zookeeper Socket Linger Time 관련 이슈

zookeeper 3.3.3 이하 버전에서는 서버와 연결을 담당하는 소켓의 Linger Time을 무조건 2초로 지정하고 있습니다.
이 값을 2초로 지정한 원인은 잘 모르겠습니다만, 아마 네트워크 응답이 느린 상황을 대비한 게 아닐까 싶습니다.

	public NIOServerCnxn(ZooKeeperServer zk, SocketChannel sock,
			SelectionKey sk, Factory factory) throws IOException 
		this.zk = zk;
		this.sock = sock;
		this.sk = sk;
		this.factory = factory;
		sock.socket().setTcpNoDelay(true);
		sock.socket().setSoLinger(true, 2);
		InetAddress addr = ((InetSocketAddress) sock.socket()
				.getRemoteSocketAddress()).getAddress();
		authInfo.add(new Id("ip", addr.getHostAddress()));
		sk.interestOps(SelectionKey.OP_READ);
	

위와 같은 linger 지정이 문제가 되는 이유는 zookeeper 서버가 클라이언트와의 연결을 종료할 때 비동기가 아니라 동기화 방식으로 세션을 닫으며, 만약 동시에 여러 개의 세션이 닫히는 상황이라면 ‘세션개수 x linger time’만큼 지연이 발생할 수 있기 때문입니다.

public void close() {
synchronized(factory.cnxns){
...

많은 경우, zookeeper 클라이언트와 서버는 같은 네트워크상에 있기 때문에 linger time이 문제가 되는 상황은 거의 없습니다. 설령 linger time이 지정되어 있다고 해도 비동기 방식으로 연결을 종료한다면 역시 문제가 되지 않습니다.
그러나 현재 zookeeper 구조에서 비동기식 방식으로 연결을 닫도록 소스를 수정하는 것은 아무래도 구조상 큰 작업으로 보입니다. (zookeeper 버전이 올라가면서 수정되기를 기다려야 할 것 같네요.)
참고로 zookeeper 3.3.4에서는 soLinger() 부분이 다음과 같이 linger time을 사용하지 않도록 변경되었습니다.

	public NIOServerCnxn(ZooKeeperServer zk, SocketChannel sock,
			SelectionKey sk, Factory factory) throws IOException 
		this.zk = zk;
		this.sock = sock;
		this.sk = sk;
		this.factory = factory;
		sock.socket().setTcpNoDelay(true);
		sock.socket().setSoLinger(false, -1);
		InetAddress addr = ((InetSocketAddress) sock.socket()
				.getRemoteSocketAddress()).getAddress();
		authInfo.add(new Id("ip", addr.getHostAddress()));
		sk.interestOps(SelectionKey.OP_READ);
	
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Sep 13, Grand Remembrances

Today is Grandparents Day in the United States. Being a Grand is a special honor. I feel very blessed that my wife and I have two grandchildren. We were able to visit them today. Yes, we are still being cautious with the coronavirus, but we also find it very difficult to not see them when they live so close. So today we did drop by to visit Jacob (age 10) and Sophia (age 7) along with their parents. We brought donuts and caught up with them. Our grandchildren are still pretty young and this is a precious time in their lives – and ours!

I wish I had known my grandparents better. We never lived in the same place. Dad was a career Air Force pilot, so we moved around a lot. But we did get to see them once in a while when they would visit us, or we them.

A Plague of Giants

There are five known magical ‘kennings’ or types: air, water, fire, earth, and plants. Each nation specializes in of these kennings, and the magic influences the society. There’s a big pitfall with this diversity of ability and locale–not everyone gets along.

Enter the Hathrim giants, or ‘lavaborn’ whose kenning is fire. Where they live the trees that fuel their fire are long gone, but the giants are definitely not welcome anywhere else. They’re big, they’re violent, and they’re ruthless. When a volcano erupts and they are forced to evacuate, they take the opportunity to relocate. They don’t care that it’s in a place where they aren’t wanted.

