MongoDB によるレジリエントなアプリケーションのビルド

<dependencies>
    <dependency>
        <groupId>org.mongodb</groupId>
        <artifactId>mongodb-driver-sync</artifactId>
        <version>4.0.1</version>
    </dependency>
</dependencies>

dependencies {
  compile 'org.mongodb:mongodb-driver-sync:4.0.1'
}

// Latest 'mongodb' version installed with npm
const MongoClient = require('mongodb').MongoClient;

// Create a variable for your connection string
String uri = "mongodb://[<username>:<password>@]hostname0<:port>[,hostname1:<port1>][,hostname2:<port2>][...][,hostnameN:<portN>]";
// Instantiate the MongoDB client with the URI
MongoClient client = MongoClients.create(uri);

// Create a variable for your connection string
const uri = "mongodb://[<username>:<password>@]hostname0<:port>[,hostname1:<port1>][,hostname2:<port2>][...][,hostnameN:<portN>]";
// Instantiate the MongoDB client with the URI
const client = new MongoClient(uri);

Unable to insert due to an error: com.mongodb.MongoWriteException:
E11000 duplicate key error collection: <db>.<collection> ...

// Declare a logger instance from java.util.logging.Logger
private static final Logger LOGGER = ...
...
try {
    InsertOneResult result = collection.insertOne(new Document()
        .append("_id", 1)
        .append("body", "I'm a goofball trying to insert a duplicate _id"));
    // Everything is OK
    LOGGER.info("Inserted document id: " + result.getInsertedId());
// Refer to the API documentation for specific exceptions to catch
} catch (MongoException me) {
    // Report the error
    LOGGER.severe("Failed due to an error: " + me);
}

...
collection.insertOne({
    _id: 1,
    body: "I'm a goofball trying to insert a duplicate _id"
})
.then(result => {
    response.sendStatus(200) // send "OK" message to the client
},
err => {
    response.sendStatus(400); // send "Bad Request" message to the client
});

1
// File: App.java
2
3
import java.util.Map;
4
import java.util.logging.Logger;
5
6
import org.bson.Document;
7
import org.json.JSONArray;
8
9
import com.mongodb.MongoException;
10
import com.mongodb.client.MongoClient;
11
import com.mongodb.client.MongoClients;
12
import com.mongodb.client.MongoCollection;
13
import com.mongodb.client.MongoDatabase;
14
15
import fi.iki.elonen.NanoHTTPD;
16
17
public class App extends NanoHTTPD {
18
    private static final Logger LOGGER = Logger.getLogger(App.class.getName());
19
20
    static int port = 3000;
21
    static MongoClient client = null;
22
23
    public App() throws Exception {
24
        super(port);
25
26
        // Replace the uri string with your MongoDB deployment's connection string
27
        String uri = "mongodb://<username>:<password>@hostname0:27017,hostname1:27017,hostname2:27017/?retryWrites=true&w=majority";
28
        client = MongoClients.create(uri);
29
30
        start(NanoHTTPD.SOCKET_READ_TIMEOUT, false);
31
        LOGGER.info("\nStarted the server: http://localhost:" + port + "/ \n");
32
    }
33
34
    public static void main(String[] args) {
35
        try {
36
            new App();
37
        } catch (Exception e) {
38
            LOGGER.severe("Couldn't start server:\n" + e);
39
        }
40
    }
41
42
    @Override
43
    public Response serve(IHTTPSession session) {
44
        StringBuilder msg = new StringBuilder();
45
        Map<String, String> params = session.getParms();
46
47
        Method reqMethod = session.getMethod();
48
        String uri = session.getUri();
49
50
        if (Method.GET == reqMethod) {
51
            if (uri.equals("/")) {
52
                msg.append("Welcome to my API!");
53
            } else if (uri.equals("/users")) {
54
                msg.append(listUsers(client));
55
            } else {
56
                msg.append("Unrecognized URI: ").append(uri);
57
            }
58
        } else if (Method.POST == reqMethod) {
59
            try {
60
                String name = params.get("name");
61
                if (name == null) {
62
                    throw new Exception("Unable to process POST request: 'name' parameter required");
63
                } else {
64
                    insertUser(client, name);
65
                    msg.append("User successfully added!");
66
                }
67
            } catch (Exception e) {
68
                msg.append(e);
69
            }
70
        }
71
72
        return newFixedLengthResponse(msg.toString());
73
    }
74
75
    static String listUsers(MongoClient client) {
76
        MongoDatabase database = client.getDatabase("test");
77
        MongoCollection<Document> collection = database.getCollection("users");
78
79
        final JSONArray jsonResults = new JSONArray();
80
        collection.find().forEach((result) -> jsonResults.put(result.toJson()));
81
82
        return jsonResults.toString();
83
    }
84
85
    static String insertUser(MongoClient client, String name) throws MongoException {
86
        MongoDatabase database = client.getDatabase("test");
87
        MongoCollection<Document> collection = database.getCollection("users");
88
89
        collection.insertOne(new Document().append("name", name));
90
        return "Successfully inserted user: " + name;
91
    }
92
}

1
const express = require('express');
2
const bodyParser = require('body-parser');
3
4
// Use the latest client libraries by installing & importing them
5
const MongoClient = require('mongodb').MongoClient;
6
7
const app = express();
8
app.use(bodyParser.json());
9
app.use(bodyParser.urlencoded({ extended: true }));
10
11
// Use a connection string that lists all hosts
12
// with retryable writes & majority write concern
13
const uri = "mongodb://<username>:<password>@hostname0:27017,hostname1:27017,hostname2:27017/?retryWrites=true&w=majority";
14
15
const client = new MongoClient(uri);
16
17
// ----- API routes ----- //
18
app.get('/', (req, res) => res.send('Welcome to my API!'));
19
20
app.get('/users', (req, res) => {
21
    const collection = client.db("test").collection("users");
22
23
    collection
24
    .find({})
25
    // In this example, 'maxTimeMS' throws an error after 5 seconds,
26
    // alerting the application to a lasting network outage
27
    .maxTimeMS(5000)
28
    .toArray((err, data) => {
29
        if (err) {
30
            // Handle errors in your application
31
            // In this example, by sending the client a message
32
            res.send("The request has timed out. Please check your connection and try again.");
33
        }
34
        return res.json(data);
35
    });
36
});
37
38
app.post('/users', (req, res) => {
39
    const collection = client.db("test").collection("users");
40
    collection.insertOne({ name: req.body.name })
41
    .then(result => {
42
        res.send("User successfully added!");
43
    }, err => {
44
        // Handle errors in your application
45
        // In this example, by sending the client a message
46
        res.send("An application error has occurred. Please try again.");
47
    })
48
});
49
// ----- End of API routes ----- //
50
51
app.listen(3000, () => {
52
    console.log(`Listening on port 3000.`);
53
    client.connect(err => {
54
        if (err) {
55
            console.log("Not connected: ", err);
56
            process.exit(0);
57
        }
58
        console.log('Connected.');
59
    });
60
});