Node js mongodriver

An introduction to thenode.js mongo driver Christian Amor Kvalheim

• Asynchronous Javascript platform built on top of V8• Single-threaded• Package manager• Awesome

Hello World Servervar http = require(http);http.createServer( function (req, res) { res.writeHead(200, {Content-Type: text/plain}); res.end(Hello Worldn); }).listen(8124, "127.0.0.1");

Hello World Server Load the http libraryvar http = require(http);http.createServer( function (req, res) { res.writeHead(200, {Content-Type: text/plain}); res.end(Hello Worldn); }).listen(8124, "127.0.0.1");

Hello World Server Load the http libraryvar http = require(http); Set up the connectionhttp.createServer( handler function (req, res) { res.writeHead(200, {Content-Type: text/plain}); res.end(Hello Worldn); }).listen(8124, "127.0.0.1");

How to get started• Install node.js (from source or package)• Install npm (node package manager)• Create an empty directory• npm install mongodb• npm install express

Let’s do some code• Using Express and Mongo• Textmate basic.js

Picking it apartvar db = new Db(node-mongo-examples, new Server(host, port, {}),{native_parser:false});db.open(function(err, db) { ... ..... app.listen(8124);var app = express.createServer();app.get(/, function(req, res){ res.send(Hello World);});

Picking it apart Creates a db using the js bson parservar db = new Db(node-mongo-examples, new Server(host, port, {}),{native_parser:false});db.open(function(err, db) { ... ..... app.listen(8124);var app = express.createServer();app.get(/, function(req, res){ res.send(Hello World);});

Picking it apart Creates a db using the js bson parservar db = new Db(node-mongo-examples, new Server(host, port, {}),{native_parser:false}); Opens the connection to the dbdb.open(function(err, db) { ... ..... app.listen(8124);var app = express.createServer();app.get(/, function(req, res){ res.send(Hello World);});

Picking it apart Creates a db using the js bson parservar db = new Db(node-mongo-examples, new Server(host, port, {}),{native_parser:false}); Opens the connection to the dbdb.open(function(err, db) { ... ..... app.listen(8124); The server is now running with access to the mongo server connectionvar app = express.createServer();app.get(/, function(req, res){ res.send(Hello World);});

Let’s add some meat• CRUD operations• Textmate basic_2.js

Picking it apart// Create methodapp.post(/location, function(req, res) { geoCodeDecorateObject(req.body.address, {description:req.body.description},function(err, object) { db.collection(locations, function(err, collection) { // Insert doc collection.insert(object, {safe:true}, function(err, result) { // Fetch all docs for rendering of list collection.find({}).toArray(function(err, items) { res.render(./basic_2.jade, {locals: {locations:items}}); }) }); }); });});

Picking it apartGeo Encode Address// Create methodapp.post(/location, function(req, res) { geoCodeDecorateObject(req.body.address, {description:req.body.description},function(err, object) { db.collection(locations, function(err, collection) { // Insert doc collection.insert(object, {safe:true}, function(err, result) { // Fetch all docs for rendering of list collection.find({}).toArray(function(err, items) { res.render(./basic_2.jade, {locals: {locations:items}}); }) }); }); });});

Picking it apart Geo Encode Address // Create method app.post(/location, function(req, res) { geoCodeDecorateObject(req.body.address, {description:req.body.description}, function(err, object) { db.collection(locations, function(err, collection) { // Insert doc collection.insert(object, {safe:true}, function(err, result) { // Fetch all docs for rendering of list collection.find({}).toArray(function(err, items) { res.render(./basic_2.jade, {locals: {locations:items}}); })Insert record, safe ensures that we trap any }); }); }); errors by doing a error check against }); mongodb

Picking it apart // Create method app.post(/location, function(req, res) { geoCodeDecorateObject(req.body.address, {description:req.body.description}, function(err, object) { db.collection(locations, function(err, collection) { // Insert doc collection.insert(object, {safe:true}, function(err, result) { // Fetch all docs for rendering of list collection.find({}).toArray(function(err, items) { res.render(./basic_2.jade, {locals: {locations:items}}); }) }); }); }); ﬁnd all records from the locations });collection. Find returns a cursor that allows for stepping through doucments

