From 1bdd4bf92c0e54efe40b372cf738527d04f90152 Mon Sep 17 00:00:00 2001
From: Sebastian Harl <sh@tokkee.org>
Date: Fri, 30 Oct 2015 00:01:52 +0100
Subject: [PATCH] grpc plugin: Implement the ListValues() RPC.

---
 proto/collectd.proto  | 18 +++++++++++++++
 src/collectd.conf.pod |  6 ++---
 src/grpc.cc           | 61 ++++++++++++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 81 insertions(+), 4 deletions(-)

diff --git a/proto/collectd.proto b/proto/collectd.proto
index 84db755b..ba60793b 100644
--- a/proto/collectd.proto
+++ b/proto/collectd.proto
@@ -27,10 +27,14 @@ syntax = "proto3";
 package collectd;
 
 import "types.proto";
+import "google/protobuf/timestamp.proto";
 
 service Collectd {
 	// Dispatch collected values to collectd.
 	rpc DispatchValues(DispatchValuesRequest) returns (DispatchValuesReply);
+
+	// Retrieve a list of all values available in collectd's value cache.
+	rpc ListValues(ListValuesRequest) returns (ListValuesReply);
 }
 
 // The arguments to DispatchValues.
@@ -41,3 +45,17 @@ message DispatchValuesRequest {
 // The response from DispatchValues.
 message DispatchValuesReply {
 }
+
+// The arguments to ListValues.
+message ListValuesRequest {
+}
+
+// The response from ListValues.
+message ListValuesReply {
+	message Value {
+		string name = 1;
+		google.protobuf.Timestamp time = 2;
+	}
+
+	repeated Value value = 1;
+}
diff --git a/src/collectd.conf.pod b/src/collectd.conf.pod
index 82562ed0..083aae81 100644
--- a/src/collectd.conf.pod
+++ b/src/collectd.conf.pod
@@ -2499,9 +2499,9 @@ source, this is optional. Otherwise the option is required.
 
 =head2 Plugin C<grpc>
 
-The I<grpc> plugin provides an RPC interface to submit values to collectd
-based on the open source gRPC framework. It exposes and end-point for
-dispatching values to the daemon.
+The I<grpc> plugin provides an RPC interface to submit values to or query
+values from collectd based on the open source gRPC framework. It exposes and
+end-point for dispatching values to the daemon.
 
 The B<gRPC> homepage can be found at L<https://grpc.io/>.
 
diff --git a/src/grpc.cc b/src/grpc.cc
index 9523fc25..abdd6b02 100644
--- a/src/grpc.cc
+++ b/src/grpc.cc
@@ -38,6 +38,8 @@ extern "C" {
 #include "configfile.h"
 #include "plugin.h"
 
+#include "daemon/utils_cache.h"
+
 	typedef struct {
 		char *addr;
 		char *port;
@@ -225,7 +227,63 @@ private:
 	collectd::DispatchValuesReply reply_;
 
 	grpc::ServerAsyncResponseWriter<collectd::DispatchValuesReply> responder_;
-};
+}; /* class DispatchValuesCall */
+
+class ListValuesCall : public Call
+{
+public:
+	ListValuesCall(collectd::Collectd::AsyncService *service, grpc::ServerCompletionQueue *cq)
+		: Call(service, cq), responder_(&ctx_)
+	{
+		Handle();
+	} /* ListValuesCall() */
+
+	virtual ~ListValuesCall()
+	{ }
+
+private:
+	void Create()
+	{
+		service_->RequestListValues(&ctx_, &request_, &responder_, cq_, cq_, this);
+	} /* Create() */
+
+	void Process()
+	{
+		new ListValuesCall(service_, cq_);
+
+		char **names = NULL;
+		cdtime_t *times = NULL;
+		size_t i, n = 0;
+
+		auto status = grpc::Status::OK;
+		if (uc_get_names(&names, &times, &n)) {
+			status = grpc::Status(grpc::StatusCode::INTERNAL,
+					grpc::string("failed to retrieve values"));
+		}
+
+		for (i = 0; i < n; i++) {
+			auto v = reply_.add_value();
+			auto t = TimeUtil::NanosecondsToTimestamp(CDTIME_T_TO_NS(times[i]));
+			v->set_name(names[i]);
+			v->set_allocated_time(new google::protobuf::Timestamp(t));
+			sfree(names[i]);
+		}
+		sfree(names);
+		sfree(times);
+
+		responder_.Finish(reply_, status, this);
+	} /* Process() */
+
+	void Finish()
+	{
+		delete this;
+	} /* Finish() */
+
+	collectd::ListValuesRequest request_;
+	collectd::ListValuesReply reply_;
+
+	grpc::ServerAsyncResponseWriter<collectd::ListValuesReply> responder_;
+}; /* class ListValuesCall */
 
 /*
  * gRPC server implementation
@@ -272,6 +330,7 @@ public:
 	{
 		// Register request types.
 		new DispatchValuesCall(&service_, cq_.get());
+		new ListValuesCall(&service_, cq_.get());
 
 		while (true) {
 			void *req = NULL;
-- 
2.11.0