Timing Cloud Functions for Firebase using an HTTP Trigger and Cron - Firecasts Video Lecture | Beast Android Development: Firebase Necessities - App Development

want to know how to time your cloud
functions of course you do
well good news I'm going to show you how
to schedule the execution of a function
on this episode of fire today I'll show
you how to implement a feature that
developers ask about a lot cron jobs
cron is used to schedule commands or
shell scripts to run periodically you
might be interested in running your
functions in the same way for my app I'd
like to send an email once a week to new
users inviting them to visit the app and
telling them about its features now
there are a couple of ways to implement
cron jobs using cloud functions using an
external service or configuring an
instance of App Engine I'll be using an
external service cron jobs org but if
you're interested in learning how to
create an app engine instance to
schedule events then check out this blog
post by a Baskins the link can be found
below here are the steps I'll be taking
to configure my weekly email I'll create
a cloud function that's triggered by an
HTTP request to a dedicated URL the
event handler for an HTTP function is
triggered when an incoming request
occurs it supports two HTTP specific
arguments which are the express request
and response objects the request object
has properties for the requests issued
by the client the response object lets
you specify the response to the client
this function I'm writing will compile a
list of new users emails from the
database it will then send those users
an email inviting them to visit the app
after I deployed a function I'll get its
dedicated URL
I will then set up a cron job to ping
that URL let's get started with creating
the HTTP trigger function I'll start in
the terminal and go to my projects
directory then install the required
dependencies if you've seen some of my
other fire casts you've probably seen
the firebase admin module before if
you'd like to know more about the admin
SDK check out the fire cast on cloud
storage triggers or the documentation
links are below I'm using a third-party
utility know mailer to handle sending
the email if you're using NPM 5.0 or
later you don't need to include the safe
but I'll use it here to show how to
install the dependencies if you're using
an earlier version of NPM
okay I've installed the dependencies now
open index jf I'll require the firebase
functions module as I always do when
using cloud functions I'll require
firebase admin which I'll use to access
the database and I'll initialize the app
with the default firebase configuration
I'll also require the no mailer module
I'll need to create a transporter object
to send the email the transporter object
is used by no mailer to determine how to
deal with the mail server to use for
delivering messages I'll configure the
transporter object to route email
through Gmail which requires the email
and password of a Google account now
here I just hard-coded my email and
password into my code for the purpose of
this example but it's better to use
environment configuration to specify
these sort of things if you're
interested in finding out more about
configure in your environment check out
the links below now keep in mind that
Gmail does have an email sending quota
so if you need to send more than 500
emails in a day you want to choose a
service design for this purpose in a
production environment you should use a
professional email sending platform like
SendGrid mailgun or mail jet find out
more in the links below
but gmail works well for showcasing this
example of course before I send the
emails I need to know who to send them
to my database structure looks like this
I have a child called users the children
of uses are you IDs under each user is
the content of the profile including
email and sign update which are the two
children I care about right now I'm
going to be making a query to the
database child users that orders the
children by sign update and then queries
all users whose sign update is within
the past week I'll put the emails in an
array of strings and then use the
JavaScript array method
join to put them together as one string
here we go I'll create and export a
function called weekly email that's
triggered by an HTTP request
I'll get the current time in
milliseconds and then use this to
compute the time seven days ago I'll
then create an array to hold the emails
I'll query the database child users
ordering the children by the value of
signup date starting at the time seven
days ago then I'll iterate through the
users getting their emails and adding
them to the array once I have an array
containing the emails I can choose my
email options and send a message I'm
just going to send a simple line of text
for the sake of the example but there
are lots of other mail options including
attachments and HTML check out the no
mailer Docs for details links are below
alright let's send these emails I'll
need the email addresses to configure
the email so I'll return the emails
array I'm going to use the then method
so that the email is only sent after I
have all of the emails in the array a
log which addresses to send the email to
the JavaScript join function joins the
elements of an array in a single string
separating elements with a comma you can
also pass a different separator as a
parameter but conveniently I need to
separate emails with commas so I don't
need to worry about this I'll create an
object to hold all the mail options I'll
put my business email as from and use
BCC so users can't see who else received
the email I'll add a simple subject and
some text thanking them for downloading
my app I'll call send mail which returns
a promise that's resolved when the email
is sent finally I'll return a response
to clean up the function either the
emails were sent or there was an error
my function is now ready to go but of
course I still need to set up the cron
job this process may be different
depending on which service you decide to
use now if you're concerned about the
security of the function and you don't
want just anyone triggering it if they
have a URL then you can set up a key to
verify the sender's authorize to trigger
the function I won't cover that now for
the sake of time but you can find an
example in the function samples linked
below
alright let's deploy this function and
try it out
I've already populated the database with
some dummy accounts with my email
address so I can confirm the function
was successful I'll run firebase deploy
I'll add the link to my cron job to
trigger once a week of course I don't
have to wait a week for the cron job to
trigger to check if this works I'll just
paste the URL into my browser
the response tells me the email was sent
and I can see in my inbox here finally I
can see the function logs in the
firebase console and there you have it a
cloud function set up to trigger at a
chosen interval and send out an email
you can check out the other fire cast to
see more ways to use cloud functions to
find out about the latest videos on
cloud functions and other firebase
features subscribe to the firebase
youtube channel thanks for watching and
I'll see you in another episode of fire
cast
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