simpledb2level

Stream SimpleDB data into a local LevelDB store

Fetch data out of SimpleDB so you can work with it locally and with all the benefits of the level* ecosystem. Can also be used for incremental fetching for ongoing synchronisation of SimpleDB.

Example

var simpledb2level = require('simpledb2level')
var awsConfig = {
    'accessKeyId'     : 'access key'
  , 'secretAccessKey' : 'secret access key'
  , 'region'          : 'ap-northeast-1'
}
var dbPath = __dirname + '/simple.db'

simpledb2level({ aws: awsConfig, db: dbPath })

API ("But wait! There's more!")

simpledb2level(options) where options can contain:

• 'aws' - (required) - the AWS config for aws-sdk.
• 'db' - (required) - the LevelDB store to write to. Can be either a String path which will be opened and closed as required, or a LevelUP instance (or LevelUP-like instance), which won't be explicitly closed when the streaming is finished.
• 'domains' - (optional) - an Array of Strings that, if supplied, will be used to restrict the domains that are copied. If you have lots of domains and only want to copy some, supply a list.
• 'domainConfig' - (optional) - a Function that will be called for each domain that can be used to return domain-specific configuration. More on this below.

'domainConfig'

If you need to do special things with particular domains then you can do it with this special callback-like function that you supply on the options.

Return an Object that has the following optional properties:

• 'criteria' - select criteria that is supplied to simpledb-stream for this domain. Use this to restrict the data being read. If you want to do incremental copying then provide a 'criteria' that will select only the most recent data.
• 'setupDb' - a Function that can be used to adjust the sublevel that the data will be written to. The function should accept a db and return a db (likely the same object, but it can be something else). Use this if you want to set up indexes or other features on the db while the data is being written.

const simpledb2level = require('simpledb2level')
    , secondary = require('level-secondary')
    , awsConfig = { ... }

var s2l = simpledb2level({
    aws          : awsConfig
  , db           : './out.db'
  , domains      : [ 'OnlyOneDomain' ]
  , domainConfig : function (domain) {
      return {
          criteria : 'time != "0" and time > "2013-12-20"'
        , setupDb  : function (db) {
            secondary(db, 'time')
            return db
          }
      }
    }
)

Events

simpledb2level() returns an EventEmitter that can be used to get more insight to what's going on.

• 'error' - as you would expect, an error occurred
• 'end' - reading and writing is finished
• 'domains' - emits an Array of domains found in SimpleDB that will be streamed to LevelDB (this list will be modified if you supply a 'domains' option).
• 'domain' - emits an object containing:
  • 'domain' - the name of the domain
  • 'stream' - a simpledb-stream that will be used to stream data out of this domain
  • 'config' - the config obtained from the 'domainConfig' function option (if any).

You can use the 'stream' for each domain to track progress if required.

LevelDB write structure

Each domain from SimpleDB will be written into a sublevel with the same name. Then each item in that domain will be written such that 'Name' becomes the key and the value is a JSON object where each attribute 'Name' / 'Value' pair is a property / value.

You can get hacky with the setupDb function to adjust how this works, but if you need more flexibility then open a pull request!

Tests

To execute the tests you need a test/aws-config.json file with your AWS credentials. The test suite will create a SimpleDB domain, test the streaming, then delete the test domain.

The test/aws-config.json file should look something like this:

{
    "accessKeyId"     : "access key"
  , "secretAccessKey" : "secret key"
  , "region"          : "ap-southeast-2"
}

License

simpledb2level is Copyright (c) 2013 Rod Vagg @rvagg and licenced under the MIT licence. All rights not explicitly granted in the MIT license are reserved. See the included LICENSE file for more details.