From 6d5ee527969472ba894f6ade5cc76a5fe7b99dea Mon Sep 17 00:00:00 2001
From: Przemyslaw Gomulka <przemyslaw.gomulka@elastic.co>
Date: Mon, 15 Jul 2019 10:52:01 +0200
Subject: [PATCH] draft for logging

---
 distribution/src/config/log4j2.properties     |  1 +
 .../routing/allocation/AllocationService.java |  1 +
 .../allocation/ClusterChangeLogMessage.java   | 19 +++++++++++++++++++
 3 files changed, 21 insertions(+)
 create mode 100644 server/src/main/java/org/elasticsearch/cluster/routing/allocation/ClusterChangeLogMessage.java

diff --git a/distribution/src/config/log4j2.properties b/distribution/src/config/log4j2.properties
index d3398fa1b5d87..4957e4310ea0e 100644
--- a/distribution/src/config/log4j2.properties
+++ b/distribution/src/config/log4j2.properties
@@ -15,6 +15,7 @@ appender.rolling.name = rolling
 appender.rolling.fileName = ${sys:es.logs.base_path}${sys:file.separator}${sys:es.logs.cluster_name}_server.json
 appender.rolling.layout.type = ESJsonLayout
 appender.rolling.layout.type_name = server
+appender.rolling.layout.esmessagefields=previous.health,current.health,reason
 
 appender.rolling.filePattern = ${sys:es.logs.base_path}${sys:file.separator}${sys:es.logs.cluster_name}-%d{yyyy-MM-dd}-%i.json.gz
 appender.rolling.policies.type = Policies
diff --git a/server/src/main/java/org/elasticsearch/cluster/routing/allocation/AllocationService.java b/server/src/main/java/org/elasticsearch/cluster/routing/allocation/AllocationService.java
index 9b22e63cf9ae5..20b67adb1d609 100644
--- a/server/src/main/java/org/elasticsearch/cluster/routing/allocation/AllocationService.java
+++ b/server/src/main/java/org/elasticsearch/cluster/routing/allocation/AllocationService.java
@@ -386,6 +386,7 @@ private void logClusterHealthStateChange(ClusterStateHealth previousStateHealth,
         ClusterHealthStatus previousHealth = previousStateHealth.getStatus();
         ClusterHealthStatus currentHealth = newStateHealth.getStatus();
         if (!previousHealth.equals(currentHealth)) {
+            logger.info(new ClusterChangeLogMessage(previousHealth,currentHealth,reason));
             logger.info("Cluster health status changed from [{}] to [{}] (reason: [{}]).", previousHealth, currentHealth, reason);
         }
     }
diff --git a/server/src/main/java/org/elasticsearch/cluster/routing/allocation/ClusterChangeLogMessage.java b/server/src/main/java/org/elasticsearch/cluster/routing/allocation/ClusterChangeLogMessage.java
new file mode 100644
index 0000000000000..be9a8c37128a1
--- /dev/null
+++ b/server/src/main/java/org/elasticsearch/cluster/routing/allocation/ClusterChangeLogMessage.java
@@ -0,0 +1,19 @@
+package org.elasticsearch.cluster.routing.allocation;
+
+import org.elasticsearch.cluster.health.ClusterHealthStatus;
+import org.elasticsearch.common.logging.ESLogMessage;
+
+import java.util.Map;
+
+public class ClusterChangeLogMessage extends ESLogMessage {
+
+    public ClusterChangeLogMessage(ClusterHealthStatus previousHealth, ClusterHealthStatus currentHealth, String reason) {
+        super(fieldMap(previousHealth, currentHealth, reason), "Cluster health status changed.");
+    }
+
+    private static Map<String, Object> fieldMap(ClusterHealthStatus previousHealth, ClusterHealthStatus currentHealth, String reason) {
+
+        return Map.of("previous.health", previousHealth, "current.health", currentHealth, "reason", reason);
+    }
+}
+