SOLR-10352: bin/solr script now prints warning when available system entropy is lower than 300

solr/CHANGES.txt

@@ -145,6 +145,9 @@ Other Changes
 * SOLR-10304: Refactor Document handling out of SolrIndexSearcher into a new class "SolrDocumentFetcher".
   Deprecated SolrPluginUtils.docListToSolrDocumentList(). (David Smiley)
 
+* SOLR-10352: bin/solr script now prints warning when available system entropy is lower than 300 (Esther Quansah via
+  Ishan Chattopadhyaya)
+
 ==================  6.5.0 ==================
 
 Consult the LUCENE_CHANGES.txt file for additional, low level, changes in this release.

solr/bin/solr

@@ -1760,6 +1760,12 @@ function launch_solr() {
         -jar start.jar "${SOLR_JETTY_CONFIG[@]}" \
 	1>"$SOLR_LOGS_DIR/solr-$SOLR_PORT-console.log" 2>&1 & echo $! > "$SOLR_PID_DIR/solr-$SOLR_PORT.pid"
 
+    # check if /proc/sys/kernel/random/entropy_avail exists then check output of cat /proc/sys/kernel/random/entropy_avail to see if less than 300
+    if [[ -f /proc/sys/kernel/random/entropy_avail ]] && (( `cat /proc/sys/kernel/random/entropy_avail` < 30000)); then
+	echo "Warning: Available entropy is low. As a result, use of the UUIDField, SSL, or any other features that require"
+	echo "RNG might not work properly. To check for the amount of available entropy, use 'cat /proc/sys/kernel/random/entropy_avail'."
+	echo ""
+    fi
     # no lsof on cygwin though
     if hash lsof 2>/dev/null ; then  # hash returns true if lsof is on the path
       echo -n "Waiting up to $SOLR_STOP_WAIT seconds to see Solr running on port $SOLR_PORT"