Replaced the static key-value attribute storage in update-form instruments
with sample-evaluated attributes, matching the log-record attr change.
The 'attr' keyword now accepts a key and a HAProxy sample expression
evaluated at runtime.
The struct (conf.h) changed from otelc_kv/attr_len to a list of
flt_otel_conf_sample entries. The parser (parser.c) calls
flt_otel_parse_cfg_sample() with n=1 per attr keyword. At runtime
(event.c) each attribute is evaluated via flt_otel_sample_eval() and
added via flt_otel_sample_add_kv() to a bare flt_otel_scope_data_kv,
which is passed to the meter.
Updated documentation, debug macro and test configurations.
Replaced the static key-value attribute storage in log-record with
sample-evaluated attributes. The 'attr' keyword now accepts a key and a
HAProxy sample expression evaluated at runtime, instead of a static string
value.
The struct (conf.h) changed from otelc_kv/attr_len to a list of
flt_otel_conf_sample entries. The parser (parser.c) calls
flt_otel_parse_cfg_sample() with n=1 per attr keyword. At runtime
(event.c) each attribute is evaluated via flt_otel_sample_eval() and added
via flt_otel_sample_add_kv() to a bare flt_otel_scope_data_kv, which is
passed to logger->log_span().
Updated documentation, debug macro and test configurations.
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.
Extended flt_otel_parse_cfg_sample() to accept log-format strings in
addition to bare sample expressions. Added lf_expr and lf_used fields
to flt_otel_conf_sample.
Extended flt_otel_sample_add() to evaluate log-format expressions when
lf_used was set.
Replaced the stub filter callbacks with full implementations that dispatch
OTel events through the scope execution engine, and added the supporting
debug, error handling and utility infrastructure.
The filter lifecycle callbacks (init, deinit, init_per_thread) now
initialize the OpenTelemetry C wrapper library, create the tracer from the
instrumentation configuration file, enable HTX stream filtering, and clean
up the configuration and memory pools on shutdown.
The stream callbacks (attach, stream_start, stream_set_backend,
stream_stop, detach, check_timeouts) create the per-stream runtime context
on attach with rate-limit based sampling, fire the corresponding OTel
events (on-stream-start, on-backend-set, on-stream-stop), manage the
idle timeout timer with reschedule logic in detach, and free the runtime
context in check_timeouts. The attach callback also registers the
required pre and post channel analyzers from the instrumentation
configuration.
The channel callbacks (start_analyze, pre_analyze, post_analyze,
end_analyze) register per-channel analyzers, map analyzer bits to event
indices via flt_otel_get_event(), and dispatch the matching events.
The end_analyze callback also fires the on-server-unavailable event
when response analyzers were configured but never executed.
The HTTP callbacks (http_headers, http_end, http_reply, and the debug-only
http_payload and http_reset) dispatch their respective request/response
events based on the channel direction.
The event dispatcher flt_otel_event_run() in event.c iterates over all
scopes matching a given event index and calls flt_otel_scope_run() for
each, sharing a common monotonic and wall-clock timestamp across all spans
within a single event.
Error handling is centralized in flt_otel_return_int() and
flt_otel_return_void(), which implement the hard-error/soft-error policy:
hard errors disable the filter for the stream, soft errors are silently
cleared.
The new debug.h header provides conditional debug macros
(FLT_OTEL_DBG_ARGS, FLT_OTEL_DBG_BUF) and the FLT_OTEL_LOG macro for
structured logging through the instrumentation's log server list. The
utility layer gained debug-only label functions for channel direction,
proxy mode, stream position, filter type, and analyzer bit name lookups.
Implemented the flt_otel_ops_check() callback that validates the parsed
OTel filter configuration after all HAProxy configuration sections have
been processed.
The check callback performs the following validations: resolves deferred
sample fetch arguments under full frontend and backend capabilities,
verifies uniqueness of filter IDs across all proxies, ensures the
instrumentation section and its configuration file are present, checks
for duplicate group and scope section names, verifies that groups are not
empty, resolves group-to-scope and instrumentation-to-group/scope
cross-references by linking placeholder entries to their definitions,
detects unused scopes, counts root spans and warns when the count differs
from one, and accumulates the required channel analyzer bits from all used
scopes into the instrumentation configuration.
The commit also added the flt_otel_counters structure to track per-event
diagnostic counters in debug builds, the FLT_OTEL_ALERT macro for
filter-scoped error messages, and the FLT_OTEL_DBG_LIST macro for
iterating and dumping named configuration lists.
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.
