I am trying to come up with a java implementation of a simple HTTP client that keeps a socket open and reuses it to query other (or same) URLs on the same host.
I have a simple implementation that uses java.net.Socket but somehow the performance when I keep the socket open is worse than when I keep creating a new one.
Results first, full executable code below:
With KeepAlive: slower starting at iteration #2
> java -server -Xms100M -Xmx100M -cp . KeepAlive 10 true
--- Warm up ---
18
61
60
60
78
62
59
60
59
60
Total exec time: 626
--- Run ---
26
59
60
61
60
59
60
60
62
58
Total exec time: 576
Recreating the socket every time gives better results:
> java -server -Xms100M -Xmx100M -cp . KeepAlive 10 false
--- Warm up ---
188
34
39
33
33
33
33
33
34
33
Total exec time: 494
--- Run ---
33
35
33
34
44
34
33
34
32
34
Total exec time: 346
KeepAlive.java (standalone, no dependencies)
import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.InputStreamReader;
import java.net.InetSocketAddress;
import java.net.Socket;
public class KeepAlive {
private static final String NL = "\r\n";
private static final int READ_SIZE = 1000;
private Socket socket;
private DataOutputStream writer;
private BufferedReader reader;
public static void main(String[] args) throws Exception {
if (args.length == 2) {
KeepAlive ka = new KeepAlive();
System.out.println("--- Warm up ---");
ka.query(Integer.parseInt(args[0]), args[1].equals("true"));
System.out.println("--- Run ---");
ka.query(Integer.parseInt(args[0]), args[1].equals("true"));
} else {
System.out.println("Usage: keepAlive <n queries> <reuse socket>");
}
}
private void query(int n, boolean reuseConnection) throws Exception {
long t0 = System.currentTimeMillis();
if (reuseConnection) {
open();
for (int i = 0; i < n; i++) {
long tq0 = System.currentTimeMillis();
query();
System.out.println(System.currentTimeMillis() - tq0);
}
close();
} else {
for (int i = 0; i < n; i++) {
long tq0 = System.currentTimeMillis();
open();
query();
close();
System.out.println(System.currentTimeMillis() - tq0);
}
}
System.out.println("Total exec time: " + (System.currentTimeMillis() - t0));
}
private void open() throws Exception {
socket = new Socket();
socket.setKeepAlive(false);
socket.connect(new InetSocketAddress("example.org", 80));
writer = new DataOutputStream(socket.getOutputStream());
reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
}
private void query() throws Exception {
StringBuilder req = new StringBuilder();
req.append("GET / HTTP/1.1").append(NL);
req.append("Host: example.org").append(NL);
req.append("Connection: Keep-Alive").append(NL);
req.append(NL);
String reqStr = req.toString();
long t0 = System.currentTimeMillis();
writer.writeBytes(reqStr);
writer.flush();
String line;
int contentLength = 0;
while ((line = reader.readLine()) != null) {
if (line.startsWith("Content-Length: ")) {
contentLength = Integer.parseInt(line.substring(16));
}
if (line.equals("")) {
char[] buf = new char[contentLength];
int offset = 0;
while (offset < contentLength) {
int len = contentLength - offset;
if (len > READ_SIZE) {
len = READ_SIZE;
}
int ret = reader.read(buf, offset, len);
if (ret == -1) {
System.out.println("End of stream. Exiting");
System.exit(1);
}
offset += ret;
}
break;
}
}
}
private void close() throws Exception {
writer.close();
reader.close();
socket.close();
}
}
Now, I'm pretty sure that either:
the web server sucks at handling the new requests fast (HTTP Keep Alive and TCP keep alive)
something is wrong with the way I use the buffered reader because that's where all the time is lost but looking at the other methods available (and I tried a few), I can't find what I need to do to fix this...
Any idea how I could make this work faster? Maybe a config to change on the server itself?...
Solution
As explained by apangin below, the slower perf is caused by Nagle's algorithm, which is enabled by default. Using setTcpNoDelay(true), I get the updated following perfs:
Without keep-alive:
java -server -Xms100M -Xmx100M -cp . KeepAlive 10 false
--- Warm up ---
49
22
25
23
23
22
23
23
28
28
Total exec time: 267
--- Run ---
31
23
23
24
25
22
23
25
33
23
Total exec time: 252
With keep-alive:
java -server -Xms100M -Xmx100M -cp . KeepAlive 10 true
--- Warm up ---
13
12
12
14
11
12
13
12
11
12
Total exec time: 168
--- Run ---
14
12
11
12
11
12
13
11
21
28
Total exec time: 158
So here, we can see the keep-alive version performing far better than the non keep-alive one for each iteration and also if comparing total execution times. :)
