1 00:00:01,050 --> 00:00:05,580 So for a while now, I've been saying that we're going to improve our air handling and that's what I 2 00:00:05,580 --> 00:00:07,030 want to take care of in this section. 3 00:00:07,740 --> 00:00:14,040 So if you recall a long time ago when we set up the app config, I put in this line in full log and 4 00:00:14,040 --> 00:00:17,550 I said, we're not doing anything with it right now, but we'll deal with that or make it. 5 00:00:17,580 --> 00:00:21,290 It'll be useful when we actually start our error handling, our improved error handling. 6 00:00:21,720 --> 00:00:23,730 And this is the case right now. 7 00:00:24,090 --> 00:00:29,820 So at the moment, we have used cash, template, cash in Fellag in production and session set in our 8 00:00:29,820 --> 00:00:30,480 app config. 9 00:00:30,630 --> 00:00:33,840 And I'm going to add another one and I'm going to call it error log. 10 00:00:34,380 --> 00:00:41,940 And what we're going to do is have two things available to us in our application configuration that 11 00:00:41,940 --> 00:00:45,360 allow us to write logs and handle errors more efficiently. 12 00:00:45,570 --> 00:00:46,800 So I've set up another one. 13 00:00:46,810 --> 00:00:52,410 So now I have info log, which is a pointer to log logger, an error log, which is also a pointer to 14 00:00:52,410 --> 00:00:59,820 log longer and log longer is something built into the application, into goes standard library. 15 00:01:00,030 --> 00:01:02,830 So now let's go back to our main function and do something with those. 16 00:01:03,210 --> 00:01:10,800 So in my main function, I in under my run part right after I declare my app in production is equal 17 00:01:10,800 --> 00:01:11,310 to fault's. 18 00:01:11,550 --> 00:01:15,600 I'm going to set up right here and it can be anywhere in this, but I'm going to put it right at the 19 00:01:15,600 --> 00:01:21,800 top of my run just after the app introduction is set to and I'm going to set up some orders. 20 00:01:21,810 --> 00:01:28,350 So let's create a longer let's create one called Infl Log and that is going to be equal to I'll have 21 00:01:28,350 --> 00:01:30,210 to declare it in a moment that I'll do that in a moment. 22 00:01:30,420 --> 00:01:35,610 That is going to be equal to log, which is a standard package built right into the standard library. 23 00:01:35,940 --> 00:01:39,810 Knew I'm creating a new logger and it's going to right. 24 00:01:39,810 --> 00:01:40,230 Where does it. 25 00:01:40,230 --> 00:01:40,540 Right. 26 00:01:40,730 --> 00:01:40,980 Right. 27 00:01:41,100 --> 00:01:44,660 Well I just want the info log right now to print to the terminal. 28 00:01:44,670 --> 00:01:52,590 So I'll just say print it to OS Standard Act, which again is built right into the standard library 29 00:01:53,100 --> 00:01:55,580 and that is our terminal window. 30 00:01:55,620 --> 00:01:56,620 That's where it's going to print it. 31 00:01:57,150 --> 00:01:58,440 So we're going to print it there. 32 00:01:58,620 --> 00:02:02,450 And then the second argument is, do you want to prefect's this log with anything? 33 00:02:02,460 --> 00:02:07,620 And I do I want to prefix it with the word info so I know that it's an information and then I'll just 34 00:02:07,620 --> 00:02:10,020 put a tab after it, which is the forward. 35 00:02:10,440 --> 00:02:15,670 He just says write the word info and then put a tab in a bunch of blank spaces after that. 36 00:02:16,440 --> 00:02:18,150 And then what do I want to write in there? 37 00:02:18,150 --> 00:02:22,370 At the end of it, we have the flag, something that we can actually append to it or deal with it. 38 00:02:22,500 --> 00:02:30,510 I'll put in the log l date, which is a date in a nice readable format, and then I'll put a pipe and 39 00:02:30,510 --> 00:02:32,430 I'll say log all time. 40 00:02:32,880 --> 00:02:36,760 And this allows me to use this info log variable, which I should declare. 