Adding a deprecation info API check for fractional byte value settings

x-pack/plugin/deprecation/src/main/java/org/elasticsearch/xpack/deprecation/DeprecationChecks.java

@@ -95,6 +95,7 @@ private DeprecationChecks() {
                     NodeDeprecationChecks::checkSingleDataNodeWatermarkSetting,
                     NodeDeprecationChecks::checkImplicitlyDisabledSecurityOnBasicAndTrial,
                     NodeDeprecationChecks::checkMonitoringExporterPassword,
+                    NodeDeprecationChecks::checkFractionalByteValueSettings,
                     NodeDeprecationChecks::checkClusterRoutingAllocationIncludeRelocationsSetting
                 )
             ).collect(Collectors.toList());

x-pack/plugin/deprecation/src/main/java/org/elasticsearch/xpack/deprecation/NodeDeprecationChecks.java

@@ -19,6 +19,7 @@
 import org.elasticsearch.common.settings.Setting;
 import org.elasticsearch.common.settings.Setting.Property;
 import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.common.unit.ByteSizeValue;
 import org.elasticsearch.common.util.concurrent.EsExecutors;
 import org.elasticsearch.common.util.set.Sets;
 import org.elasticsearch.env.Environment;
@@ -38,6 +39,7 @@
 
 import java.util.ArrayList;
 import java.util.Comparator;
+import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Locale;
@@ -595,4 +597,31 @@ static DeprecationIssue checkClusterRoutingAllocationIncludeRelocationsSetting(f
             DeprecationIssue.Level.CRITICAL
         );
     }
+
+    static DeprecationIssue checkFractionalByteValueSettings(final Settings settings,
+                                                             final PluginsAndModules pluginsAndModules,
+                                                             final ClusterState clusterState,
+                                                             final XPackLicenseState licenseState) {
+        Map<String, String> fractionalByteSettings = new HashMap<>();
+        for (String key : settings.keySet()) {
+            try {
+                settings.getAsBytesSize(key, ByteSizeValue.ZERO);
+                String stringValue = settings.get(key);
+                if (stringValue.contains(".")) {
+                    fractionalByteSettings.put(key, stringValue);
+                }
+            } catch (Exception ignoreThis) {
+                // We expect anything that is not a byte setting to throw an exception, but we don't care about those
+            }
+        }
+        if (fractionalByteSettings.isEmpty()) {
+            return null;
+        }
+        String url = "https://www.elastic.co/guide/en/elasticsearch/reference/master/logging.html#deprecation-logging";
+        String message = "support for fractional byte size values is deprecated and will be removed in a future release";
+        String details = "change the following settings to non-fractional values: [" +
+            fractionalByteSettings.entrySet().stream().map(fractionalByteSetting -> fractionalByteSetting.getKey() + "->" +
+            fractionalByteSetting.getValue()).collect(Collectors.joining(", ")) + "]";
+        return new DeprecationIssue(DeprecationIssue.Level.WARNING, message, url, details, false, null);
+    }
 }

x-pack/plugin/deprecation/src/test/java/org/elasticsearch/xpack/deprecation/NodeDeprecationChecksTests.java

@@ -863,4 +863,32 @@ public void testImplicitlyConfiguredSecurityOnGoldPlus() {
         final List<DeprecationIssue> issues = getDeprecationIssues(settings, pluginsAndModules, licenseState);
         assertThat(issues, empty());
     }
+
+    public void testCheckFractionalByteValueSettings() {
+        String settingKey = "network.tcp.send_buffer_size";
+        String unit = randomFrom(new String[] {"k", "kb", "m", "mb", "g", "gb", "t", "tb", "p", "pb"});
+        float value = Math.abs(randomFloat());
+        String settingValue = value + unit;
+        String unaffectedSettingKey = "some.other.setting";
+        String unaffectedSettingValue = "54.32.43mb"; //Not an actual number, so we don't expect to see a deprecation log about it
+        final Settings nodeSettings =
+            Settings.builder().put(settingKey, settingValue).put(unaffectedSettingKey, unaffectedSettingValue).build();
+        final XPackLicenseState licenseState = new XPackLicenseState(Settings.EMPTY, () -> 0);
+        final ClusterState clusterState = ClusterState.EMPTY_STATE;
+        final DeprecationIssue expectedIssue = new DeprecationIssue(DeprecationIssue.Level.WARNING,
+            "support for fractional byte size values is deprecated and will be removed in a future release",
+            "https://www.elastic.co/guide/en/elasticsearch/reference/master/logging.html#deprecation-logging",
+            String.format(Locale.ROOT,
+                "change the following settings to non-fractional values: [%s->%s]",
+                settingKey,
+                settingValue),
+            false, null
+        );
+        assertThat(
+            NodeDeprecationChecks.checkFractionalByteValueSettings(nodeSettings, null, clusterState, licenseState),
+            equalTo(expectedIssue)
+        );
+        assertWarnings(String.format(Locale.ROOT,"Fractional bytes values are deprecated. Use non-fractional bytes values instead: [%s] " +
+            "found for setting [%s]", settingValue, settingKey));
+    }
 }