4.2.10/lib/sidekiq/processor.rb: 135:in `block (4 levels) in process'
    ….0/gems/sidekiq-4.2.10/lib/sidekiq/middleware/chain.rb: 128:in `block in invoke'
    ….0/gems/sidekiq-4.2.10/lib/sidekiq/middleware/chain.rb: 130:in `block in invoke'
    …-4.2.10/lib/sidekiq/middleware/server/active_record.rb:   6:in `call'
    ….0/gems/sidekiq-4.2.10/lib/sidekiq/middleware/chain.rb: 130:in `block in invoke'
    …idekiq-4.2.10/lib/sidekiq/middleware/server/logging.rb:  10:in `call'
    ….0/gems/sidekiq-4.2.10/lib/sidekiq/middleware/chain.rb: 130:in `block in invoke'
    …kiq-4.2.10/lib/sidekiq/middleware/server/retry_jobs.rb:  74:in `call'
    ….0/gems/sidekiq-4.2.10/lib/sidekiq/middleware/chain.rb: 130:in `block in invoke'
    ….0/gems/sidekiq-4.2.10/lib/sidekiq/middleware/chain.rb: 133:in `invoke'
    …ems/2.3.0/gems/sidekiq-4.2.10/lib/sidekiq/processor.rb: 134:in `block (3 levels) in process'
    …/gems/2.3.0/gems/sidekiq-4.2.10/lib/sidekiq/logging.rb:  32:in `with_context'
    …ems/2.3.0/gems/sidekiq-4.2.10/lib/sidekiq/processor.rb: 132:in `block (2 levels) in process'
    …ems/2.3.0/gems/sidekiq-4.2.10/lib/sidekiq/processor.rb: 183:in `stats'
    …ems/2.3.0/gems/sidekiq-4.2.10/lib/sidekiq/processor.rb: 131:in `block in process'
     /var/lib/gems/2.3.0/gems/sidekiq-4.2.10/lib/sidekiq.rb:  35:in `block in <module:Sidekiq>'
    …ems/2.3.0/gems/sidekiq-4.2.10/lib/sidekiq/processor.rb: 126:in `process'
    …ems/2.3.0/gems/sidekiq-4.2.10/lib/sidekiq/processor.rb:  82:in `process_one'
    …ems/2.3.0/gems/sidekiq-4.2.10/lib/sidekiq/processor.rb:  70:in `run'
    …lib/gems/2.3.0/gems/sidekiq-4.2.10/lib/sidekiq/util.rb:  17:in `watchdog'
    …lib/gems/2.3.0/gems/sidekiq-4.2.10/lib/sidekiq/util.rb:  26:in `block in safe_thread'

My best guess is that this was caused by TomTom responding with an
error, which we weren't handling previously. In that case, the response
would be a JSON string, but include an `'error'` field instead of
`'matrix'` and `'summary'`. Thus, when we'd try to
`matrix_json['matrix']`, it would fail.

Add a new method that checks for errors before we try to parse
`WayCost`s. If a server error is detected, we log the message to the
Rails log and return an empty array.

Refs #6884

1 files changed, 18 insertions, 1 deletions

diff --git a/lib/tom_tom/matrix.rb b/lib/tom_tom/matrix.rb
index b0c8cc335..b57495f3f 100644
--- a/lib/tom_tom/matrix.rb
+++ b/lib/tom_tom/matrix.rb
@@ -20,11 +20,19 @@ module TomTom
         req.body = build_request_body(points)
       end
 
+      matrix_json = JSON.parse(response.body)
+
+      check_for_error_response(matrix_json)
+
       extract_costs_to_way_costs!(
         way_costs,
         points_with_ids,
-        JSON.parse(response.body)
+        matrix_json
       )
+    rescue RemoteError => e
+      Rails.logger.error "TomTom::Matrix server error: #{e}"
+
+      []
     end
 
     def points_from_way_costs(way_costs)
@@ -76,6 +84,12 @@ module TomTom
       })
     end
 
+    def check_for_error_response(matrix_json)
+      if matrix_json.has_key?('error')
+        raise RemoteError, matrix_json['error']['description']
+      end
+    end
+
     def extract_costs_to_way_costs!(way_costs, points, matrix_json)
       way_costs = []
 
@@ -110,5 +124,8 @@ module TomTom
 
       way_costs
     end
+
+
+    class RemoteError < RuntimeError; end
   end
 end