Sessions

Coherence uses the concept of a Session to manage a set of related Coherence resources, such as maps and/or caches. When using the Coherence Python Client, a Session connects to a specific gRPC endpoint and uses a specific serialization format to marshal requests and responses. This means that different sessions using different serializers may connect to the same server endpoint. Typically, for efficiency the client and server would be configured to use matching serialization formats to avoid deserialization of data on the server, but this does not have to be the case. If the server is using a different serializer for the server-side caches, it must be able to deserialize the client’s requests, so there must be a serializer configured on the server to match that used by the client.

Note

Currently, the Coherence Python client only supports JSON serialization

A Session is constructed using an Options instance, or a generic object with the same keys and values.

The currently supported arguments foe Options are:

  • address - the address of the Coherence gRPC proxy. This defaults to localhost:1408.

  • request_timeout_seconds - the gRPC request timeout in seconds. This defaults to 30.0.

  • channel_options - per-request gRPC channel options.

  • tls_options - options related to the configuration of TLS.

    • enabled - determines if TLS is enabled or not. This defaults to false (NOTE: assumes true if all three COHERENCE_TLS_* (see subsequent bullets) environment variables are defined)

    • ca_cert_path - the path to the CA certificate. This may be configured using the environment variable COHERENCE_TLS_CERTS_PATH

    • client_cert_path - the path to the client certificate. This may be configured with the environment variable COHERENCE_TLS_CLIENT_CERT

    • client_key_path - the path to the client certificate key. This may be configured with the environment variable COHERENCE_TLS_CLIENT_KEY

from coherence import NamedCache, Session
import asyncio

   # create a new Session to the Coherence server
    session: Session = Session(None)
This is the simplest invocation which assumes the following defaults:

  • address is localhost:1408

  • request_timeout_seconds is 30.0

  • tls_options is disabled

To use values other than the default, create a new Options instance, configure as desired, and pass it to the constructor of the Session:

from coherence import NamedCache, Session
import asyncio

   # create a new Session to the Coherence server
    addr: str = 'example.com:4444'
    opt: Options = Options(addr, default_scope, default_request_timeout, default_format)
    session: Session = Session(opt)

It’s also possible to control the default address the session will bind to by providing an address via the COHERENCE_SERVER_ADDRESS environment variable. The format of the value would be the same as if you configured it programmatically as the above example shows. The default timeout can also be configured using COHERENCE_CLIENT_REQUEST_TIMEOUT environment variable.

Once the session has been constructed, it will now be possible to create maps and caches.