Managing Connections using the .NET SDK with Couchbase Server

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    This section describes how to connect the .NET SDK to a Couchbase cluster. It contains best practices as well as information on TLS/SSL and other advanced connection options.

    Connecting to a Cluster

    A connection to a Couchbase Server cluster is represented by a Cluster object. A Cluster provides access to Buckets, Scopes, and Collections, as well as various Couchbase services and management interfaces. The simplest way to create a Cluster object is to call Cluster.ConnectAsync() with a connection string, username, and password:

    var cluster = await Cluster.ConnectAsync("couchbase://localhost", "username", "passord");
    var bucket =  await cluster.BucketAsync("travel-sample");
    var collection = bucket.DefaultCollection();
    
    // You can access multiple buckets using the same Cluster object.
    var anotherBucket = await cluster.BucketAsync("beer-sample");
    
    // You can access collections other than the default
    // if your version of Couchbase Server supports this feature.
    var customerA = bucket.Scope("customer-a");
    var widgets = customerA.Collection("widgets");
    
    // For a graceful shutdown, disconnect from the cluster when the program ends.
    await cluster.DisposeAsync();
    If you are connecting to a version of Couchbase Server older than 6.5, it will be more efficient if the addresses are those of data (KV) nodes. You will in any case, with 6.0 and earlier, need to open a `Bucket instance before connecting to any other HTTP services (such as Query or Search.

    In a production environment, your connection string should include the addresses of multiple server nodes in case some are currently unavailable. Multiple addresses may be specified in a connection string by delimiting them with commas:

    var cluster = await Cluster.ConnectAsync("192.168.56.101,192.168.56.102", "username", "password");
    You don’t need to include the address of every node in the cluster. The client fetches the full address list from the first node it is able to contact.

    Connection Strings

    A Couchbase connection string is a comma-delimited list of IP addresses and/or hostnames, optionally followed by a list of parameters.

    The parameter list is just like the query component of a URI; name-value pairs have an equals sign (=) separating the name and value, with an ampersand (&) between each pair. Just as in a URI, the first parameter is prefixed by a question mark (?).

    Simple connection string with one seed node
    127.0.0.1
    Connection string with two seed nodes
    nodeA.example.com,nodeB.example.com
    Connection string with two parameters
    127.0.0.1?io.networkResolution=external&timeout.kvTimeout=10s

    Currently, as of .NET SDK Version 3.0.2 there is only partial mapping of query parameters to options properties. This will change in future versions and the entire list of mappings will be found in the client settings reference.

    A connection string may optionally be prefixed by either "couchbase://" or "couchbases://". If "couchbases://" is used, the client will use secure connections (TLS/SSL) if a valid certificate is configured or you can use the ClusterOptions.EnableTls flag.

    Connection Lifecycle

    Most of the high-level classes in the .NET SDK are designed to be safe for concurrent use by multiple threads. You will get the best performance if you share and reuse instances of Cluster, Bucket, Scope, and Collection, all of which are thread-safe.

    We recommend creating a single Cluster instance when your application starts up, and sharing this instance throughout your application. If you know at startup time which buckets, scopes, and collections your application will use, we recommend obtaining them from the Cluster at startup time and sharing those instances throughout your application as well.

    Before your application stops, gracefully shut down the client by calling the Dispose method of each Cluster you created. In older applications this can be done in Application_Start and Application_End in your Global.asax file. For newer applictions we suggest using Dependency Injection and Startup.cs file.

    Dependency Injection

    There is a special .NET Core style Dependency Injection (DI) framework for Cluster and Buckets. It simplifies cluster configuration, lifetime management, and bucket injection. You can find it on NuGet.org: NuGet package. Or using the NuGet Package Manager, add the dependency directly to your project:

    Install-Package Couchbase.Extensions.DependencyInjection -Version 3.0.0

    Adding Couchbase To The Services Collection

    The easiest way to get started in a Web application is to use the ConfigureService method in the Services.cs:

    public void ConfigureServices(IServiceCollection services)
    {
        services.AddControllers();
    
        services.AddCouchbase(Configuration.GetSection("Couchbase"));
        services.AddCouchbaseBucket<INamedBucketProvider>("");
    }

