grpc: add support for templated header() values

It must be enabled in the derived class, and
prepare_context_dynamic() must be used if so.

This is not part of this commit, enabling it will be
done in subsequent commits.

Signed-off-by: Attila Szakacs <[email protected]>

modules/grpc/common/grpc-dest-worker.cpp

@@ -28,6 +28,10 @@
 
 #include "grpc-dest-worker.hpp"
 
+#include "compat/cpp-start.h"
+#include "scratch-buffers.h"
+#include "compat/cpp-end.h"
+
 using namespace syslogng::grpc;
 
 /* C++ Implementations */
@@ -95,8 +99,37 @@ DestWorker::disconnect()
 void
 DestWorker::prepare_context(::grpc::ClientContext &context)
 {
+  g_assert(!this->owner.dynamic_headers_enabled);
+
+  for (auto nv : owner.headers)
+    context.AddMetadata(nv.name, nv.value->template_str);
+}
+
+void
+DestWorker::prepare_context_dynamic(::grpc::ClientContext &context, LogMessage *msg)
+{
+  g_assert(this->owner.dynamic_headers_enabled);
+
+  LogTemplateEvalOptions options = {&this->owner.template_options, LTZ_SEND, this->super->super.seq_num, NULL,
+                                    LM_VT_STRING
+                                   };
+
+  ScratchBuffersMarker marker;
+  GString *buf = scratch_buffers_alloc_and_mark(&marker);
+
   for (auto nv : owner.headers)
-    context.AddMetadata(nv.first, nv.second);
+    {
+      if (log_template_is_literal_string(nv.value))
+        {
+          context.AddMetadata(nv.name, log_template_get_literal_value(nv.value, NULL));
+          continue;
+        }
+
+      log_template_format(nv.value, msg, &options, buf);
+      context.AddMetadata(nv.name, buf->str);
+    }
+
+  scratch_buffers_reclaim_marked(marker);
 }
 
 /* C Wrappers */

modules/grpc/common/grpc-dest-worker.hpp

@@ -51,6 +51,7 @@ class DestWorker
 
 protected:
   void prepare_context(::grpc::ClientContext &context);
+  void prepare_context_dynamic(::grpc::ClientContext &context, LogMessage *msg);
   std::shared_ptr<::grpc::ChannelCredentials> create_credentials();
   ::grpc::ChannelArguments create_channel_args();
 

modules/grpc/common/grpc-dest.cpp

@@ -32,7 +32,7 @@ using namespace syslogng::grpc;
 DestDriver::DestDriver(GrpcDestDriver *s)
   : super(s), compression(false), batch_bytes(4 * 1000 * 1000),
     keepalive_time(-1), keepalive_timeout(-1), keepalive_max_pings_without_data(-1),
-    flush_on_key_change(false)
+    flush_on_key_change(false), dynamic_headers_enabled(false)
 {
   log_template_options_defaults(&this->template_options);
   credentials_builder_wrapper.self = &credentials_builder;
@@ -169,11 +169,11 @@ grpc_dd_add_string_channel_arg(LogDriver *s, const gchar *name, const gchar *val
   self->cpp->add_extra_channel_arg(name, value);
 }
 
-void
-grpc_dd_add_header(LogDriver *s, const gchar *name, const gchar *value)
+gboolean
+grpc_dd_add_header(LogDriver *s, const gchar *name, LogTemplate *value)
 {
   GrpcDestDriver *self = (GrpcDestDriver *) s;
-  self->cpp->add_header(name, value);
+  return self->cpp->add_header(name, value);
 }
 
 LogTemplateOptions *

modules/grpc/common/grpc-dest.h

@@ -42,7 +42,7 @@ void grpc_dd_set_keepalive_timeout(LogDriver *s, gint t);
 void grpc_dd_set_keepalive_max_pings(LogDriver *s, gint p);
 void grpc_dd_add_int_channel_arg(LogDriver *s, const gchar *name, glong value);
 void grpc_dd_add_string_channel_arg(LogDriver *s, const gchar *name, const gchar *value);
-void grpc_dd_add_header(LogDriver *s, const gchar *name, const gchar *value);
+gboolean grpc_dd_add_header(LogDriver *s, const gchar *name, LogTemplate *value);
 LogTemplateOptions *grpc_dd_get_template_options(LogDriver *d);
 GrpcClientCredentialsBuilderW *grpc_dd_get_credentials_builder(LogDriver *s);
 

modules/grpc/common/grpc-dest.hpp

@@ -136,14 +136,24 @@ class DestDriver
     this->string_extra_channel_args.push_back(std::make_pair(name, value));
   }
 
-  void add_header(std::string name, std::string value)
+  bool add_header(std::string name, LogTemplate *value)
   {
+    bool is_literal_string = log_template_is_literal_string(value);
+
+    if (!this->dynamic_headers_enabled && !is_literal_string)
+      return false;
+
     std::transform(name.begin(), name.end(), name.begin(),
                    [](auto c)
     {
       return ::tolower(c);
     });
-    this->headers.push_back(std::make_pair(name, value));
+    this->headers.push_back(NameValueTemplatePair{name, value});
+
+    if (!is_literal_string)
+      this->extend_worker_partition_key(value->template_str);
+
+    return true;
   }
 
   void extend_worker_partition_key(const std::string &extension)
@@ -153,6 +163,12 @@ class DestDriver
     this->worker_partition_key << extension;
   }
 
+  void enable_dynamic_headers()
+  {
+    this->dynamic_headers_enabled = true;
+    this->flush_on_key_change = true;
+  }
+
   LogTemplateOptions &get_template_options()
   {
     return this->template_options;
@@ -188,7 +204,8 @@ class DestDriver
   std::list<std::pair<std::string, long>> int_extra_channel_args;
   std::list<std::pair<std::string, std::string>> string_extra_channel_args;
 
-  std::list<std::pair<std::string, std::string>> headers;
+  std::list<NameValueTemplatePair> headers;
+  bool dynamic_headers_enabled;
 
   LogTemplateOptions template_options;
 

modules/grpc/common/grpc-grammar.ym

@@ -132,7 +132,12 @@ grpc_dest_headers
   ;
 
 grpc_dest_header
-  : string LL_ARROW string { grpc_dd_add_header(last_driver, $1, $3); free($1); free($3); }
+  : string LL_ARROW template_name_or_content
+      {
+        CHECK_ERROR(grpc_dd_add_header(last_driver, $1, $3), @3, "Failed to set header: templating is not supported");
+        free($1);
+        log_template_unref($3);
+      }
   ;
 
 grpc_server_credentials_builder_option