1 00:00:01,870 --> 00:00:07,780 So it's time to try hooking our bookings application up to our database, and we're going to do that 2 00:00:07,780 --> 00:00:09,680 using a driver package. 3 00:00:09,700 --> 00:00:14,560 So what I'm going to do is go to my internal packages, because this is a package that is specific to 4 00:00:14,560 --> 00:00:17,320 my application, not going to be of use to anybody else. 5 00:00:17,890 --> 00:00:20,590 And I'll create a new directory and I will call that driver, 6 00:00:24,700 --> 00:00:25,970 which I'd better name Driver. 7 00:00:26,410 --> 00:00:27,760 So let's refactor that. 8 00:00:27,910 --> 00:00:30,640 Rename it driver. 9 00:00:31,600 --> 00:00:38,980 OK, and inside of that, I will create a new go file, which I will call Driver Don't Go, and I will 10 00:00:38,980 --> 00:00:46,090 add that to my git repository and this is going to be the means by which we actually connect our application 11 00:00:46,180 --> 00:00:47,050 to a database. 12 00:00:47,050 --> 00:00:54,250 And the very first thing I'm going to do is create a type and that type will be called DB because it's 13 00:00:54,250 --> 00:00:57,250 going to hold a database connection and it's a structure. 14 00:00:57,550 --> 00:01:01,510 And inside of that it's going to have one member, which I'll call sequel, because it's where all of 15 00:01:01,510 --> 00:01:02,740 our school stuff is going to go. 16 00:01:03,040 --> 00:01:08,880 And it's a pointer to sequel DB, which should be important for me and it is good. 17 00:01:09,340 --> 00:01:10,870 And let's put a comment on this. 18 00:01:11,320 --> 00:01:19,810 DB holds the database connection pool and the reason I'm creating a struct is because right now it's 19 00:01:19,810 --> 00:01:22,570 going to hold a driver for postgrads. 20 00:01:22,960 --> 00:01:26,510 But I might want a driver for a different database at some point in the future. 21 00:01:26,530 --> 00:01:31,150 And by making it a struct, I can put whatever I want in the member here just by adding a new member 22 00:01:31,150 --> 00:01:38,860 or substituting the value for skilled DB to, say, Amaria DB connection, which also uses the DB appointer 23 00:01:38,860 --> 00:01:39,760 to Scooter Libby. 24 00:01:40,240 --> 00:01:41,340 So I have that type created. 25 00:01:42,460 --> 00:01:47,500 Now I'm going to create a variable and the variable I'm going to call DB Con and it's going to be equal 26 00:01:47,500 --> 00:01:56,500 to a reference to my DV type and I'm going to have to use the curly quotes or curly brackets because 27 00:01:56,500 --> 00:01:59,350 I'm initializing it and making it empty all in one step. 28 00:02:00,280 --> 00:02:02,640 Now I'm going to define a few constants, OK? 29 00:02:03,280 --> 00:02:07,930 We didn't use these when we created our simple database program, but we're going to use them in this 30 00:02:07,930 --> 00:02:08,140 one. 31 00:02:08,140 --> 00:02:14,290 And I'm going to define certain things like what's the maximum number of open database connections I 32 00:02:14,290 --> 00:02:14,710 can have? 33 00:02:14,710 --> 00:02:19,570 So I'll call it Max Open DB con and I'll set that to a reasonable number, which is 10. 34 00:02:19,690 --> 00:02:23,260 Never have more than 10 connections to the database open at any given time. 35 00:02:24,010 --> 00:02:28,690 And then I'll create another constant which I'll call Max Idol DB connections. 36 00:02:29,230 --> 00:02:35,170 How many connections can remain in the pool but remain idle and I'll set that to five, which is a nice 37 00:02:35,170 --> 00:02:35,890 reasonable number. 38 00:02:36,550 --> 00:02:40,560 And what's the maximum lifetime for a database connection? 39 00:02:40,690 --> 00:02:51,280 So I'll call this Max DB lifetime and that will be equal to five seconds, five times time, dot minute 40 00:02:51,280 --> 00:02:52,990 or five minutes, not five seconds. 41 00:02:54,130 --> 00:02:55,990 So that automatically imparts the time for me. 42 00:02:55,990 --> 00:03:01,240 Now, these are three constants I'm going to use to define the nature of my connection pool. 43 00:03:02,200 --> 00:03:09,580 So the very first thing I want to do is create a connection pool Soulis create a function func Connect 44 00:03:09,580 --> 00:03:10,090 sequel. 45 00:03:12,480 --> 00:03:17,040 And that's going to take an argument which will be a string, a database connection string, which I'll 46 00:03:17,040 --> 00:03:19,530 call DSN, that's what people typically call this. 47 00:03:19,540 --> 00:03:26,310 It's just a string and it's going to return to possible things, a pointer to my DBS type that I just 48 00:03:26,310 --> 00:03:29,700 defined a moment ago and potentially an error if something goes wrong. 