added support for a new custom webhook event 'config.update'

src/main/java/com/erudika/scoold/ScooldConfig.java

@@ -3076,6 +3076,14 @@ public String rewriteInboundLinksWithFQDN() {
 		return getConfigParam("rewrite_inbound_links_with_fqdn", "");
 	}
 
+	@Documented(position = 3010,
+			identifier = "cluster_nodes",
+			category = "Miscellaneous",
+			description = "Total number of nodes present in the cluster when Scoold is deployed behind a reverse proxy.")
+	public int clusterNodes() {
+		return getConfigInt("cluster_nodes", 1);
+	}
+
 	/* **********************************************************************************************************/
 
 	public boolean inDevelopment() {

src/main/java/com/erudika/scoold/api/ApiController.java

@@ -922,6 +922,7 @@ public String configSet(HttpServletRequest req, HttpServletResponse res) {
 		ConfigFactory.invalidateCaches();
 		CONF.store();
 		pc.setAppSettings(CONF.getParaAppSettings());
+		triggerConfigUpdateEvent(CONF.getConfigMap());
 		return config(req, res);
 	}
 
@@ -945,6 +946,7 @@ public void configSet(@PathVariable String key, HttpServletRequest req, HttpServ
 			if (CONF.getParaAppSettings().containsKey(key)) {
 				pc.addAppSetting(key, value);
 			}
+			triggerConfigUpdateEvent(Collections.singletonMap(CONF.getConfigRootPrefix() + "." + key, value));
 		}
 	}
 
@@ -987,6 +989,28 @@ private List<String> readSpaces(String... spaces) {
 		return readSpaces(Arrays.asList(spaces));
 	}
 
+	private void triggerConfigUpdateEvent(Map<String, Object> payload) {
+		int nodes = CONF.clusterNodes();
+		if (nodes > 1) {
+			Para.asyncExecute(() -> {
+				Webhook trigger = new Webhook();
+				trigger.setId(Utils.getNewId());
+				trigger.setUpdate(true);
+				trigger.setUpdateAll(true);
+				trigger.setSecret("{{secretKey}}");
+				trigger.setActive(true);
+				trigger.setUrlEncoded(false);
+				trigger.setTargetUrl(CONF.serverUrl() + "/webhooks/config");
+				trigger.setTriggeredEvent("config.update");
+				trigger.setCustomPayload(payload);
+				// the goal is to saturate the load balancer and hopefully the payload reaches all nodes behind it
+				trigger.setRepeatedDeliveryAttempts(nodes * 2);
+				Para.getCache().put("lastConfigUpdate", trigger.getId());
+				pc.create(trigger);
+			});
+		}
+	}
+
 	@ExceptionHandler({Exception.class})
 	public Map<String, Object> handleException(Exception ex, WebRequest request, HttpServletResponse res) {
 		Map<String, Object> error = new HashMap<>(2);

src/main/java/com/erudika/scoold/api/WebhooksController.java

@@ -0,0 +1,86 @@
+/*
+ * Copyright 2013-2022 Erudika. https://erudika.com
+ *
+ * Licensed 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.
+ *
+ * For issues and patches go to: https://github.com/erudika
+ */
+package com.erudika.scoold.api;
+
+import com.erudika.para.client.ParaClient;
+import com.erudika.para.core.utils.Config;
+import com.erudika.para.core.utils.Para;
+import com.erudika.para.core.utils.ParaObjectUtils;
+import com.erudika.para.core.utils.Utils;
+import com.erudika.scoold.ScooldConfig;
+import static com.erudika.scoold.api.ApiController.logger;
+import com.erudika.scoold.utils.ScooldUtils;
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.typesafe.config.ConfigFactory;
+import java.util.Collections;
+import java.util.Map;
+import javax.inject.Inject;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import org.apache.commons.lang3.StringUtils;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+/**
+ * Handles various webhook events.
+ * @author Alex Bogdanovski [[email protected]]
+ */
+@RestController
+@RequestMapping(value = "/webhooks", produces = "application/json")
+public class WebhooksController {
+
+	private final ScooldUtils utils;
+	private final ParaClient pc;
+	private static final ScooldConfig CONF = ScooldUtils.getConfig();
+
+	@Inject
+	public WebhooksController(ScooldUtils utils) {
+		this.utils = utils;
+		this.pc = utils.getParaClient();
+	}
+
+	@PostMapping("/config")
+	public void updateConfig(HttpServletRequest req, HttpServletResponse res) throws JsonProcessingException {
+		Map<String, Object> entity = readEntity(req);
+		if (entity.containsKey("signature") && entity.containsKey("payload") &&
+				entity.getOrDefault("event", "").equals("config.update")) {
+			String payload = (String) entity.get("payload");
+			String signature = (String) entity.get("signature");
+			String id = (String) entity.get(Config._ID);
+			boolean alreadyUpdated = id.equals(Para.getCache().get("lastConfigUpdate"));
+			if (StringUtils.equals(signature, Utils.hmacSHA256(payload, CONF.paraSecretKey())) && !alreadyUpdated) {
+				Map<String, Object> configMap = ParaObjectUtils.getJsonReader(Map.class).readValue(payload);
+				configMap.entrySet().forEach((entry) -> {
+					System.setProperty(entry.getKey(), entry.getValue().toString());
+				});
+				ConfigFactory.invalidateCaches();
+				CONF.store();
+			}
+		}
+	}
+
+	private Map<String, Object> readEntity(HttpServletRequest req) {
+		try {
+			return ParaObjectUtils.getJsonReader(Map.class).readValue(req.getInputStream());
+		} catch (Exception ex) {
+			logger.error(null, ex);
+		}
+		return Collections.emptyMap();
+	}
+}