Safe or not• Mongo Insert/Update/Delete are async• 2nd call to lastError required to check for the success of the operation• safe option ensures the second error call• you can also run the driver in strict mode

Picking it apart// Delete methodapp.del(/location, function(req, res) { var id = ObjectID.createFromHexString(req.body.id); db.collection(locations, function(err, collection) { collection.remove({_id:id}, {safe:true}, function(err, numberOfDeletedRecords) { // Fetch all docs for rendering of list collection.find({}).toArray(function(err, items) { res.render(./basic_3.jade, {locals: {locations:items}}); }) }) });});

Picking it apart Convert hex string to// Delete method objectIDapp.del(/location, function(req, res) { var id = ObjectID.createFromHexString(req.body.id); db.collection(locations, function(err, collection) { collection.remove({_id:id}, {safe:true}, function(err, numberOfDeletedRecords) { // Fetch all docs for rendering of list collection.find({}).toArray(function(err, items) { res.render(./basic_3.jade, {locals: {locations:items}}); }) }) });});

Picking it apart Convert hex string to// Delete method objectIDapp.del(/location, function(req, res) { var id = ObjectID.createFromHexString(req.body.id); db.collection(locations, function(err, collection) { collection.remove({_id:id}, {safe:true}, function(err, numberOfDeletedRecords) { // Fetch all docs for rendering of list collection.find({}).toArray(function(err, items) { res.render(./basic_3.jade, {locals: {locations:items}}); }) }) Remove the document using the speciﬁc id });}); passed in, using safe.

Picking it apart// Get methodapp.get(/location, function(req, res) { var id = ObjectID.createFromHexString(req.body.id); db.collection(locations, function(err, collection) { collection.findOne({_id:id}, function(err, item) { // Fetch all docs for rendering of list collection.find({}).toArray(function(err, items) { res.render(./basic_4.jade, {locals: {locations:items, location:item}}); }) }) });});

Picking it apart Convert hex string to// Get methodapp.get(/location, function(req, res) { objectID var id = ObjectID.createFromHexString(req.body.id); db.collection(locations, function(err, collection) { collection.findOne({_id:id}, function(err, item) { // Fetch all docs for rendering of list collection.find({}).toArray(function(err, items) { res.render(./basic_4.jade, {locals: {locations:items, location:item}}); }) }) });});

Picking it apart Convert hex string to// Get methodapp.get(/location, function(req, res) { objectID var id = ObjectID.createFromHexString(req.body.id); db.collection(locations, function(err, collection) { collection.findOne({_id:id}, function(err, item) { // Fetch all docs for rendering of list collection.find({}).toArray(function(err, items) { res.render(./basic_4.jade, {locals: {locations:items, location:item}}); }) }) Locate one document by id });});

Picking it apart// Update methodapp.put(/location, function(req, res) { var id = ObjectID.createFromHexString(req.body.id); db.collection(locations, function(err, collection) { collection.findOne({_id:id}, function(err, object) { object.description = req.body.description; object.address = req.body.address; geoCodeDecorateObject(req.body.address, object, function(err, object) { collection.update({_id:object._id}, object, {safe:true}, function(err,numberOfUpdatedObjects) { // Fetch all docs for rendering of list collection.find({}).toArray(function(err, items) { res.render(./basic_5.jade, {locals: {locations:items}}); }) }) })

Picking it apart// Update methodapp.put(/location, function(req, res) { Locate object we wish var id = ObjectID.createFromHexString(req.body.id); to modify db.collection(locations, function(err, collection) { collection.findOne({_id:id}, function(err, object) { object.description = req.body.description; object.address = req.body.address; geoCodeDecorateObject(req.body.address, object, function(err, object) { collection.update({_id:object._id}, object, {safe:true}, function(err,numberOfUpdatedObjects) { // Fetch all docs for rendering of list collection.find({}).toArray(function(err, items) { res.render(./basic_5.jade, {locals: {locations:items}}); }) }) })

