[cpp/monlib] add ability to mangle name in prometheus decoder

commit_hash:ef6584bf0941f50d0833dacd3b5d14cfc1cd30a8

3 files changed, 83 insertions, 5 deletions

diff --git a/library/cpp/monlib/encode/prometheus/prometheus.h b/library/cpp/monlib/encode/prometheus/prometheus.h
index c6982996990..6467836a6a6 100644
--- a/library/cpp/monlib/encode/prometheus/prometheus.h
+++ b/library/cpp/monlib/encode/prometheus/prometheus.h
@@ -1,5 +1,7 @@
 #pragma once
 
+#include <functional>
+
 #include <library/cpp/monlib/encode/encoder.h>
 #include <library/cpp/monlib/encode/format.h>
 
@@ -18,6 +20,12 @@ namespace NMonitoring {
 
     struct TPrometheusDecodeSettings {
         EPrometheusDecodeMode Mode{EPrometheusDecodeMode::DEFAULT};
+        /*
+         * Mangles the label that is equal to metricNameLabel. The
+         * new name must be not equal to any already present in the
+         * metric sample.
+         */
+        std::function<TString(TStringBuf)> NameMangler{};
     };
 
     IMetricEncoderPtr EncoderPrometheus(IOutputStream* out, TStringBuf metricNameLabel = "sensor");
diff --git a/library/cpp/monlib/encode/prometheus/prometheus_decoder.cpp b/library/cpp/monlib/encode/prometheus/prometheus_decoder.cpp
index 5ccc854cab2..c74fc9f4a82 100644
--- a/library/cpp/monlib/encode/prometheus/prometheus_decoder.cpp
+++ b/library/cpp/monlib/encode/prometheus/prometheus_decoder.cpp
@@ -525,14 +525,27 @@ namespace NMonitoring {
             }
 
             void ConsumeLabels(TStringBuf name, const TLabelsMap& labels) {
-                Y_PARSER_ENSURE(labels.count(MetricNameLabel_) == 0,
-                    "label name '" << MetricNameLabel_ <<
-                    "' is reserved, but is used with metric: " << name << LabelsToStr(labels));
+                auto it = labels.find(MetricNameLabel_);
+                if(it != labels.end() && !Settings_.NameMangler) {
+                    Y_PARSER_ENSURE(false,
+                        "label name '" << MetricNameLabel_ <<
+                        "' is reserved, but is used with metric: " << name << LabelsToStr(labels));
+                }
+                const bool labelClashPresent = it != labels.end();
 
                 Consumer_->OnLabelsBegin();
                 Consumer_->OnLabel(MetricNameLabel_, TString(name)); // TODO: remove this string allocation
-                for (const auto& it: labels) {
-                    Consumer_->OnLabel(it.first, it.second);
+                for (const auto& [k, v]: labels) {
+                    if(labelClashPresent && k == MetricNameLabel_) {
+                        auto newKey = Settings_.NameMangler(k);
+                            Y_PARSER_ENSURE(!labels.contains(newKey),
+                                "after mangling label name: " << MetricNameLabel_ <<
+                                " the resulting label is: " << newKey <<
+                                "but it is already used in: " << LabelsToStr(labels));
+                        Consumer_->OnLabel(newKey, v);
+                        continue;
+                    }
+                    Consumer_->OnLabel(k, v);
                 }
                 Consumer_->OnLabelsEnd();
             }
diff --git a/library/cpp/monlib/encode/prometheus/prometheus_decoder_ut.cpp b/library/cpp/monlib/encode/prometheus/prometheus_decoder_ut.cpp
index 4dbb4b574bb..f6b3eb01667 100644
--- a/library/cpp/monlib/encode/prometheus/prometheus_decoder_ut.cpp
+++ b/library/cpp/monlib/encode/prometheus/prometheus_decoder_ut.cpp
@@ -105,6 +105,63 @@ Y_UNIT_TEST_SUITE(TPrometheusDecoderTest) {
         }
     }
 
+    Y_UNIT_TEST(NameAlreadyPresent) {
+        constexpr auto inputMetrics =
+            "# A normal comment.\n"
+            "#\n"
+            "# TYPE name counter\n"
+            "name{sensor=\"some_name\",labelname=\"val1\",basename=\"basevalue\"} NaN\n"
+            "name{labelname=\"val2\",basename=\"basevalue\"} Nan\n"
+            "name {labelname=\"val3\",basename=\"basevalue\"} 2.3 1234567890\n"
+            "# HELP name two-line\\n doc  str\\\\ing\n";
+
+        try {
+            auto samples = Decode(inputMetrics);
+        } catch(...) {
+            return;
+        }
+        UNIT_ASSERT(false);
+    }
+
+    Y_UNIT_TEST(NameAlreadyPresentButMangled) {
+        constexpr auto inputMetrics =
+            "# A normal comment.\n"
+            "#\n"
+            "# TYPE name counter\n"
+            "name{sensor=\"some_name\",labelname=\"val1\",basename=\"basevalue\"} NaN\n"
+            "name{labelname=\"val2\",basename=\"basevalue\"} Nan\n"
+            "name {labelname=\"val3\",basename=\"basevalue\"} 2.3 1234567890\n"
+            "# HELP name two-line\\n doc  str\\\\ing\n";
+
+        try {
+            auto samples = Decode(inputMetrics, TPrometheusDecodeSettings{.NameMangler = [](auto s) -> TString {
+                                      return TStringBuilder{}<<"mm_" << s;
+                                  }});
+        } catch(...) {
+            UNIT_ASSERT(false);
+        }
+    }
+
+    Y_UNIT_TEST(MangledNameClash) {
+        constexpr auto inputMetrics =
+            "# A normal comment.\n"
+            "#\n"
+            "# TYPE name counter\n"
+            "name{mm_sensor=\"other\",sensor=\"some_name\",labelname=\"val1\",basename=\"basevalue\"} NaN\n"
+            "name{labelname=\"val2\",basename=\"basevalue\"} Nan\n"
+            "name {labelname=\"val3\",basename=\"basevalue\"} 2.3 1234567890\n"
+            "# HELP name two-line\\n doc  str\\\\ing\n";
+
+        try {
+            auto samples = Decode(inputMetrics, TPrometheusDecodeSettings{.NameMangler = [](auto s) -> TString {
+                                      return TStringBuilder{}<<"mm_" << s;
+                                  }});
+        } catch(...) {
+            return;
+        }
+        UNIT_ASSERT(false);
+    }
+
     Y_UNIT_TEST(Counter) {
         constexpr auto inputMetrics =
             "# A normal comment.\n"