Amazonica DynamoDB Atomic Counter

[ma...@datasnap.io]

Has anyone used Amazonica to implement an atomic counter in DynamoDB?

I plan on having a Dynamo table with only one entry, something that looks like {"id": "counter", "count": 28734}, where the count acts as an atomic counter. Then use the update-item function to increment the count, regardless of it's value.

I'm struggling to formulate the correct amazonica.aws.dynamodb/update-item function call.

I have something like this currently:

> (dynamo-client/put-item cred

    :table-name "atomic-counter"

    :item {:id "counter" :count 0})

{:consumed-capacity-units 1.0}

> (dynamo-client/get-item cred

    :table-name "atomic-counter"

    :key "counter")

{:item {:count "0", :id "counter"}, :consumed-capacity-units 0.5

> (dynamo-client/update-item cred

    :table-name "atomic-counter"

    :key "counter"

    :attributeUpdates {:count "add"})

UnsupportedOperationException nth not supported on this type: Character clojure.lang.RT.nthFrom (RT.java:857) 

I've tried a few other variations on the value for attributeUpdates.count.

Any help would be greatly appreciated!

[ma...@datasnap.io]

If anyone is interested, my solution was:

> (dynamo-client/update-item cred

    :table-name "atomic-counter"

    :key "counter"

    :attributeUpdates {:count {:value 1 :action "ADD"}})

{:consumed-capacity-units 1.0}

> (dynamo-client/get-item cred

    :table-name "atomic-counter"

    :key "counter")

{:item {:count "1", :id "counter"}, :consumed-capacity-units 0.5}