neo4j

errors = require './errors' utils = require './utils' # This value is used to construct a Date instance, and unfortunately, neither # Infinity nor Number.MAX_VALUE are valid Date inputs. There's also no simple # max value for Dates either (http://stackoverflow.com/a/11526569/132978), # so we arbitrarily do one year ahead. Hopefully this doesn't matter. FAR_FUTURE_MS = Date.now() + 1000 * 60 * 60 * 24 * 365 # http://neo4j.com/docs/stable/rest-api-transactional.html module.exports = class Transaction constructor: (@_db) -> @_id = null @_expires = null @_pending = false @_committed = false @_rolledBack = false # Convenience helper for nice getter syntax: # (NOTE: This does *not* support sibling setters, as we don't need it, # but it's possible to add support.) get = (props) => for name, getter of props Object.defineProperty @::, name, configurable: true # For developer-friendliness, e.g. tweaking. enumerable: true # So these show up in console.log, etc. get: getter # This nice getter syntax uses implicit braces, however. # coffeelint: disable=no_implicit_braces get STATE_OPEN: -> 'open' get STATE_PENDING: -> 'pending' get STATE_COMMITTED: -> 'committed' get STATE_ROLLED_BACK: -> 'rolled back' get STATE_EXPIRED: -> 'expired' get expiresAt: -> if @_expires new Date @_expires else # This transaction hasn't been created yet, so far future: new Date FAR_FUTURE_MS get expiresIn: -> if @_expires @expiresAt - (new Date) else # This transaction hasn't been created yet, so far future. # Unlike for the Date instance above, we can be less arbitrary; # hopefully it's never a problem to return Infinity here. Infinity get state: -> switch # Order matters here. # E.g. a request could have been made just before the expiry time, # and we won't know the new expiry time until the server responds. # # TODO: The server could also receive it just *after* the expiry # time, which'll cause it to return an unhelpful `UnknownId` error; # should we handle that edge case in our `cypher` callback below? # when @_pending then @STATE_PENDING when @_committed then @STATE_COMMITTED when @_rolledBack then @STATE_ROLLED_BACK when @expiresIn <= 0 then @STATE_EXPIRED else @STATE_OPEN # For the above getters. # coffeelint: enable=no_implicit_braces # NOTE: CoffeeLint currently false positives on this next line. # https://github.com/clutchski/coffeelint/issues/458 # coffeelint: disable=no_implicit_braces cypher: (opts={}, cb) -> # coffeelint: enable=no_implicit_braces # Check predictable error cases to provide better messaging sooner. # All of these are `ClientErrors` within the `Transaction` category. # http://neo4j.com/docs/stable/status-codes.html#_status_codes errMsg = switch @state when @STATE_PENDING # This would otherwise throw a `ConcurrentRequest` error. 'A request within this transaction is currently in progress. Concurrent requests within a transaction are not allowed.' when @STATE_EXPIRED # This would otherwise throw an `UnknownId` error. 'This transaction has expired. You can get the expiration time of a transaction through its `expiresAt` (Date) and `expiresIn` (ms) properties. To prevent a transaction from expiring, execute any action or call `renew` before the transaction expires.' when @STATE_COMMITTED # This would otherwise throw an `UnknownId` error. 'This transaction has been committed. Transactions cannot be reused; begin a new one instead.' when @STATE_ROLLED_BACK # This would otherwise throw an `UnknownId` error. 'This transaction has been rolled back. Transactions get automatically rolled back on any DatabaseErrors, as well as any errors during a commit. That includes auto-commit queries (`{commit: true}`). Transactions cannot be reused; begin a new one instead.' if errMsg # TODO: Should we callback this error instead? (And if so, should we # `process.nextTick` that call?) # I *think* that these cases are more likely to be code bugs than # legitimate runtime errors, so the benefit of throwing sync'ly is # fail-fast behavior, and more helpful stack traces. throw new errors.ClientError errMsg # The only state we should be in at this point is 'open'. @_pending = true @_db.cypher opts, (err, results) => @_pending = false # If this transaction still exists, no state changes for us: if @_id return cb err, results # Otherwise, this transaction was destroyed -- either committed or # rolled back -- so update our state accordingly. # Much easier to derive whether committed than whether rolled back, # because commits can only happen when explicitly requested. if opts.commit and not err @_committed = true else @_rolledBack = true cb err, results , @ commit: (cb) -> @cypher {commit: true}, cb rollback: (cb) -> @cypher {rollback: true}, cb renew: (cb) -> @cypher {}, cb # # Updates this Transaction instance with data from the given transactional # endpoint response. # _updateFromResponse: (resp) -> if not resp throw new Error 'Unexpected: no transactional response!' {body, headers, statusCode} = resp {transaction} = body if not transaction # This transaction has been destroyed (either committed or rolled # back). Our state will get updated in the `cypher` callback above. @_id = @_expires = null return # Otherwise, this transaction exists. # The returned object always includes an updated expiry time... @_expires = new Date transaction.expires # ...but only includes the URL (from which we can parse its ID) # the first time, via a Location header for a 201 Created response. # We can short-circuit if we already have our ID. return if @_id if statusCode isnt 201 throw new Error 'Unexpected: transaction returned by Neo4j, but it was never 201 Created, so we have no ID!' if not transactionURL = headers['location'] throw new Error 'Unexpected: transaction response is 201 Created, but with no Location header!' @_id = utils.parseId transactionURL