#Erldyn

##DynamoDB API DynamoDB functions are converted to underscore_case functions of arity 1:

• batch_get_item/1,
• batch_write_item/1,
• create_table/1,
• delete_item/1,
• delete_table/1,
• describe_table/1,
• get_item/1,
• list_tables/1,
• put_item/1,
• query/1,
• scan/1,
• update_item/1,
• update_table/1]

The single parameter is JSON as defined by the DynamoDB API, and the returns are either:

• {ok, #{...}},
• [{ok, #{...}}, ...],
• or {error, #{...})

where the maps are map versions of DynamoDB, JSON returns.

###Batch Functions The batch functions (batch_get_item/1 and batch_write_item/1) can return partial results. The unprocessed items will be resubmitted automatically, consequently, these functions return a list of maps - one for each partial result.

##Convenience Methods Convenience methods (new_table/3, save_table/1, and add_parameter/3) are provided for simplifying the process of building the correct strcture for defining and creating tables.

##Exponential Back-Off Exponentional back-off is used such that appropriate failures, or partial results, are retried according to an exponential, back-off algorithm, not to exceed one minute total for the entire operation.

###Configuration erldyn:config(#{}) is used to set the dynamoDb endpoint (i.e., "https://dynamodb.us-west-2.amazonaws.com/"), and to optionally set the Amazon, access-key and secret-key assumin AWS Securtiy Token Service is not being used. For example:

=> ConfigMap = #{endpoint => "https://dynamodb.us-west-2.amazonaws.com/",
              access_key => "XXXXXXXXXXX",
              secret_key => "YYYYYYYYYY"},
=> erldyn:config(ConfigMap).
=> ok

If, AWS AIM services are being used, config/1 is only used to configure the endpoint, and the AIM service is used to fetch temporary credentials automatically. The configuration file provides the AWS metadata endpoint and a flag indicating that AIM should be used:

[
 {erldyn,
  [
   %% DynamoDb endpoint and metadata uri.
   {endpoint, "https://dynamodb.us-west-2.amazonaws.com/"},
   {metadata, "http://169.254.169.254/latest/meta-data/iam/security-credentials/"},
   {aim, false}
  ]}
 ].

##Authorization All http operations are PUTS, and Version 4 of the Signature authorizaion header is used.

Secret Key and Access Keys can be fetched from OS environment variables (AWS_ACCESS_KEY_ID, and AWS_SECRET_ACCESS_KEY) or set/changed via config/1.

If AWS Security Token Service is being used then only the endpointthe Token can only be supplied via the config map.

The DynamoDB Endpoint is provided via the same config/1 function, and is parsed to determine service, streaming service, host and region.

=> ConfigMap = #{endpoint => "https://dynamodb.us-west-2.amazonaws.com/",
              access_key => "XXXXXXXXXXX",
              secret_key => "YYYYYYYYYY",
              token => "ZZZZZZZZZZZZ"}.
=> erldyn:config(ConfigMap).
=> ok

Dependencies

Lager for logging, jsone for json <--> map translation, and rebar3 for building

Build

erldyn uses rebar3

$ make compile
$ make clean
$ make doc
$ make check
$ make run

Running

Assuming that $ make has been previously executed:

$ export AWS_SECRET_ACCESS_KEY="WIcKN27efefff499Pd9iqBpm3hEkas0rsDzoSA"
$ export AWS_ACCESS_KEY_ID="AKERTJFFIFATLGIJFJLA"

$ make run
erl -pa _build/default/lib/*/ebin
Erlang/OTP 18 [erts-7.1] [source-2882b0c] [64-bit] [smp:8:8] [async-threads:10] [hipe] [kernel-poll:false]

Eshell V7.1  (abort with ^G)

1> erldyn:config(#{endpoint => "https://dynamodb.us-west-2.amazonaws.com/"}).
ok
2> erldyn:list_tables("{}").
{ok,#{<<"TableNames">> => [<<"Forum">>,<<"Reply">>,<<"Thread">>,<<"Wizzards">>]}}