I first read Kevin Hearne’s Iron Druid books and loved them (also the quirky The Tales of Pell), so was curious about this new venture, starting with A PLAGUE OF GIANTS. Think Avatar: The Last Airbender meets Jim Butcher’s Codex Alera series. Elemental magic, a variety of races, different lands. And it’s all thrown at you from page one.

But this story is told a little differently. It starts at the end of the war, after a difficult victory, and a bard with earth kenning uses his magic to re-tell the story of the war to a city of refugees. And it’s this movement back and forth in time and between key players in this war that we get a singularly grand view of the war as a whole. Hearne uses this method to great effect.

There are so many interesting characters in this book that I can’t cover them all here. Often in books like this such a large cast of ‘main’ character can make the storytelling suffer, especially since they don’t have a lot of interaction with each other for the first 3/4 of the book–but it doesn’t suffer, thankfully. And the characterization is good enough, despite these short bursts, that by the end we understand these people and care about what happens to them.

If there were a main character it would be Dervan, a historian who is assigned to record (also spy on?) the bard’s stories. He finds himself caught up in machinations he feels unfit to survive. Fintan is the bard from another country, who at first is rather mysterious and his true personality is hidden by the stories he tells; it takes a while to understand him. Gorin Mogen is the leader of the Hathrim giants who decide to find a new land to settle. He’s hard to like, but as far as villains go, you understand his motivations and he can be even a little convincing. There’s Abhi, the son of hunters, who decides hunting isn’t the life for him–and unexpectedly finds himself on a quest for the sixth kenning. And Gondel Vedd, a scholar of linguistics who finds himself tasked with finding a way to communicate with a race of giants never seen before (definitely not Hathrim) and stumbles onto a mystery no one could have guessed: there may be a seventh kenning.

There are other characters, but what makes them all interesting is that they’re regular people (well, maybe not Gorin Mogen or the viceroy–he’s a piece of work) who become heroes in their own little ways, whether it’s the teenage girl who isn’t afraid to share vital information, to the scholars who suddenly find how crucial their minds are to the survival of a nation, to the humble public servants who find bravery when they need it most. This is a story of loss, love, redemption, courage, unity, and overcoming despair to not give up. All very human experiences by simple people who do extraordinary things.

Hearne’s worldbuilding is engaging. He doesn’t bottle feed you, at first it feels like drinking from a hydrant, but then you settle in and pick up things along the way. Then he shows you stuff with a punch to the gut. This is no fluffy world with simple magic without price. All the magic has a price, and more often than not it leads you straight to death’s door. For most people just the seeking of the magic will kill you. I particularly enjoyed the scenes with Ahbi and his discovery of the sixth kenning and everything associated with it. But giants? I mean, really? It isn’t bad enough fighting people who can control fire that you have to add that they’re twice the size of normal people? For Hearne if it’s war, the stakes are pretty high, and it gets ugly.

The benefit of the storytelling style is that the book, despite its length, moves along steadily (Hearne is no novice, here). The bits of story lead you along without annoying cliffhangers (mostly), and I never got bored with the switch between characters. It was easy to move between them, and they were recognizable enough that I got lost or confused. The end of the novel felt a little abrupt, but I guess that has more to do with I was ready for the story to continue, despite the exiting climax.

If you’re looking for epic fantasy with fun storytelling and clever worldbuilding, check out A PLAGUE OF GIANTS.

The post A Plague of Giants appeared first on Elitist Book Reviews.

The Artwork Of Gary Choo

Gary Choo is a concept artist/illustrator based in Singapore. I’ve know Gary for a good many years ( 17, actually ), working together in animation studios in Singapore like Silicon Illusions and Lucasfilm. Gary currently runs an art team at Mighty Bear Games, but when time allows he also draws covers for Marvel comics, and they’re amazing –

The Art Of Gary Choo
The Art Of Gary Choo
The Art Of Gary Choo
The Art Of Gary Choo
The Art Of Gary Choo

To see more of Gary’s work or to engage him for freelance work, head down to his ArtStation.

The post The Art Of Gary Choo appeared first on Halcyon Realms – Art Book Reviews – Anime, Manga, Film, Photography.

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