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Consul Part 3: Key/Value store and Web UI - YouTube
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hi i'm andre
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and in the last two console videos we've
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learned how to do a service discovery
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using the http and dns api self-console
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and we've learned how to use console
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templates to make use of that
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information to configure services
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today i'd like to show you how you can
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use
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the key value store of console to
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actually
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coordinate or configure parts of your
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services dynamically
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and how to use the web uif console to
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easily do so
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as you can see the environment is about
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the same as we left it after the last
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video
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we've got two constant lines one console
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server
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only thing i've done is i've updated all
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of them to console.70
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and in order to set an item in the key
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value saw
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you just use the http put methods
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on the endpoint v1 kv for key value
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and then you can think of a path
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yourself in my case
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i'm setting the number of web server
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workers
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for specific hosts so i'll be setting
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calls or client one and workers to eight
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and if i fetch the same value again you
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can see
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that console added some more information
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to it
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there you are you get a creation index
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you can you could have set some flags
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and of course you get the value itself
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but it doesn't look like the number 8 we
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put in there
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that is because in order to be
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encoding agnostic console will use
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base64 encoding on your values
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you get the same value out that you put
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into it
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now let's stop our console server we
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already set the
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client access id to be any ip on the
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server so you can
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have clients access the server from
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anywhere in the network and we have the
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dash ui option
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so we'll have the web interface started
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with the control server
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now just to get rid of the error
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messages
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we'll also restart both of the clients
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it's not really necessary but
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there we are now let's start a web
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browser go to our console server and it
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will redirect you
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to the ui portion of the url space
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and there you are you can have a look at
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different services in your network
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you can have a look at your different
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nodes in the network you also get some
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information about the nodes can also
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have it
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within server centric view
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and of course you can access the key
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value store
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there we are we just set the key for
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console client 1 and the num worker
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straight
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let's use the ui to change it to 12
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and when we fetch the value from any of
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the console clients
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we get a different base64 encoded value
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and if we decode it
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we get surprise surprise
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the number 12 just as we entered it in
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the web ui
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but now let's put the original value of
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8 back in
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and you see it's back to the original
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base
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encoded value it's the same we had
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before
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so it's 8 again
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just to make things a little more
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interesting we'll add
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a key for the second client
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so we'll add the number of workers for
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console client two
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and we set it to a different value say 4
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and we do it on the same note because
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key value items in console are shared
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among all the members of a cluster so
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you can easily
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set and access it from any of your
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clients
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and you cannot only configure your load
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balancer weights with it
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you could also coordinate things with it
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you could
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set a global maintenance flag for
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example to have all your web servers
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render out a maintenance page while
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you're updating the web application in
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the background
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you could point all your web
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web application servers to your central
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database server
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and have an easy time switching the
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database server to
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the other master master master replica
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sets or something like that
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now we'll go back to the console master
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and
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run console template to have our load
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balancer config rendered out
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and let's have a look at it
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and you see it's still just rendering
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the two servers as an upstream
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it'll use the substream servers
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to balance among them
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any request it gets if we wanted to add
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weights to it we would have to do this
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just at weight equals well the actual
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weight
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but if we did this it would be
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overwritten the next time
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we run the console template daemon so
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let's adjust the template
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we don't want to add a static value we
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actually want to use
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the value start in the key value style
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to do this
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you can easily extend the templates
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the go templates support
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a function called key or default which
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will either give you
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the value of a specific key or if it
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doesn't find that key
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it will give it it will render out the
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default value
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so let's say the default will be one
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but somehow our key names are
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not very static they are dependent on
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the hostname
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and this is a bit of a nuisance in
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golden templates because we would
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we will actually have to print
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the name of our notes
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and the string of the item name
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to have it fill in the actual
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key name of hostname slash them workers
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it feels a bit like a clutch but you can
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get used to it it's
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not that complicated and
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now we rent out the template and have a
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look at it
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there we go we get the correct key
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value for each server
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and now let's delete the key for
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console client 2 just to make things
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interesting and to see that the
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default value actually works
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let's render the template again
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and look into it and you will see that
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now
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contour client 2 has a weight of 1
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because that's what we said as a default
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and this concludes the planned parts of
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my series about the console service
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discovery demon
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if you've got any further questions feel
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free to leave a comment
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if you like this sort of videos
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subscribe to my channel
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and for now thanks for watching and
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have a nice day
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