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/**
* Copyright 1&1 Internet AG, https://github.com/1and1/
*
* 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 net.oneandone.jasmin.model;
import net.oneandone.graph.CyclicDependency;
import net.oneandone.jasmin.main.Servlet;
import net.oneandone.sushi.fs.GetLastModifiedException;
import net.oneandone.sushi.io.Buffer;
import net.oneandone.sushi.util.Strings;
import javax.servlet.http.HttpServletResponse;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.HashMap;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.Semaphore;
import java.util.concurrent.atomic.AtomicLong;
import java.util.zip.GZIPInputStream;
import java.util.zip.GZIPOutputStream;
public class Engine {
public static final String ENCODING = "utf-8";
public final Repository repository;
private final Semaphore computeSemaphore;
public final HashCache hashCache;
public final ContentCache contentCache;
private final HashMap pending;
/** of compressed content */
public AtomicLong requestedBytes;
public Engine(Repository repository) {
this(repository, 8, 1000000, 10000000);
}
public Engine(Repository repository, int maxComputeThreads, int hashSize, int contentSize) {
this.repository = repository;
this.computeSemaphore = new Semaphore(maxComputeThreads);
this.hashCache = new HashCache(hashSize);
this.contentCache = new ContentCache(contentSize);
this.pending = new HashMap<>();
this.requestedBytes = new AtomicLong();
}
/** number of threads that could compute a unique path */
public int load() {
return pending.size();
}
public long requestedBytes() {
return requestedBytes.get();
}
public long computedBytes() {
return contentCache.addedBytes();
}
public long removedBytes() {
return contentCache.removedBytes();
}
/**
* Output is prepared in-memory before the response is written because
* a) that's the common case where output is cached. If output is to big for this, that whole caching doesn't work
* b) I send sent proper error pages
* c) I can return the number of bytes actually written
* @return bytes written or -1 if building the module content failed.
*/
public int request(String path, HttpServletResponse response, boolean gzip) throws IOException {
Content content;
byte[] bytes;
try {
content = doRequest(path);
} catch (IOException e) {
Servlet.LOG.error("request failed: " + e.getMessage(), e);
response.setStatus(500);
response.setContentType("text/html");
try (Writer writer = response.getWriter()) {
writer.write("" + e.getMessage() + "
");
writer.write("
");
printException(e, writer);
writer.write("");
}
return -1;
}
if (gzip) {
// see http://cs193h.stevesouders.com and "High Performance Websites", by Steve Souders
response.setHeader("Content-Encoding", "gzip");
bytes = content.bytes;
} else {
bytes = unzip(content.bytes);
}
response.addHeader("Vary", "Accept-Encoding");
response.setBufferSize(0);
response.setContentType(content.mimeType);
response.setCharacterEncoding(ENCODING); // TODO: inspect header - does this have an effect?
if (content.lastModified != -1) {
response.setDateHeader("Last-Modified", content.lastModified);
}
response.getOutputStream().write(bytes);
return bytes.length;
}
private void printException(Throwable e, Writer writer) throws IOException {
writer.write("type: " + e.getClass() + "
\n");
writer.write("message: " + e.getMessage() + "
\n");
for (StackTraceElement element : e.getStackTrace()) {
writer.write(" " + element.toString() + "
\n");
}
if (e.getCause() != null && e.getCause() != e) {
writer.write("
\n");
writer.write("... cause by ...
\n");
writer.write("
\n");
printException(e.getCause(), writer);
}
}
/** Convenience method for testing */
public String request(String path) throws IOException {
Content content;
content = doRequest(path);
return new String(unzip(content.bytes), ENCODING);
}
/* @return -1 (i.e: unknown) when not cached; not computed */
public long getLastModified(String path) throws GetLastModifiedException {
String hash;
Content content;
hash = hashCache.probe(path);
if (hash != null) {
content = contentCache.probe(hash);
if (content != null) {
return content.lastModified;
}
}
return -1;
}
public void free() {
hashCache.resize(0);
contentCache.resize(0);
}
//--
private Content doRequest(String path) throws IOException {
Content result;
result = doRequestNoStats(path);
requestedBytes.addAndGet(result.bytes.length);
return result;
}
/** @return gzip compressed content */
private Content doRequestNoStats(String path) throws IOException {
AtomicLong l;
String hash;
Content content;
CountDownLatch gate;
while (true) {
hash = hashCache.lookup(path);
if (hash != null) {
content = contentCache.lookup(hash);
if (content != null) {
return content;
}
}
synchronized (pending) {
gate = pending.get(path);
if (gate == null) {
gate = new CountDownLatch(1);
if (pending.put(path, gate) != null) {
throw new IllegalStateException(path);
}
// we're the first thread to request this path -- compute it
break;
} else {
if (gate.getCount() != 1) {
throw new IllegalStateException(path + " " + gate.getCount());
}
}
}
try {
// wait until the thread that's computing this path has finished
gate.await();
} catch (InterruptedException e) {
// continue
}
// continue loop - content is either cached now or we try to re-compute it
}
return doCompute(path, gate);
}
private Content doCompute(String path, CountDownLatch gate) throws IOException {
try {
computeSemaphore.acquire();
} catch (InterruptedException e) {
throw new IllegalStateException(e);
}
try {
return doComputeUnlimited(path, gate);
} finally {
computeSemaphore.release();
}
}
/** exactly one thread will invoke this method for one path */
private Content doComputeUnlimited(String path, CountDownLatch gate) throws IOException {
long startContent;
long endContent;
ByteArrayOutputStream result;
References references;
byte[] bytes;
String hash;
Content content;
if (gate.getCount() != 1) {
throw new IllegalStateException(path + " " + gate.getCount());
}
startContent = System.currentTimeMillis();
try {
try {
references = repository.resolve(Request.parse(path));
} catch (CyclicDependency e) {
throw new RuntimeException(e.toString(), e);
} catch (IOException e) {
throw new IOException(path + ": " + e.getMessage(), e);
}
result = new ByteArrayOutputStream();
try (OutputStream dest = new GZIPOutputStream(result); Writer writer = new OutputStreamWriter(dest, ENCODING)) {
references.writeTo(writer);
}
bytes = result.toByteArray();
endContent = System.currentTimeMillis();
hash = hash(bytes);
content = new Content(references.type.getMime(), references.getLastModified(), bytes);
hashCache.add(path, hash, endContent /* that's where hash computation starts */, 0 /* too small for meaningful measures */);
contentCache.add(hash, content, startContent, endContent - startContent);
} finally {
synchronized (pending) {
if (gate.getCount() != 1) {
throw new IllegalStateException(path + " " + gate.getCount());
}
if (pending.remove(path) != gate) {
throw new IllegalStateException();
}
gate.countDown();
}
}
return content;
}
private static final MessageDigest DIGEST;
static {
try {
DIGEST = MessageDigest.getInstance("SHA");
} catch (NoSuchAlgorithmException e) {
throw new IllegalStateException(e);
}
}
private static String hash(byte[] bytes) {
byte[] result;
synchronized (DIGEST) {
result = DIGEST.digest(bytes);
}
return Strings.toHex(result);
}
private static byte[] unzip(byte[] bytes) {
// TODO: pool?
try {
return new Buffer().readBytes(new GZIPInputStream(new ByteArrayInputStream(bytes)));
} catch (IOException e) {
throw new IllegalStateException("unexpected IOException from ByteArrayInputStream: " + e.getMessage(), e);
}
}
}
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