Watcher: Increase HttpClient parallel sent requests (#30130)

The HTTPClient used in watcher is based on the apache http client. The
current client is using a lot of defaults - which are not always
optimal. Two of those defaults are the maximum number of total
connections and the maximum number of connections to a single route.

If one of those limits is reached, the HTTPClient waits for a connection
to be finished thus acting in a blocking fashion. In order to prevent
this when many requests are being executed, we increase the limit of
total connections as well as the connections per route (a route is
basically an endpoint, which also contains proxy information, not
containing an URL, just hosts).

On top of that an additional option has been set to evict
long running connections, which can potentially be reused after some
time. As this requires an additional background thread, this required
some changes to ensure that the httpclient is closed properly. Also the
timeout for this can be configured.

Author: spinscale

docs/CHANGELOG.asciidoc

@@ -320,6 +320,14 @@ these instead of the multi-argument versions. ({pull}29623[#29623])
 
 Recovery::
 * Require translogUUID when reading global checkpoint {pull}28587[#28587] (issue: {issue}28435[#28435])
+Watcher HTTP client used in watches now allows more parallel connections to the
+same endpoint and evicts long running connections. ({pull}30130[#30130])
+
+The cluster state listener to decide if watcher should be
+stopped/started/paused now runs far less code in an executor but is more
+synchronous and predictable. Also the trigger engine thread is only started on
+data nodes. And the Execute Watch API can be triggered regardless is watcher is
+started or stopped. ({pull}30118[#30118])
 
 Added put index template API to the high level rest client ({pull}30400[#30400])
 

x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/LocalStateCompositeXPackPlugin.java

@@ -28,6 +28,7 @@
 import org.elasticsearch.common.util.PageCacheRecycler;
 import org.elasticsearch.common.util.concurrent.ThreadContext;
 import org.elasticsearch.common.xcontent.NamedXContentRegistry;
+import org.elasticsearch.core.internal.io.IOUtils;
 import org.elasticsearch.env.Environment;
 import org.elasticsearch.env.NodeEnvironment;
 import org.elasticsearch.http.HttpServerTransport;
@@ -38,6 +39,7 @@
 import org.elasticsearch.ingest.Processor;
 import org.elasticsearch.license.LicenseService;
 import org.elasticsearch.license.XPackLicenseState;
+import org.elasticsearch.persistent.PersistentTasksExecutor;
 import org.elasticsearch.plugins.ActionPlugin;
 import org.elasticsearch.plugins.AnalysisPlugin;
 import org.elasticsearch.plugins.ClusterPlugin;
@@ -57,9 +59,9 @@
 import org.elasticsearch.transport.Transport;
 import org.elasticsearch.transport.TransportInterceptor;
 import org.elasticsearch.watcher.ResourceWatcherService;
-import org.elasticsearch.persistent.PersistentTasksExecutor;
 import org.elasticsearch.xpack.core.ssl.SSLService;
 
+import java.io.IOException;
 import java.nio.file.Path;
 import java.util.ArrayList;
 import java.util.Collection;
@@ -391,6 +393,11 @@ public List<PersistentTasksExecutor<?>> getPersistentTasksExecutor(ClusterServic
                 .collect(toList());
     }
 
+    @Override
+    public void close() throws IOException {
+        IOUtils.close(plugins);
+    }
+
     private <T> List<T> filterPlugins(Class<T> type) {
         return plugins.stream().filter(x -> type.isAssignableFrom(x.getClass())).map(p -> ((T)p))
                 .collect(Collectors.toList());

x-pack/plugin/watcher/src/main/java/org/elasticsearch/xpack/watcher/Watcher.java

@@ -30,6 +30,7 @@
 import org.elasticsearch.common.unit.TimeValue;
 import org.elasticsearch.common.util.concurrent.EsExecutors;
 import org.elasticsearch.common.xcontent.NamedXContentRegistry;
+import org.elasticsearch.core.internal.io.IOUtils;
 import org.elasticsearch.env.Environment;
 import org.elasticsearch.env.NodeEnvironment;
 import org.elasticsearch.index.IndexModule;
@@ -219,6 +220,7 @@ public class Watcher extends Plugin implements ActionPlugin, ScriptPlugin {
 
     private static final Logger logger = Loggers.getLogger(Watcher.class);
     private WatcherIndexingListener listener;
+    private HttpClient httpClient;
 
