Redis Crash Course

in this video i'm going to be covering everything you need to know about redis starting with what redis is moving on to how to install it all of the commands you need to know and then finally ending up with a real world example of how you would implement redis yourself this is a really important video to watch because redis can be included in every single production level application and it's going to make your application more performant so let's get started now [Music] welcome back to web dev simplified my name is kyle and my job is to simplify the web for you so you can start building your dream project sooner so if that sounds interesting make sure you subscribe to the channel for more videos just like this now redis is essentially a type of database and more specifically it is a nosql database but it's not very similar to any other nosql databases it's definitely not similar to mongodb and it's obviously very different than sql databases like postgres and mysql and this is because redis doesn't really have any idea of tables or documents and instead all of the data in redis is stored inside of key value pairs so think about a json object you have the key name and you have the value kyle this is essentially a key value pair and redis is just like one giant json object that has key value pairs and that's all that you have inside of redis so it's not very good at storing a bunch of structured data like you have in sql but it's really good for storing you know individual key value pairs that you need to access or get data from another important thing to note about redis is that unlike a normal database that runs on your disk and stores all your information on disk redis actually runs inside of your working memory your ram on your computer and this means that redis is incredibly fast because it's all working inside of ram but it's much more volatile because if all of a sudden your system crashes you're going to lose everything that's in redis unless you're backing it up consistently which is why redis is generally not used as like an actual persistent database store like you have with mongodb and postgres and instead it's used more for caching where you take things that are really you know things that you access a lot or things that take a long time to compute and you store those values inside of redis that way when you need to access them in the future it's incredibly quick since redis is in the memory already loaded it's milliseconds to get data as opposed to hundreds of milliseconds or even seconds of time to get data from a traditional database really the important thing to realize about redis is that it's going to be built on top of a traditional database almost always you're going to have your mongodb or postgres database in the background and you're going to have redis sitting in front of that database and any time that you have a really long or slow query to your database or you have data you access all the time but doesn't change that much what you're going to do is you're going to store that data inside of redis as well as inside your database and then when you go to get that information if it's already in redis you can access that data in milliseconds as opposed to going all the way to the database computing the data and then coming all the way back which is going to take you hundreds to even thousands of milliseconds depending on how complex your data is so redis is going to take your app and make it hundreds to even thousands of times faster when it comes to querying these pieces of information this is going to become very apparent at the end of this video when we take the real world application and we're going to speed this application up by about 10 to 50 times just by implementing redis so with that said let's actually talk about how we can install redis installing redis on your computer is really simple if you have a mac or linux computer if you use mac just use homebrew to do the install and if you're on linux just use your package manager of choice to install it it's just called redis it's that simple but if you're on windows it's a bit more complex because there is no way to install redis on windows instead you need to go through the windows subsystem for linux which is pretty simple to install i'll include a link down in the description on how to install it and once you do essentially you can run linux on your windows machine super easily so as you can see i am currently inside of a linux terminal using the windows subsystem for linux on my computer and then all you need to do in order to install this if you're using ubuntu is just say sudo apt get install and then just type in redis and then you need to type in your password that you set up for your account and it's going to go through and install the redis for me for you it'll take a little bit longer to download but i already have it downloaded so it's pretty quick and then once you get it installed just type in redis dash server this is going to start up your redis server and as you can see it just prints out a bunch of information and it says running in standalone mode on port 6379 and that's just the default port for redis so now redis is running on port 6379 so in order to access redis we just need to open up a new terminal and if you're on windows make sure you open up a windows sub linux terminal here and then we can just type in redis dash cli and now we can actually access redis and run commands kind of like you could do a node with a cli so for example one thing that we could do inside of here is just type quit and that exists out of the cli obviously we want to be in the cli though so the very first thing we can do is add things to our database because like i said this is a key value paired database so the main thing that you're going to do is setting a value for a key and getting a value for a key so we can type in set and it can be all uppercase all lowercase it doesn't matter generally the idea though is to use all capitals then we're just going to type in our key our key is just going to be name and we'll put in a value of kyle and then we hit enter and you can see it said okay to check to see if this worked we can type in git and the name of our key which is just name and as you can see we get the value of kyle being returned back to us and you'll notice something about redis is that pretty much everything you store inside of redis is going to be a type of string by default so if we set for example age equal to 26 and then we come here and we get our age you're going to notice it comes back as this kind of string type technically redis is smart enough to know this is an integer but it really doesn't matter because when you're accessing and dealing with these things they're pretty much always going to come back to you as strings when you're dealing with redis now with redis we can also do a delete so i could say you know delete age and now if i do git