[bugfix] Change severity of negative stats messages from WARN to DEBUG(elastic#60375)

Author: RickyLau

server/src/main/java/org/elasticsearch/monitor/os/OsProbe.java

@@ -92,7 +92,7 @@ public long getFreePhysicalMemorySize() {
         try {
             final long freeMem = (long) getFreePhysicalMemorySize.invoke(osMxBean);
             if (freeMem < 0) {
-                logger.warn("OS reported a negative free memory value [{}]", freeMem);
+                logger.debug("OS reported a negative free memory value [{}]", freeMem);
                 return 0;
             }
             return freeMem;
@@ -113,7 +113,7 @@ public long getTotalPhysicalMemorySize() {
         try {
             final long totalMem = (long) getTotalPhysicalMemorySize.invoke(osMxBean);
             if (totalMem < 0) {
-                logger.warn("OS reported a negative total memory value [{}]", totalMem);
+                logger.debug("OS reported a negative total memory value [{}]", totalMem);
                 return 0;
             }
             return totalMem;
@@ -134,7 +134,7 @@ public long getFreeSwapSpaceSize() {
         try {
             final long mem = (long) getFreeSwapSpaceSize.invoke(osMxBean);
             if (mem < 0) {
-                logger.warn("OS reported a negative free swap space size [{}]", mem);
+                logger.debug("OS reported a negative free swap space size [{}]", mem);
                 return 0;
             }
             return mem;
@@ -155,7 +155,7 @@ public long getTotalSwapSpaceSize() {
         try {
             final long mem = (long) getTotalSwapSpaceSize.invoke(osMxBean);
             if (mem < 0) {
-                logger.warn("OS reported a negative total swap space size [{}]", mem);
+                logger.debug("OS reported a negative total swap space size [{}]", mem);
                 return 0;
             }
             return mem;

server/src/main/java/org/elasticsearch/monitor/os/OsStats.java

@@ -236,7 +236,7 @@ public ByteSizeValue getUsed() {
                 //
                 // We intentionally check for (total == 0) rather than (total - free < 0) so as not to hide
                 // cases where (free > total) which would be a different bug.
-                logger.warn("cannot compute used swap when total swap is 0 and free swap is " + free);
+                logger.debug("cannot compute used swap when total swap is 0 and free swap is " + free);
                 return new ByteSizeValue(0);
             }
             return new ByteSizeValue(total - free);
@@ -304,7 +304,7 @@ public ByteSizeValue getUsed() {
                 //
                 // We intentionally check for (total == 0) rather than (total - free < 0) so as not to hide
                 // cases where (free > total) which would be a different bug.
-                logger.warn("cannot compute used memory when total memory is 0 and free memory is " + free);
+                logger.debug("cannot compute used memory when total memory is 0 and free memory is " + free);
                 return new ByteSizeValue(0);
             }
             return new ByteSizeValue(total - free);