Added "log-record" as the third OpenTelemetry signal alongside traces
(span) and metrics (instrument). This includes the
flt_otel_conf_log_record structure definition, parser keyword defines,
the otel-scope section parser with optional "id", "event", "span", and
"attr" keywords followed by sample fetch expressions or a log-format
string, init/free lifecycle, scope list wiring, log-format evaluation
in flt_otel_scope_run_instrument_record(), a test configuration example,
log-record span reference validation in flt_otel_check(), and logger
handle creation, startup, and teardown in the filter lifecycle.
Added the "instrument" keyword to otel-scope sections for recording metric
measurements alongside traces.
Introduced flt_otel_conf_instrument holding instrument type, description,
unit, sample expressions, and optional key-value attributes. The
supported synchronous integer-precision instrument types were counters,
histograms, up-down counters, and gauges.
Instruments followed a two-form design: a "create" form defined a new
instrument with its type and value expression, while an "update" form
recorded measurements against an existing instrument with per-scope
attributes.
Instrument creation was performed lazily at first use with HA_ATOMIC_CAS
to guarantee thread-safe one-time initialization. The configuration
check phase validated that every update-form had a matching create-form
definition and that create-form names were unique across all scopes.
The meter lifecycle was integrated into filter init and deinit, starting
the meter alongside the tracer and shutting it down during cleanup.
Added span link support, allowing a span to reference other spans or
extracted contexts without establishing a parent relationship.
Introduced the flt_otel_conf_link structure and added a links list to
flt_otel_conf_span. The parser accepted both an inline syntax on the span
declaration line ("span <name> link <target>") and a standalone multi-
argument form ("link <span> ..."), each creating a conf_link entry
appended to the span's link list.
At runtime, each configured link name was resolved against the active
spans and extracted contexts in the runtime context. Resolved references
were collected into flt_otel_scope_data_link entries and passed to the C
wrapper add_link API during span creation.
Initialization, cleanup, and debug dump routines were added for the link
data structures at both configuration and runtime levels.
Added the configuration structures that model the OTel filter's
instrumentation hierarchy and the utility functions that support the
configuration parser.
The configuration is organized as a tree rooted at flt_otel_conf, which
holds the proxy reference, filter identity, and lists of groups and
scopes. Below it, flt_otel_conf_instr carries the instrumentation
settings: tracer handle, rate limiting, hard-error mode, logging state,
channel analyzers, and placeholder references to groups and scopes.
Groups (flt_otel_conf_group) aggregate scopes by name. Scopes
(flt_otel_conf_scope) bind an event to its ACL condition, span context
declarations, span definitions and a list of spans scheduled for
finishing. Spans (flt_otel_conf_span) carry attributes, events,
baggages and status entries, each represented as flt_otel_conf_sample
structures that pair a key with concatenated sample-expression arguments.
All configuration types share a common header macro (FLT_OTEL_CONF_HDR)
that embeds an identifier string, its length, a configuration line number,
and a list link. Their init and free functions are generated by the
FLT_OTEL_CONF_FUNC_INIT and FLT_OTEL_CONF_FUNC_FREE macros in
conf_funcs.h, with per-type custom initialization and cleanup bodies.
The utility layer in util.c provides argument counting and concatenation
for the configuration parser, sample data to string conversion covering
boolean, integer, IPv4, IPv6, string and HTTP method types, and debug
helpers for dumping argument arrays and linked list state.