41 00:02:36,780 --> 00:02:37,890 So let's do that right now. 42 00:02:38,250 --> 00:02:41,130 We'll just say var info log 43 00:02:44,430 --> 00:02:48,870 is of type star logged logger and I'll do the air along to this. 44 00:02:49,110 --> 00:02:50,520 We're going to be using that in a moment. 45 00:02:50,970 --> 00:02:51,630 Error log. 46 00:02:53,940 --> 00:02:55,820 So I've created my info log here. 47 00:02:56,190 --> 00:03:03,420 Now I can make that part of my app wide variable abdon info log is equal to input. 48 00:03:04,410 --> 00:03:08,490 I could have done this on one line and just said the info log is equal to all of this, but I think 49 00:03:08,490 --> 00:03:09,240 this is more readable. 50 00:03:09,690 --> 00:03:13,710 Now let's set up an error log and I want an error log. 51 00:03:13,960 --> 00:03:18,120 I actually when I go to a final version of this, I want to read it to a file, but I'm not going to 52 00:03:18,120 --> 00:03:19,170 worry about that right now. 53 00:03:19,200 --> 00:03:20,610 I'll just make the error log. 54 00:03:20,610 --> 00:03:25,170 Also write to the terminal, which is useful for development purposes, because I don't have to keep 55 00:03:25,170 --> 00:03:28,200 opening an external file to see if there are any errors or to read it here. 56 00:03:28,680 --> 00:03:32,340 So we'll make error log equal to log new. 57 00:03:32,730 --> 00:03:34,410 And where do I want it to write right now? 58 00:03:34,410 --> 00:03:36,030 I want to write to OS Standard out 59 00:03:41,940 --> 00:03:49,580 and I want to prefix that with error and a tab and what do I want to write to it? 60 00:03:49,590 --> 00:03:53,160 Well, I want to write something a little bit more sophisticated to the error. 61 00:03:53,170 --> 00:04:04,350 Look, OK, so I'll make it right to, I'll have the log lda same as before and then a pipe and then 62 00:04:04,350 --> 00:04:06,600 log all time, same as before. 63 00:04:06,780 --> 00:04:12,720 But then I'll put at the end of that a little bit more information log l short file, which will actually 64 00:04:12,720 --> 00:04:14,940 give me information about the error. 65 00:04:15,600 --> 00:04:19,490 And now that I've created that I can actually put that in my site. 66 00:04:19,490 --> 00:04:19,640 Right. 67 00:04:19,650 --> 00:04:23,220 Config airlock is equal to here. 68 00:04:23,220 --> 00:04:29,580 Look now the fact that I've done that, the fact that I've created those two things means it's available 69 00:04:29,580 --> 00:04:32,580 to available to me anywhere I want to use it. 70 00:04:33,030 --> 00:04:35,670 And there's lots of places I probably want to use it. 71 00:04:35,940 --> 00:04:40,890 I could go back and just every time I want to write an error message instead of going log, print line 72 00:04:41,130 --> 00:04:45,660 or format dot print line, I could use my error log or my info log. 73 00:04:46,140 --> 00:04:49,020 But I want to be a little more sophisticated about this. 74 00:04:49,020 --> 00:04:51,720 So what I'm going to do now is create a new package. 75 00:04:52,230 --> 00:04:57,480 I'm going to go back to Internal because it's an internal package only useful to us in this application. 76 00:04:57,870 --> 00:04:59,910 I'll create a new directory and I'll call that help. 77 00:05:00,350 --> 00:05:05,570 And here's where I'm going to put things that are useful that I can use in various parts of my application 78 00:05:06,440 --> 00:05:08,650 and just call them by calling the helpers package. 79 00:05:08,840 --> 00:05:16,460 So let's create a new file on that, a new go file, which I'll just call helpers, helpers Dutko and 80 00:05:16,460 --> 00:05:17,820 I will add it to the repository. 