Aws::DynamoDB::Client describe_table returning nil with VCR

[kdiogenes]

While using Dynamoid with VCR I started to perceive random failures on my tests. I can't identify the root of the problem, but I think it's something related with Aws::DynamoDB::Client describe_table method.

This is the the stacktrace of the error during the test execution:

     NoMethodError:
       undefined method `[]' for nil:NilClass
     # /home/kadu/.rvm/gems/ruby-2.5.1@kceprb/gems/dynamoid-2.2.0/lib/dynamoid/adapter_plugin/aws_sdk_v2.rb:1003:in `hash_key'
     # /home/kadu/.rvm/gems/ruby-2.5.1@kceprb/gems/dynamoid-2.2.0/lib/dynamoid/adapter_plugin/aws_sdk_v2.rb:771:in `key_stanza'
     # /home/kadu/.rvm/gems/ruby-2.5.1@kceprb/gems/dynamoid-2.2.0/lib/dynamoid/adapter_plugin/aws_sdk_v2.rb:429:in `get_item'
     # /home/kadu/.rvm/gems/ruby-2.5.1@kceprb/gems/dynamoid-2.2.0/lib/dynamoid/adapter.rb:151:in `block (3 levels) in <class:Adapter>'
     # /home/kadu/.rvm/gems/ruby-2.5.1@kceprb/gems/dynamoid-2.2.0/lib/dynamoid/adapter.rb:53:in `benchmark'
     # /home/kadu/.rvm/gems/ruby-2.5.1@kceprb/gems/dynamoid-2.2.0/lib/dynamoid/adapter.rb:151:in `block (2 levels) in <class:Adapter>'
     # /home/kadu/.rvm/gems/ruby-2.5.1@kceprb/gems/dynamoid-2.2.0/lib/dynamoid/adapter.rb:91:in `read'
     # /home/kadu/.rvm/gems/ruby-2.5.1@kceprb/gems/dynamoid-2.2.0/lib/dynamoid/finders.rb:100:in `find_by_id'
     # /home/kadu/.rvm/gems/ruby-2.5.1@kceprb/gems/dynamoid-2.2.0/lib/dynamoid/identity_map.rb:31:in `find_by_id'
     # /home/kadu/.rvm/gems/ruby-2.5.1@kceprb/gems/dynamoid-2.2.0/lib/dynamoid/document.rb:118:in `exists?'

The problem in this method is that schema is nil, this is the content of the hash_key method:

@hash_key ||= schema[:key_schema].find { |d| d[:key_type] == HASH_KEY  }.try(:attribute_name).to_sym

I put a breakpoint in dynamoid-2.2.0/lib/dynamoid/adapter_plugin/aws_sdk_v2.rb @ line 804 Dynamoid::AdapterPlugin::AwsSdkV2#describe_table: and this is the output of some calls I have made manually:

    801: def describe_table(table_name, reload = false)
    802:   (!reload && table_cache[table_name]) || begin
    803:     binding.pry
 => 804:     table_cache[table_name] = Table.new(client.describe_table(table_name: table_name).data)
    805:   end
    806: end

[1] pry(#<Dynamoid::AdapterPlugin::AwsSdkV2>)> client.describe_table(table_name: table_name).data
=> #<struct Aws::DynamoDB::Types::DescribeTableOutput table=nil>
[2] pry(#<Dynamoid::AdapterPlugin::AwsSdkV2>)> table_name
=> "ceps-prod"
[3] pry(#<Dynamoid::AdapterPlugin::AwsSdkV2>)> client.describe_table(table_name: table_name).data
=> #<struct Aws::DynamoDB::Types::DescribeTableOutput table=nil>
[4] pry(#<Dynamoid::AdapterPlugin::AwsSdkV2>)> client.describe_table(table_name: table_name).data
=> #<struct Aws::DynamoDB::Types::DescribeTableOutput table=nil>
[5] pry(#<Dynamoid::AdapterPlugin::AwsSdkV2>)> client.describe_table(table_name: table_name).data
=> #<struct Aws::DynamoDB::Types::DescribeTableOutput
 table=
  #<struct Aws::DynamoDB::Types::TableDescription
   attribute_definitions=[#<struct Aws::DynamoDB::Types::AttributeDefinition attribute_name="cep", attribute_type="N">],
   table_name="ceps-prod",
   key_schema=[#<struct Aws::DynamoDB::Types::KeySchemaElement attribute_name="cep", key_type="HASH">],
   table_status="ACTIVE",
   creation_date_time=2018-06-18 00:48:01 -0300,
   provisioned_throughput=
    #<struct Aws::DynamoDB::Types::ProvisionedThroughputDescription
     last_increase_date_time=1969-12-31 21:00:00 -0300,
     last_decrease_date_time=1969-12-31 21:00:00 -0300,
     number_of_decreases_today=0,
     read_capacity_units=100,
     write_capacity_units=20>,
   table_size_bytes=256,
   item_count=2,
   table_arn="arn:aws:dynamodb:ddblocal:000000000000:table/ceps-prod",
   table_id=nil,
   local_secondary_indexes=nil,
   global_secondary_indexes=nil,
   stream_specification=nil,
   latest_stream_label=nil,
   latest_stream_arn=nil,
   restore_summary=nil,
   sse_description=nil>>

I'm using a local dynamodb with the dynamodb-local gem. I also used a dynamodb in AWS and have the same error.

Appreciate any help with this issue, thanks!

[andrykonchin]

I may guess the table isn't created yet.

Table creation is asynchronous operation in DynamoDB. So there is a very small possibility the slow dynamodb-local causes the issue.

You can check it by passing sync: true option to<Document>.create_table method call before tests running. There are several config options you may need to play with - sync_retry_wait_seconds and sync_retry_max_times.

Default values are:

config.sync_retry_wait_seconds = 0
config.sync_retry_max_times = 3

[kdiogenes]

I put the following in my DynamoidReset module, as pointed by https://www.rubydoc.info/gems/dynamoid/2.2.0#Test_Environment:

Dynamoid.included_models.each do |model|
  begin
    model.create_table(sync: true)
  rescue
    retry
  end
end

Still getting the same error.

[kdiogenes]

I configured VCR to ignore all request to localhost and also configured dynamoid with:

module DynamoidTruncate
  def self.all
    if Dynamoid.adapter.list_tables
      Dynamoid.adapter.list_tables.each do |table|
        if table =~ /^#{Dynamoid::Config.namespace}/
          Dynamoid.adapter.truncate(table)
        end
      end
    end
    Dynamoid.included_models.each(&:create_table)
  end
end

RSpec.configure do |config|
  config.before(:suite) do
    Dynamoid.included_models.each do |model|
      begin
        model.create_table(sync: true)
      rescue
        retry
      end
    end
  end

  config.before(:each) do
    DynamoidTruncate.all
  end
end

It's working know 🎉

[andrykonchin]

Actually it makes sense to create table synchronously as well here in DynamoidTruncate.all:

Dynamoid.included_models.each(&:create_table)

[kdiogenes]

I decided to not drop my tables, only truncate it. I run RAILS_ENV=test bundle exec rake dynamoid:create_tables in my CI to create the tables before the tests run. It's working awesome!