Prometheus remote write backend (#6062)

* Add Prometheus remote write backend prototype

* Fix autotools issues

* Send HTTP POST request

* Add parameters to HTTP header

* Discard HTTP responce 200

* Update CMake build configuration

* Fix Codacy issue

* Check for C++ binary

* Fix compilation without remote write backend

* Add options to the installer script

* Fix configure script warning

* Fix make dist

* Downgrade to ByteSize for better compatibility

* Integrate remote write more tightly into the existing backends code

* Cleanup

* Fix build error

* Parse host tags

* Fix Codacy issue

* Fix counters for buffered data

* Rename preprocessor symbol

* Better error handling

* Cleanup

* Update the documentation

1 files changed, 117 insertions, 0 deletions

diff --git a/backends/prometheus/remote_write/remote_write.cc b/backends/prometheus/remote_write/remote_write.cc
new file mode 100644
index 0000000000..91d4305ba7
--- /dev/null
+++ b/backends/prometheus/remote_write/remote_write.cc
@@ -0,0 +1,117 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include <snappy.h>
+#include "remote_write.pb.h"
+#include "remote_write.h"
+
+using namespace prometheus;
+
+
+google::protobuf::Arena arena;
+WriteRequest *write_request;
+
+void init_write_request() {
+    GOOGLE_PROTOBUF_VERIFY_VERSION;
+    write_request = google::protobuf::Arena::CreateMessage<WriteRequest>(&arena);
+}
+
+void clear_write_request() {
+    write_request->clear_timeseries();
+}
+
+void add_host_info(const char *name, const char *instance, const char *application, const char *version, const int64_t timestamp) {
+    TimeSeries *timeseries;
+    Sample *sample;
+    Label *label;
+
+    timeseries = write_request->add_timeseries();
+
+    label = timeseries->add_labels();
+    label->set_name("__name__");
+    label->set_value(name);
+
+    label = timeseries->add_labels();
+    label->set_name("instance");
+    label->set_value(instance);
+
+    if(application) {
+        label = timeseries->add_labels();
+        label->set_name("application");
+        label->set_value(application);
+    }
+
+    if(version) {
+        label = timeseries->add_labels();
+        label->set_name("version");
+        label->set_value(version);
+    }
+
+    sample = timeseries->add_samples();
+    sample->set_value(1);
+    sample->set_timestamp(timestamp);
+}
+
+// adds tag to the last created timeseries
+void add_tag(char *tag, char *value) {
+    TimeSeries *timeseries;
+    Label *label;
+
+    timeseries = write_request->mutable_timeseries(write_request->timeseries_size() - 1);
+
+    label = timeseries->add_labels();
+    label->set_name(tag);
+    label->set_value(value);
+}
+
+void add_metric(const char *name, const char *chart, const char *family, const char *dimension, const char *instance, const double value, const int64_t timestamp) {
+    TimeSeries *timeseries;
+    Sample *sample;
+    Label *label;
+
+    timeseries = write_request->add_timeseries();
+
+    label = timeseries->add_labels();
+    label->set_name("__name__");
+    label->set_value(name);
+
+    label = timeseries->add_labels();
+    label->set_name("chart");
+    label->set_value(chart);
+
+    label = timeseries->add_labels();
+    label->set_name("family");
+    label->set_value(family);
+
+    if(dimension) {
+        label = timeseries->add_labels();
+        label->set_name("dimension");
+        label->set_value(dimension);
+    }
+
+    label = timeseries->add_labels();
+    label->set_name("instance");
+    label->set_value(instance);
+
+    sample = timeseries->add_samples();
+    sample->set_value(value);
+    sample->set_timestamp(timestamp);
+}
+
+size_t get_write_request_size(){
+    size_t size = (size_t)snappy::MaxCompressedLength(write_request->ByteSize());
+
+    return (size < INT_MAX)?size:0;
+}
+
+int pack_write_request(char *buffer, size_t *size) {
+    std::string uncompressed_write_request;
+    if(write_request->SerializeToString(&uncompressed_write_request) == false) return 1;
+
+    snappy::RawCompress(uncompressed_write_request.data(), uncompressed_write_request.size(), buffer, size);
+
+    return 0;
+}
+
+void protocol_buffers_shutdown() {
+    google::protobuf::ShutdownProtobufLibrary();
+}