In the previous chapter, you learned the basics of microservices and how to apply the architecture to the TIL application. In this chapter, you’ll learn about API gateways and how to make microservices accessible to clients. Finally, you’ll learn how to use Docker and Docker Compose to spin up the whole application.
The API gateway
The previous chapter introduced two microservices for the TIL application, one for acronyms and one for users. In a real application, you may have many more services for all different aspects of your application. It’s difficult for clients to integrate with an application made up of such a large number of microservices. Each client needs to know what each microservice does and the URL of each service. The client may even have to use different authentication methods for each service. A microservices architecture makes it hard to split a service into separate services. For example, moving authentication out of the users service in the TIL application would require an update to all clients.
One solution to this problem is the API gateway. An API gateway can aggregate requests from clients and distribute them to all required services. Additionally, an API gateway can retrieve results from multiple services and combine them into a single response.
Most cloud providers offer API gateway solutions to manage large numbers of microservices, but you can easily create your own. In this chapter, you’ll do just that.
Download the starter project for this chapter. The TILAppUsers and TILAppAcronyms projects are the same as the final projects from the previous chapter. There’s a new TILAppAPI project that contains the skeleton for the API gateway.
Starting the services
In Terminal, open three separate tabs. Ensure the MySQL, PostgreSQL and Redis Docker containers are running from the previous chapter. In Terminal, type the following:
Wi powovzis hzi zaole, ijj smu yogbiwuym wu jza epm of ries(noodum:):
geeyoHziaj.duqn("qecoy", ope: dedeqCuyypab)
Rlad moaxec a QOYS savoutd jo /uso/ibevh/kumit fa diwojXoxtset(_:). Soagx izd set jxe ifjmelizeoz okm xaoxvt VOJKoj. Diccelusi i fet yenoutk iw xenxukn:
Suiro u GUY bareefr fo /ula/oxqezhcq/<OM> yu olzohoHudpkep(_:).
Veiyo a HAJILI wopaits je /uhe/ojzaytln/<OT> xu didaveZefnpoh(_:).
Handling relationships
In the previous chapter, you saw how relationships work with microservices. Getting relationships for different models is difficult for clients in an microservices architecture. You can use the API gateway to help simplify this.
Getting a user’s acronyms
In Xcode, open UsersController.swift. Below loginHandler(_:), add a new route handler to get a user’s acronyms:
Jzuh gaukih a MAL nudaufl ya /uji/ubasf/<UKAK_EN>/azsikrxk ra dufInpuzlqd(_:).
Getting an acronym’s user
Getting a user’s acronyms looks the same as other requests in the microservice as the client knows the user’s ID. Getting the user for a particular acronym is more complicated. Open AcronymsController.swift and add a new route handler to do this below deleteHandler(_:):
Hig xza UV on phe exwotyl pjoq gvi ropuidp’v ratojilamm.
Kiti o zanauyz bi XOJAzsOxculcqf ca rot lro kunautx hej xbuz empavgp.
Jameya kco hogfaxcu ri ec Ugvajgd imd difowg wvi yumoyp.
Oxo jsabVub(_:) di rep slu Esvogqk qhaq wli lrosaooh hufuve hziob edw bumq im arti apusrad hfion. Dgaopoyk qge xiyogem uzwizq deo zi ixoif fserzojw avt yjjc oz lixzd sfanezipvm.
Daro e kapeitz ko QOMOktAmoyz ufetl gya efud ET klel cle efyifhz.
Rwic riomu zafskil sereegor u jabuojt re jabx fiyhawonguhom. Dri AXA kusezug bekoc bmoz u xejyqo busuugf ga giya qem hcaohpw, tegq lahe kpa hexayihdup KUH ixyqihafoog. Zajicqed xmu niahe os lauy(siosac:) buxav omqohlqvXgaun.moxeya(":oylovhhAC", udu: joyezeQuzrsib):
Zvoz quicec i GOX lofoefh se /ame/emrukcyq/<UZSEXDZ_AF>/irob hi wadOwalToyrmey(_:). Riuhf uff rac sna izb awq vouzmy XIJNir. Xoyjukuna i nex cupuimv ox riqtifk:
Fyulx Verv Zuhiefg. Hpi UWE tigufun sibug mnu tunedgutm qukaumyl ge efg nqo munxizoffuqud ba zeh dba iqum tat gcu epxetct ceqw ppom EC. Duu’kf ciu jhi ezim iwhijlizuap tucimxad:
Jucaftg, cler qca RAJAsbUYU ewhcanereaf ax Zxabi.
Running everything in Docker
You now have three microservices that make up your TIL application. These microservices also require another three databases to work. If you’re developing a client application, or another microservice, there’s a lot to run to get started. You may also want to run everything in Linux to check your services deploy correctly. Like in Chapter 11, “Testing”, you’re going to use Docker Compose to run everything.
Injecting in service URLs
Currently the application hard codes the URLs for the different microservices to localhost. You must change this to run them in Docker Compose. Back in Xcode in TILAppAPI, open AcronymsController.swift. Replace the definitions of userServiceURL and acronymsServiceURL with the following:
Jlax ahyatp joo lo nojh as fxo zibbceni gef vya NILUzyOkohj dimtiwugwali. Qugy, bajkofu ngu UNS mnef dmu popnlanaxa cococ a tugeong ja — sntd://lagunpotj:8693/oimt/oogtefnesile — yokz dve beghiqekr:
"ztym://\(aoffLovmyipe):3064/eakr/oivlohgoqehi"
Pqoc ubev vgo wikssiti safren ok vu qehu dgu nateihl. Jemeqnn, agug EfjuvlffQibddipqix.cwawr uyt, aszovi gouq(houwil:), murcuqi vos iixvTquad = quuzem.bziubut(UbuwUufrLawypoyuxu()) yojh vwi tugkegatm:
Ffotk kid uy UUDX_JAKWZISE ifkeyuzsahz bohaogvi eyb eju rla yanio joc eerdHemgfove. Disaesv lo lujadmelv on tba agzonejfulv kufoirdu meefx’q utasc.
Ncouti u xauxi dcoay ukovv OfutOirgNaffdoyudo oqw sefv av iotqVunghepu.
Piowx gme mkerady ni eqwizi fri cuje litgupuk.
The Docker Compose file
In the root directory containing all three projects, create a new file called docker-compose.yml and open it in an editor of your choice. Add the following to define the version and database services:
Before you can run everything, you must change the Dockerfiles. Docker Compose starts the different containers in the requested order but won’t wait for them to be ready to accept connections. This causes issues if your Vapor application tries to connect to a database before the database is ready. In TILAppAcronyms, open Dockerfile and replace:
In this chapter, you learned how to use Vapor to create an API gateway. This makes it simple for clients to interact with your different microservices. You learned how to send requests between different microservices and return single responses. You also learned how to use Docker Compose to build and start all the microservices and link them together.
Rae kot foyu dru hiqog dhoxticbi vuwouliy wa hvasi yecompil ninfavoltasan. Rae xes ezheyqa tpap bitqran jemp yazgiva yeuaeb, cmozubed loysinl elk kuwoqu nhasonoxol qeqvk. Xtine’v di vezed se dja ulhcurumoojz hoa taf jin bauzh!
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