49 00:03:30,030 --> 00:03:33,930 OK, so let's create a new database. 50 00:03:34,200 --> 00:03:38,310 And I'm going to do that by calling another function that I'm going to create right now. 51 00:03:38,790 --> 00:03:43,320 And that's going to be called new database func new database. 52 00:03:45,570 --> 00:03:53,280 And it's going to take a DSN, which is of type string and it's going to return a pointer to a sequel 53 00:03:53,280 --> 00:03:57,080 DB, which I want to get from postgrads and potentially an error. 54 00:03:57,090 --> 00:03:57,890 Something goes wrong. 55 00:03:58,650 --> 00:04:00,180 So let's create the connection. 56 00:04:00,180 --> 00:04:03,810 And we do that exactly as we did in the other application. 57 00:04:04,020 --> 00:04:12,420 We just say DB error is assign the value of school open and it's going to be of type in our case, PJI 58 00:04:12,420 --> 00:04:18,210 X and it's going to take the DSM, the data, the string to connect to the database, which doesn't 59 00:04:18,210 --> 00:04:24,060 exist yet, but it will by the time we actually call us and then we check for an error if error is not 60 00:04:24,060 --> 00:04:24,720 equal to nil. 61 00:04:28,440 --> 00:04:36,590 Then return nil because we don't have a database connection pool and the error otherwise keep going. 62 00:04:38,160 --> 00:04:41,850 So let's try testing it so we know how to do that. 63 00:04:42,120 --> 00:04:48,540 If error equals dbag ping, I'm going to do this all in one thing and the error is not equal to nil, 64 00:04:49,170 --> 00:04:53,910 then return nil and the error. 65 00:04:55,260 --> 00:04:59,460 So that will test our database connection just like we did in our other simple program. 66 00:04:59,820 --> 00:05:04,830 But I'm using a shorthand here to check for the error and to see if it's nil all in one step. 67 00:05:05,340 --> 00:05:09,810 And if everything works properly, then we'll return our DB and nil. 68 00:05:10,230 --> 00:05:11,250 So now we have our connection. 69 00:05:11,550 --> 00:05:14,420 So we're going to call that up here in Connect Sigma. 70 00:05:17,570 --> 00:05:22,430 So we'll get our connection, our database, cool, I'll just call that D for the sake of argument and 71 00:05:22,430 --> 00:05:28,430 error is new database and we're going to pass it, the DSM that this function receives as a parameter 72 00:05:29,270 --> 00:05:31,430 if error is not equal to nil. 73 00:05:31,460 --> 00:05:36,200 And what I'm going to do here is just die, because if I can't connect to the database, I can't go 74 00:05:36,200 --> 00:05:37,610 any further with our application. 75 00:05:37,730 --> 00:05:40,040 So I'll just say panic error. 76 00:05:40,970 --> 00:05:45,200 And it's OK to panic here, because if this doesn't work, I don't want anything else to start up. 77 00:05:45,200 --> 00:05:47,200 The program just doesn't work. 78 00:05:47,990 --> 00:05:54,290 Now, if it does work, then Deal will have some values and I can actually set these constants to certain 79 00:05:54,290 --> 00:05:56,480 parameters that are available for that connection pool. 80 00:05:56,600 --> 00:06:08,990 So I can say dot set, max open DB connections, so Max open and I'll set out to Max open DB comp in 81 00:06:08,990 --> 00:06:19,580 the same way I can say set Max vital cons to Max Idol cards and finally set Max DB. 82 00:06:20,090 --> 00:06:23,030 Sorry, set Max. 83 00:06:25,470 --> 00:06:29,430 Secon, Max, secon, max lifetime. 84 00:06:31,350 --> 00:06:34,500 Max, idle time, max lifetime, please. 85 00:06:35,880 --> 00:06:43,410 There we are to Max DBE Lifetime, so I've set some parameters on my database connection for sensible 86 00:06:43,410 --> 00:06:48,510 ones that will stop it from growing out of control, that will remove idle connections and return them 87 00:06:48,510 --> 00:06:53,400 to the database when they're not being used and used and will ensure that we have a certain lifetime 88 00:06:53,400 --> 00:06:54,870 for all of our database connections. 89 00:06:55,470 --> 00:07:00,660 Now let's take our Dickon Con that we divide up defined up here and assign a value to it. 90 00:07:00,780 --> 00:07:06,360 DB Con only has one one member and that is equal and that's going to be equal to. 91 00:07:07,920 --> 00:07:10,890 And just because I can, I'm going to test the database again. 