Picking it apart// Update methodapp.put(/location, function(req, res) { Locate object we wish var id = ObjectID.createFromHexString(req.body.id); to modify db.collection(locations, function(err, collection) { collection.findOne({_id:id}, function(err, object) { object.description = req.body.description; object.address = req.body.address; geoCodeDecorateObject(req.body.address, object, function(err, object) { collection.update({_id:object._id}, object, {safe:true}, function(err,numberOfUpdatedObjects) { // Fetch all docs for rendering of list collection.find({}).toArray(function(err, items) { res.render(./basic_5.jade, {locals: {locations:items}}); }) }) }) Update document using the id to select what document to update

Let’s add some meat• Final with search• Textmate basic_6.js

Picking it apartdb.open(function(err, db) { if(err) throw err // !!! CHANGE db.ensureIndex("locations", {loc:"2d"}, function(err, result) { if(err) throw err app.listen(8124); })});

Picking it apartdb.open(function(err, db) { if(err) throw err // !!! CHANGE db.ensureIndex("locations", {loc:"2d"}, function(err, result) { if(err) throw err app.listen(8124); })}); Ensures there is a 2d geospatial index on the attribute loc on any document in the locations collection

Picking it apartvar geoCodeDecorateObject = function(address, object, callback) { var googleGeoCodeApi = {host: maps.googleapis.com, port: 80,path: /maps/api/geocode/json?sensor=false&address= +escape(address), method: GET }; var clientReq = http.get(googleGeoCodeApi, function(clientRes) { var data = []; clientRes.on(data, function(chunk) { data.push(chunk.toString()); }); clientRes.on(end, function() { var googleObject = JSON.parse(data.join()); object.address = address; object.geodata = googleObject.results.pop(); // !!! CHANGE object.loc = {long:object.geodata.geometry.location.lng,lat:object.geodata.geometry.location.lat}; callback(null, object); });

Picking it apartvar geoCodeDecorateObject = function(address, object, callback) { var googleGeoCodeApi = {host: maps.googleapis.com, port: 80,path: /maps/api/geocode/json?sensor=false&address= +escape(address), method: GET }; var clientReq = http.get(googleGeoCodeApi, function(clientRes) { var data = []; clientRes.on(data, function(chunk) { data.push(chunk.toString()); We are adding a loc }); clientRes.on(end, function() { attribute to all var googleObject = JSON.parse(data.join()); documents with object.address = address; object.geodata = googleObject.results.pop(); longtidude and // !!! CHANGE latitude in the right object.loc = {long:object.geodata.geometry.location.lng,lat:object.geodata.geometry.location.lat}; order for mongodb to callback(null, object); }); search

Picking it apart// !!! CHANGE// Search optionapp.post(/search, function(req, res) { geoCodeDecorateObject(req.body.address, {}, function(err, object) { // Unpack geo object var long = object.geodata.geometry.location.lng; var lat = object.geodata.geometry.location.lat db.collection(locations, function(err, collection) { collection.find({loc : {$near: [long, lat], $maxDistance:parseFloat(req.body.distance)}}).toArray(function(err, geoItems) { // Fetch all docs for rendering of list collection.find({}).toArray(function(err, items) { res.render(./basic_6.jade, {locals: {locations:items,results:geoItems}}); }) }); }); });});

Picking it apart Encode address for// !!! CHANGE// Search option searchingapp.post(/search, function(req, res) { geoCodeDecorateObject(req.body.address, {}, function(err, object) { // Unpack geo object var long = object.geodata.geometry.location.lng; var lat = object.geodata.geometry.location.lat db.collection(locations, function(err, collection) { collection.find({loc : {$near: [long, lat], $maxDistance:parseFloat(req.body.distance)}}).toArray(function(err, geoItems) { // Fetch all docs for rendering of list collection.find({}).toArray(function(err, items) { res.render(./basic_6.jade, {locals: {locations:items,results:geoItems}}); }) }); }); });});

