MaximeFrancoeur

Debug with GDB on macOS 11

The big reason to do this is that LLDB has no ability to "follow-fork-mode child", in other words, a multi-process target that doesn't have a single-process mode (or, a bug that only manifests when in multi-process mode) is going to be difficult or impossible to debug, especially if you have to run the target over and over in order to make the bug manifest. If you have a repeatable bug, no big deal, break on the fork from the parent process and attach to the child in a second lldb instance. Otherwise, read on.

Install GDB

Don't make the mistake of thinking you can just brew install gdb. Currently this is version 10.2 and it's mostly broken, with at least two annoying bugs as of April 29th 2021, but the big one is https://sourceware.org/bugzilla/show_bug.cgi?id=24069

$ xcode-select install  # install the XCode command-line tools

MaximeFrancoeur

-- Two dashes start a one-line comment.

--[[
     Adding two ['s and ]'s makes it a
     multi-line comment.
--]]

----------------------------------------------------
-- 1. Variables and flow control.
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MaximeFrancoeur

Safari iframe cookie workaround

Safari by default discards cookies set in an iframe unless the host that's serving the iframe has set a cookie before, outside the iframe. Safari is the only browser that does this.

The 10k foot view

In order to get around the issue, the parent (src) and child/iframed/remote (dest) site have to work together, if the source site only wants users to access the destination via the iframe and can't assume that the user has visited the destination host before.

MaximeFrancoeur

import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;

public class HelloCovariance {
  public static void main(String[] args) {
    ConcurrentHashMap<String, String> properties = new ConcurrentHashMap<>();
    Set<String> keySet = properties.keySet();
  }
}

MaximeFrancoeur

find ./ -type f -exec perl -pi -e 's/\r\n|\n|\r/\n/g' {} \;

MaximeFrancoeur

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
import java.io.UnsupportedEncodingException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
public class HMAC {

  public static void main(String[] args) throws Exception {
    System.out.println(hmacDigest("The quick brown fox jumps over the lazy dog", "key", "HmacSHA1"));
  }

MaximeFrancoeur

Session Management in an Autoscaling Environment

Problem Statement

User sessions in J2EE and LAMP stacks have traditionally been handled in memory by the application server handling the user request. Because of that, load balancers have been configured to use sticky sessions. By sticky sessions we mean that once the user has visited the site, they will be assigned an app server and will return to that server for subsequent requests. The load balancers typically handle that by referencing the users session cookie.

Elastic cloud environments differ from traditional server configurations in that they have a variable number of servers based on traffic loads whereas traditional configurations had a fixed number of servers. When traffic volumes decline it is necessary to vaporize servers. In doing so, we would lose user sessions (essentially forcing a logout) unless we come up with a new strategy for session management.

A new approach

After much research, it is clear that the best

MaximeFrancoeur

public class PomVersion {
    final private static Logger LOGGER = LogManager.getLogger(PomVersion.class);

    final static String VERSION = loadVersion();

    private static String loadVersion() {
        Properties properties = new Properties();
        try {
            InputStream inStream = PomVersion.class.getClassLoader().getResourceAsStream("version.properties");
            properties.load(inStream);

MaximeFrancoeur

@Mock private SmtpConnection smtpConnection;
 
private void mockSmtpConnection() {
    final ArgumentCaptor<String> recipient = ArgumentCaptor.forClass(String.class);
    final ArgumentCaptor<String> subject = ArgumentCaptor.forClass(String.class);
    final ArgumentCaptor<String> body = ArgumentCaptor.forClass(String.class);
 
    when(smtpConnection.setRecipient(recipient.capture()))
        .thenReturn(smtpConnection);
    when(smtpConnection.setSubject(subject.capture()))

MaximeFrancoeur

class BaseService {
    public void save(){
        validate();
    }
}

public ChildService extends BaseService{
    public void save(){
        super.save()
        load();