Core: Add DateFormatter interface for java time parsing

server/src/main/java/org/elasticsearch/action/admin/cluster/allocation/ClusterAllocationExplanation.java

@@ -191,7 +191,7 @@ private XContentBuilder unassignedInfoToXContent(UnassignedInfo unassignedInfo,
         builder.startObject("unassigned_info");
         builder.field("reason", unassignedInfo.getReason());
         builder.field("at",
-            UnassignedInfo.DATE_TIME_FORMATTER.format(Instant.ofEpochMilli(unassignedInfo.getUnassignedTimeInMillis())));
+            UnassignedInfo.DATE_TIME_FORMATTER.print(Instant.ofEpochMilli(unassignedInfo.getUnassignedTimeInMillis())));
         if (unassignedInfo.getNumFailedAllocations() >  0) {
             builder.field("failed_allocation_attempts", unassignedInfo.getNumFailedAllocations());
         }

server/src/main/java/org/elasticsearch/cluster/metadata/IndexGraveyard.java

@@ -28,7 +28,7 @@
 import org.elasticsearch.common.io.stream.Writeable;
 import org.elasticsearch.common.settings.Setting;
 import org.elasticsearch.common.settings.Settings;
-import org.elasticsearch.common.time.CompoundDateTimeFormatter;
+import org.elasticsearch.common.time.DateFormatter;
 import org.elasticsearch.common.time.DateFormatters;
 import org.elasticsearch.common.xcontent.ContextParser;
 import org.elasticsearch.common.xcontent.ObjectParser;
@@ -368,8 +368,7 @@ public static final class Tombstone implements ToXContentObject, Writeable {
             TOMBSTONE_PARSER.declareString((b, s) -> {}, new ParseField(DELETE_DATE_KEY));
         }
 
-        static final CompoundDateTimeFormatter FORMATTER =
-            DateFormatters.forPattern("strict_date_optional_time").withZone(ZoneOffset.UTC);
+        static final DateFormatter FORMATTER = DateFormatters.forPattern("strict_date_optional_time").withZone(ZoneOffset.UTC);
 
         static ContextParser<Void, Tombstone> getParser() {
             return (parser, context) -> TOMBSTONE_PARSER.apply(parser, null).build();
@@ -434,7 +433,7 @@ public int hashCode() {
 
         @Override
         public String toString() {
-            String date = FORMATTER.format(Instant.ofEpochMilli(deleteDateInMillis));
+            String date = FORMATTER.print(Instant.ofEpochMilli(deleteDateInMillis));
             return "[index=" + index + ", deleteDate=" + date + "]";
         }
 

server/src/main/java/org/elasticsearch/cluster/routing/UnassignedInfo.java

@@ -31,7 +31,7 @@
 import org.elasticsearch.common.settings.Setting;
 import org.elasticsearch.common.settings.Setting.Property;
 import org.elasticsearch.common.settings.Settings;
-import org.elasticsearch.common.time.CompoundDateTimeFormatter;
+import org.elasticsearch.common.time.DateFormatter;
 import org.elasticsearch.common.time.DateFormatters;
 import org.elasticsearch.common.unit.TimeValue;
 import org.elasticsearch.common.xcontent.ToXContentFragment;
@@ -48,8 +48,7 @@
  */
 public final class UnassignedInfo implements ToXContentFragment, Writeable {
 
-    public static final CompoundDateTimeFormatter DATE_TIME_FORMATTER =
-        DateFormatters.forPattern("dateOptionalTime").withZone(ZoneOffset.UTC);
+    public static final DateFormatter DATE_TIME_FORMATTER = DateFormatters.forPattern("dateOptionalTime").withZone(ZoneOffset.UTC);
 
     public static final Setting<TimeValue> INDEX_DELAYED_NODE_LEFT_TIMEOUT_SETTING =
         Setting.positiveTimeSetting("index.unassigned.node_left.delayed_timeout", TimeValue.timeValueMinutes(1), Property.Dynamic,
@@ -411,7 +410,7 @@ public static long findNextDelayedAllocation(long currentNanoTime, ClusterState
     public String shortSummary() {
         StringBuilder sb = new StringBuilder();
         sb.append("[reason=").append(reason).append("]");
-        sb.append(", at[").append(DATE_TIME_FORMATTER.format(Instant.ofEpochMilli(unassignedTimeMillis))).append("]");
+        sb.append(", at[").append(DATE_TIME_FORMATTER.print(Instant.ofEpochMilli(unassignedTimeMillis))).append("]");
         if (failedAllocations >  0) {
             sb.append(", failed_attempts[").append(failedAllocations).append("]");
         }
@@ -434,7 +433,7 @@ public String toString() {
     public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
         builder.startObject("unassigned_info");
         builder.field("reason", reason);
-        builder.field("at", DATE_TIME_FORMATTER.format(Instant.ofEpochMilli(unassignedTimeMillis)));
+        builder.field("at", DATE_TIME_FORMATTER.print(Instant.ofEpochMilli(unassignedTimeMillis)));
         if (failedAllocations >  0) {
             builder.field("failed_attempts", failedAllocations);
         }

server/src/main/java/org/elasticsearch/common/Table.java

@@ -19,7 +19,7 @@
 
 package org.elasticsearch.common;
 