Picking it apart Encode address for// !!! CHANGE// Search option searchingapp.post(/search, function(req, res) { geoCodeDecorateObject(req.body.address, {}, function(err, object) { // Unpack geo object var long = object.geodata.geometry.location.lng; var lat = object.geodata.geometry.location.lat db.collection(locations, function(err, collection) { collection.find({loc : {$near: [long, lat], $maxDistance:parseFloat(req.body.distance)}}).toArray(function(err, geoItems) { // Fetch all docs for rendering of list collection.find({}).toArray(function(err, items) { res.render(./basic_6.jade, {locals: {locations:items,results:geoItems}}); }) }); Search for all items $near our address at }); }); $maxDistance});

Other features• Cursors• Grid FS

Cursors• toArray Function• each Function• streamRecords Function

toArraycollection.find().toArray(function(err, documents){ test.deepEqual([1, 2, 3], documents[0].b); // Lets close the db test.done();});

toArray Fetches all docs in one go for the query. Use with cautioncollection.find().toArray(function(err, documents){ test.deepEqual([1, 2, 3], documents[0].b); // Lets close the db test.done();});

eachcollection.find({}, {sort:[[age, 1]]}).each(function(err, item){ if(item != null) { // Do work } else { // Finished }});

each Fetches docs in batches and allows iteration over resultscollection.find({}, {sort:[[age, 1]]}).each(function(err, item){ if(item != null) { // Do work } else { // Finished }});

each Fetches docs in batches and allows iteration over resultscollection.find({}, {sort:[[age, 1]]}).each(function(err, item){ if(item != null) { // Do work } else { // Finished }}); Returns null when no more results available

streamRecords var stream = collection.find({}, {limit : 3}).streamRecords();stream.on(end, function() { // No more results in the pipe});stream.on(data,function(data){ // Item});

streamRecords var stream = collection.find({}, {limit : 3}).streamRecords();stream.on(end, function() { // No more results in the pipe});stream.on(data,function(data){ // Item}); When an item is ready the event ‘data’ is triggered

streamRecords var stream = collection.find({}, {limit : 3}).streamRecords(); When no more itemsstream.on(end, function() { are available // No more results in the pipe});stream.on(data,function(data){ // Item}); When an item is ready the event ‘data’ is triggered

streamRecords var stream = collection.find({}, {limit : 3}).streamRecords(); When no more itemsstream.on(end, function() { are available // No more results in the pipe}); REFERED Pstream.on(data,function(data){ // Item}); When an item is ready the event ‘data’ is triggered

Grid FS• Write and read a ﬁle• Stream a ﬁle

Write a ﬁlevar gridStore = new GridStore(client, test_gs_writing_file, w);gridStore.open(function(err, gridStore) {gridStore.writeFile(./test_gs_weird_bug.png, function(err, gridStore) { GridStore.read(client, test_gs_writing_file, function(err, fileData) { });

Write a ﬁlevar gridStore = new GridStore(client, test_gs_writing_file, w);gridStore.open(function(err, gridStore) {gridStore.writeFile(./test_gs_weird_bug.png, function(err, gridStore) { Writes the ﬁle in chunks to mongodb (avoids freezing the eventloop in node.js) GridStore.read(client, test_gs_writing_file, function(err, fileData) { });

Write a filevar gridStore = new GridStore(client, test_gs_writing_file, w);gridStore.open(function(err, gridStore) {gridStore.writeFile(./test_gs_weird_bug.png, function(err, gridStore) { Writes the file in chunks to mongodb (avoids freezing the eventloop in node.js) GridStore.read(client, test_gs_writing_file, function(err, fileData) { }); Read the whole file. Careful with the memory

