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Try to eager load Servlets at startup. #23970

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Jun 6, 2022
Merged

Try to eager load Servlets at startup. #23970

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2 changes: 2 additions & 0 deletions appserver/web/web-core/src/main/java/org/apache/catalina/Wrapper.java
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Original file line number Diff line number Diff line change
Expand Up @@ -341,6 +341,8 @@ public interface Wrapper extends Container {
*/
public void load() throws ServletException;

public void tryLoad() throws ServletException;


/**
* Remove the specified initialization parameter from this servlet.
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53 changes: 37 additions & 16 deletions appserver/web/web-core/src/main/java/org/apache/catalina/core/StandardContext.java
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Expand Up @@ -4977,37 +4977,58 @@ public boolean alternateResourcesStop() {
*/
public void loadOnStartup(Container children[]) throws LifecycleException {
// Collect "load on startup" servlets that need to be initialized
Map<Integer, List<Wrapper>> map = new TreeMap<>();
Map<Integer, List<Wrapper>> loadOnStartupServlets = new TreeMap<>();
List<Wrapper> nonLoadOnStartupServlets = new ArrayList<>();

for (Container aChildren : children) {
Wrapper wrapper = (Wrapper) aChildren;

int loadOnStartup = wrapper.getLoadOnStartup();
if (loadOnStartup < 0) {
continue;
nonLoadOnStartupServlets.add(wrapper);
} else {
loadOnStartupServlets.computeIfAbsent(loadOnStartup, e -> new ArrayList<>())
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Suggested change
loadOnStartupServlets.computeIfAbsent(loadOnStartup, e -> new ArrayList<>())
loadOnStartupServlets.computeIfAbsent(loadOnStartup, ArrayList::new)

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I think arraylist::new will not work, as the key will be input into the ctor. With the key being an integer and the ctor setting the size, they will cause an out of memory with the huge key values being used.

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Wow, Arjan is right, I had the same idea, we discussed it in a chat and I started googling:
https://community.sonarsource.com/t/java-bug-using-collectors-tomap-with-arraylist-new/7661

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I'm happy to learn it now and not from the GF bug 😄

.add(wrapper);
}
}

Integer key = loadOnStartup;
List<Wrapper> list = map.get(key);
if (list == null) {
list = new ArrayList<>();
map.put(key, list);
// Combine the load on startup and non load on startup in one list, with the
// latter loading after the ones with an explicit priority (load level).
List<Wrapper> allServlets = new ArrayList<>();
for (List<Wrapper> samePriorityServlets : loadOnStartupServlets.values()) {
for (Wrapper wrapper : samePriorityServlets) {
allServlets.add(wrapper);
}
list.add(wrapper);
}

// Load the collected "load on startup" servlets
for (List<Wrapper> list : map.values()) {
for (Wrapper wrapper : list) {
try {
wrapper.load();
} catch (ServletException e) {
getServletContext().log(
format(rb.getString(SERVLET_LOAD_EXCEPTION), neutralizeForLog(getName())),
StandardWrapper.getRootCause(e));
for (Wrapper wrapper : allServlets) {
try {
wrapper.load();
} catch (ServletException e) {
getServletContext().log(
format(rb.getString(SERVLET_LOAD_EXCEPTION), neutralizeForLog(getName())),
StandardWrapper.getRootCause(e));

// NOTE: load errors (including a servlet that throws
// UnavailableException from the init() method) are NOT
// fatal to application startup
throw new LifecycleException(StandardWrapper.getRootCause(e));
}
}

if (Boolean.parseBoolean(System.getProperty("glassfish.try.preload.servlets", "true"))) {
// Also load the other servlets, which is one way to pass the CDI TCK, specifically
// ContainerEventTest#testProcessInjectionTargetEventFiredForServlet and adhere to the rule
// that injection points for Servlets have to be processed during start.
for (Wrapper wrapper : nonLoadOnStartupServlets) {
try {
wrapper.tryLoad();
} catch (Throwable t) {
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One day I will remove all these dangerous "catch-all" blocks. ;-)

// Only log errors, don't fail anything.
getServletContext().log(
format(rb.getString(SERVLET_LOAD_EXCEPTION), neutralizeForLog(getName())),
t);
}
}
}
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17 changes: 17 additions & 0 deletions appserver/web/web-core/src/main/java/org/apache/catalina/core/StandardWrapper.java
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Original file line number Diff line number Diff line change
Expand Up @@ -1114,6 +1114,23 @@ public synchronized void load() throws ServletException {
initServlet(instance);
}

@Override
public synchronized void tryLoad() throws ServletException {
try {
instance = loadServlet();
initServlet(instance);
} catch (Throwable t) {
instance = null;
available = 0l;
classLoadTime = 0;
loadTime = 0l;
instanceInitialized = false;

throw t;
}
}


/**
* Creates an instance of the servlet, if there is not already at least one initialized instance.
*/
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