otel: Add OpenTelemetry functionality to NGINX Unit

.editorconfig

@@ -1,6 +1,6 @@
 root = true
 
-[{configure,{*.{c,cpp,h,go,java,js,py,rs}}]
+[{configure,{*.{c,cpp,h,go,java,js,py,rs}}}]
 charset = utf-8
 end_of_line = lf
 insert_final_newline = true

auto/help

@@ -52,6 +52,8 @@ cat << END
 
   --njs                enable njs library usage
 
+  --otel               enable otel library usage
+
   --debug              enable debug logging
 
   --fuzz=ENGINE        enable fuzz testing

auto/make

@@ -7,7 +7,6 @@
 
 $echo "creating $NXT_MAKEFILE"
 
-
 cat << END > $NXT_MAKEFILE
 
 # Pretty print compiler etc actions...
@@ -22,6 +21,8 @@ AR =			$AR
 
 EXTRA_CFLAGS =
 CFLAGS = 		$NXT_CFLAGS $NXT_CC_OPT $CFLAGS \$(EXTRA_CFLAGS)
+RUST_FLAGS =
+NXT_OTEL_LIB_LOC =
 
 NXT_EXEC_LINK =		$NXT_EXEC_LINK $NXT_LD_OPT
 NXT_SHARED_LOCAL_LINK =	$NXT_SHARED_LOCAL_LINK $NXT_LD_OPT
@@ -62,6 +63,9 @@ D := 0
 
 ifeq (\$D,1)
         CFLAGS += -O0
+        RUST_FLAGS += --debug
+else
+        RUST_FLAGS += --release
 endif
 
 # Optionally disable -Werror with
@@ -76,6 +80,18 @@ END
 
 fi
 
+# potentially set otel lib location
+if [ $NXT_OTEL = YES ]; then
+cat << END >> $NXT_MAKEFILE
+
+ifeq (\$D,1)
+	NXT_OTEL_LIB_LOC = $NXT_OTEL_LIB_DIR/target/debug/libotel.a
+else
+	NXT_OTEL_LIB_LOC = $NXT_OTEL_LIB_DIR/target/release/libotel.a
+endif
+
+END
+fi
 
 # The include paths list.
 
@@ -138,14 +154,14 @@ cat << END >> $NXT_MAKEFILE
 
 libnxt:	$NXT_BUILD_DIR/lib/$NXT_LIB_SHARED $NXT_BUILD_DIR/lib/$NXT_LIB_STATIC
 
-$NXT_BUILD_DIR/lib/$NXT_LIB_SHARED: \$(NXT_LIB_OBJS)
+$NXT_BUILD_DIR/lib/$NXT_LIB_SHARED: \$(NXT_LIB_OBJS) \$(NXT_OTEL_LIB_LOC)
 	\$(PP_LD) \$@
 	\$(v)\$(NXT_SHARED_LOCAL_LINK) -o \$@ \$(NXT_LIB_OBJS) \\
-		$NXT_LIBM $NXT_LIBS $NXT_LIB_AUX_LIBS
+		$NXT_LIBM $NXT_LIBS $NXT_LIB_AUX_LIBS \$(NXT_OTEL_LIB_LOC)
 
-$NXT_BUILD_DIR/lib/$NXT_LIB_STATIC: \$(NXT_LIB_OBJS)
+$NXT_BUILD_DIR/lib/$NXT_LIB_STATIC: \$(NXT_LIB_OBJS) \$(NXT_OTEL_LIB_LOC)
 	\$(PP_AR) \$@
-	\$(v)$NXT_STATIC_LINK \$@ \$(NXT_LIB_OBJS)
+	\$(v)$NXT_STATIC_LINK \$@ \$(NXT_LIB_OBJS) \$(NXT_OTEL_LIB_LOC)
 
 $NXT_BUILD_DIR/lib/$NXT_LIB_UNIT_STATIC: \$(NXT_LIB_UNIT_OBJS) \\
 		$NXT_BUILD_DIR/share/pkgconfig/unit.pc \\
@@ -359,11 +375,11 @@ $echo >> $NXT_MAKEFILE
 cat << END >> $NXT_MAKEFILE
 
