feat: Expose ledger cache full and disabled to prometheus (#1957)

Fixes #1771

src/data/LedgerCache.hpp

@@ -21,6 +21,7 @@
 
 #include "data/LedgerCacheInterface.hpp"
 #include "data/Types.hpp"
+#include "util/prometheus/Bool.hpp"
 #include "util/prometheus/Counter.hpp"
 #include "util/prometheus/Label.hpp"
 #include "util/prometheus/Prometheus.hpp"
@@ -77,8 +78,16 @@ class LedgerCache : public LedgerCacheInterface {
     mutable std::shared_mutex mtx_;
     std::condition_variable_any cv_;
     uint32_t latestSeq_ = 0;
-    std::atomic_bool full_ = false;
-    std::atomic_bool disabled_ = false;
+    util::prometheus::Bool full_{PrometheusService::boolMetric(
+        "ledger_cache_full",
+        util::prometheus::Labels{},
+        "Whether ledger cache full or not"
+    )};
+    util::prometheus::Bool disabled_{PrometheusService::boolMetric(
+        "ledger_cache_disabled",
+        util::prometheus::Labels{},
+        "Whether ledger cache is disabled or not"
+    )};
 
     // temporary set to prevent background thread from writing already deleted data. not used when cache is full
     std::unordered_set<ripple::uint256, ripple::hardened_hash<>> deletes_;

tests/common/util/MockPrometheus.hpp

@@ -158,9 +158,9 @@ struct MockPrometheusImpl : PrometheusInterface {
     {
         std::unique_ptr<MetricBase> metric;
         auto const key = name + labelsString;
-        if constexpr (std::is_same_v<MetricType, GaugeInt>) {
+        if constexpr (std::is_same_v<MetricType, GaugeInt> or std::is_same_v<MetricType, Bool>) {
             auto& impl = counterIntImpls[key];
-            metric = std::make_unique<MetricType>(name, labelsString, impl);
+            metric = std::make_unique<GaugeInt>(name, labelsString, impl);
         } else if constexpr (std::is_same_v<MetricType, CounterInt>) {
             auto& impl = counterUintImpls[key];
             metric = std::make_unique<MetricType>(name, labelsString, impl);
@@ -235,7 +235,7 @@ struct WithMockPrometheus : virtual ::testing::Test {
         if (!mockPrometheusPtr->metrics.contains(key))
             mockPrometheusPtr->makeMetric<MetricType>(std::move(name), std::move(labelsString));
 
-        if constexpr (std::is_same_v<MetricType, GaugeInt>) {
+        if constexpr (std::is_same_v<MetricType, GaugeInt> or std::is_same_v<MetricType, Bool>) {
             return mockPrometheusPtr->counterIntImpls[key];
         } else if constexpr (std::is_same_v<MetricType, CounterInt>) {
             return mockPrometheusPtr->counterUintImpls[key];

tests/unit/CMakeLists.txt

@@ -11,6 +11,7 @@ target_sources(
           data/AmendmentCenterTests.cpp
           data/BackendCountersTests.cpp
           data/BackendInterfaceTests.cpp
+          data/LedgerCacheTests.cpp
           data/cassandra/AsyncExecutorTests.cpp
           data/cassandra/ExecutionStrategyTests.cpp
           data/cassandra/RetryPolicyTests.cpp

tests/unit/data/LedgerCacheTests.cpp

@@ -0,0 +1,68 @@
+//------------------------------------------------------------------------------
+/*
+    This file is part of clio: https://github.com/XRPLF/clio
+    Copyright (c) 2025, the clio developers.
+
+    Permission to use, copy, modify, and distribute this software for any
+    purpose with or without fee is hereby granted, provided that the above
+    copyright notice and this permission notice appear in all copies.
+
+    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
+    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+    ANY  SPECIAL,  DIRECT,  INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
+    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+//==============================================================================
+
+#include "data/LedgerCache.hpp"
+#include "util/LoggerFixtures.hpp"
+#include "util/MockPrometheus.hpp"
+#include "util/prometheus/Bool.hpp"
+
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+
+using namespace data;
+
+struct LedgerCacheTest : util::prometheus::WithPrometheus, NoLoggerFixture {
+    LedgerCache cache;
+};
+
+TEST_F(LedgerCacheTest, defaultState)
+{
+    EXPECT_FALSE(cache.isDisabled());
+    EXPECT_FALSE(cache.isFull());
+    EXPECT_EQ(cache.size(), 0u);
+    EXPECT_EQ(cache.latestLedgerSequence(), 0u);
+}
+
+struct LedgerCachePrometheusMetricTest : util::prometheus::WithMockPrometheus, NoLoggerFixture {
+    LedgerCache cache;
+};
+
+TEST_F(LedgerCachePrometheusMetricTest, setDisabled)
+{
+    auto& disabledMock = makeMock<util::prometheus::Bool>("ledger_cache_disabled", {});
+
+    EXPECT_CALL(disabledMock, set(1));
+    cache.setDisabled();
+
+    EXPECT_CALL(disabledMock, value()).WillOnce(testing::Return(1));
+    EXPECT_TRUE(cache.isDisabled());
+}
+
+TEST_F(LedgerCachePrometheusMetricTest, setFull)
+{
+    auto& fullMock = makeMock<util::prometheus::Bool>("ledger_cache_full", {});
+    auto& disabledMock = makeMock<util::prometheus::Bool>("ledger_cache_disabled", {});
+
+    EXPECT_CALL(disabledMock, value()).WillOnce(testing::Return(0));
+    EXPECT_CALL(fullMock, set(1));
+    cache.setFull();
+
+    EXPECT_CALL(fullMock, value()).WillOnce(testing::Return(1));
+    EXPECT_TRUE(cache.isFull());
+}