Adding a warning header when a license is about to expire

server/src/main/java/org/elasticsearch/http/DefaultRestChannel.java

@@ -123,7 +123,7 @@ public void sendResponse(RestResponse restResponse) {
 
             // Add all custom headers
             addCustomHeaders(httpResponse, restResponse.getHeaders());
-            addCustomHeaders(httpResponse, threadContext.getResponseHeaders());
+            addCustomHeaders(httpResponse, restResponse.filterHeaders(threadContext.getResponseHeaders()));
 
             // If our response doesn't specify a content-type header, set one
             setHeaderField(httpResponse, CONTENT_TYPE, restResponse.contentType(), false);

server/src/main/java/org/elasticsearch/rest/RestResponse.java

@@ -89,4 +89,8 @@ public Map<String, List<String>> getHeaders() {
             return customHeaders;
         }
     }
+
+    public Map<String, List<String>> filterHeaders(Map<String, List<String>> headers) {
+        return headers;
+    }
 }

x-pack/plugin/core/src/main/java/org/elasticsearch/license/LicenseService.java

@@ -81,6 +81,11 @@ public class LicenseService extends AbstractLifecycleComponent implements Cluste
      */
     static final TimeValue GRACE_PERIOD_DURATION = days(7);
 
+    /**
+     * Period before the license expires when warning starts being added to the response header
+     */
+    static final TimeValue LICENSE_EXPIRATION_WARNING_PERIOD = days(7);
+
     public static final long BASIC_SELF_GENERATED_LICENSE_EXPIRATION_MILLIS =
         XPackInfoResponse.BASIC_SELF_GENERATED_LICENSE_EXPIRATION_MILLIS;
 
@@ -124,7 +129,7 @@ public class LicenseService extends AbstractLifecycleComponent implements Cluste
 
     public static final String LICENSE_JOB = "licenseJob";
 
-    private static final DateFormatter DATE_FORMATTER = DateFormatter.forPattern("EEEE, MMMM dd, yyyy");
+    public static final DateFormatter DATE_FORMATTER = DateFormatter.forPattern("EEEE, MMMM dd, yyyy");
 
     private static final String ACKNOWLEDGEMENT_HEADER = "This license update requires acknowledgement. To acknowledge the license, " +
         "please read the following messages and update the license again, this time with the \"acknowledge=true\" parameter:";
@@ -475,7 +480,7 @@ private void updateLicenseState(LicensesMetadata licensesMetadata) {
     protected void updateLicenseState(final License license, Version mostRecentTrialVersion) {
         if (license == LicensesMetadata.LICENSE_TOMBSTONE) {
             // implies license has been explicitly deleted
-            licenseState.update(License.OperationMode.MISSING, false, mostRecentTrialVersion);
+            licenseState.update(License.OperationMode.MISSING, false, license.expiryDate(), mostRecentTrialVersion);
             return;
         }
         if (license != null) {
@@ -488,7 +493,7 @@ protected void updateLicenseState(final License license, Version mostRecentTrial
                 // date that is near Long.MAX_VALUE
                 active = time >= license.issueDate() && time - GRACE_PERIOD_DURATION.getMillis() < license.expiryDate();
             }
-            licenseState.update(license.operationMode(), active, mostRecentTrialVersion);
+            licenseState.update(license.operationMode(), active, license.expiryDate(), mostRecentTrialVersion);
 
             if (active) {
                 if (time < license.expiryDate()) {

x-pack/plugin/core/src/main/java/org/elasticsearch/license/LicenseStateListener.java

@@ -15,7 +15,7 @@
 public interface LicenseStateListener {
 
     /**
-     * Callback when the license state changes. See {@link XPackLicenseState#update(License.OperationMode, boolean, Version)}.
+     * Callback when the license state changes. See {@link XPackLicenseState#update(License.OperationMode, boolean, long, Version)}.
      */
     void licenseStateChanged();
 

x-pack/plugin/core/src/main/java/org/elasticsearch/license/XPackLicenseState.java

@@ -8,6 +8,8 @@
 import org.elasticsearch.Version;
 import org.elasticsearch.common.Nullable;
 import org.elasticsearch.common.Strings;
+import org.elasticsearch.common.SuppressForbidden;
+import org.elasticsearch.common.logging.HeaderWarning;
 import org.elasticsearch.common.logging.LoggerMessageFormat;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.license.License.OperationMode;
@@ -19,17 +21,21 @@
 import java.util.EnumMap;
 import java.util.LinkedHashMap;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
 import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.LongAccumulator;
 import java.util.function.BiFunction;
 import java.util.function.Function;
 import java.util.function.LongSupplier;
 import java.util.function.Predicate;
 import java.util.stream.Collectors;
 
+import static org.elasticsearch.license.LicenseService.LICENSE_EXPIRATION_WARNING_PERIOD;
+
 /**
  * A holder for the current state of the license for all xpack features.
  */
@@ -395,7 +401,7 @@ private static boolean isBasic(OperationMode mode) {
         return mode == OperationMode.BASIC;
     }
 
-    /** A wrapper for the license mode and state, to allow atomically swapping. */
+    /** A wrapper for the license mode, state, and expiration date, to allow atomically swapping. */
     private static class Status {
 
         /** The current "mode" of the license (ie license type). */
@@ -404,9 +410,13 @@ private static class Status {
         /** True if the license is active, or false if it is expired. */
         final boolean active;
 
