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Simplifying ContextManagers and avoid new Lists when creating or reac…
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…tivating snapshots.

This should be a significant performance improvement.

Signed-off-by: Sjoerd Talsma <sjoerdtalsma@users.noreply.github.com>
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@sjoerdtalsma
sjoerdtalsma committed Nov 8, 2024
1 parent 7932f71 commit 46680b7
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Showing 4 changed files with 140 additions and 100 deletions.
138 changes: 45 additions & 93 deletions context-propagation-core/src/main/java/nl/talsmasoftware/context/core/ContextManagers.java
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Original file line number Diff line number Diff line change
Expand Up @@ -19,13 +19,9 @@
import nl.talsmasoftware.context.api.ContextManager;
import nl.talsmasoftware.context.api.ContextSnapshot;
import nl.talsmasoftware.context.api.ContextSnapshot.Reactivation;
import nl.talsmasoftware.context.api.ContextTimer;

import java.util.ArrayList;
import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
import java.util.ServiceLoader;
import java.util.ListIterator;
import java.util.logging.Level;
import java.util.logging.Logger;

Expand All @@ -43,15 +39,6 @@
public final class ContextManagers {
private static final Logger LOGGER = Logger.getLogger(ContextManagers.class.getName());

/**
* Sometimes a single, fixed classloader may be necessary (e.g. #97)
*/
private static volatile ClassLoader classLoaderOverride = null;

private static volatile List<ContextManager<?>> contextManagers = null;

private static volatile List<ContextTimer> contextTimers = null;

/**
* Private constructor to avoid instantiation of this class.
*/
Expand All @@ -72,32 +59,26 @@ private ContextManagers() {
* @return A new snapshot that can be reactivated elsewhere (e.g. a background thread)
* within a try-with-resources construct.
*/
@SuppressWarnings("rawtypes")
public static nl.talsmasoftware.context.api.ContextSnapshot createContextSnapshot() {
final long start = System.nanoTime();
final List<ContextManager<?>> managers = new LinkedList<>();
final List<Object> values = new LinkedList<>();
Long managerStart = null;
for (ContextManager<?> manager : getContextManagers()) {
managerStart = System.nanoTime();
final List<ContextManager> managers = ServiceCache.cached(ContextManager.class);
final Object[] values = new Object[managers.size()];

for (ListIterator<ContextManager> it = managers.listIterator(); it.hasNext(); ) {
final ContextManager manager = it.next();
long managerStart = System.nanoTime();
try {
final Object activeContextValue = manager.getActiveContextValue();
if (activeContextValue != null) {
values.add(activeContextValue);
managers.add(manager);
if (LOGGER.isLoggable(Level.FINEST)) {
LOGGER.finest("Active context value of " + manager + " added to new snapshot: " + activeContextValue);
}
Timers.timed(System.nanoTime() - managerStart, manager.getClass(), "getActiveContext");
} else if (LOGGER.isLoggable(Level.FINEST)) {
LOGGER.log(Level.FINEST, "There is no active context for " + manager + " in this snapshot.");
}
values[it.previousIndex()] = getActiveContextValue(manager);
Timers.timed(System.nanoTime() - managerStart, manager.getClass(), "getActiveContext");
} catch (RuntimeException rte) {
LOGGER.log(Level.WARNING, "Exception obtaining active context from " + manager + " for snapshot.", rte);
LOGGER.log(Level.WARNING, "Error obtaining active context from " + manager + " (in thread " + Thread.currentThread().getName() + ").", rte);
Timers.timed(System.nanoTime() - managerStart, manager.getClass(), "getActiveContext.exception");
}
}

final ContextSnapshotImpl result = new ContextSnapshotImpl(managers, values);
if (managerStart == null && LOGGER.isLoggable(Level.FINER)) {
if (managers.isEmpty() && LOGGER.isLoggable(Level.FINER)) {
LOGGER.finer(result + " was created but no ContextManagers were found! "
+ " Thead=" + Thread.currentThread()
+ ", ContextClassLoader=" + Thread.currentThread().getContextClassLoader());
Expand Down Expand Up @@ -126,17 +107,14 @@ public static nl.talsmasoftware.context.api.ContextSnapshot createContextSnapsho
public static void clearActiveContexts() {
final long start = System.nanoTime();
Long managerStart = null;
for (ContextManager<?> manager : getContextManagers()) {
for (ContextManager<?> manager : ServiceCache.cached(ContextManager.class)) {
managerStart = System.nanoTime();
try {
manager.clear();
if (LOGGER.isLoggable(Level.FINEST)) {
LOGGER.finest("Active context of " + manager + " was cleared.");
}
clear(manager);
Timers.timed(System.nanoTime() - managerStart, manager.getClass(), "clear");
} catch (RuntimeException rte) {
LOGGER.log(Level.WARNING, "Exception clearing active context from " + manager + ".", rte);
contextManagers = null;
LOGGER.log(Level.WARNING, "Error clearing active context from " + manager + ".", rte);
ServiceCache.clear();
Timers.timed(System.nanoTime() - managerStart, manager.getClass(), "clear.exception");
}
}
Expand Down Expand Up @@ -170,71 +148,44 @@ public static void clearActiveContexts() {
* @since 1.0.5
*/
public static synchronized void useClassLoader(ClassLoader classLoader) {
if (classLoaderOverride == classLoader) {
LOGGER.finest(() -> "Maintaining classloader override as " + classLoader + " (unchanged)");
return;
}
LOGGER.fine(() -> "Updating classloader override to " + classLoader + " (was: " + classLoaderOverride + ")");
classLoaderOverride = classLoader;
contextManagers = null;
contextTimers = null;
}

