Manage the DPF licensing logic using the server context

This example shows how to manage the licensing logic of a DPF server using a ServerContext.

You can prevent DPF from checking licenses out and blocking increments by using the Entry context.

Warning

You cannot start a new InProcess server, as starting an InProcess server means linking the DPF binaries to your current Python process. If your local InProcess server is already set to Premium, you cannot set it back to Entry. Since InProcess is the default server type, put the commands to set the Entry server context at the start of your script.

Note

This example requires DPF 6.1 (Ansys 2023R2) or above. For more information, see Compatibility.

# Import necessary modules
from ansys.dpf import core as dpf
from ansys.dpf.core.core import errors

Start a server as Entry to prevent using licensed operators

server = dpf.start_local_server(
    context=dpf.AvailableServerContexts.entry,
    config=dpf.AvailableServerConfigs.GrpcServer,
    as_global=False,
)
# The context is shown as Entry
print(server.context)

# A server of type InProcess being linked to the current Python process,
# if an InProcess server already exists as Premium, you cannot set it back as Entry.

Server Context of type LicensingContextType.entry with no xml path

Create a dummy Field

field = dpf.Field(server=server)
field.append([0.0, 0.0, 0.0], 1)
print(field)

# Instantiate an Entry (not licensed) DPF operator
op_entry = dpf.operators.math.add_constant(field=field, ponderation=2.0, server=server)

# Instantiate a Premium (licensed) DPF operator
op_premium = dpf.operators.filter.field_high_pass(field=field, threshold=0.0, server=server)

DPF  Field
  Location: Nodal
  Unit:
  1 entities
  Data: 3 components and 1 elementary data

  IDs                   data
  ------------          ----------
  1                     0.000000e+00   0.000000e+00   0.000000e+00

Operators with the Entry context

# Using unlicensed DPF operators is possible
out = op_entry.eval()
print(out)

# While using license ones is blocked, raising an error
try:
    op_premium.eval()
except errors.DPFServerException as e:
    print(e)

DPF  Field
  Location: Nodal
  Unit:
  1 entities
  Data: 3 components and 1 elementary data

  IDs                   data
  ------------          ----------
  1                     2.000000e+00   2.000000e+00   2.000000e+00



a 'data processing core error' error occurred: core::field::high_pass:2<-DPF issue due to licensing context: execution stopped. Apply Premium context to unlock this capability.

Operators with the Premium context

# Set the default server context as Premium for new servers
dpf.set_default_server_context(dpf.AvailableServerContexts.premium)
# or in our case, apply the Premium context to the current server
server.apply_context(dpf.AvailableServerContexts.premium)

# Licensed operators can now check a license out and run
out = op_premium.eval()
print(out)

DPF  Field
  Location: Nodal
  Unit:
  0 entities
  Data: 3 components and 0 elementary data

When Premium, using a LicenseContextManaged allows you to control your interaction with a license It gives direct control over when the license check-out and check-in occur, as well as which license increment is used, and for what maximum duration.

# Use the LicenseContextManager to block a specific increment for a limited duration
with dpf.LicenseContextManager(increment_name="preppost", license_timeout_in_seconds=1.0) as lic:
    # Instantiate the licensed operator
    out = op_premium.eval()
    print(out)

DPF  Field
  Location: Nodal
  Unit:
  0 entities
  Data: 3 components and 0 elementary data