 //    public List<NamedWriteableRegistry.Entry> getNamedWriteables() {
 //        List<NamedWriteableRegistry.Entry> entries = new ArrayList<>();
@@ -285,7 +287,7 @@ public Collection<Object> createComponents(Client client, ClusterService cluster
         // TODO: add more auth types, or remove this indirection
         HttpAuthRegistry httpAuthRegistry = new HttpAuthRegistry(httpAuthFactories);
         HttpRequestTemplate.Parser httpTemplateParser = new HttpRequestTemplate.Parser(httpAuthRegistry);
-        final HttpClient httpClient = new HttpClient(settings, httpAuthRegistry, getSslService());
+        httpClient = new HttpClient(settings, httpAuthRegistry, getSslService());
 
         // notification
         EmailService emailService = new EmailService(settings, cryptoService, clusterService.getClusterSettings());
@@ -630,4 +632,9 @@ public List<BootstrapCheck> getBootstrapChecks() {
     public List<ScriptContext> getContexts() {
         return Arrays.asList(Watcher.SCRIPT_SEARCH_CONTEXT, Watcher.SCRIPT_EXECUTABLE_CONTEXT, Watcher.SCRIPT_TEMPLATE_CONTEXT);
     }
+
+    @Override
+    public void close() throws IOException {
+        IOUtils.closeWhileHandlingException(httpClient);
+    }
 }

x-pack/plugin/watcher/src/main/java/org/elasticsearch/xpack/watcher/common/http/HttpClient.java

@@ -46,6 +46,7 @@
 
 import javax.net.ssl.HostnameVerifier;
 import java.io.ByteArrayOutputStream;
+import java.io.Closeable;
 import java.io.IOException;
 import java.io.InputStream;
 import java.net.URI;
@@ -56,9 +57,13 @@
 import java.util.List;
 import java.util.Map;
 
-public class HttpClient extends AbstractComponent {
+public class HttpClient extends AbstractComponent implements Closeable {
 
     private static final String SETTINGS_SSL_PREFIX = "xpack.http.ssl.";
+    // picking a reasonable high value here to allow for setups with lots of watch executions or many http inputs/actions
+    // this is also used as the value per route, if you are connecting to the same endpoint a lot, which is likely, when
+    // you are querying a remote Elasticsearch cluster
+    private static final int MAX_CONNECTIONS = 500;
 
     private final HttpAuthRegistry httpAuthRegistry;
     private final CloseableHttpClient client;
@@ -84,6 +89,10 @@ public HttpClient(Settings settings, HttpAuthRegistry httpAuthRegistry, SSLServi
         SSLConnectionSocketFactory factory = new SSLConnectionSocketFactory(sslService.sslSocketFactory(sslSettings), verifier);
         clientBuilder.setSSLSocketFactory(factory);
 
+        clientBuilder.evictExpiredConnections();
+        clientBuilder.setMaxConnPerRoute(MAX_CONNECTIONS);
+        clientBuilder.setMaxConnTotal(MAX_CONNECTIONS);
+
         client = clientBuilder.build();
     }
 
@@ -251,6 +260,11 @@ private URI createURI(HttpRequest request) {
         }
     }
 
+    @Override
+    public void close() throws IOException {
+        client.close();
+    }
+
     /**
      * Helper class to have all HTTP methods except HEAD allow for an body, including GET
      */

x-pack/plugin/watcher/src/test/java/org/elasticsearch/xpack/watcher/actions/webhook/WebhookActionTests.java

@@ -44,7 +44,6 @@
 import org.junit.Before;
 
 import javax.mail.internet.AddressException;
-
 import java.io.IOException;
 import java.util.Map;
 