    Injecting Couchbase Buckets

    To get a couchbase bucket, simply inject IBucketNamedProvider and call GetBucketAsync. Be sure that you don’t dispose the IBucket, it’s a singleton that will be reused through the application.

    public class HomeController : Controller
    {
        private readonly ILogger<HomeController> _logger;
        private readonly ITravelSampleBucketProvider _provider;
    
        public HomeController(ILogger<HomeController> logger, INamedBucketProvider provider)
        {
            _logger = logger;
            _provider = provider;
        }
    
        public async Task<IActionResult> IndexAsync()
        {
            var bucket = await _provider.GetBucketAsync();
            //do some work
    
            return View();
        }
    }

    Simplifying Injecting Bucket Names

    public interface IMyBucketProvider : INamedBucketProvider
    {
    }

    To further simplify dependency injection, you can setup to inject specific buckets. First, create an interface for each bucket that inherits from INamedBucketProvider. This interface must be public and left empty.

    You can then configure your bucket interfaces during IServiceCollection setup.

    public void ConfigureServices(IServiceCollection services)
    {
        services.AddControllers();
    
        services.AddCouchbase(Configuration.GetSection("Couchbase"));
        services.AddCouchbaseBucket<IMyBucketProvider>("my-bucket");
    }

    The interface you created can now be injected into controllers or business logic, and the GetBucketAsync method will return the specified bucket. You are no longer required to know the name of the bucket in the controller, improving separation of concerns in your application.

    public class HomeController : Controller
    {
        private readonly ILogger<HomeController> _logger;
        private readonly ITravelSampleBucketProvider _provider;
    
        public HomeController(ILogger<HomeController> logger, IMyBucketProvider provider)
        {
            _logger = logger;
            _provider = provider;
        }
    
        public async Task<IActionResult> IndexAsync()
        {
            var bucket = await _provider.GetBucketAsync();
            //do some work
    
            return View();
        }
    }

    Shutdown

    During application shutdown it’s best to close the Couchbase connections gracefully. You can do this using the ICouchbaseLifetimeService.` For Asp.Net Core, you can call this service from the ApplicationStopped cancellation token of IHostApplicationLifetime.

    public void Configure(IApplicationBuilder app, IWebHostEnvironment env, IHostApplicationLifetime applicationLifetime)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }
    
        app.UseRouting();
    
        app.UseAuthorization();
    
        app.UseEndpoints(endpoints =>
        {
            endpoints.MapControllers();
        });
    
    
         applicationLifetime.ApplicationStopped.Register(async () =>
            {
                await app.ApplicationServices.GetRequiredService<ICouchbaseLifetimeService>().CloseAsync()
                    .ConfigureAwait(false);
            }
        );
    }

    Secure Connections

    Couchbase Server Enterprise Edition supports full encryption of client-side traffic using Transport Layer Security (TLS). That includes key-value type operations, queries, and configuration communication. Make sure you have the Enterprise Edition of Couchbase Server before proceeding with configuring encryption on the client side.

    To configure encryption for the .NET SDK:

    1. Get the CA certificate from the cluster and save it in a text file.

    2. Enable encryption on the client side and point it to the file containing the certificate.

    It is important to make sure you are transferring the certificate in an encrypted manner from the server to the client side, so either copy it through SSH or through a similar secure mechanism.

    If you are running on localhost and just want to enable TLS for a development machine, just copying and pasting it suffices — so long as you use 127.0.0.1 rather than localhost in the connection string. This is because the certificate will not match the name localhost. Setting TLSSkipVerify is a workaround if you need to use couchbases://localhost.

    Navigate in the admin UI to Settings  Cluster and copy the input box of the TLS certificate into a file on your machine (which we will refer to as cluster.cert). It looks similar to this:

    -----BEGIN CERTIFICATE-----
    MIICmDCCAYKgAwIBAgIIE4FSjsc3nyIwCwYJKoZIhvcNAQEFMAwxCjAIBgNVBAMT
    ASowHhcNMTMwMTAxMDAwMDAwWhcNNDkxMjMxMjM1OTU5WjAMMQowCAYDVQQDEwEq
    MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAzz2I3Gi1XcOCNRVYwY5R
    ................................................................
    mgDnQI8nw2arBRoseLpF6WNw22CawxHVOlMceQaGOW9gqKNBN948EvJJ55Dhl7qG
    BQp8sR0J6BsSc86jItQtK9eQWRg62+/XsgVCmDjrB5owHPz+vZPYhsMWixVhLjPJ
    mkzeUUj/kschgQ0BWT+N+pyKAFFafjwFYtD0e5NwFUUBfsOyQtYV9xu3fw+T2N8S
    itfGtmmlEfaplVGzGPaG0Eyr53g5g2BgQbi5l5Tt2awqhd22WOVbCalABd9t2IoI
    F4+FjEqAEIr1mQepDaNM0gEfVcgd2SzGhC3yhYFBAH//8W4DUot5ciEhoBs=
    -----END CERTIFICATE-----

    The next step is to enable encryption and import the certificate.

    var cluster = await Cluster.ConnectAsync(new ClusterOptions
        {
            EnableTls = true
        }
        .WithConnectionString("couchbase://127.0.0.1")
        .WithCredentials("username", "password"));

    Importing the Certificate into Windows

    For development, do the following steps to install the certificate:

    1. Open Notepad or your favorite text editor using "Run as administrator".

    2. Copy the contents of the certificate into the editor.

    3. Save as type "All files" and specify the ".crt" file extension.

    4. Right click on the file after saving it and click "Install Certificate".

    5. Select "Current User" or "Local Machine" depending upon who you want to access the certificate.

    6. Select "Next" and then store it as "Trusted Root Certificate Authority".

    Importing the Certificate into MacOS

    1. Copy the certificate into a text file with the extension ".crt".

    2. Double click on the file and add it to "system" and approve with your password or fingerprint.

    3. Double click on the file and expand the "trust" area, mark it as trusted instead of system default.

    4. Exit and approve.

    Importing the Certificate into GNU/Linux

    Although different distributions differ slightly in the details of their certificate handling, they will be similar to one of the two patterns below. Refer to your distribution’s documentation for precise instructions.

    • Debian and Ubuntu

    • RHEL and CentOS

    $ cd /usr/local/share/ca-certificates/

    Name a sub-directory to hold the Couchbase certificate:

    $ mkdir couchbase-cert
    $ cp /path/to/my-certificate.crt couchbase-cert/
    Ensure that the permissions are correct
    $ chmod 755 couchbase-cert ; chmod 644 couchbase-cert/my-certificate.crt
    Update ca-certificates configuration to include the newly imported certificate
    sudo dpkg-reconfigure ca-certificates
    Commit the changes
    $ sudo update-ca-certificates
    $ sudo cp my-certificate.crt /etc/pki/ca-trust/source/anchors/
    $ sudo update-ca-trust extract

    Certificate Verification

    If you want to verify it’s actually working, you can use a tool like tcpdump. For example, an unencrypted upsert request looks like this (using sudo tcpdump -i lo0 -A -s 0 port 11210):

    E..e..@.@.............+......q{...#..Y.....
    .E...Ey........9........................id{"key":"value"}
    
    After enabling encryption, you cannot inspect the traffic in cleartext (same upsert request, but watched on port 11207 which is the default encrypted port):
    
    E.....@.@.............+....Z.'yZ..#........
    ..... ...xuG.O=.#.........?.Q)8..D...S.W.4.-#....@7...^.Gk.4.t..C+......6..)}......N..m..o.3...d.,.	...W.....U..
    .%v.....4....m*...A.2I.1.&.*,6+..#..#.5

    Using DNS SRV records

    As an alternative to specifying multiple hosts in your program, you can get the actual bootstrap node list from a DNS SRV record. The following steps are necessary to make it work:

    1. Set up your DNS server to respond properly from a DNS SRV request.

    2. Enable it on the SDK and point it towards the DNS SRV entry.

    Your DNS server should be set up like this (one row for each bootstrap node):

    _couchbase._tcp.example.com.  3600  IN  SRV  0  0  11210  node1.example.com.
    _couchbase._tcp.example.com.  3600  IN  SRV  0  0  11210  node2.example.com.
    _couchbase._tcp.example.com.  3600  IN  SRV  0  0  11210  node3.example.com.
    The ordering, priorities, and weighting are completely ignored and should not be set on the records to avoid ambiguities.