age you can see it returns to me null here because there is no age at all because i deleted that key so we can set keys we can get keys and we can delete keys and finally we can also just have this command called exists and this is just you type in a key for example name whoops if i spell name correctly and you can see it returns to us one saying that this is true and when i typed name incorrectly it returns 0 which means false so you can determine whether or not this key exists or not so that's kind of like the most basic things that you can do inside of redis for setting getting deleting and checking if they exist also what you can do is check to find all the keys that match a certain pattern so if you just put star this is going to get you all the keys right now we only have one key which is name so that's why it's returning to us name this is a great way just to see what's inside of your database you can also get rid of everything in your database by just typing flush all hit enter and now we check our keys you're going to notice we have no keys at all and this is a really great way to just clear everything out if you're having problems with your caching you can just clear the entire cache and now there's nothing at all inside of it but i can go back and i can say set name kyle and then i can get name and as you can see it's returning to me that name also if you want to just clear out the input just type the word clear that's going to clear everything out for you and then a few additional things that i really want to talk about is the idea of expiration so if we just type in ttl and then the key name which our case is name this stands for time to live and as you can see this time to live is negative one that just means it has no expiration at all it's going to live forever but you can actually make keys so that they expire at some point i could for example type in expire and then name and i want it to expire in 10 seconds and now when i check the ttl for name you can see that this is constantly counting down and once it gets all the way down to zero it's going to completely delete this key so as you can see one now we're essentially negative two negative two means it is gone now if we do get name you can see there is no longer anything for this name key because we'd expired it after 10 minutes and if you want to make sure a key expires when you set it you can use the command set ex and that's going to give you a key in our case name we can give it how long we want it to last let's say 10 seconds and then the value of kyle so it works just like set but you can actually put the expiration right here and now when i ttl that name you can see it's constantly counting down from 10 and once it gets all the way down to zero it's going to delete that key now that covers most of what you're going to be doing inside of redis since you're mostly going to be dealing with strings but red is also a support for handling arrays in the form of list and they also have hashes for kind of storing like json objects so let's talk a list first in red is if you want to add an item to a list you're going to say l push and this is going to add an item to the start of your list that's what the l stands for it stands for left or start so we can give our list a name which is our key let's just say friends and then we're going to give this thing a value that we're pushing on so let's just push on john here and now we have a key friends that has john inside of the array of it so we could say git friends and you're going to notice it's saying hey this is the wrong type we can't get this and that's because git only works for strings if we want to print out a list we need to do instead is say l range then we say friends which is the key that we want to get and then we say we start at index 1 and stop at index negative 1. that means get all the items in the list as you can see we get john being printed out because that's the only thing in the list let's push another item to the left or the start of our list so we can say l push inside of friends because that's the name of our array and we can say we want to push in sally here as well and now if we get all the values you can see sally got pushed to the front and then john got added on also with these list you can push on the end or the right hand side by using r push it works the same way as l push but it's going to add it to the end of the array so let's put in here you know mic and if we check this you can now see that mike got put onto the end of the array you can also take items on and off of the array by using something called l pop and r pop they are going to be the left and the right hand pop so l pop you just type in friends and it's going to take the first item on the left or the start of our array take it off and return it to us so it took sally away from the array returned it to us and now if we look at our array you can see sally is gone if we do our pop of friends and we now print out our array you can see it got rid of mike which was the last item in our array so it took out the thing on the right hand side a list like this is really useful for any type of queue or stack that you want to have like let's say you have a messaging app and you want to cache the five most recent messages from a user well you can constantly just push on to the array so you could do like an l push to push onto the top of the array and then you could do an r pop to remove the last item that way you always make sure you have five things in there and it's going to be the most recent five and once you get a newer item it's gonna push off the oldest one and put this newest one right on top of it that'd be a great use case for this list type the next thing i want to talk about is sets and sets are very similar to list because they're like an array structure but it's a unique array if you know anything about sets inside a javascript which i'll link up a video i've done on them up in the top right in the cards a set is essentially just a list that is completely unique every value in the list is unique and it's not put in particular order like an array is so if you want to create a set you have to prefix everything with s so we can say like s add and then we can give it a key unless we'll say here that we have hobbies and inside of here we're going to pass in a value this is very similar to like pushing to an array but we're adding to this set so let's just push in here the hobby of weight lifting and you'll notice i wrap this in quotes if i have more than one word so now if i want to get all the things inside of here we can say s members oops s members and this is just going to print out everything inside of that thing so hobbies is the thing we want to check and as you can see we got all the values inside of hobbies being printed out and like i said with sets it's essentially completely unique so if i try to add weightlifting back in here again you can see