@@ -219,10 +218,9 @@ private WebhookActionFactory webhookFactory(HttpClient client) {
 
     public void testThatSelectingProxyWorks() throws Exception {
         Environment environment = TestEnvironment.newEnvironment(Settings.builder().put("path.home", createTempDir()).build());
-        HttpClient httpClient = new HttpClient(Settings.EMPTY, authRegistry,
-                new SSLService(environment.settings(), environment));
 
-        try (MockWebServer proxyServer = new MockWebServer()) {
+        try (HttpClient httpClient = new HttpClient(Settings.EMPTY, authRegistry,
+            new SSLService(environment.settings(), environment)); MockWebServer proxyServer = new MockWebServer()) {
             proxyServer.start();
             proxyServer.enqueue(new MockResponse().setResponseCode(200).setBody("fullProxiedContent"));
 

x-pack/plugin/watcher/src/test/java/org/elasticsearch/xpack/watcher/common/http/HttpClientTests.java

@@ -77,6 +77,7 @@ public void init() throws Exception {
     @After
     public void shutdown() throws Exception {
         webServer.close();
+        httpClient.close();
     }
 
     public void testBasics() throws Exception {
@@ -184,17 +185,18 @@ public void testHttps() throws Exception {
                     .setSecureSettings(secureSettings)
                     .build();
         }
-        httpClient = new HttpClient(settings, authRegistry, new SSLService(settings, environment));
-        secureSettings = new MockSecureSettings();
-        // We can't use the client created above for the server since it is only a truststore
-        secureSettings.setString("xpack.ssl.keystore.secure_password", "testnode");
-        Settings settings2 = Settings.builder()
-                .put("xpack.ssl.keystore.path", getDataPath("/org/elasticsearch/xpack/security/keystore/testnode.jks"))
-                .setSecureSettings(secureSettings)
-                .build();
+        try (HttpClient client = new HttpClient(settings, authRegistry, new SSLService(settings, environment))) {
+            secureSettings = new MockSecureSettings();
+            // We can't use the client created above for the server since it is only a truststore
+            secureSettings.setString("xpack.ssl.keystore.secure_password", "testnode");
+            Settings settings2 = Settings.builder()
+                    .put("xpack.ssl.keystore.path", getDataPath("/org/elasticsearch/xpack/security/keystore/testnode.jks"))
+                    .setSecureSettings(secureSettings)
+                    .build();
 
-        TestsSSLService sslService = new TestsSSLService(settings2, environment);
-        testSslMockWebserver(sslService.sslContext(), false);
+            TestsSSLService sslService = new TestsSSLService(settings2, environment);
+            testSslMockWebserver(client, sslService.sslContext(), false);
+        }
     }
 
     public void testHttpsDisableHostnameVerification() throws Exception {
@@ -217,18 +219,19 @@ public void testHttpsDisableHostnameVerification() throws Exception {
                     .setSecureSettings(secureSettings)
                     .build();
         }
-        httpClient = new HttpClient(settings, authRegistry, new SSLService(settings, environment));
-        MockSecureSettings secureSettings = new MockSecureSettings();
-        // We can't use the client created above for the server since it only defines a truststore
-        secureSettings.setString("xpack.ssl.keystore.secure_password", "testnode-no-subjaltname");
-        Settings settings2 = Settings.builder()
-                .put("xpack.ssl.keystore.path",
-                        getDataPath("/org/elasticsearch/xpack/security/transport/ssl/certs/simple/testnode-no-subjaltname.jks"))
-                .setSecureSettings(secureSettings)
-                .build();
+        try (HttpClient client = new HttpClient(settings, authRegistry, new SSLService(settings, environment))) {
+            MockSecureSettings secureSettings = new MockSecureSettings();
+            // We can't use the client created above for the server since it only defines a truststore
+            secureSettings.setString("xpack.ssl.keystore.secure_password", "testnode-no-subjaltname");
+            Settings settings2 = Settings.builder()
+                    .put("xpack.ssl.keystore.path",
+                            getDataPath("/org/elasticsearch/xpack/security/transport/ssl/certs/simple/testnode-no-subjaltname.jks"))
+                    .setSecureSettings(secureSettings)
+                    .build();
 
