Managing Connections

This section describes how to connect the Python SDK to a Couchbase cluster. It contains best practices as well as information on TLS/SSL and advanced connection options, and a sub-page on troubleshooting Cloud connections.

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.connect() with a connection string, username, and password:

Couchbase Capella
Self-Managed Couchbase Server

# Update this to your cluster
endpoint = "--your-instance--.dp.cloud.couchbase.com"
username = "username"
password = "Password!123"
bucket_name = "travel-sample"
# User Input ends here.

# Connect options - authentication
auth = PasswordAuthenticator(username, password)

# get a reference to our cluster
options = ClusterOptions(auth)
# Sets a pre-configured profile called "wan_development" to help avoid latency issues
# when accessing Capella from a different Wide Area Network
# or Availability Zone(e.g. your laptop).
options.apply_profile('wan_development')
cluster = Cluster.connect('couchbases://{}'.format(endpoint), options)

# Wait until the cluster is ready for use.
cluster.wait_until_ready(timedelta(seconds=5))

Note, the client certificate for connecting to a Capella cluster is included in the SDK installation.

# Update this to your cluster
username = "Administrator"
password = "password"
bucket_name = "travel-sample"
# User Input ends here.

# Connect options - authentication
auth = PasswordAuthenticator(
    username,
    password,
)

# Get a reference to our cluster
# NOTE: For non-TLS/SSL connection use 'couchbase://<your-ip-address>' instead
cluster = Cluster.connect('couchbases://your-ip', ClusterOptions(auth))

# Wait until the cluster is ready for use.
cluster.wait_until_ready(timedelta(seconds=5))

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:

cluster = Cluster.connect("couchbase://node1.example.com,node2.example.com", ClusterOptions(PasswordAuthenticator("Administrator", "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.

Waiting for Bootstrap Completion

Opening resources is asynchronous. That is, the call to cluster.bucket or Cluster.connect will complete instantly, and opening that resource will continue in the background.

WaitUntilReady()

For some of the SDKs, such as Java, you’ll see a recommendation to use waitUntilReady(), which ensures that the bucket resource is fully loaded before proceeding.

Although this is an element of the SDK bootstrapping RFC, it’s not required for successful operation of the "wrapper" SDKs (Node.js, PHP, Python, and Ruby — wrappers over the C++ SDK), as Cluster.connect() blocks until bootstrap is complete and a cluster config is seen. Any bootstrap errors are returned there.

Other timeout issues may occur when using the SDK located geographically separately from the Couchbase Server cluster — this is not recommended in production deployments, but often occurs during development. See the Cloud section below for some suggestions of settings adjustments.

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

couchbase://127.0.0.1

Connection string with two seed nodes

couchbase://nodeA.example.com,nodeB.example.com

Connection string with two parameters

couchbases://127.0.0.1?compression=on&redaction=on

The full list of recognized parameters is documented in the client settings reference. Any client setting with a system property name may also be specified as a connection string parameter.

A connection string may optionally be prefixed by either "couchbase://" or "couchbases://", the latter signifying a TLS connection.

Connection Options

Configuring client settings with ClusterOptions() is the preferred option for configuring connection parameters. More details can be found in the API reference.

Connection Lifecycle

Most of the high-level classes in the Python SDK are designed to be safe for concurrent use by multiple threads. For asynchronous modes, you will get the best performance if you share and reuse instances of Cluster, Bucket, Scope, and Collection, all of which are thread-safe. For synchronous mode, it is better to use separate instances in different threads.

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.

Secure Connections

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

If the client cannot load or was not built with OpenSSL, attempting a TLS connection will result in a 'FEATURE_UNAVAILABLE'.

For TLS certificate verification the SDK uses the following CA certificates:

The certificates in the Mozilla Root CA bundle (bundled with the SDK as of 4.1.5 and obtained from curl).
The certificates in OpenSSL’s default CA certificate store.
The self-signed root certificate that is used to sign the Couchbase Capella certificates.

The OpenSSL defaults can be overridden using the SSL_CERT_DIR and SSL_CERT_FILE environment variables. The SSL_CERT_DIR variable is used to set a specific directory in which the client should look for individual certificate files, whereas the SSL_CERT_FILE environment variable is used to point to a single file containing one or more certificates. More information can be found in the relevant OpenSSL documentation.

Loading the Mozilla certificates can be disabled by setting the disable_mozilla_ca_certificates property of ClusterOptions.