we got 0 being returned saying that it was a false it could not add this because it's already there and if we check you can see it didn't add it we only have just that one thing inside there weightlifting also with this we can do a remove so we can just say sram that stands for remove from hobbies and we want to remove that value of weight lifting and now if we check our members you can see that it's an empty list there's nothing at all inside of it now finally i want to talk about hashes and hashes are just another key value pair so you can think of it as like a key value pair inside of a key value pair but with hashes you can't have hashes inside of hashes so it's like a json object but you can't have any nesting at all inside of it it's just one set of key value pairs so to do anything with hashes you're going to prefix every command with an h so if we want to set a value we could say h set and let's just say that we want to have a person the field we want to set as their name and we want to give it the value of kyle so now what we can do is we can say h get and we want to get person and we want to get the name from that person and you can see it returns to us kyle and if we wanted to get everything about that person we could just use get all type in person now you can see we have the key name and the value of kyle so it prints out the key first and then the value second and we can add other things so if we go back to each set we can instead set an age so let's say that we want to do an h set for our person we want to set the age and we're going to set it to a value of 26. now we do a get all you can see we have a name of kyle and we have an age of 26 and we can get individual properties so for example i could say you know get just the name or i could say just the age for that person or we could do that get all again and get all the different key value pairs you can also do an hdel which is going to be a delete so let's say that i wanted to delete the age property and now i printed everything out you can see there's only the name right here and also i could do an exist so i could say h exists and i could say person and name and you can see that returns true with the integer of one and age returns false with the integer of zero so hashes are essentially a great way if you need to store like key value pairs inside of an individual key but like i mentioned at the beginning almost everything you're going to be doing inside of redis is going to be dealing specifically with string so you're going to be doing like sets and gits and expirations and that's like 95 of what you need to do inside of redis so speaking of that let me show you a real world example of how you would take redis and implement it inside of the back end of an application to speed it up by about 10 to 50 times so here i have a really simple express node.js application with two different endpoints one is for getting all of the photos and one is for getting an individual folder and in each one of these endpoints all that we do is we call out this json placeholder api to get a list of photos or we call it to get an individual photo and here we also have the option to pass in an album id to just limit the size of the list and this code you can just imagine this right here could be anything it could be calling a database calling some other api this is just like your main code that runs inside of your server and this is pretty slow code because there's a lot of data to fetch and it's calling out to an api which is always going to be pretty slow on the right hand side here we have my own version of postman that i created if you're interested in learning how i created this i have a whole video on it linked up in the description for you but if we just query out to http local host 3000 which if we scroll down here that is what this server is running on and we go to slash photos and i click send here you can see down here we get our response which has a ton of information inside of as you can see there's essentially 35 000 lines of code inside of here being returned and it took about 370 milliseconds and if i do a few more sends you can see it's around that ballpark of about 300 to 400 milliseconds every time i make this request and if i get an individual photo for example photo one click send you can see it's quite a bit faster because there's a lot less data but it's still taking you know almost 100 milliseconds for this to run and this photos one is taking quite a while like i said you know 300 to 400 milliseconds now this three to four hundred milliseconds isn't like the end of the world but you can imagine a query that takes much longer maybe one two three seconds to run and if you have to wait for that every time you load your web page obviously that's a terrible user experience so instead what we're gonna do is use redis to cache this information so that way whenever we make a request after it's been cached we're going to get it directly from redis which is going to be way way quicker so let me just come in here and we're going to install redis so i'm just going to open up a new tab here i'm going to say npm i redis just like that it's going to go through it's going to install redis for us let's go back to where we were before now we have our application running and we can import redis so we can say const redis is equal to requiring of redis and now that we have redis here this is actually going to be essentially like a class that we can use so we can get an instance of redis so we can say that we want to get our client which is just saying redis dot create client and instead of here we can just pass it nothing and it's going to use all the default parameters or you can pass it specifically a url so if you're going to push this up to production you're going to want to pass in the url for your production instance of redis but for our case we're just using the local host version that's running on the default port so we can just leave this completely blank and we actually have access now to redis so to make sure that redis is running i have a windows terminal open up over here for linux i can just type in redis server and that's going to start up redis and if we just expand this a little bit you can see that it's saying it started up redis and it's saying that it's accessible so let's just minimize that back down a little bit let's start up our server we'll say run dev start here just like that so our server is running everything's working we have this redis client i'll even just rename this to redis client now in order to use this redis client you're going to use it just like you would use normal redis so if we come down here we can say like red is client dot set that's going to allow us to set or we can say set ex and that's going to allow us to set with an expiration time every command i just taught you in redis is going to be used on this redis client here so let's do just a simple set with an