-        TestsSSLService sslService = new TestsSSLService(settings2, environment);
-        testSslMockWebserver(sslService.sslContext(), false);
+            TestsSSLService sslService = new TestsSSLService(settings2, environment);
+            testSslMockWebserver(client, sslService.sslContext(), false);
+        }
     }
 
     public void testHttpsClientAuth() throws Exception {
@@ -241,19 +244,20 @@ public void testHttpsClientAuth() throws Exception {
                 .build();
 
         TestsSSLService sslService = new TestsSSLService(settings, environment);
-        httpClient = new HttpClient(settings, authRegistry, sslService);
-        testSslMockWebserver(sslService.sslContext(), true);
+        try (HttpClient client = new HttpClient(settings, authRegistry, sslService)) {
+            testSslMockWebserver(client, sslService.sslContext(), true);
+        }
     }
 
-    private void testSslMockWebserver(SSLContext sslContext, boolean needClientAuth) throws IOException {
+    private void testSslMockWebserver(HttpClient client, SSLContext sslContext, boolean needClientAuth) throws IOException {
         try (MockWebServer mockWebServer = new MockWebServer(sslContext, needClientAuth)) {
             mockWebServer.enqueue(new MockResponse().setResponseCode(200).setBody("body"));
             mockWebServer.start();
 
             HttpRequest.Builder request = HttpRequest.builder("localhost", mockWebServer.getPort())
                     .scheme(Scheme.HTTPS)
                     .path("/test");
-            HttpResponse response = httpClient.execute(request.build());
+            HttpResponse response = client.execute(request.build());
             assertThat(response.status(), equalTo(200));
             assertThat(response.body().utf8ToString(), equalTo("body"));
 
@@ -288,14 +292,14 @@ public void testHttpResponseWithAnyStatusCodeCanReturnBody() throws Exception {
 
     @Network
     public void testHttpsWithoutTruststore() throws Exception {
-        HttpClient httpClient = new HttpClient(Settings.EMPTY, authRegistry, new SSLService(Settings.EMPTY, environment));
-
-        // Known server with a valid cert from a commercial CA
-        HttpRequest.Builder request = HttpRequest.builder("www.elastic.co", 443).scheme(Scheme.HTTPS);
-        HttpResponse response = httpClient.execute(request.build());
-        assertThat(response.status(), equalTo(200));
-        assertThat(response.hasContent(), is(true));
-        assertThat(response.body(), notNullValue());
+        try (HttpClient client = new HttpClient(Settings.EMPTY, authRegistry, new SSLService(Settings.EMPTY, environment))) {
+            // Known server with a valid cert from a commercial CA
+            HttpRequest.Builder request = HttpRequest.builder("www.elastic.co", 443).scheme(Scheme.HTTPS);
+            HttpResponse response = client.execute(request.build());
+            assertThat(response.status(), equalTo(200));
+            assertThat(response.hasContent(), is(true));
+            assertThat(response.body(), notNullValue());
+        }
     }
 
     public void testThatProxyCanBeConfigured() throws Exception {
@@ -307,15 +311,16 @@ public void testThatProxyCanBeConfigured() throws Exception {
                     .put(HttpSettings.PROXY_HOST.getKey(), "localhost")
                     .put(HttpSettings.PROXY_PORT.getKey(), proxyServer.getPort())
                     .build();
-            HttpClient httpClient = new HttpClient(settings, authRegistry, new SSLService(settings, environment));
 
             HttpRequest.Builder requestBuilder = HttpRequest.builder("localhost", webServer.getPort())
                     .method(HttpMethod.GET)
                     .path("/");
 