-        Status(OperationMode mode, boolean active) {
+        /** The current expiration date of the license; Long.MAX_VALUE if not available yet. */
+        final long licenseExpiryDate;
+
+        Status(OperationMode mode, boolean active, long licenseExpiryDate) {
             this.mode = mode;
             this.active = active;
+            this.licenseExpiryDate = licenseExpiryDate;
         }
     }
 
@@ -420,7 +430,7 @@ private static class Status {
     // XPackLicenseState. However, if status is read multiple times in a method, it can change in between
     // reads. Methods should use `executeAgainstStatus` and `checkAgainstStatus` to ensure that the status
     // is only read once.
-    private volatile Status status = new Status(OperationMode.TRIAL, true);
+    private volatile Status status = new Status(OperationMode.TRIAL, true, Long.MAX_VALUE);
 
     public XPackLicenseState(Settings settings, LongSupplier epochMillisProvider) {
         this.listeners = new CopyOnWriteArrayList<>();
@@ -468,12 +478,13 @@ private boolean checkAgainstStatus(Predicate<Status> statusPredicate) {
      *
      * @param mode   The mode (type) of the current license.
      * @param active True if the current license exists and is within its allowed usage period; false if it is expired or missing.
+     * @param expirationDate Expiration date of the current license.
      * @param mostRecentTrialVersion If this cluster has, at some point commenced a trial, the most recent version on which they did that.
      *                               May be {@code null} if they have never generated a trial license on this cluster, or the most recent
      *                               trial was prior to this metadata being tracked (6.1)
      */
-    void update(OperationMode mode, boolean active, @Nullable Version mostRecentTrialVersion) {
-        status = new Status(mode, active);
+    void update(OperationMode mode, boolean active, long expirationDate, @Nullable Version mostRecentTrialVersion) {
+        status = new Status(mode, active, expirationDate);
         listeners.forEach(LicenseStateListener::licenseStateChanged);
     }
 
@@ -509,12 +520,26 @@ public boolean isActive() {
     /**
      * Checks whether the given feature is allowed, tracking the last usage time.
      */
+    @SuppressForbidden(reason = "Argument to Math.abs() is definitely not Long.MIN_VALUE")
     public boolean checkFeature(Feature feature) {
         boolean allowed = isAllowed(feature);
         LongAccumulator maxEpochAccumulator = lastUsed.get(feature);
+        final long licenseExpiryDate = getLicenseExpiryDate();
+        final long diff = licenseExpiryDate - System.currentTimeMillis();
         if (maxEpochAccumulator != null) {
             maxEpochAccumulator.accumulate(epochMillisProvider.getAsLong());
         }
+
+        if (feature.minimumOperationMode.compareTo(OperationMode.BASIC) > 0 &&
+            LICENSE_EXPIRATION_WARNING_PERIOD.getMillis() > diff) {
+            final long days = TimeUnit.MILLISECONDS.toDays(diff);
+            final String expiryMessage = (days == 0 && diff > 0)? "expires today":
+                (diff > 0? String.format(Locale.ROOT, "will expire in [%d] days", days):
+                    String.format(Locale.ROOT, "expired on [%s]", LicenseService.DATE_FORMATTER.formatMillis(licenseExpiryDate)));
+            HeaderWarning.addWarning("Your license {}. " +
+                "Contact your administrator or update your license for continued use of features", expiryMessage);
+        }
+
         return allowed;
     }
 
@@ -631,6 +656,11 @@ public boolean isAllowedByLicense(OperationMode minimumMode, boolean needActive)
         });
     }
 
+    /** Return the current license expiration date. */
+    public long getLicenseExpiryDate() {
+        return executeAgainstStatus(status -> status.licenseExpiryDate);
+    }
+
     /**
      * A convenient method to test whether a feature is by license status.
      * @see #isAllowedByLicense(OperationMode, boolean)

x-pack/plugin/core/src/test/java/org/elasticsearch/license/TestUtils.java

@@ -360,21 +360,23 @@ public static class AssertingLicenseState extends XPackLicenseState {
         public final List<License.OperationMode> modeUpdates = new ArrayList<>();
         public final List<Boolean> activeUpdates = new ArrayList<>();
         public final List<Version> trialVersionUpdates = new ArrayList<>();
+        public final List<Long> expirationDateUpdates = new ArrayList<>();
 
         public AssertingLicenseState() {
             super(Settings.EMPTY, () -> 0);
         }
 
         @Override
-        void update(License.OperationMode mode, boolean active, Version mostRecentTrialVersion) {
+        void update(License.OperationMode mode, boolean active, long expirationDate, Version mostRecentTrialVersion) {
             modeUpdates.add(mode);
             activeUpdates.add(active);
+            expirationDateUpdates.add(expirationDate);
             trialVersionUpdates.add(mostRecentTrialVersion);
         }
     }
 
     /**
-     * A license state that makes the {@link #update(License.OperationMode, boolean, Version)}
+     * A license state that makes the {@link #update(License.OperationMode, boolean, long, Version)}
      * method public for use in tests.
      */
     public static class UpdatableLicenseState extends XPackLicenseState {
@@ -387,8 +389,8 @@ public UpdatableLicenseState(Settings settings) {
         }
 
         @Override
-        public void update(License.OperationMode mode, boolean active, Version mostRecentTrialVersion) {
-            super.update(mode, active, mostRecentTrialVersion);
+        public void update(License.OperationMode mode, boolean active, long expirationDate, Version mostRecentTrialVersion) {
+            super.update(mode, active, expirationDate, mostRecentTrialVersion);
         }
     }