When it came time to build a product demonstration for the Couchbase Connect Conference the following requirements were established:<\/p>\n
[1] It must be a live demo, with audience participation — no canned movies or powerpoint only presentations. \u00a0The bar was set high with significant risk.
\n[2] It must demonstrate the power of Couchbase 3.0 and show realtime consistency of data between clusters in different datacenters (XDCR).
\n[3] It must be agile, leveraging the power of the new Couchbase 2.0 SDK’s.
\n[4] The application needs to be code complete in 4 days to reinforce how development with Couchbase is ideal for the agile enterprise.
\n[5] Tell the world how it was done, and prove it by publishing the source code.<\/p>\n
It was decided that an auction application, spread over two web servers in two different datacenters talking to two different clusters would achieve the objective. \u00a0 A Salt Lake City Cluster, and a London Cluster will maintain consistency with bidirectional replication between them using XDCR. \u00a0 The new DCP protocol in Couchbase 3.0 means that consistency would only be limited by wirespeed. \u00a0 An application server in each datacenter running node.js handles traffic in each region. \u00a0The code can be downloaded from couchbaselabs repo on github. <\/a>**<\/p>\n In addition to using node.js<\/a> with Express and the Couchbase 2.0 SDK, bootstrap was used for front end development. \u00a0 The 2.0 SDK’s are a remarkable achievment, and include significant new advancements that simplify development. \u00a0 Information on the 2.0 SDK’s and why Couchbase continues to extend development leadership within the market can be found in our developer portal.<\/a><\/p>\n While no authentication is needed for a just for fun auction, \u00a0a means of identifying users and concurrent sessions is still required. \u00a0A simple login form stores a cookie with a user id for each session. \u00a0 The login function checks if the user exists, and if there is any filtered words violations prior to creating a session cookie.<\/p>\n Then a very small \u00a0“middleware” function checks if a user has setup a session prior to routing incoming requests.<\/p>\n A further “middleware” function checks to see if a countdown is set or if this auction is closed.<\/p>\nApplication Design<\/span><\/h2>\n
Session Management<\/h3>\n
\nfilterScan(<\/span>newUser,<\/span> function<\/span> (<\/span>filtcb)<\/span> {<\/span>
\nif<\/span> (<\/span>filtcb)<\/span> {<\/span>
\ndb.read<\/span>(<\/span>newUser,<\/span> function<\/span> (<\/span>err,<\/span> user)<\/span> {<\/span>
\nif<\/span> (<\/span>err &&<\/span> err.code<\/span> ===<\/span> couchbase.errors<\/span>.keyNotFound<\/span>)<\/span> {<\/span>
\nres.cookie<\/span>(<\/span>‘user’<\/span>,<\/span> newUser)<\/span>;<\/span>
\ndb.upsert<\/span>(<\/span>newUser,<\/span> 0<\/span>,<\/span> function<\/span> (<\/span>err,<\/span> res)<\/span> {<\/span>
\nif<\/span> (<\/span>err)<\/span> {<\/span>
\nconsole.log<\/span>(<\/span>“LOGIN:ERROR CREATING:”<\/span> +<\/span> err)<\/span>;<\/span>
\ndone(<\/span>“LOGIN:ERROR CREATING:”<\/span> +<\/span> err,<\/span> null<\/span>)<\/span>;<\/span>
\nreturn<\/span>;<\/span>
\n}<\/span>
\nconsole.log<\/span>(<\/span>“LOGIN:”<\/span> +<\/span> newUser +<\/span> “:SUCCESS”<\/span>)<\/span>;<\/span>
\ndone(<\/span>null<\/span>,<\/span> “LOGIN:”<\/span> +<\/span> newUser +<\/span> “:SUCCESS”<\/span>)<\/span>;<\/span>
\nreturn<\/span>;<\/span>
\n}<\/span>)<\/span>;<\/span>
\n}<\/span> else<\/span> {<\/span>
\nif<\/span> (<\/span>user)<\/span> {<\/span>
\nconsole.log<\/span>(<\/span>“LOGIN:ERROR:”<\/span> +<\/span> newUser +<\/span> ” EXISTS”<\/span>)<\/span>;<\/span>
\ndone(<\/span>“LOGIN:ERROR:”<\/span> +<\/span> newUser +<\/span> ” exists — please choose a different username”<\/span>,<\/span> null<\/span>)<\/span>;<\/span>
\nreturn<\/span>;<\/span>
\n}<\/span>
\nconsole.log<\/span>(<\/span>“LOGIN:ERROR:END:”<\/span> +<\/span> err)<\/span>;<\/span>
\ndone(<\/span>“LOGIN:ERROR”<\/span> +<\/span> err,<\/span> null<\/span>)<\/span>;<\/span>
\nreturn<\/span>;<\/span>
\n}<\/span>
\n}<\/span>)<\/span>;<\/span>
\n}<\/span> else<\/span> {<\/span>
\nconsole.log<\/span>(<\/span>“LOGIN:ERROR:WORD VIOLATION”<\/span>)<\/span>;<\/span>
\ndone(<\/span>“LOGIN:ERROR, PROHIBITED TERM IN USERNAME”<\/span>,<\/span> null<\/span>)<\/span>;<\/span>
\nreturn<\/span>;<\/span>
\n}<\/span>
\n}<\/span>)<\/span>;<\/span>
\n}<\/span><\/div>\n<\/div>\n
\nif<\/span> (<\/span>req.cookies<\/span>.user<\/span>)<\/span> {<\/span>
\nreturn<\/span> next(<\/span>)<\/span>;<\/span>
\n}<\/span>
\nres.redirect<\/span>(<\/span>‘\/’<\/span>)<\/span>;<\/span>
\n}<\/span><\/div>\n<\/div>\n
\ndb.read<\/span>(<\/span>‘state’<\/span>,<\/span>function<\/span>(<\/span>err,<\/span>done)<\/span>{<\/span>
\nif<\/span>(<\/span>done.value<\/span>.active<\/span>)<\/span> {<\/span>
\nreturn<\/span> next(<\/span>)<\/span>;<\/span>
\n}<\/span>else<\/span>{<\/span>
\nif<\/span>(<\/span>done.value<\/span>.countdown<\/span> !=<\/span> “none”<\/span>)<\/span>
\n{<\/span>
\nres.render<\/span>(<\/span>‘countdown.jade’<\/span>)<\/span>;<\/span>
\n}<\/span>else<\/span> {<\/span>
\ndb.read<\/span>(<\/span>‘bike’<\/span>,<\/span> function<\/span> (<\/span>err,<\/span> cb)<\/span> {<\/span>
\nres.render<\/span>