expiration and we're going to say for this we want to set something for all of our photos so we're going to set it with a key of photos like this and we want to set an expiration let's just say that we're going to create a default expiration up here so we're going to say const default expiration is just going to be like 3 600 seconds that's essentially the same as one hour so there's our default expiration and our value for this is going to be the value we get from right here so let me just bring this down a little bit and we can say that we want to store the value of data inside of here except for this data right here is an array of values and inside of redis we can only really store strings so we need to make sure we json.stringify this to convert this into a string to store it inside of redis now if we save this and we just send on our page here what's going to happen is nothing new is going to happen you can see it's still taking you know quite a while to do this command but now we're storing our information inside of redis with this expiration here and we're storing this data so what we can do is we can essentially go over open up a new terminal tab here we can say redis cli and we can just say keys star and as you can see we have that photos key right here which has the value of you know this 35 000 lines of json now that's really great but right now we're not actually getting that information because every time we run this we're just getting the data and saving it to redis what i want to do instead is check does redis have this information and if so skip essentially all of this code right here so we can say redis client.get and what we want to do is we want to get to something with the id or with the key here of photos and then this is going to take in a callback that has an error and it also has our data in our case our data is just all of our different photos but they're going to be as a string so what we need to do is if we have an error then i just want to essentially console dot air out the air now the next thing i want to do is check to see if we have some photos so if our photos is not equal to null well then that means that we had some data returned to us so we can actually use that data to return down to our user so we can essentially just say here return res.json and we want to json.parse these photos because remember this is returned to us as a string so if we have photos already saved just return them down to the user otherwise what we want to do is we want to get that data and we want to set it so we want to take all the code that we were doing every single time and now we're only going to run that code to query the api and actually set the data inside of redis if we don't already have it inside of there and then obviously we're going to make sure we just json that information down now all that we've done inside of here is we've wrapped everything inside of this redis client git and if we're able to get information we return it immediately otherwise we go through we query our you know database or api whatever it is and then send the data down so now what's going to happen is when i click send over here you're going to notice something interesting it looks like when i click send nothing works so if we come over here you can see we have an error if i scroll up it's just saying that this await keyword is not able to be used and we need to be inside an async function so let's just make sure this is an async function right here now if i save you can see we no longer get any errors we click send and you can see the time is now 63 milliseconds so we went from 400 milliseconds down to 60. we click send again now we're down you know 37 milliseconds it's super super quick and that's because we're just pulling this directly from our redis cache if i just put a simple console log inside of here that says cache it and i'm going to put another console log inside of here that says cache miss so if we hit the cache and we got it immediately it's going to print out cache hit otherwise if we didn't we're going to print out cache miss as you can see we're hitting the cache every single time that's where this cache hit is coming from now if we come over to here whoops to here where we have our cli open we just say flush all that's going to clear out our entire database we now no longer have that key as you can see so if we go back here we should see that when we first search it's going to give us cache miss and of course it's giving us an error let's see what this is just saying data is not defined we have data here data here data here we just need to move this inside the else there we go that should fix that error so now if we just make sure we clear that back out again let's just whoops clear everything go back over to here and now we click send you're going to see said cache missed and it took 400 milliseconds so pretty slow we click send again it's a cache hit and now it only took 36 milliseconds that is way way faster that's 10 times faster immediately right there and we click send every single time it's going to be a cache hit now one problem with this initial setup though is it doesn't work with this album id if i add in a query param for our album id and let's just say we do album id of 2 and i click send you can see i still get all the albums with id1 the album's id 87 and so on and that's because it's still hitting this cache of photos we need to make sure that our cache key takes into account everything that could change so for example if the album id changes we want this key here to change so what i would like to do here is essentially just add in our album id and we're going to put the value of that album id onto the end of our key so now our key is for any photo that has an album id or doesn't have an album id the only other thing we have left to do is make sure we use the same key down here where we're actually setting our redis key so now if we save this and we test this if we have an album id of two click send you can see we get only the things that the album id of two it took about 127 milliseconds click send again now it took six milliseconds i mean that's way way way faster that's like 20 30 times faster if we do an album id of three click send it takes a long time the first time but every other time is incredibly quick and if we have no album id click send it takes a while and then every other call after that is pretty quick and we can actually check that by coming over here and just saying keys star you can see that we have a key for just photos which is just from before our database we didn't flush it properly we have it for when the album ideas three when the album id is two and then we don't have any album id at all so this is essentially all the different things being cached inside of our database this is really great now all we have to do is add caching down here to this section of our application but you'll notice when we do this that