81 00:05:18,500 --> 00:05:20,210 So what am I going to put in this helper's file? 82 00:05:20,420 --> 00:05:26,150 Well, to start with, one of the things I want to have access to in the Helper's file is my at my site 83 00:05:26,150 --> 00:05:26,810 white config. 84 00:05:26,810 --> 00:05:31,820 So I'll create a new variable called app and that's going to be a pointer to config app config. 85 00:05:32,240 --> 00:05:39,440 So I have that variable declared, but I need some method of actually populating it with the site where 86 00:05:39,440 --> 00:05:40,040 I can fix. 87 00:05:40,040 --> 00:05:43,130 So I'll create a new function func New Helper's. 88 00:05:43,640 --> 00:05:45,470 And that will take one argument right now. 89 00:05:45,470 --> 00:05:50,740 A Stargate app config app config. 90 00:05:50,750 --> 00:05:55,160 So it takes we're going to pass this function, our application and we're not going to return anything 91 00:05:55,460 --> 00:05:57,230 and all we'll do is set up equal to. 92 00:05:58,730 --> 00:06:03,890 So when I call this, which I'm going to do right now, when I call this function, say, from our main 93 00:06:03,890 --> 00:06:09,920 dock, go where I'm doing it everywhere else, I can do this, duplicate that and make this helper's 94 00:06:11,630 --> 00:06:19,880 new helper's when I call it now when this application is set up, this run function is called, it will 95 00:06:19,880 --> 00:06:25,040 actually populate that variable app in Helper's with a pointer to config. 96 00:06:25,400 --> 00:06:27,950 So now I have access to it and I should give this a comment. 97 00:06:30,230 --> 00:06:33,830 Sets up app config for helper's. 98 00:06:34,850 --> 00:06:35,210 All right. 99 00:06:35,470 --> 00:06:37,630 Now what I want to have in this helper's function. 100 00:06:37,910 --> 00:06:42,920 Well there are what I'm trying to do in this, this section of the course is deal with errors. 101 00:06:43,340 --> 00:06:48,110 And if you think about it logically, there are two kinds of errors that we can have on a regular basis. 102 00:06:48,620 --> 00:06:55,130 We can have client errors where the client did something wrong, or we can have server errors where 103 00:06:55,130 --> 00:06:59,030 despite our best efforts, something went wrong with the server. 104 00:06:59,040 --> 00:07:03,500 So our code through an error, maybe it panicked and then recovered from it, whatever it may be. 105 00:07:03,950 --> 00:07:09,860 But what I effectively have are two kinds of errors, func client error, and that's going to have to 106 00:07:09,860 --> 00:07:10,790 take some parameters. 107 00:07:10,790 --> 00:07:11,720 And what am I going to Pasek? 108 00:07:11,720 --> 00:07:17,870 Well, when you have a client error, one of the things that's really useful is to have the response 109 00:07:17,870 --> 00:07:18,150 writer. 110 00:07:18,200 --> 00:07:20,600 So let's assume we're going to pass it. 111 00:07:20,600 --> 00:07:25,700 The response Frieder HGP DOT response writer, because we might need to write something to the client. 112 00:07:26,240 --> 00:07:29,570 And then when they gave the error, we will have a status. 113 00:07:29,570 --> 00:07:36,110 We'll know what kind of error that was, whatever it may be, a bad request, 400 or a 403, whatever, 114 00:07:36,110 --> 00:07:40,760 but you're going to get a status and that's what that'll be in the form of an ENT and this won't return 115 00:07:40,760 --> 00:07:41,140 anything. 116 00:07:41,270 --> 00:07:46,730 So I'm going to leave that empty for right now and I'll create the second useful function func server 117 00:07:46,730 --> 00:07:47,120 error. 118 00:07:48,170 --> 00:07:49,850 Something went wrong with the server. 