SERVER-62794 Fix BucketCatalog memory threshold initialization

4 files changed, 24 insertions, 6 deletions

diff --git a/src/mongo/db/timeseries/bucket_catalog.cpp b/src/mongo/db/timeseries/bucket_catalog.cpp
index 0b7feabab1c..77e3e7f3490 100644
--- a/src/mongo/db/timeseries/bucket_catalog.cpp
+++ b/src/mongo/db/timeseries/bucket_catalog.cpp
@@ -644,8 +644,7 @@ void BucketCatalog::_expireIdleBuckets(ExecutionStats* stats,
     // As long as we still need space and have entries and remaining attempts, close idle buckets.
     int32_t numClosed = 0;
     while (!_idleBuckets.empty() &&
-           _memoryUsage.load() > static_cast<std::uint64_t>(
-                                     gTimeseriesIdleBucketExpiryMemoryUsageThresholdBytes.load()) &&
+           _memoryUsage.load() > getTimeseriesIdleBucketExpiryMemoryUsageThresholdBytes() &&
            numClosed <= gTimeseriesIdleBucketExpiryMaxCountPerAttempt) {
         Bucket* bucket = _idleBuckets.back();
 
diff --git a/src/mongo/db/timeseries/timeseries.idl b/src/mongo/db/timeseries/timeseries.idl
index 6d1888a6f38..d3ede8fd3c3 100644
--- a/src/mongo/db/timeseries/timeseries.idl
+++ b/src/mongo/db/timeseries/timeseries.idl
@@ -50,10 +50,11 @@ server_parameters:
         validator: { gte: 1 }
     "timeseriesIdleBucketExpiryMemoryUsageThreshold":
         description: "The threshold in bytes for bucket catalog memory usage above which idle
-                      buckets will be expired"
+                      buckets will be expired. If set to a non-positive number, the threshold will
+                      be automatically over-written to be 2.5% of system memory."
         set_at: [ startup, runtime ]
         cpp_varname: "gTimeseriesIdleBucketExpiryMemoryUsageThresholdBytes"
-        validator: { gte: 1 }
+        default: 0
     "timeseriesIdleBucketExpiryMaxCountPerAttempt":
         description: "The maximum number of buckets that may be closed due to expiry at each attempt"
         set_at: [ startup ]
diff --git a/src/mongo/db/timeseries/timeseries_global_options.cpp b/src/mongo/db/timeseries/timeseries_global_options.cpp
index 9d3adcb541d..5f4e3193c77 100644
--- a/src/mongo/db/timeseries/timeseries_global_options.cpp
+++ b/src/mongo/db/timeseries/timeseries_global_options.cpp
@@ -31,7 +31,24 @@
 
 namespace mongo {
 
-AtomicWord<long long> gTimeseriesIdleBucketExpiryMemoryUsageThresholdBytes{static_cast<long long>(
-    ProcessInfo::getSystemMemSizeMB() * 25 * 1024)};  // ~2.5% of system memory
+AtomicWord<long long> gTimeseriesIdleBucketExpiryMemoryUsageThresholdBytes{-1};
+
+uint64_t getTimeseriesIdleBucketExpiryMemoryUsageThresholdBytes() {
+    long long userValue = gTimeseriesIdleBucketExpiryMemoryUsageThresholdBytes.load();
+    if (userValue > 0) {
+        return static_cast<uint64_t>(userValue);
+    }
+
+    const uint64_t systemBasedValue{ProcessInfo::getSystemMemSizeMB() * 25 *
+                                    1024};  // ~2.5% of system memory
+    while (!gTimeseriesIdleBucketExpiryMemoryUsageThresholdBytes.compareAndSwap(&userValue,
+                                                                                systemBasedValue)) {
+        if (userValue > 0) {
+            return static_cast<uint64_t>(userValue);
+        }
+    }
+
+    return systemBasedValue;
+}
 
 }  // namespace mongo
diff --git a/src/mongo/db/timeseries/timeseries_global_options.h b/src/mongo/db/timeseries/timeseries_global_options.h
index 540d4ebc83b..2e13432e8e9 100644
--- a/src/mongo/db/timeseries/timeseries_global_options.h
+++ b/src/mongo/db/timeseries/timeseries_global_options.h
@@ -34,5 +34,6 @@
 namespace mongo {
 
 extern AtomicWord<long long> gTimeseriesIdleBucketExpiryMemoryUsageThresholdBytes;
+uint64_t getTimeseriesIdleBucketExpiryMemoryUsageThresholdBytes();
 
 }  // namespace mongo