92 00:07:10,890 --> 00:07:16,070 So I'll create another function here called func test DB. 93 00:07:16,350 --> 00:07:24,900 It has to take my connection pool which is a call and again it's a pointer to sequel DB and it returns 94 00:07:24,900 --> 00:07:25,680 potentially there. 95 00:07:27,270 --> 00:07:29,990 And let's test the database just like we did in our main program. 96 00:07:30,810 --> 00:07:39,600 So we'll say error equals dot pain and if error is not equal to nil, then what I want to do, I want 97 00:07:39,600 --> 00:07:41,340 to return my error. 98 00:07:46,930 --> 00:07:54,400 And this has to be a sign, OK, and otherwise return no, return no. 99 00:07:56,200 --> 00:08:04,360 So I will call Testbeds back up here in Connect sequel will just say error equals test Debe and we'll 100 00:08:04,360 --> 00:08:06,070 pass it our connection pool, which is deep. 101 00:08:06,400 --> 00:08:09,700 If error is not equal to now, what do I want to do? 102 00:08:09,880 --> 00:08:19,090 I want to return nil and error, otherwise return my connection pool, which is in this case the DB 103 00:08:19,090 --> 00:08:25,090 con variable that I that I have created and the signed my connection pool two and nil. 104 00:08:26,870 --> 00:08:29,100 All right, so that should work. 105 00:08:29,120 --> 00:08:30,470 Now, let's put some comments in here. 106 00:08:31,070 --> 00:08:32,270 What does Connect sequel do? 107 00:08:33,260 --> 00:08:35,390 Connect sequel creates. 108 00:08:37,290 --> 00:08:40,490 Database pool for postgrads. 109 00:08:41,820 --> 00:08:43,160 And what does testing do? 110 00:08:46,720 --> 00:08:50,650 Tries to ping the database. 111 00:08:53,590 --> 00:08:55,610 And finally need a new database. 112 00:08:55,630 --> 00:08:58,810 What does that do need? 113 00:08:58,840 --> 00:09:09,150 Base creates a new database for the application and that should be our connection pool. 114 00:09:09,670 --> 00:09:11,860 So that's enough for this time. 115 00:09:11,860 --> 00:09:14,350 In the next lecture, we'll start working with this. 116 00:09:16,300 --> 00:09:21,670 Actually, that wasn't quite enough, I forgot to do one thing and hopefully you noticed it, I do this 117 00:09:21,670 --> 00:09:22,330 sometimes. 118 00:09:22,330 --> 00:09:30,670 I neglected to actually tell our application, our bookings application, that it's using the package 119 00:09:30,670 --> 00:09:31,520 from Zhaxi. 120 00:09:31,540 --> 00:09:33,030 So let's import that. 121 00:09:33,280 --> 00:09:37,050 So I'm in the command prompt at the root level of my application. 122 00:09:37,480 --> 00:09:49,480 I just say, go get and it's at GitHub, dot com slash Zhaxi slash PJI X slash version four and I go 123 00:09:49,480 --> 00:09:55,210 get that so that I should have imported it into my Goman file and it looks like it did. 124 00:09:55,400 --> 00:09:55,810 Yep. 125 00:09:55,810 --> 00:09:56,410 There it is. 126 00:09:56,890 --> 00:09:58,440 And now I need to use it up here. 127 00:09:58,480 --> 00:10:09,880 And last time we just use one thing we used underscore GitHub dot com slash Zhaxi slash PGP version 128 00:10:09,880 --> 00:10:10,480 four. 129 00:10:10,480 --> 00:10:13,840 But I'm actually going to import two more things that we will be using as time goes on. 130 00:10:13,840 --> 00:10:15,130 We may as well import them right now. 131 00:10:15,790 --> 00:10:23,500 So I'm going to duplicate this line and change this part where it says PGP version for too long, which 132 00:10:23,500 --> 00:10:27,370 gives me access to the subroutines, will be using a little while. 133 00:10:27,670 --> 00:10:36,520 And I'm also going to import Zhaxi slash PGP version of Forgacs Steedle IP. 134 00:10:36,910 --> 00:10:38,380 So those are the three that I want. 135 00:10:39,310 --> 00:10:40,420 I think I got that wrong there. 136 00:10:46,090 --> 00:10:46,880 Got a pee in their. 137 00:10:53,450 --> 00:10:54,890 Jack see slash. 138 00:10:56,990 --> 00:11:04,580 PG version for there, that's it, and let's just format this so it sort of them correctly perfect. 139 00:11:05,060 --> 00:11:05,960 So sorry about that. 140 00:11:05,960 --> 00:11:10,730 I neglected to import those and nothing will work without those because database sequel needs to have 141 00:11:10,730 --> 00:11:11,770 an underlying driver. 142 00:11:11,780 --> 00:11:13,940 And in this case, we're just using pigs. 143 00:11:14,300 --> 00:11:19,340 And those three libraries will give us everything we need to work with the database as we continue in 144 00:11:19,340 --> 00:11:19,790 the course. 145 00:11:19,970 --> 00:11:23,300 So now we're ready to hook this up in the next lecture or two.