119 00:07:50,780 --> 00:07:56,270 And for here, in this case, I'm still going to want the response writer because I'm going to have 120 00:07:56,270 --> 00:07:58,280 to write some kind of response to the client. 121 00:07:58,640 --> 00:08:01,220 But rather than the status in this point, we're going to have an error. 122 00:08:01,770 --> 00:08:03,710 I know I'm going to have an error when I do that. 123 00:08:03,710 --> 00:08:05,930 An error is of type error. 124 00:08:07,820 --> 00:08:10,130 So there are my two functions. 125 00:08:10,160 --> 00:08:12,620 Let's deal with the first one first, the client error. 126 00:08:13,250 --> 00:08:15,280 And what am I going to do here? 127 00:08:15,290 --> 00:08:19,550 Well, what I'm going to do right now is throw in HTP error because of the client error. 128 00:08:19,550 --> 00:08:24,620 I need to give them some kind of response and built into the standard library. 129 00:08:24,620 --> 00:08:31,730 We have HTTP error, so I'll use an error and it takes two arguments. 130 00:08:31,880 --> 00:08:36,320 It takes a response rate, which I have, because I'm taking that as one of the parameters for this. 131 00:08:37,070 --> 00:08:39,310 And it also has an error string. 132 00:08:39,560 --> 00:08:41,210 Well, I don't know what that is. 133 00:08:41,360 --> 00:08:42,650 Yeah, I actually do. 134 00:08:42,740 --> 00:08:43,940 I now have the status. 135 00:08:43,940 --> 00:08:44,520 That's easy. 136 00:08:44,540 --> 00:08:49,790 The third one is the status, so I know I can pass the status, but I can actually again use the built 137 00:08:49,790 --> 00:08:57,230 in functionality of the standard library to say http status text and then pass it the status. 138 00:08:58,340 --> 00:08:59,790 And the last thing is the end. 139 00:08:59,810 --> 00:09:01,790 What kind of status am I going to be returning? 140 00:09:01,800 --> 00:09:02,750 Well, I already have that. 141 00:09:02,750 --> 00:09:04,610 I'm passing it as an argument status. 142 00:09:05,480 --> 00:09:14,120 So there is one thing I can do a cleaner, but I can also if I want to write to the error log or write 143 00:09:14,120 --> 00:09:15,230 to the info log. 144 00:09:15,470 --> 00:09:19,520 So what I want to do here, let's just say we're going to write to the envelope just for the sake of 145 00:09:19,520 --> 00:09:19,910 argument. 146 00:09:20,060 --> 00:09:28,250 I can now because I have that that application we can think I can say app dot info, log dot print line 147 00:09:28,490 --> 00:09:30,260 and then I can put whatever I want in here. 148 00:09:30,620 --> 00:09:31,910 So what am I going to put in here? 149 00:09:31,910 --> 00:09:39,050 I can say client error with status of and then pass the status. 150 00:09:40,700 --> 00:09:45,170 So now I can actually write to to a log file and that's not terribly useful, but that's just demonstrating 151 00:09:45,170 --> 00:09:51,530 that we now have access to this info log in the same way if we actually have an error, I want as much 152 00:09:51,530 --> 00:09:54,820 information as I can possibly get about that error. 153 00:09:55,340 --> 00:09:59,720 So one of the things I can do is actually get a trace of the error using some of the. 154 00:09:59,790 --> 00:10:04,560 Functionality built into the standard library, so I'm going to create a variable called Trece, which 155 00:10:04,560 --> 00:10:08,280 is going to trace the nature of the error and that will hold a string. 156 00:10:08,280 --> 00:10:13,770 And that string is going to be built up using our font format package formatted as print F. 157 00:10:14,310 --> 00:10:19,280 And inside of that, I'm going to put in a string that consists of a series of placeholders. 158 00:10:19,290 --> 00:10:22,160 The first one will be a string and will populate that in a moment. 