Stream a ﬁlevar gridStore = new GridStore(client, "test_gs_read_stream", "r");gridStore.open(function(err, gs) { var stream = gs.stream(true); stream.on("data", function(chunk) { // Received a chunk of data }); stream.on("end", function() { // Finished streaming });});

Stream a ﬁlevar gridStore = new GridStore(client, "test_gs_read_stream", "r");gridStore.open(function(err, gs) { var stream = gs.stream(true); Receive a chunk and do something stream.on("data", function(chunk) { // Received a chunk of data }); stream.on("end", function() { // Finished streaming });});

Stream a ﬁlevar gridStore = new GridStore(client, "test_gs_read_stream", "r");gridStore.open(function(err, gs) { var stream = gs.stream(true); Receive a chunk and do something stream.on("data", function(chunk) { // Received a chunk of data }); Finshed stream the ﬁle stream.on("end", function() { // Finished streaming });});

Stream a ﬁlevar gridStore = new GridStore(client, "test_gs_read_stream", "r");gridStore.open(function(err, gs) { var stream = gs.stream(true); Receive a chunk and do something stream.on("data", function(chunk) { // Received a chunk of data }); Finshed stream the ﬁle stream.on("end", function() { // Finished streaming PR EFE RED });});

Typical starting problemsfor(var i = 0; i < 100; i++) { collection.insert({i:i});}collection.count(function(err, count) { // count is > 0 <= 100});

Typical starting problemsfor(var i = 0; i < 100; i++) { collection.insert({i:i});} All executed in parallel, non- deterministic end of executioncollection.count(function(err, count) { // count is > 0 <= 100});

Typical starting problemsfor(var i = 0; i < 100; i++) { collection.insert({i:i});} All executed in parallel, non- deterministic end of executioncollection.count(function(err, count) { // count is > 0 <= 100}); All inserts MAY have been written to disk so passes most of the time. But with Pooling NO WAY

Typical starting problemsfor(var i = 0; i < 100; i++) { collection.insert({i:i}, {safe:true}, function(err, result) { // Do something });}??????????????????????????????collection.count(function(err, count) { // count is > 0 <= 100});

Typical starting problemsfor(var i = 0; i < 100; i++) { collection.insert({i:i}, {safe:true}, function(err, result) { // Do something });} How do we handle the callbacks??????????????????????????????collection.count(function(err, count) { // count is > 0 <= 100});

Typical starting problemsfor(var i = 0; i < 100; i++) { collection.insert({i:i}, {safe:true}, function(err, result) { // Do something });} How do we handle the callbacks??????????????????????????????collection.count(function(err, count) { // count is > 0 <= 100}); How do we get to this code ??????

Typical starting problemsfor(var i = 0; i < 100; i++) { collection.insert({i:i}, {safe:true}, function(err, result) { // Do something });} How do we handle the callbacks??????????????????????????????collection.count(function(err, count) { // count is > 0 <= 100}); How do we get to this code ?????? Many possible solutions

My Choosen Solution https://github.com/creationix/step Step( function insert() { var group = this.group(); for(var i = 0; i < 100; i++) { collection.insert({i:i}, {safe:true}, group()); } }, function finished() { collection.count(function(err, count) { // Count is 100 :) }); })

My Choosen Solution https://github.com/creationix/step Step( function insert() { var group = this.group(); for(var i = 0; i < 100; i++) { collection.insert({i:i}, {safe:true}, group()); } }, Ensures all the inserts are ﬁnished before calling the next function function finished() { collection.count(function(err, count) { // Count is 100 :) }); })

My Choosen Solution https://github.com/creationix/step Step( function insert() { var group = this.group(); for(var i = 0; i < 100; i++) { collection.insert({i:i}, {safe:true}, group()); } }, Ensures all the inserts are ﬁnished before calling the next function function finished() { collection.count(function(err, count) { // Count is 100 :) }); }) When all inserts are done :)

DONE Code onhttps://github.com/christkv/mongodb-hamburg

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Node js mongodriver

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