logic is almost identical to what we've done up inside of here so i want to extract this out into a function i can reuse everywhere that's going to do the caching for me so what i want to do is just come down all the way here and we're going to create a function and we're going to call this git or set cache and it's going to take in a key and it's going to take in a callback and the callback is what we're going to call to actually get the value for our cache so instead of here the first thing i want to do is turn this into a promise because it's much easier to work with promises so we're going to return a new promise that has a resolve whoops resolve and a reject insider here and then we're going to use that redis client and we're going to see if we can get a key so we're going to try to get to that key and if we can't get that key we're going to have here an error and our data and then what i want to do inside of here is if we have an error then i obviously just want to reject that error and return so we don't do anything else at all then i want to see if our data is not equal to null that means we have some data so i want to resolve that data and i want to make sure i convert it back into json so we're going to json parse this data since we're constantly converting everything to a string to store it inside of our database now if neither of these are true then that means that we don't have data essentially we missed our cache and what i want to do is i want to get fresh data this either means that we haven't queried this page yet or it expired after this default expiration here essentially it's just not in our cache so we're going to call that callback but the important thing is this callback is going to be asynchronous so we're going to make sure that we await this callback and make sure that this here is an async function just like that now we're going to have our fresh data and what i want to do is i want to take my redis client and i want to set that fresh data so we can use set exe for our key we're going to use that default expiration and we're going to store in here our brand new fresh data so now we're saving that inside of our cache so next time we can take this shortcut and not have to worry about calling this long running callback and then what i want to do is just resolve that fresh data and it's important here that this fresh data i convert this to a string before i store it since redis can't really handle something that's not a string so now we have this handy dandy function called get or set cache it just takes in a key and a callback that we call if for some reason it doesn't work so way up here what we can do is we can say get or set cache this is going to return to us essentially some photos it's going to be equal to that and this is a promise so we need to make sure that we await that and in here we're going to pass it our key which we can just copy from right here and then we need to pass it our callback and the callback is really super straightforward it's just this callback down here where we're going to be getting our data so we're getting our data and then we need to return that data our callback is just how do we get the information we want to store in the cache and this is how we get it and let's just make sure we return it down here so now i can take all this code that we wrote right here completely get rid of it and down here i can just say res.json and send back our photos since that's what we called this variable right up here so now if i save this let's see if this still works obviously we have an error saying that a weight is only valid in an async function let's just make sure this is an async function here now we have no more errors i want to go over real quickly and just flush everything from our database so we have a completely fresh redis to work with and let's click send here and you're going to notice it takes about 427 milliseconds but the next time it only takes 39 it's storing that in the cache if we add in the album id we add an album id of two for example click send you can see 80 milliseconds the first time and five the second time so quite a bit faster we can try the same thing with three and you can see again it down to four milliseconds and if we check our keys over here you can see we have those three different keys for undefined two and three so now i want to essentially do the exact same thing i want to take this code and i'll make it work down here so let's just copy what we have right here we're gonna paste it down inside of here and instead our data is going to be got by this query right here where we're just querying the api with this particular id so we're just replacing how we get our data with the data that was right inside of here and then we're going to change our key because our key is not going to be based on an album id it's going to be based on an id so a lot of times in redis when you're working with namespaces or with data that has you know multiple ids or multiple entries you just have the namespace followed by a colon and then you can put in for example the id which in our case is request.params.id so what this is saying is hey we have some photos namespace and we're going to get an id'd value from it this is just a naming convention you can use whatever you want you could put a hyphen in here you could put an underscore you could put nothing at all it just is a nice thing to have here so that we can easily say this is a photo and the photo has you know an id of one for example this is going to return to us a single photo which we're going to return as our data down here so now with that done we should hopefully build a query something like photos slash one click send the first time it took 126 milliseconds and the next time it took six milliseconds let's get photos three you can see the first time it was slow and the second time it's much faster every other time after that is going to be very very fast and if we check our keys you can see we have a key for photos colon one and photos colon three which are the two different ids that we checked for and that is everything you need to know to get started with redis if you enjoyed that video and want to figure out how i made that postman clone just click over here for that and also subscribe to the channel for more videos just like this thank you very much for watching and have a good day

Channel: Web Dev Simplified

Views: 74,281

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Keywords: webdevsimplified, redis crash course, redis, redis tutorial, learn redis in 30 minutes, redis cache, redis nodejs, redis node js, redis js, redis node.js, redis javascript, redis cache js, redis example, redis commands, redis json, redis hash, redis list, redis set, redis expiration, redis sdk, redis js tutorial, redis nodejs tutorial, redis for beginners, what is redis, wds

Id: jgpVdJB2sKQ

Length: 27min 30sec (1650 seconds)

Published: Tue Jun 29 2021