159 00:10:23,340 --> 00:10:31,560 The second one will be again, which gives me a new line, like he writes a tab and writes a new line 160 00:10:32,040 --> 00:10:34,150 and then I'm going to put another string. 161 00:10:35,220 --> 00:10:37,350 And so I have two placeholders to replace. 162 00:10:37,350 --> 00:10:39,930 The first one will be the nature of the error itself. 163 00:10:39,930 --> 00:10:40,620 Will I have that? 164 00:10:40,620 --> 00:10:46,860 Because I've passed it as a parameter right here so I can go error error, which will print the error 165 00:10:46,860 --> 00:10:48,000 message as a string. 166 00:10:48,300 --> 00:10:54,660 And then I want the actual stack trace the detailed information about the nature of the error that took 167 00:10:54,660 --> 00:10:55,110 place. 168 00:10:55,320 --> 00:10:59,550 And I can get that from debug, which is built right into the standard library. 169 00:10:59,880 --> 00:11:02,580 And the method or the function I want to call on that is stuck. 170 00:11:03,930 --> 00:11:04,340 All right. 171 00:11:04,470 --> 00:11:11,100 So now I've got this trace string, this variable trace that consists of the error message and then 172 00:11:11,100 --> 00:11:14,510 a new line and then the stack trace associated with the error message. 173 00:11:14,520 --> 00:11:19,500 And that's really useful information when you're trying to figure out what went wrong, you need that 174 00:11:19,500 --> 00:11:24,780 information so we can say this right now, our error log, which we're going to use in a moment, just 175 00:11:24,780 --> 00:11:29,400 writes it to the standard, writes it to the standard, out to the terminal. 176 00:11:29,940 --> 00:11:36,330 But when we go into production, we can have our log right to a file and actually put a put a directive 177 00:11:36,330 --> 00:11:38,490 in here that might send a text or send an email. 178 00:11:38,820 --> 00:11:44,370 It can let someone know that something went wrong and then they can go open the log file and look at 179 00:11:44,370 --> 00:11:46,230 the error message and go fix the problem. 180 00:11:46,480 --> 00:11:48,660 But for right now, let's just write this error. 181 00:11:48,660 --> 00:11:50,370 Log to the window. 182 00:11:50,400 --> 00:12:00,330 Apter error log dot print line and I'll write my Trece and then I need to give some kind of feedback 183 00:12:00,330 --> 00:12:03,900 to the user, which is why I'm actually having this response right here. 184 00:12:03,900 --> 00:12:11,460 So let's again call htp dot error on error and it wants a response writer, which I have. 185 00:12:11,610 --> 00:12:15,930 We want the status text in this case the status Texas internal server error. 186 00:12:15,930 --> 00:12:21,600 But I'm going to be, you know, absolutely technically correct and use the status text function. 187 00:12:22,020 --> 00:12:30,300 And what I'll pass it is the the code for internal server error, which is HDP status, internal server 188 00:12:30,300 --> 00:12:31,770 error right there. 189 00:12:32,520 --> 00:12:38,970 And then I need the last part for my third parameter to call error is, again, the code and it's http 190 00:12:38,970 --> 00:12:43,560 dot status, internal server error and that will do it. 191 00:12:43,710 --> 00:12:48,810 Now I have two functions available to be available to me, to helper functions where I can actually 192 00:12:49,080 --> 00:12:51,810 print or handle an error in a useful fashion. 193 00:12:52,860 --> 00:12:54,810 So I created this helper package. 194 00:12:54,810 --> 00:13:00,960 I haven't done anything with it except to initialize the application config from Main Go in. 195 00:13:00,960 --> 00:13:06,390 The next lecture will go put this in a few places where we can centralize our error handling.