-import org.elasticsearch.common.time.CompoundDateTimeFormatter;
+import org.elasticsearch.common.time.DateFormatter;
 import org.elasticsearch.common.time.DateFormatters;
 
 import java.time.Instant;
@@ -85,7 +85,7 @@ public Table endHeaders() {
         return this;
     }
 
-    private static final CompoundDateTimeFormatter FORMATTER = DateFormatters.forPattern("HH:mm:ss").withZone(ZoneOffset.UTC);
+    private static final DateFormatter FORMATTER = DateFormatters.forPattern("HH:mm:ss").withZone(ZoneOffset.UTC);
 
     public Table startRow() {
         if (headers.isEmpty()) {
@@ -95,7 +95,7 @@ public Table startRow() {
         if (withTime) {
             long time = System.currentTimeMillis();
             addCell(TimeUnit.SECONDS.convert(time, TimeUnit.MILLISECONDS));
-            addCell(FORMATTER.format(Instant.ofEpochMilli(time)));
+            addCell(FORMATTER.print(Instant.ofEpochMilli(time)));
         }
         return this;
     }

server/src/main/java/org/elasticsearch/common/time/DateFormatter.java

@@ -0,0 +1,133 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.elasticsearch.common.time;
+
+import java.time.ZoneId;
+import java.time.format.DateTimeParseException;
+import java.time.temporal.TemporalAccessor;
+import java.time.temporal.TemporalField;
+import java.util.Arrays;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+public interface DateFormatter {
+
+    /**
+     * Try to parse input to a java time TemporalAccessor
+     * @param input                   An arbitrary string resembling the string representation of a date or time
+     * @throws DateTimeParseException If parsing fails, this exception will be thrown.
+     *                                Note that it can contained suppressed exceptions when several formatters failed parse this value
+     * @return                        The java time object containing the parsed input
+     */
+    TemporalAccessor parse(String input);
+
+    /**
+     * Create a copy of this formatter that is configured to parse dates in the specified time zone
+     *
+     * @param zoneId The time zone to act on
+     * @return       A copy of the date formatter this has been called on
+     */
+    DateFormatter withZone(ZoneId zoneId);
+
+    /**
+     * Print the supplied java time accessor in a string based representation according to this formatter
+     *
+     * @param accessor The temporal accessor used to format
+     * @return         The string result for the formatting
+     */
+    String print(TemporalAccessor accessor);
+
+    /**
+     * A name based format for this formatter. Can be one of the registered formatters like <code>epoch_millis</code> or
+     * a configured format like <code>HH:mm:ss</code>
+     *
+     * @return The name of this formatter
+     */
+    String format();
+
+    /**
+     * Configure a formatter using default fields for a TemporalAccessor that should be used in case
+     * the supplied date is not having all of those fields
+     *
+     * @param fields A <code>Map&lt;TemporalField, Long&gt;</code> of fields to be used as fallbacks
+     * @return       A new date formatter instance, that will use those fields during parsing
+     */
+    DateFormatter parseDefaulting(Map<TemporalField, Long> fields);
+
+    /**
+     * Merge several date formatters into a single one. Useful if you need to have several formatters with
+     * different formats act as one, for example when you specify a
+     * format like <code>date_hour||epoch_millis</code>
+     *
+     * @param formatters The list of date formatters to be merged together
+     * @return           The new date formtter containing the specified date formatters
+     */
+    static DateFormatter merge(DateFormatter ... formatters) {
+        return new MergedDateFormatter(formatters);
+    }
+
+    class MergedDateFormatter implements DateFormatter {
+
+        private final String format;
+        private final DateFormatter[] formatters;
+
+        MergedDateFormatter(DateFormatter ... formatters) {
+            this.formatters = formatters;
+            this.format = Arrays.stream(formatters).map(DateFormatter::format).collect(Collectors.joining("||"));
+        }
+
+        @Override
+        public TemporalAccessor parse(String input) {
+            DateTimeParseException failure = null;
+            for (DateFormatter formatter : formatters) {
+                try {
+                    return formatter.parse(input);
+                } catch (DateTimeParseException e) {
+                    if (failure == null) {
+                        failure = e;
+                    } else {
+                        failure.addSuppressed(e);
+                    }
+                }
+            }
+            throw failure;
+        }
+
+        @Override
+        public DateFormatter withZone(ZoneId zoneId) {
+            return new MergedDateFormatter(Arrays.stream(formatters).map(f -> f.withZone(zoneId)).toArray(DateFormatter[]::new));
+        }
+
+        @Override
+        public String print(TemporalAccessor accessor) {
+            return formatters[0].print(accessor);
+        }
+
+        @Override
+        public String format() {
+            return format;
+        }
+
+        @Override
+        public DateFormatter parseDefaulting(Map<TemporalField, Long> fields) {
+            return new MergedDateFormatter(Arrays.stream(formatters).map(f -> f.parseDefaulting(fields)).toArray(DateFormatter[]::new));
+        }
+    }
+}