@SuppressWarnings({"unchecked", "rawtypes"})
private static List<ContextManager<?>> getContextManagers() {
if (contextManagers == null) {
synchronized (ContextManagers.class) {
if (contextManagers == null) {
contextManagers = (List) load(ContextManager.class);
}
}
}
return contextManagers;
ServiceCache.useClassLoader(classLoader);
}

static List<ContextTimer> getContextTimers() {
if (contextTimers == null) {
synchronized (ContextManagers.class) {
if (contextTimers == null) {
contextTimers = load(ContextTimer.class);
}
}
}
return contextTimers;
private static Object getActiveContextValue(ContextManager<?> manager) {
final Object activeContextValue = manager.getActiveContextValue();
LOGGER.finest(() -> activeContextValue == null
? "There is no active context value for " + manager + " (in thread " + Thread.currentThread().getName() + ")."
: "Active context value of " + manager + " in " + Thread.currentThread().getName() + ": " + activeContextValue);
return activeContextValue;
}

private static <T> List<T> load(Class<T> type) {
ArrayList<T> list = new ArrayList<>();
if (classLoaderOverride == null) {
ServiceLoader.load(type).forEach(list::add);
} else {
ServiceLoader.load(type, classLoaderOverride).forEach(list::add);
}
list.trimToSize();
return Collections.unmodifiableList(list);
private static void clear(ContextManager<?> manager) {
manager.clear();
LOGGER.finest(() -> "Active context of " + manager + " was cleared.");
}

/**
* Implementation of the <code>createContextSnapshot</code> functionality that can reactivate all values from the
* snapshot in each corresponding {@link ContextManager}.
*/
@SuppressWarnings("rawtypes")
private static final class ContextSnapshotImpl implements nl.talsmasoftware.context.api.ContextSnapshot {
private static final ContextManager[] MANAGER_ARRAY = new ContextManager[0];
private final ContextManager[] managers;
private static final class ContextSnapshotImpl implements ContextSnapshot {
private final List<ContextManager> managers;
private final Object[] values;

private ContextSnapshotImpl(List<ContextManager<?>> managers, List<Object> values) {
this.managers = managers.toArray(MANAGER_ARRAY);
this.values = values.toArray();
private ContextSnapshotImpl(List<ContextManager> managers, Object[] values) {
this.managers = managers;
this.values = values;
}

public Reactivation reactivate() {
final long start = System.nanoTime();
final List<Context<?>> reactivatedContexts = new ArrayList<Context<?>>(managers.length);
final Context[] reactivatedContexts = new Context[managers.size()];
try {
for (int i = 0; i < managers.length && i < values.length; i++) {
reactivatedContexts.add(reactivate(managers[i], values[i]));
for (ListIterator<ContextManager> it = managers.listIterator(); it.hasNext(); ) {
final ContextManager manager = it.next();
final Object value = values[it.previousIndex()];
reactivatedContexts[it.previousIndex()] = value != null ? reactivate(manager, value) : null;
}
ReactivationImpl reactivation = new ReactivationImpl(reactivatedContexts);
Timers.timed(System.nanoTime() - start, nl.talsmasoftware.context.api.ContextSnapshot.class, "reactivate");
Expand All @@ -251,7 +202,7 @@ public Reactivation reactivate() {
reactivationException.addSuppressed(rte);
}
}
contextManagers = null;
ServiceCache.clear();
throw reactivationException;
}
}
Expand All @@ -269,7 +220,7 @@ private Context reactivate(ContextManager contextManager, Object snapshotValue)

@Override
public String toString() {
return "ContextSnapshot{size=" + managers.length + '}';
return "ContextSnapshot{size=" + managers.size() + '}';
}
}

Expand All @@ -278,18 +229,19 @@ public String toString() {
* when it is closed itself.<br>
* This context contains no meaningful value in itself and purely exists to close the reactivated contexts.
*/
@SuppressWarnings("rawtypes")
private static final class ReactivationImpl implements Reactivation {
private final List<Context<?>> reactivated;
private final Context[] reactivated;

private ReactivationImpl(List<Context<?>> reactivated) {
private ReactivationImpl(Context[] reactivated) {
this.reactivated = reactivated;
}

public void close() {
RuntimeException closeException = null;
// close in reverse order of reactivation
for (int i = this.reactivated.size() - 1; i >= 0; i--) {
Context<?> reactivated = this.reactivated.get(i);
for (int i = this.reactivated.length - 1; i >= 0; i--) {
Context<?> reactivated = this.reactivated[i];
if (reactivated != null) try {
reactivated.close();
} catch (RuntimeException rte) {
Expand All @@ -302,7 +254,7 @@ public void close() {

