Backport PR #8865 (#8875)

---------

**Commit 1:**
[es/versionCheck] prevent spamming logs with compatibility warnings

* Original sha: bb95cf874c
* Authored by spalger <email@spalger.com> on 2016-10-27T20:48:36Z

**Commit 2:**
[es/versionCheck] clarify new var and reason for check

* Original sha: cda9594859
* Authored by spalger <email@spalger.com> on 2016-10-27T22:36:43Z

**Commit 3:**
[es/versionCheck] explain why we need to track per-server

* Original sha: 5eb9ccdc41
* Authored by spalger <email@spalger.com> on 2016-10-27T23:30:41Z

src/core_plugins/elasticsearch/lib/__tests__/check_es_version.js

@@ -17,7 +17,7 @@ describe('plugins/elasticsearch', () => {
 
     beforeEach(function () {
       server = {
-        log: _.noop,
+        log: sinon.stub(),
         // This is required or else we get a SetupError.
         config: () => ({
           get: sinon.stub(),
@@ -95,5 +95,41 @@ describe('plugins/elasticsearch', () => {
         expect(e).to.be.a(SetupError);
       }
     });
+
+    it('warns if a node is only off by a patch version', async () => {
+      setNodes('5.1.1');
+      await checkEsVersion(server, KIBANA_VERSION);
+      sinon.assert.callCount(server.log, 2);
+      expect(server.log.getCall(0).args[0]).to.contain('debug');
+      expect(server.log.getCall(1).args[0]).to.contain('warning');
+    });
+
+    it('only warns once per node list', async () => {
+      setNodes('5.1.1');
+
+      await checkEsVersion(server, KIBANA_VERSION);
+      sinon.assert.callCount(server.log, 2);
+      expect(server.log.getCall(0).args[0]).to.contain('debug');
+      expect(server.log.getCall(1).args[0]).to.contain('warning');
+
+      await checkEsVersion(server, KIBANA_VERSION);
+      sinon.assert.callCount(server.log, 3);
+      expect(server.log.getCall(2).args[0]).to.contain('debug');
+    });
+
+    it('warns again if the node list changes', async () => {
+      setNodes('5.1.1');
+
+      await checkEsVersion(server, KIBANA_VERSION);
+      sinon.assert.callCount(server.log, 2);
+      expect(server.log.getCall(0).args[0]).to.contain('debug');
+      expect(server.log.getCall(1).args[0]).to.contain('warning');
+
+      setNodes('5.1.2');
+      await checkEsVersion(server, KIBANA_VERSION);
+      sinon.assert.callCount(server.log, 4);
+      expect(server.log.getCall(2).args[0]).to.contain('debug');
+      expect(server.log.getCall(3).args[0]).to.contain('warning');
+    });
   });
 });

src/core_plugins/elasticsearch/lib/check_es_version.js

@@ -9,6 +9,16 @@ import semver from 'semver';
 import isEsCompatibleWithKibana from './is_es_compatible_with_kibana';
 import SetupError from './setup_error';
 
+/**
+ *  tracks the node descriptions that get logged in warnings so
+ *  that we don't spam the log with the same message over and over.
+ *
+ *  There are situations, like in testing or multi-tenancy, where
+ *  the server argument changes, so we must track the previous
+ *  node warnings per server
+ */
+const lastWarnedNodesForServer = new WeakMap();
+
 module.exports = function checkEsVersion(server, kibanaVersion) {
   server.log(['plugin', 'debug'], 'Checking Elasticsearch version');
 
@@ -50,16 +60,20 @@ module.exports = function checkEsVersion(server, kibanaVersion) {
         ip: node.ip,
       }));
 
-      server.log(['warning'], {
-        tmpl: (
-          'You\'re running Kibana <%= kibanaVersion %> with some newer versions of ' +
-          'Elasticsearch. Update Kibana to the latest version to prevent compatibility issues: ' +
-          '<%= getHumanizedNodeNames(nodes).join(", ") %>'
-        ),
-        kibanaVersion,
-        getHumanizedNodeNames,
-        nodes: simplifiedNodes,
-      });
+      // Don't show the same warning over and over again.
+      const warningNodeNames = getHumanizedNodeNames(simplifiedNodes).join(', ');
+      if (lastWarnedNodesForServer.get(server) !== warningNodeNames) {
+        lastWarnedNodesForServer.set(server, warningNodeNames);
+        server.log(['warning'], {
+          tmpl: (
+            `You're running Kibana ${kibanaVersion} with some newer versions of ` +
+            'Elasticsearch. Update Kibana to the latest version to prevent compatibility issues: ' +
+            warningNodeNames
+          ),
+          kibanaVersion,
+          nodes: simplifiedNodes,
+        });
+      }
     }
 
     if (incompatibleNodes.length) {