Httpd add possibility to configure custom attributes and resources (#14)

Author: TomRoSystems

instrumentation/httpd/opentelemetry.conf

@@ -32,4 +32,7 @@ OpenTelemetryPath /tmp/output-spans
 
 # OpenTelemetryIgnoreInbound off
 
+# OpenTelemetrySetResource service.name apache-web-server
+# OpenTelemetrySetAttribute foo bar
+
 </IfModule>

instrumentation/httpd/src/otel/mod_otel.cpp

@@ -172,7 +172,7 @@ static int opentel_log_transaction(request_rec *r)
 /////////////////////////////////////////////////
 
 static int proxy_fixup_handler(request_rec *r)
-{ // adding outbound headers and setting span attribiutes
+{ // adding outbound headers and setting span attributes
   request_rec *req = r->main ? r->main : r;
 
   ExtraRequestData *req_data;
@@ -252,7 +252,7 @@ static int proxy_end_handler(int *status, request_rec *r)
   }
 
   int st_code = (status && *status) ? *status:r->status;
-  char *proxy_error = apr_table_get(r->notes, "error-notes");
+  const char *proxy_error = apr_table_get(r->notes, "error-notes");
   if (proxy_error)
   {
     req_data_out->span->SetStatus(opentelemetry::trace::StatusCode::kError, proxy_error);
@@ -316,6 +316,18 @@ const char *otel_set_endpoint(cmd_parms *cmd, void *cfg, const char *arg)
   return NULL;
 }
 
+const char *otel_set_attribute(cmd_parms *cmd, void *cfg, const char *attrName, const char *attrValue)
+{
+  config.attributes[attrName] = attrValue;
+  return NULL;
+}
+
+const char *otel_set_resource(cmd_parms *cmd, void *cfg, const char *attrName, const char *attrValue)
+{
+  config.resources[attrName] = attrValue;
+  return NULL;
+}
+
 const char *otel_cfg_batch(cmd_parms *cmd,
                            void *cfg,
                            const char *max_queue_size,
@@ -357,6 +369,16 @@ static const command_rec opentel_directives[] = {
                   NULL,
                   RSRC_CONF,
                   "Set endpoint for exporter"),
+    AP_INIT_TAKE2("OpenTelemetrySetAttribute",
+                  otel_set_attribute,
+                  NULL,
+                  RSRC_CONF,
+                  "Set additional attribute for each span"),
+    AP_INIT_TAKE2("OpenTelemetrySetResource",
+                  otel_set_resource,
+                  NULL,
+                  RSRC_CONF,
+                  "Set resource"),
     AP_INIT_TAKE3("OpenTelemetryBatch",
                   otel_cfg_batch,
                   NULL,

instrumentation/httpd/src/otel/opentelemetry.cpp

@@ -85,8 +85,16 @@ void initTracer()
     processor = std::make_shared<sdktrace::SimpleSpanProcessor>(std::move(exporter));
   }
 
+  // add custom-configured resources
+  for(auto &it:config.resources)
+  {
+    resAttrs[it.first] = it.second;
+  }
+
   auto provider = nostd::shared_ptr<opentelemetry::trace::TracerProvider>(
-      new sdktrace::TracerProvider(processor));
+    new sdktrace::TracerProvider(processor,
+    opentelemetry::sdk::resource::Resource::Create(resAttrs))
+  );
 
   // Set the global trace provider
   opentelemetry::trace::Provider::SetTracerProvider(provider);
@@ -131,6 +139,11 @@ void ExtraRequestData::StartSpan(const HttpdStartSpanAttributes& attrs)
   {
     span->SetAttribute(kAttrNETPeerIP, startAttrs.net_ip);
   }
+  // add custom-configured attributes
+  for(auto &it:config.attributes)
+  {
+    span->SetAttribute(it.first, it.second);
+  }
 }
 
 void ExtraRequestData::EndSpan(const HttpdEndSpanAttributes& attrs)

instrumentation/httpd/src/otel/opentelemetry.h

@@ -18,6 +18,7 @@
 #define HTTPD_OPENTELEMETRY_H_
 
 #include <fstream>
+#include <unordered_map>
 
 #include "opentelemetry/exporters/ostream/span_exporter.h"
 #include "opentelemetry/sdk/trace/batch_span_processor.h"
@@ -54,6 +55,8 @@ struct OtelConfig
   // context propagation
   bool ignore_inbound;
   OtelPropagation propagation;
+  std::unordered_map<std::string, std::string> attributes;
+  std::unordered_map<std::string, std::string> resources;
   OtelConfig() : ignore_inbound(true) {}
 };
 
@@ -86,7 +89,7 @@ struct ExtraRequestData
   nostd::shared_ptr<opentelemetry::v0::trace::Span> span;
   HttpdStartSpanAttributes startAttrs;
   HttpdEndSpanAttributes endAttrs;
-  // Sets attribiutes for HTTP request.
+  // Sets attributes for HTTP request.
   void StartSpan(const HttpdStartSpanAttributes &attrs);
   void EndSpan(const HttpdEndSpanAttributes &attrs);
   // we are called from apache when apr_pool_t is being cleaned after request

instrumentation/httpd/tests/01-create-root-span.sh

@@ -27,7 +27,7 @@ check_results() {
    check 'span kind' Server
    [ "`getSpanField span_id`" != "`getSpanField parent_span_id`" ] || fail "Bad span: span.id same as parent span.id"
 
-   echo Checking span attribiutes
+   echo Checking span attributes
    declare -A SPAN_ATTRS
    # transforms "http.method: GET, http.flavor: http, ..." into SPAN_ATTRS[http.method] = GET
    IFS=',' read -ra my_array <<< "`getSpanField attributes`"