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/*-
* Copyright (C) 2011, 2018 Oracle and/or its affiliates. All rights reserved.
*
* This file was distributed by Oracle as part of a version of Oracle NoSQL
* Database made available at:
*
* http://www.oracle.com/technetwork/database/database-technologies/nosqldb/downloads/index.html
*
* Please see the LICENSE file included in the top-level directory of the
* appropriate version of Oracle NoSQL Database for a copy of the license and
* additional information.
*/
package oracle.kv.impl.as;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.util.ArrayList;
import java.util.List;
import com.sun.net.httpserver.HttpExchange;
import com.sun.net.httpserver.HttpHandler;
import com.sun.net.httpserver.HttpServer;
/**
* Tiny http server for delivering health status of a service to
* an orchestration service such as Kubernetes.
*
* Usage: Define one or more HealthCheckers to test the health of the service;
* add them to a HealthServer, and call start(). GET Requests to the path
* "/healthz" return a response code 200 if the checkers all return true;
* 500 otherwise. See the main() method for sample usage.
*
* @see
* https://kubernetes.io/docs/tasks/configure-pod-container/configure-liveness-readiness-probes/#defining-a-liveness-http-request
*/
public class HealthServer {
/* The path of the GET request. */
static final String path = "/healthz";
@FunctionalInterface
public interface HealthChecker {
/**
* @return true: service is healthy;
* false: service is unhealthy and should be restarted.
*/
boolean doCheck();
}
private final List checkers;
private final HttpServer server;
public HealthServer(int port) throws IOException {
checkers = new ArrayList<>();
InetSocketAddress isa = new InetSocketAddress(port);
server = HttpServer.create(isa, 0);
server.createContext(path, new Handler());
}
public void addChecker(HealthChecker c) {
checkers.add(c);
}
public void start() {
server.start();
}
public void stop() {
server.stop(0);
}
class Handler implements HttpHandler {
@Override
public void handle(HttpExchange exchange) throws IOException {
if ("GET".equalsIgnoreCase(exchange.getRequestMethod())) {
exchange.getResponseHeaders().set("Content-Type", "text/plain");
boolean result = true;
for (HealthChecker c : checkers) {
if (! c.doCheck()) {
result = false;
break;
}
}
if (result) {
exchange.sendResponseHeaders(200, 0);
} else {
exchange.sendResponseHeaders(500, 0);
}
exchange.getResponseBody().close();
}
}
}
public static void main(String[] args) throws IOException {
final HealthServer h = new HealthServer(8080);
h.addChecker(new HealthChecker() {
private int counter = 1;
@Override
public boolean doCheck() {
/* We are alternately healthy and unhealthy */
return (counter++ % 2 == 1);
}
});
h.start();
}
}