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, 29 insertions, 0 deletions

diff --git a/spec/lib/tom_tom/matrix_spec.rb b/spec/lib/tom_tom/matrix_spec.rb
index 605f1d254..be63447d4 100644
--- a/spec/lib/tom_tom/matrix_spec.rb
+++ b/spec/lib/tom_tom/matrix_spec.rb
@@ -149,6 +149,35 @@ RSpec.describe TomTom::Matrix do
     end
   end
 
+  describe "#check_for_error_response" do
+    it "raises an RemoteError when an 'error' key is present in the response" do
+      response_body = {
+        'formatVersion' => '0.0.1',
+        'error' => {
+          'description' => 'Output format: csv is unsupported.'
+        }
+      }
+
+      expect {
+        matrix.check_for_error_response(response_body)
+      }.to raise_error(
+        TomTom::Matrix::RemoteError,
+        'Output format: csv is unsupported.'
+      )
+    end
+
+    it "doesn't raise errors with a normal response" do
+      response_body = {
+        'formatVersion' => '0.0.1',
+        'matrix' => []
+      }
+
+      expect {
+        matrix.check_for_error_response(response_body)
+      }.to_not raise_error
+    end
+  end
+
   describe "#extract_costs_to_way_costs!" do
     it "puts distance & time costs in way_costs" do
       way_costs = [