The HTTP connection manager supports the following runtime settings:

% of requests with a remote address that will have their IPv4 address mapped to IPv6. Defaults to 0. use_remote_address must also be enabled. See represent_ipv4_remote_address_as_ipv4_mapped_ipv6 for more details.
% of requests that will be force traced if the x-client-trace-id header is set. Defaults to 100.
% of requests that will be traced after all other checks have been applied (force tracing, sampling, etc.). Defaults to 100.
% of requests that will be randomly traced. See here for more information. This runtime control is specified in the range 0-10000 and defaults to 10000. Thus, trace sampling can be specified in 0.01% increments.