 $NXT_BUILD_DIR/sbin/$NXT_DAEMON:	$NXT_BUILD_DIR/lib/$NXT_LIB_STATIC \\
-				\$(NXT_OBJS)
+				\$(NXT_OBJS) \$(NXT_OTEL_LIB_LOC)
 	\$(PP_LD) \$@
 	\$(v)\$(NXT_EXEC_LINK) -o \$@ \$(CFLAGS) \\
 		\$(NXT_OBJS) $NXT_BUILD_DIR/lib/$NXT_LIB_STATIC \\
-		$NXT_LIBM $NXT_LIBS $NXT_LIB_AUX_LIBS
+		$NXT_LIBM $NXT_LIBS $NXT_LIB_AUX_LIBS \$(NXT_OTEL_LIB_LOC)
 
 END
 
@@ -535,10 +551,6 @@ cat << END > Makefile
 
 include $NXT_MAKEFILE
 
-.PHONY: clean
-clean:
-		rm -rf $NXT_BUILD_DIR *.dSYM Makefile
-
 .PHONY: help
 help:
 	@echo "Variables to control make/build behaviour:"
@@ -551,4 +563,24 @@ help:
 	@echo
 	@echo "  Variables can be combined."
 
+.PHONY: clean
+clean:
+		rm -rf $NXT_BUILD_DIR *.dSYM Makefile
+END
+
+if [ $NXT_OTEL = YES ]; then
+    cat << END >> Makefile
+		cd "$NXT_OTEL_LIB_DIR" && cargo clean
 END
+
+NXT_OTEL_DEPS=" \
+    build/src/nxt_otel.o \
+    src/otel/src/lib.rs \
+"
+
+    cat << END >> $NXT_MAKEFILE
+
+\$(NXT_OTEL_LIB_LOC): $NXT_OTEL_DEPS
+	cargo build \$(RUST_FLAGS) --manifest-path $NXT_OTEL_LIB_DIR/Cargo.toml
+END
+fi

auto/options

@@ -27,6 +27,7 @@ NXT_CYASSL=NO
 NXT_POLARSSL=NO
 
 NXT_NJS=NO
+NXT_OTEL=NO
 
 NXT_TEST_BUILD_EPOLL=NO
 NXT_TEST_BUILD_EVENTPORT=NO
@@ -112,6 +113,7 @@ do
         --polarssl)                      NXT_POLARSSL=YES                    ;;
 
         --njs)                           NXT_NJS=YES                         ;;
+        --otel)                          NXT_OTEL=YES                        ;;
 
         --test-build-epoll)              NXT_TEST_BUILD_EPOLL=YES            ;;
         --test-build-eventport)          NXT_TEST_BUILD_EVENTPORT=YES        ;;

auto/otel

@@ -0,0 +1,54 @@
+
+# Copyright (C) NGINX, Inc.
+
+if [ $NXT_OTEL = YES ]; then
+
+    $echo "checking for OTEL requirements:"
+
+    $echo -n "  - checking for rust compiler ... "
+    if [ -z $(which rustc 2>/dev/null) ]; then
+        $echo "not found"
+        exit 1;
+    fi
+    $echo "found"
+
+    $echo -n "  - checking for cargo ... "
+    if [ -z $(which cargo 2>/dev/null) ]; then
+        $echo "not found."
+        exit 1;
+    fi
+    $echo "found"
+
+    $echo -n "  - "
+
+    nxt_feature="OpenSSL library"
+    nxt_feature_run=yes
+    nxt_feature_incs=
+    nxt_feature_libs="-lssl -lcrypto"
+    nxt_feature_test="#include <openssl/ssl.h>
+
+                      int main(void) {
+                          SSL_library_init();
+                          return 0;
+                      }"
+    . auto/feature
+
+    if [ ! $nxt_found = yes ]; then
+        $echo
+        $echo $0: error: OpenTelemetry support requires OpenSSL.
+        $echo
+        exit 1;
+    fi
+
+    NXT_OTEL_LIBS="-lssl -lcrypto"
+    if [ $(which pkg-config) ]; then
+        NXT_OTEL_LIBS="$(pkg-config openssl --cflags --libs)"
+    fi
+    cat << END >> $NXT_AUTO_CONFIG_H
+
+#ifndef NXT_HAVE_OTEL
+#define NXT_HAVE_OTEL 1
+#endif
+
+END
+fi

auto/sources

@@ -127,6 +127,10 @@ if [ "$NXT_NJS" != "NO" ]; then
     NXT_LIB_SRCS="$NXT_LIB_SRCS src/nxt_js.c src/nxt_http_js.c src/nxt_script.c"
 fi
 