Metadata from the Python SDK’s C++ core provides information about where OpenSSL’s default certificate store is located, which version of the Mozilla CA certificate store was bundled, and other useful details. You can get the metadata using the following command:

$ python3 -c "from couchbase import get_metadata; print(get_metadata(detailed=True))"

{
 ...
 'mozilla_ca_bundle_date': 'Tue Jan 10 04:12:06 2023 GMT',
 'mozilla_ca_bundle_embedded': True,
 'mozilla_ca_bundle_sha256': 'fb1ecd641d0a02c01bc9036d513cb658bbda62a75e246bedbc01764560a639f0',
 'mozilla_ca_bundle_size': 137,
 ...
 'openssl_default_cert_dir': '/opt/homebrew/etc/openssl@1.1/certs',
 'openssl_default_cert_dir_env': 'SSL_CERT_DIR',
 'openssl_default_cert_file': '/opt/homebrew/etc/openssl@1.1/cert.pem',
 'openssl_default_cert_file_env': 'SSL_CERT_FILE',
 ...
}

With debug-level logging enabled, if the Mozilla certificates have been loaded, a message with the information about the version of the Mozilla CA certificate store will be outputted. For example:

loading 137 CA certificates from Mozilla bundle. Update date: "Tue Jan 10 04:12:06 2023 GMT", SHA256: "fb1ecd641d0a02c01bc9036d513cb658bbda62a75e246bedbc01764560a639f0"

Couchbase Capella
Couchbase Server

The Python SDK bundles Capella’s standard root certificate by default. This means you don’t need any additional configuration to enable TLS — simply use couchbases:// in your connection string.

Capella’s root certificate is not signed by a well known CA (Certificate Authority). However, as the certificate is bundled with the SDK, it is trusted by default.

Certificates from the Mozilla Root CA store are now bundled with the SDK (as of version 4.1.5). If the server’s certificate is signed by a well-known CA (e.g., GoDaddy, Verisign, etc.), you don’t need to configure the cert_path property in the PasswordAuthenticator — simply use couchbases:// in your connection string.

You can still provide a certificate explicitly if necessary:

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

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.crt). 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 by connecting to a cluster with the 'couchbases://' protocol in the connection string and pass it the path to the certificate file via an Authenticator, or via '?cert_path=…' in the connection string itself.

cluster = Cluster("couchbases://your-ip",ClusterOptions(PasswordAuthenticator("Administrator","password",cert_path="/path/to/cluster.crt")))

Then use this custom Cluster when opening the connection to the cluster.

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

Alternate Addresses and Custom Ports

If your Couchbase Server cluster is running in a containerized, port mapped, or otherwise NAT’d environment like Docker or Kubernetes, a client running outside that environment may need additional information in order to connect the cluster. Both the client and server require special configuration in this case.

On the server side, each server node must be configured to advertise its external address as well as any custom port mapping. This is done with the setting-alternate-address CLI command — see the command line docs. A node configured in this way will advertise two addresses: one for connecting from the same network, and another for connecting from an external network.

On the client side, the externally visible ports must be used when connecting. If the external ports are not the default, you can specify custom ports through the connection string.

int customKvPort = 1234;
int customManagerPort = 2345;
Set<SeedNode> seedNodes = new HashSet<>(Arrays.asList(
  SeedNode.create("127.0.0.1",
      Optional.of(customKvPort),
      Optional.of(customManagerPort))));

Cluster cluster = Cluster.connect(seedNodes, "username", "password");

In a deployment that uses multi-dimensional scaling, a custom KV port is only applicable for nodes running the KV service. A custom manager port may be specified regardless of which services are running on the node.

In many cases the client is able to automatically select the correct set of addresses to use when connecting to a cluster that advertises multiple addresses. If the detection heuristic fails in your environment, you can override it by setting the io.networkResolution client setting to default if the client and server are on the same network, or external if they’re on different networks.

Any TLS certificates must be set up at the point where the connections are being made.

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. For Capella, where you only have one endpoint provided, it’s good practice to always enable DNS-SRV on the client.

The following steps are necessary to make it work:

Set up your DNS server to respond properly from a DNS SRV request.
Enable it on the SDK and point it towards the DNS SRV entry.

Setting up the DNS Server

Capella gives you DNS-SRV by default — these instructions are for self-managed clusters, where you are responsible for your own DNS records.

Your DNS server zone file should be set up like this, with one row for each bootstrap (KV, a.k.a. Data Service) node:

; Service.Protocol.Domain	TTL	Class	Type	Priority	Weight	 Port	Target
_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.

The first line comment is not needed in the record, we are showing the column headers here for illustration purposes. The myriad complexities of DNS are beyond the scope of this document, but note that SRV records must point to an A record, not a CNAME.

The order in which you list the nodes — and any value entered for Priority or Weight — will be ignored by the SDK. Nevertheless, best practice here is to set them to 0, avoiding ambiguity.

Also note, the above is for connections using TLS. Should you be using an insecure connection (in testing or development, or totally within a firewalled environment), then your records would look like:

_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.

Specifying DNS-SRV for the SDK

The connection string must be to a single hostname, with no explicit port specifier, pointing to the DNS SRV entry — couchbases://example.com.
DNS-SRV must be enabled in the client settings.

DNS SRV bootstrapping is enabled by default in the Python SDK. In order to make the SDK use the SRV records, you need to pass in the hostname from your records (here example.com):

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

We strongly recommend that the client and server are in the same LAN-like environment (e.g. AWS Region). 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 Couchbase Capella 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.

Async APIs

The Couchbase Python SDK provides first-class support for asynchronous programming. The supported asynchronous APIs offer a similar API to the synchronous API.

Methods in the asynchronous API return instances of the relevant Async API:

Future for asyncio (acouchbase.cluster.Cluster supplies the relevant Cluster object)
Deferred for Twisted

Reference our asynchronous programming page for more details.

Next Steps

Certificate Authentication