    If you plan to use secure connections, you use _couchbases instead:

    _couchbases._tcp.example.com.  3600  IN  SRV  0  0  11207  node1.example.com.
    _couchbases._tcp.example.com.  3600  IN  SRV  0  0  11207  node2.example.com.
    _couchbases._tcp.example.com.  3600  IN  SRV  0  0  11207  node3.example.com.

    DNS SRV Bootstrapping

    DNS SRV bootstrapping is available in the .NET SDK from version 2.1.0. In order to make the SDK actually use the SRV records, you just need to pass in the host name from your records (here example.com):

    var cluster = await Cluster.ConnectAsync(new ClusterOptions
        {
            EnableTls = true
        }
        .WithConnectionString("couchbases://[YOUR DNS CONNECTION STRING]")
        .WithCredentials("username", "password"));

    If the DNS SRV records could not be loaded properly you’ll get the exception logged and the given host name will be used as a A record lookup.

        [INF] Error trying to retrieve DNS SRV entries. (addddf06)
        DnsClient.DnsResponseException: Query 63320 => _couchbase._tcp.10.143.200.101 IN SRV on 2001:4860:4860::8888:53 failed with an error.

    Also, if you pass in more than one node, DNS SRV bootstrap will not be initiated and regular bootstrapping will occur.

    Waiting for Bootstrap Completion

    Depending on the environment and network latency, bootstrapping the SDK fully might take a little longer than the default key-value timeout of 2.5 seconds, so you may see timeouts during bootstrap. To prevent those early timeouts from happening, you can use the waitUntilReady method.

    If you are working at the Cluster level, then add to the cluster() in the earlier example:

    var cluster = await Cluster.ConnectAsync("couchbase://127.0.0.1", "username", "password");
    await cluster.WaitUntilReadyAsync(TimeSpan.FromSeconds(10));
    var bucket = await cluster.BucketAsync("default");
    var collection = bucket.DefaultCollection();

    Or more fully:

    public class ClusterExample
    {
        public async Task Main(string[] args)
        {
            var cluster = await Cluster.ConnectAsync("couchbase://127.0.0.1", "username", "password");
            await cluster.WaitUntilReadyAsync(TimeSpan.FromSeconds(10));
            var bucket = await cluster.BucketAsync("default");
            var collection = bucket.DefaultCollection();
            //..
        }
    }

    If you are working at the Bucket level, then the Bucket-level waitUntilReady does the same as the Cluster-level version, plus it waits for the K-V (data) sockets to be ready.

    public class ClusterExample2
    {
        public async Task Main(string[] args)
        {
            var cluster = await Cluster.ConnectAsync("couchbase://127.0.0.1", "username", "password");
            var bucket = await cluster.BucketAsync("default");
            await bucket.WaitUntilReadyAsync(TimeSpan.FromSeconds(10));
            var collection = bucket.DefaultCollection();
            //..
        }
    }

    Other timeout issues may occur when using the SDK located geographically separately from the Couchbase Server cluster — this is not recommended. See the Cloud section below for some suggestions of settings adjustments.

    Working in the Cloud

    For most use cases, connecting client software using a Couchbase SDK to the new Couchbase Cloud service is similar to connecting to an on-premises Couchbase Cluster. The use of DNS-SRV. Altermate Address, and TLS is covered above.

    We strongly recommend that the client and server are in the same LAN-like environment (e.g. AWS Availability Zone). As this may not always be possible during development, read the guidance on working with constrained network environments. More details on connecting your client code to the Couchbase Cloud can be found in the Cloud docs.

    Troubleshooting Connections to Cloud

    Some DNS caching providers (notably, home routers) can’t handle an SRV record that’s large — if you have DNS-SRV issues with such a set-up, reduce your DNS-SRV to only include three records. [For development only, not production.]. Our Troubleshooting Cloud Connections page will help you to diagnose this and other problems — as well as introducing the SDK doctor tool.

    Additional Resources

    • Our Authentication page covers connecting with LDAP and Certificate Authentication.

    • Connecting from SDK to Couchbase Server is best done wih both being in the same LAN-like environment or Cloud Availability Zone. This is not always possible at the development stage, where you may be using a local laptop for SDK development against a Couchbase Cloud Server, so help is available for timeout issues in such unsupported configurations in our Troubleshooting Cloud Connections page.