+if [ "$NXT_OTEL" != "NO" ]; then
+    NXT_LIB_SRCS="$NXT_LIB_SRCS src/nxt_otel.c"
+fi
+
 NXT_LIB_EPOLL_SRCS="src/nxt_epoll_engine.c"
 NXT_LIB_KQUEUE_SRCS="src/nxt_kqueue_engine.c"
 NXT_LIB_EVENTPORT_SRCS="src/nxt_eventport_engine.c"

auto/summary

@@ -30,6 +30,7 @@ Unit configuration summary:
   TLS support: ............... $NXT_OPENSSL
   Regex support: ............. $NXT_REGEX
   njs support: ............... $NXT_NJS
+  otel support: .............. $NXT_OTEL
 
   process isolation: ......... $NXT_ISOLATION
   cgroupv2: .................. $NXT_HAVE_CGROUP

configure

@@ -179,6 +179,12 @@ if [ $NXT_NJS != NO ]; then
     . auto/njs
 fi
 
+NXT_OTEL_LIB_DIR=src/otel
+if [ $NXT_OTEL != NO ]; then
+    . auto/otel
+    NXT_LIB_AUX_LIBS="$NXT_LIB_AUX_LIBS $NXT_OTEL_LIBS"
+fi
+
 . auto/make
 . auto/fuzzing
 . auto/summary

docs/unit-openapi.yaml

@@ -3090,6 +3090,68 @@ paths:
         "404":
           $ref: "#/components/responses/responseNotFound"
 
+  /config/settings/telemetry:
+    summary: "Endpoint for the `telemetry` object in `settings`"
+    get:
+      operationId: getSettingsTelemetry
+      summary: "Retrieve the `telemetry` object from settings"
+      description: "Retrieves the `telemetry` object that represents Unit's
+        [Telemetry settings](https://unit.nginx.org/configuration/#settings)."
+      tags:
+        - settings
+        - config
+      responses:
+        "200":
+          description: "Ok; the `telemetry` object exists in the configuration."
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/configSettingsTelemetry"
+        "404":
+          $ref: "#/components/responses/responseNotFound"
+
+    put:
+      operationId: putSettingsTelemetry
+      summary: "Create or update the `telemetry` object in settings"
+      description: "Creates or updates the `telemetry` object that represents Unit's
+        [Telemetry settings](https://unit.nginx.org/configuration/#settings)."
+      tags:
+        - settings
+        - config
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              $ref: "#/components/schemas/configSettingsTelemetry"
+      responses:
+        "200":
+          $ref: "#/components/responses/responseOkUpdated"
+
+        "400":
+          $ref: "#/components/responses/responseBadRequest"
+
+        "404":
+          $ref: "#/components/responses/responseNotFound"
+
+        "500":
+          $ref: "#/components/responses/responseInternalError"
+
+    delete:
+      operationId: deleteSettingsTelemetry
+      summary: "Delete the telemetry object"
+      description: "Deletes the `telemetry` object from the configuration."
+      tags:
+        - settings
+        - config
+
+      responses:
+        "200":
+          $ref: "#/components/responses/responseOkDeleted"
+
+        "404":
+          $ref: "#/components/responses/responseNotFound"
+
   /config/settings/http:
     summary: "Endpoint for the `http` object in `settings`"
 
@@ -6545,10 +6607,38 @@ components:
         Unit settings."
 
       properties:
+        telemetry:
+          description: "Represents global telemetry settings in Unit."
+          $ref: "#/components/schemas/configSettingsTelemetry"
+
         http:
           description: "Represents global HTTP settings in Unit."
           $ref: "#/components/schemas/configSettingsHttp"
 
+    # /config/settings/telemetry
+    configSettingsTelemetry:
+      type: object
+      description: "An object whose options represent global telemetry settings in Unit."
+      required: ["endpoint"]
+      properties:
+        batch_size:
+          type: integer
+          description: "Number of spans to cache before sending to telemetry collector."
+          default: 128
+
+        endpoint:
+          type: string
+          description: "A valid endpoint to which Unit can send OpenTelemetry spans."
+
+        protocol:
+          type: string
+          description: "Protocol to use when communicating with the aforementioned endpoint."
+
+        sampling_ratio:
+          type: number
+          default: 1
+          description: "A number in between 0 and 1 that describes the percent of requests traced"
+
     # /config/settings/http
     configSettingsHttp:
       type: object