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In the last video we put together some sync code inside of our query.

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Before we test this out we did try to make use of axial sin here but unfortunately our query service

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does not yet have axles installed.

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We haven't even required it into this index dot J as file so I got gonna go up to the very top of this

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file.

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I'm going to require in axioms I'll save this all then go back over to my terminal.

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I'm gonna find the terminal window that is running my memory service I'm going to stop that thing I'll

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install axles really quickly and they'll start that server backup OK.

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ALEX Good.

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So now we need to make sure that we can actually test this out effectively.

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So I'm going to just go ahead and stop that server even though we just started it up.

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So now we do not have any access to query.

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It just doesn't exist but hopefully we can try to create some posts comments and whatever else those

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events will be cached or stored by our event bus and then as soon as we launch query hopefully query

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should be precinct and get all the different events that it has missed over time.

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Let's try this out making sure that the query service is not running.

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I'm going to go over to my browser I'm gonna refresh the page.

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You'll notice I've gotten error inside my console right now and that is to be expected because the query

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service does not exist.

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Right now it's not running at all but I should be able to create a post so I'll go ahead and create

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a post something like new post and submit now in theory this post has been created and we've gone through

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that entire process of storing it on the post service and so on.

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If I refresh right now I get another error again because the query server is done doesn't exist.

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So now let's go back over to our terminal.

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We'll go ahead and launch the query service and as soon as we do so it should reach out to our event

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bus.

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You'll notice there are some errors here you could ignore them.

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It should reach out to our event bus and try to receive all the different events that it has missed.

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It's going to start up the query service and you'll notice right away its process in event of post created

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that's the event that it had missed.

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So if I now go back with the browser I can refresh and there's my post.

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Now they benefit to this approach.

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If I kill my query service once again.

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So now it's dead again.

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Now I can start to maybe create some comments I can say comment no one I can create a comment.

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Number two I can create even an invalid comment something with the word orange in it.

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Something is going to get rejected.

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Now if I refresh again once again I don't see anything because the query services down in the query

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service has completely missed all these different events.

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It hasn't seen any of the come and created any of the comment moderated or the common updated events.

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Now let's relaunch query and instantly it's going to process all those different events that it just

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missed out on.

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Now if I go back to the browser I can refresh looks like the C and taking just a moment chances are

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it's gonna refresh way faster for you.

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There we go.

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And now we can see that the query service is online and 100 percent up to date.

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We've got our post we've got those comments and the comment that was rejected as well.

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All right so you gotta admit that's pretty neat.

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So this 100 hundred percent really deals with this issue of a service being brought online at some point

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in time the future or possibly the case in which a service goes down for some very small period of time

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and misses out on a couple of that events.

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We're going to use this strategy very heavily as we start to work on our next application.

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Now if you see some issues with this approach and there are some problems inside of here without a doubt

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don't sweat it.

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There are corner cases and we are going to cover these corner cases particularly around the possibility

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of having like persistent data.

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Right now none of our data is persistent we store it inside of some in-memory data structure that's

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lost instantly whenever a service goes down but if we were using a database where we were storing these

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posts and comments inside of some database would say that query service you might be thinking Hey we'll

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get into some trouble here if we try to run the same event or process in the same event twice.

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Again if you're thinking that don't sweat it.

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There are solutions to it that we're going to implement in our next application.

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Okay.

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So this entire idea of sinking events looks like it's pretty handy.

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So pause right here continue in just a minute.