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@@ -8,7 +8,6 @@ import play.Play;
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import play.core.NamedThreadFactory;
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import play.libs.F;
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import play.libs.Json;
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-
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import play.mvc.Controller;
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import play.mvc.Result;
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import scala.concurrent.ExecutionContext;
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@@ -18,7 +17,10 @@ import utils.Predicated;
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import java.util.ArrayList;
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import java.util.List;
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import java.util.Random;
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-import java.util.concurrent.*;
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+import java.util.concurrent.LinkedBlockingQueue;
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+import java.util.concurrent.ThreadLocalRandom;
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+import java.util.concurrent.ThreadPoolExecutor;
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+import java.util.concurrent.TimeUnit;
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public class Application extends Controller {
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@@ -38,39 +40,48 @@ public class Application extends Controller {
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new NamedThreadFactory("dbEc"));
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private static final ExecutionContext dbEc = ExecutionContexts.fromExecutorService(tpe);
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- // A predicate for checking our ability to service database requests is determined by ensuring that the request
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- // queue doesn't fill up beyond a certain threshold. For convenience we use the max number of connections * the max
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- // # of db requests per web request to determine this threshold. It is a rough check as we don't know how many
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- // queries we're going to make or what other threads are running in parallel etc. Nevertheless, the check is
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- // adequate in order to throttle the acceptance of requests to the size of the pool.
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+ public static Result json() {
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+ final ObjectNode result = OBJECT_MAPPER.createObjectNode();
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+ result.put("message", "Hello World!");
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+ return ok(result);
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+ }
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+
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+ // If the thread-pool used by the database grows too large then our server
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+ // is probably struggling, and we should start dropping requests. Set
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+ // the max size of our queue something above the number of concurrent
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+ // connections that we need to handle.
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public static class IsDbAvailable implements Predicate {
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@Override
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public boolean condition() {
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- return (tpe.getQueue().size() < maxConnections * MAX_QUERIES_PER_REQUEST);
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+ return tpe.getQueue().size() <= 1024;
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}
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}
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- public static Result json() {
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- final ObjectNode result = OBJECT_MAPPER.createObjectNode();
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- result.put("message", "Hello World!");
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- return ok(result);
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+ @Predicated(predicate = IsDbAvailable.class, failed = SERVICE_UNAVAILABLE)
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+ public static F.Promise<Result> db() {
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+ return getRandomWorlds(1).map(new F.Function<List<World>, Result>() {
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+ @Override
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+ public Result apply(List<World> worlds) {
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+ return ok(Json.toJson(worlds.get(0)));
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+ }
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+ });
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}
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-
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@Predicated(predicate = IsDbAvailable.class, failed = SERVICE_UNAVAILABLE)
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- public static F.Promise<Result> db(final Integer queries) {
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- final Random random = ThreadLocalRandom.current();
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- final List<F.Promise<? extends World>> promises = new ArrayList<F.Promise<? extends World>>(queries);
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- for (int i = 0; i < queries; ++i) {
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- final F.Promise<World> p = F.Promise.promise(new F.Function0<World>() {
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- @Override
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- public World apply() throws Throwable {
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- return World.findById(Long.valueOf(random.nextInt(TEST_DATABASE_ROWS) + 1));
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- }
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- }, dbEc);
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- promises.add(p);
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+ public static F.Promise<Result> queries(final String queryCountString) {
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+ int queryCount;
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+ try {
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+ queryCount = Integer.parseInt(queryCountString, 10);
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+ } catch (NumberFormatException e) {
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+ queryCount = 1;
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+ }
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+ if (queryCount < 1) {
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+ queryCount = 1;
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+ } else if (queryCount > 500) {
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+ queryCount = 500;
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}
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- return F.Promise.sequence(promises).map(new F.Function<List<World>, Result>() {
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+
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+ return getRandomWorlds(queryCount).map(new F.Function<List<World>, Result>() {
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@Override
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public Result apply(List<World> worlds) {
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return ok(Json.toJson(worlds));
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@@ -78,4 +89,20 @@ public class Application extends Controller {
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});
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}
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+ private static F.Promise<List<World>> getRandomWorlds(final int n) {
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+ return F.Promise.promise(new F.Function0<List<World>>() {
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+ @Override
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+ public List<World> apply() throws Throwable {
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+ Random random = ThreadLocalRandom.current();
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+ List<World> worlds = new ArrayList<World>(n);
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+ for (int i = 0; i < n; ++i) {
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+ long randomId = random.nextInt(TEST_DATABASE_ROWS) + 1;
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+ World world = World.findById(randomId);
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+ worlds.add(world);
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+ }
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+ return worlds;
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+ }
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+ }, dbEc);
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+ }
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+
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}
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Donovan Muller