@Override
public String toString() {
return "ContextSnapshot.Reactivation{size=" + reactivated.size() + '}';
return "ContextSnapshot.Reactivation{size=" + reactivated.length + '}';
}
}
}
91 changes: 91 additions & 0 deletions context-propagation-core/src/main/java/nl/talsmasoftware/context/core/ServiceCache.java
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Original file line number Diff line number Diff line change
@@ -0,0 +1,91 @@
/*
* Copyright 2016-2024 Talsma ICT
*
* 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.
*/
package nl.talsmasoftware.context.core;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.ServiceLoader;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.logging.Logger;

/**
* Cache for resolved services.
*
* <p>
* This is required because the ServiceLoader itself is not thread-safe due to its internal lazy iterator.
*/
class ServiceCache {
private static final Logger LOGGER = Logger.getLogger(ServiceCache.class.getName());

/**
* Internal concurrent map as cache.
*/
@SuppressWarnings("rawtypes")
private static final ConcurrentMap<Class, List> CACHE = new ConcurrentHashMap<>();

/**
* Sometimes a single, fixed classloader may be necessary (e.g. #97)
*/
private static volatile ClassLoader classLoaderOverride = null;

static synchronized void useClassLoader(ClassLoader classLoader) {
if (classLoaderOverride == classLoader) {
LOGGER.finest(() -> "Maintaining classloader override as " + classLoader + " (unchanged)");
return;
}
LOGGER.fine(() -> "Updating classloader override to " + classLoader + " (was: " + classLoaderOverride + ")");
classLoaderOverride = classLoader;
CACHE.clear();
}

@SuppressWarnings("unchecked")
static <T> List<T> cached(Class<T> serviceClass) {
return (List<T>) CACHE.computeIfAbsent(serviceClass, ServiceCache::load);
}

static void clear() {
CACHE.clear();
}

/**
* Loads the service implementations of the requested type.
*
* <p>
* This method is synchronized because ServiceLoader is not thread-safe.
* Fortunately this only gets called after a cache miss, so should not affect performance.
*
* <p>
* The returned {@code List} will be {@linkplain Collections#unmodifiableList(List) unmodifiable}.
*
* @param serviceType The service type to load.
* @param <T> The service type to load.
* @return Unmodifiable list of service implementations.
*/
private synchronized static <T> List<T> load(Class<T> serviceType) {
final ArrayList<T> services = new ArrayList<>();
final ServiceLoader<T> loader = classLoaderOverride == null
? ServiceLoader.load(serviceType)
: ServiceLoader.load(serviceType, classLoaderOverride);
for (T service : loader) {
services.add(service);
}
services.trimToSize();
// TODO debug logging
return Collections.unmodifiableList(services);
}
}
2 changes: 1 addition & 1 deletion context-propagation-core/src/main/java/nl/talsmasoftware/context/core/Timers.java
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Original file line number Diff line number Diff line change
Expand Up @@ -25,7 +25,7 @@ final class Timers {
private static final Logger TIMING_LOGGER = Logger.getLogger(Timers.class.getName());

static void timed(long durationNanos, Class<?> type, String method) {
for (ContextTimer delegate : ContextManagers.getContextTimers()) {
for (ContextTimer delegate : ServiceCache.cached(ContextTimer.class)) {
delegate.update(type, method, durationNanos, TimeUnit.NANOSECONDS);
}
if (TIMING_LOGGER.isLoggable(Level.FINEST)) {
Expand Down
9 changes: 3 additions & 6 deletions ...xt-propagation-core/src/test/java/nl/talsmasoftware/context/core/ContextSnapshotTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,6 @@
import nl.talsmasoftware.context.dummy.DummyContextManager;
import org.junit.jupiter.api.Test;

import java.io.Closeable;
import java.io.IOException;

import static org.hamcrest.MatcherAssert.assertThat;
Expand All @@ -36,9 +35,7 @@ public class ContextSnapshotTest {

@Test
public void testSnapshotToString() {
try (Context<String> ctx = MGR.initializeNewContext("Dummy value")) {
assertThat(ContextManagers.createContextSnapshot(), hasToString(startsWith("ContextSnapshot{size=")));
}
assertThat(ContextManagers.createContextSnapshot(), hasToString(startsWith("ContextSnapshot{size=")));
}

@Test
Expand All @@ -48,9 +45,9 @@ public void testSnapshotReactivate() throws IOException {
try (Context<String> ctx2 = MGR.initializeNewContext("New value")) {
assertThat(MGR.getActiveContextValue(), is("New value"));

try (Closeable reactivation = snapshot.reactivate()) {
try (ContextSnapshot.Reactivation reactivation = snapshot.reactivate()) {
assertThat(MGR.getActiveContextValue(), is("Old value"));
assertThat(reactivation, hasToString(startsWith("ReactivatedContext{size=")));
assertThat(reactivation, hasToString(startsWith("ContextSnapshot.Reactivation{size=")));
}

assertThat(MGR.getActiveContextValue(), is("New value"));
Expand Down

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