-            HttpResponse response = httpClient.execute(requestBuilder.build());
-            assertThat(response.status(), equalTo(200));
-            assertThat(response.body().utf8ToString(), equalTo("fullProxiedContent"));
+            try (HttpClient client = new HttpClient(settings, authRegistry, new SSLService(settings, environment))) {
+                HttpResponse response = client.execute(requestBuilder.build());
+                assertThat(response.status(), equalTo(200));
+                assertThat(response.body().utf8ToString(), equalTo("fullProxiedContent"));
+            }
 
             // ensure we hit the proxyServer and not the webserver
             assertThat(webServer.requests(), hasSize(0));
@@ -386,16 +391,16 @@ public void testProxyCanHaveDifferentSchemeThanRequest() throws Exception {
                     .setSecureSettings(secureSettings)
                     .build();
 
-            HttpClient httpClient = new HttpClient(settings, authRegistry, new SSLService(settings, environment));
-
             HttpRequest.Builder requestBuilder = HttpRequest.builder("localhost", webServer.getPort())
                     .method(HttpMethod.GET)
                     .scheme(Scheme.HTTP)
                     .path("/");
 
-            HttpResponse response = httpClient.execute(requestBuilder.build());
-            assertThat(response.status(), equalTo(200));
-            assertThat(response.body().utf8ToString(), equalTo("fullProxiedContent"));
+            try (HttpClient client = new HttpClient(settings, authRegistry, new SSLService(settings, environment))) {
+                HttpResponse response = client.execute(requestBuilder.build());
+                assertThat(response.status(), equalTo(200));
+                assertThat(response.body().utf8ToString(), equalTo("fullProxiedContent"));
+            }
 
             // ensure we hit the proxyServer and not the webserver
             assertThat(webServer.requests(), hasSize(0));
@@ -413,16 +418,17 @@ public void testThatProxyCanBeOverriddenByRequest() throws Exception {
                     .put(HttpSettings.PROXY_PORT.getKey(), proxyServer.getPort() + 1)
                     .put(HttpSettings.PROXY_HOST.getKey(), "https")
                     .build();
-            HttpClient httpClient = new HttpClient(settings, authRegistry, new SSLService(settings, environment));
 
             HttpRequest.Builder requestBuilder = HttpRequest.builder("localhost", webServer.getPort())
                     .method(HttpMethod.GET)
                     .proxy(new HttpProxy("localhost", proxyServer.getPort(), Scheme.HTTP))
                     .path("/");
 
-            HttpResponse response = httpClient.execute(requestBuilder.build());
-            assertThat(response.status(), equalTo(200));
-            assertThat(response.body().utf8ToString(), equalTo("fullProxiedContent"));
+            try (HttpClient client = new HttpClient(settings, authRegistry, new SSLService(settings, environment))) {
+                HttpResponse response = client.execute(requestBuilder.build());
+                assertThat(response.status(), equalTo(200));
+                assertThat(response.body().utf8ToString(), equalTo("fullProxiedContent"));
+            }
 
             // ensure we hit the proxyServer and not the webserver
             assertThat(webServer.requests(), hasSize(0));
@@ -535,12 +541,13 @@ public void testMaxHttpResponseSize() throws Exception {
         Settings settings = Settings.builder()
                 .put(HttpSettings.MAX_HTTP_RESPONSE_SIZE.getKey(), new ByteSizeValue(randomBytesLength - 1, ByteSizeUnit.BYTES))
                 .build();
-        HttpClient httpClient = new HttpClient(settings, authRegistry, new SSLService(environment.settings(), environment));
 
         HttpRequest.Builder requestBuilder = HttpRequest.builder("localhost", webServer.getPort()).method(HttpMethod.GET).path("/");
 
-        IOException e = expectThrows(IOException.class, () -> httpClient.execute(requestBuilder.build()));
-        assertThat(e.getMessage(), startsWith("Maximum limit of"));
+        try (HttpClient client = new HttpClient(settings, authRegistry, new SSLService(environment.settings(), environment))) {
+            IOException e = expectThrows(IOException.class, () -> client.execute(requestBuilder.build()));
+            assertThat(e.getMessage(), startsWith("Maximum limit of"));
+        }
     }
 
     public void testThatGetRedirectIsFollowed() throws Exception {