WEBVTT 1 00:00.000 --> 00:03.320 Okay friends, so let's talk about YAML. 2 00:03.320 --> 00:06.520 Now all YAML is is a data serialization language. 3 00:06.520 --> 00:09.200 And the big thing about this particular file format 4 00:09.200 --> 00:12.080 is that we have an emphasis on human readability. 5 00:12.080 --> 00:15.280 So maybe perhaps you are familiar with other file formats 6 00:15.280 --> 00:18.680 such as JSON or perhaps even XML. 7 00:18.680 --> 00:22.080 And ultimately they allow us to do a similar thing with data. 8 00:22.080 --> 00:23.960 The data is just presented a different way 9 00:23.960 --> 00:26.220 and each of these have their own rule sets. 10 00:26.220 --> 00:29.280 So how about we discuss some of the rules behind YAML 11 00:29.280 --> 00:30.960 as well as see some examples WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 11 00:29.280 --> 00:30.960 as well as see some examples 12 00:30.960 --> 00:33.680 so that we can actually see what this really looks like. 13 00:33.680 --> 00:35.480 Okay, so the very first thing to say 14 00:35.480 --> 00:37.880 and this is very, very important to understand 15 00:37.880 --> 00:40.840 is that YAML is a white space sensitive. 16 00:40.840 --> 00:43.040 Reason being is that with respect to YAML 17 00:43.040 --> 00:47.140 we have a very big emphasis on the concept of indentation. 18 00:47.140 --> 00:49.200 So when we begin to explore some examples 19 00:49.200 --> 00:52.120 you're going to see that we can actually associate 20 00:52.120 --> 00:55.440 particular elements within a YAML document together 21 00:55.440 --> 00:57.160 using this concept of indentation. 22 00:57.160 --> 00:59.640 And if you get the indentation wrong 23 00:59.640 --> 01:02.240 the association between different elements WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 23 00:59.640 --> 01:02.240 the association between different elements 24 01:02.240 --> 01:04.360 can become confused and in some cases 25 01:04.360 --> 01:06.320 just become completely invalid. 26 01:06.320 --> 01:08.400 So really, really, really be aware 27 01:08.400 --> 01:10.600 of the type of indentation that you use. 28 01:10.600 --> 01:12.200 Now with respect to YAML 29 01:12.200 --> 01:15.520 you can use four spaces indentation. 30 01:15.520 --> 01:17.240 This is fairly commonly used 31 01:17.240 --> 01:19.800 but the general convention the most common way 32 01:19.800 --> 01:22.000 is in fact to use two spaces. 33 01:22.000 --> 01:23.760 Now there is no hard and fast rule 34 01:23.760 --> 01:25.520 that you have to use one or the other. 35 01:25.520 --> 01:27.400 These are the more common implementations 36 01:27.400 --> 01:30.200 like I say with two spaces being the most popular. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 36 01:27.400 --> 01:30.200 like I say with two spaces being the most popular. 37 01:30.200 --> 01:32.320 As such because of this convention 38 01:32.320 --> 01:34.640 I myself prefer to use two spaces 39 01:34.640 --> 01:36.760 that just keeps things a little bit neater. 40 01:36.760 --> 01:38.600 So in my particular examples 41 01:38.600 --> 01:41.160 that is the convention I'm going to follow. 42 01:41.160 --> 01:42.400 Now whilst it's not important 43 01:42.400 --> 01:45.880 if you happen to use two or four spaces indentation 44 01:45.880 --> 01:47.360 the main thing we want to remember 45 01:47.360 --> 01:49.560 is that we do not want to mix and match them. 46 01:49.560 --> 01:52.320 You know use four spaces for one part of the document 47 01:52.320 --> 01:53.920 and then suddenly start using two. 48 01:53.920 --> 01:56.400 This is absolutely not what we want to do. 49 01:56.400 --> 01:57.920 Basically pick something that you like 50 01:57.920 --> 02:00.080 and just stick with it. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 50 01:57.920 --> 02:00.080 and just stick with it. 51 02:00.080 --> 02:02.640 Now also to be clear you may have the temptation 52 02:02.640 --> 02:05.080 to use tabs for your indentation 53 02:05.080 --> 02:07.400 but realistically the rules of YAML specify 54 02:07.400 --> 02:09.640 that you should be using spaces instead 55 02:09.640 --> 02:11.600 so actually use that space bar. 56 02:11.600 --> 02:15.000 Now if you happen to be absolutely adamant on using tabs 57 02:15.000 --> 02:17.840 you just find it quicker to get that indentation. 58 02:17.840 --> 02:19.680 You can still use a tab key 59 02:19.680 --> 02:22.640 but what I suggest you do is you configure your text editor 60 02:22.640 --> 02:26.520 to actually convert the tabs into spaces that way 61 02:26.520 --> 02:29.240 even if you press the tab to get quick indentation 62 02:29.240 --> 02:31.160 ultimately under the hood it's going to be translated WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 62 02:29.240 --> 02:31.160 ultimately under the hood it's going to be translated 63 02:31.160 --> 02:32.520 and converted into spaces 64 02:32.520 --> 02:34.240 that will keep things nice and consistent 65 02:34.240 --> 02:36.200 with the expected rules of YAML. 66 02:36.200 --> 02:38.120 Now another thing to note in YAML 67 02:38.120 --> 02:40.800 is that we happen to denote the start of a YAML document 68 02:40.800 --> 02:42.200 with three hyphens. 69 02:42.200 --> 02:45.040 So when we happen to be writing our Ansible Playbooks 70 02:45.040 --> 02:46.440 this is what you can expect to see 71 02:46.440 --> 02:48.720 at the beginning of a particular play. 72 02:48.720 --> 02:50.880 Just to be clear though this is not actually 73 02:50.880 --> 02:53.320 an enforced convention you can absolutely create 74 02:53.320 --> 02:55.840 a YAML document without these three hyphens. 75 02:55.840 --> 02:57.520 This is just a general standard 76 02:57.520 --> 02:59.560 used to denote the start of a YAML document. 77 02:59.560 --> 03:02.880 In fact if you want to have multiple YAML documents WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 77 02:59.560 --> 03:02.880 In fact if you want to have multiple YAML documents 78 03:02.880 --> 03:04.760 within the same file so to speak 79 03:04.760 --> 03:06.320 you can break up that document 80 03:06.320 --> 03:09.320 ultimately creating these new YAML Paragraphs so to speak 81 03:09.320 --> 03:11.240 by using these three hyphens 82 03:11.240 --> 03:13.200 that is going to separate them out. 83 03:13.200 --> 03:15.120 Now another big advantage of YAML 84 03:15.120 --> 03:17.400 and one of the reasons why it's very very popular 85 03:17.400 --> 03:20.200 for configuration files is that allows us to use 86 03:20.200 --> 03:21.480 this hash symbol. 87 03:21.480 --> 03:22.920 Now the use of the hash symbol itself 88 03:22.920 --> 03:24.640 isn't actually a revelation. 89 03:24.640 --> 03:26.640 Rather what I'm talking about is what this hash symbol 90 03:26.640 --> 03:29.360 allows us to do, it allows us to create comments. 91 03:29.360 --> 03:32.200 Now if you are familiar with the JSON format WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 91 03:29.360 --> 03:32.200 Now if you are familiar with the JSON format 92 03:32.200 --> 03:34.280 JSON is rather human readable 93 03:34.280 --> 03:36.120 but one of the big downfalls within JSON 94 03:36.120 --> 03:38.400 is that you do not have the ability for comments. 95 03:38.400 --> 03:40.040 Now one of YAML's primary use cases 96 03:40.040 --> 03:41.680 is for creating configuration files 97 03:41.680 --> 03:44.520 having the ability to pair a configuration 98 03:44.520 --> 03:46.560 with a particular comment beside it 99 03:46.560 --> 03:48.520 giving the reader some type of context 100 03:48.520 --> 03:51.760 about what this configuration is actually supposed to do. 101 03:51.760 --> 03:55.200 This is one of the big ones that we get with the YAML format. 102 03:55.200 --> 03:56.760 Another thing that we should be aware of 103 03:56.760 --> 03:59.480 is that YAML files are going to end in the extension 104 03:59.480 --> 04:02.960 either .YML or .YAML. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 104 03:59.480 --> 04:02.960 either .YML or .YAML. 105 04:02.960 --> 04:06.160 Now generally speaking the more common use 106 04:06.160 --> 04:07.960 is to just say .YAML. 107 04:07.960 --> 04:11.400 However for whatever reason and the Ansible Ecosystems fear 108 04:11.400 --> 04:14.280 we tend to use .YML so as such 109 04:14.280 --> 04:15.880 this is going to be the convention 110 04:15.880 --> 04:18.480 that I'm going to follow within this particular course. 111 04:18.480 --> 04:20.400 Just be aware that this is not mandatory 112 04:20.400 --> 04:22.880 if you do see .YAML, do not freak out 113 04:22.880 --> 04:25.440 it still is absolutely fine and accepted. 114 04:25.440 --> 04:28.320 So let's take a look at an example YAML documents. 115 04:28.320 --> 04:31.760 So here's a tip, when working with YAML WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 115 04:28.320 --> 04:31.760 So here's a tip, when working with YAML 116 04:31.760 --> 04:34.000 one of the best things to do is to make use 117 04:34.000 --> 04:36.120 of an online YAML parser. 118 04:36.120 --> 04:37.400 Pretty much what these will do 119 04:37.400 --> 04:40.720 is they will programmatically assess your YAML documents 120 04:40.720 --> 04:42.400 and if you have any type of errors 121 04:42.400 --> 04:44.000 perhaps you have an indentation error 122 04:44.000 --> 04:46.640 perhaps you're using some type of invalid character. 123 04:46.640 --> 04:50.120 Whatever it is, this particular parser here 124 04:50.120 --> 04:52.040 or any parser online for example 125 04:52.040 --> 04:53.960 will be able to detect that problem 126 04:53.960 --> 04:55.480 and point out how to remedy it. 127 04:55.480 --> 04:57.040 So really when you're writing playbooks 128 04:57.040 --> 04:59.160 this can save you quite a lot of time. 129 04:59.160 --> 05:01.040 So if we just collect one of these parsers WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 129 04:59.160 --> 05:01.040 So if we just collect one of these parsers 130 05:01.040 --> 05:03.640 let's maybe go with YAML parser online right here 131 05:03.640 --> 05:04.920 on code beautify. 132 05:04.920 --> 05:06.280 So on the left hand side here 133 05:06.280 --> 05:09.720 what I've done is pasted in a very simple YAML document 134 05:09.720 --> 05:10.560 that I created. 135 05:10.560 --> 05:12.120 Notice at the very top of the document 136 05:12.120 --> 05:13.840 we have our three hyphened right here 137 05:13.840 --> 05:16.760 the noting that this is the beginning of a new YAML doc. 138 05:16.760 --> 05:18.440 And then we have some information 139 05:18.440 --> 05:20.760 to see the name and the corresponding value 140 05:20.760 --> 05:22.000 as John McGovern. 141 05:22.000 --> 05:25.560 We have an age of 99 which is not my actual age 142 05:25.560 --> 05:28.200 thankfully and we have an email 143 05:28.200 --> 05:30.960 and the corresponding value we have UK citizen WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 143 05:28.200 --> 05:30.960 and the corresponding value we have UK citizen 144 05:30.960 --> 05:32.680 and then we have something called true. 145 05:32.680 --> 05:35.280 This happens to be known as a billion value. 146 05:35.280 --> 05:37.080 This is supported in YAML 147 05:37.080 --> 05:38.800 which pretty much allows us to have this type 148 05:38.800 --> 05:40.920 of binary logic as something true 149 05:40.920 --> 05:43.200 or as something false we'll get to see more of this 150 05:43.200 --> 05:44.800 later on throughout this course. 151 05:44.800 --> 05:46.760 Just to understand that we can have a regular text 152 05:46.760 --> 05:48.600 or sentences so to speak. 153 05:48.600 --> 05:50.360 These are known as strings. 154 05:50.360 --> 05:52.640 We can actually have numerical values here 155 05:52.640 --> 05:54.520 which would be known as integers. 156 05:54.520 --> 05:55.600 These are your numbers. 157 05:55.600 --> 05:57.600 And we have these billion values here. 158 05:57.600 --> 05:59.120 Now there actually are more data types 159 05:59.120 --> 06:00.600 that we can specify within YAML. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 159 05:59.120 --> 06:00.600 that we can specify within YAML. 160 06:00.600 --> 06:03.080 We'll talk about more of that in an upcoming video. 161 06:03.080 --> 06:04.480 And we also have some information 162 06:04.480 --> 06:06.320 about what skills I can do. 163 06:06.320 --> 06:08.800 And really this is what a very simple YAML document 164 06:08.800 --> 06:09.640 looks like. 165 06:09.640 --> 06:11.720 Now of course as the data becomes more complex, 166 06:11.720 --> 06:13.240 becomes more populated, 167 06:13.240 --> 06:16.320 things can be a little bit more complicated to look at. 168 06:16.320 --> 06:18.040 But really so long as you understand 169 06:18.040 --> 06:20.080 the actual rows of YAML, 170 06:20.080 --> 06:23.000 you can map out all this data programmatically. 171 06:23.000 --> 06:24.840 So this could be a file for the configurations 172 06:24.840 --> 06:26.880 that you want to have across all of your servers 173 06:26.880 --> 06:27.760 within a network. 174 06:27.760 --> 06:29.240 By following the rows of YAML, 175 06:29.240 --> 06:30.680 we can have this information, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 175 06:29.240 --> 06:30.680 we can have this information, 176 06:30.680 --> 06:33.160 any standardized and programmatic way 177 06:33.160 --> 06:34.520 that is consistent. 178 06:34.520 --> 06:35.720 And as we can see here, 179 06:35.720 --> 06:37.880 fairly easy to read for a human. 180 06:37.880 --> 06:39.200 You may not be great at programming 181 06:39.200 --> 06:40.600 but I'm pretty sure you can understand 182 06:40.600 --> 06:42.720 and interpret what we're actually seeing here 183 06:42.720 --> 06:43.760 on the left hand side. 184 06:43.760 --> 06:45.280 Now the cool thing like I said about things 185 06:45.280 --> 06:46.840 like these YAML parsers, 186 06:46.840 --> 06:49.440 is there allows us to see where you may have went wrong. 187 06:49.440 --> 06:50.600 So say for example, 188 06:50.600 --> 06:52.360 if I remove the three hyphens, 189 06:52.360 --> 06:56.000 notice that the YAML document is still actually valid. 190 06:56.000 --> 06:58.240 Well, they may be visually instructive. 191 06:58.240 --> 06:59.520 They're not actually necessary 192 06:59.520 --> 07:01.080 to construct the YAML documents. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 192 06:59.520 --> 07:01.080 to construct the YAML documents. 193 07:01.080 --> 07:03.360 However, what if I happen to do something like say, 194 07:03.360 --> 07:04.680 this in the document, 195 07:04.680 --> 07:06.120 notice on the left hand side, 196 07:06.120 --> 07:07.800 we have this little X telling us 197 07:07.800 --> 07:09.320 that we have some type of error. 198 07:09.320 --> 07:11.200 And it tells us that we have now introduced 199 07:11.200 --> 07:13.280 an unknown tag into the document. 200 07:13.280 --> 07:15.480 And we can see here on the right hand side, 201 07:15.480 --> 07:17.880 the rendered value is now simply null, 202 07:17.880 --> 07:20.440 as opposed to the value of the name. 203 07:20.440 --> 07:22.400 Similarly, if I just happened to start typing 204 07:22.400 --> 07:25.040 in some absolute garbage into the document right here, 205 07:25.040 --> 07:26.480 look at this on the right hand side, 206 07:26.480 --> 07:28.280 we can clearly see that we have an error. 207 07:28.280 --> 07:30.600 This is not valid YAML at all. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 207 07:28.280 --> 07:30.600 This is not valid YAML at all. 208 07:30.600 --> 07:32.160 And we can actually see here, 209 07:32.160 --> 07:34.400 the line number where the problem is introduced, 210 07:34.400 --> 07:35.240 line number three. 211 07:35.240 --> 07:36.880 So we know starting right here, 212 07:36.880 --> 07:39.440 this is where the problem begins, so if we remove this, 213 07:39.440 --> 07:41.440 we can see we still have a problem on line four. 214 07:41.440 --> 07:42.600 So we remove line four, 215 07:42.600 --> 07:44.360 we see we have a problem on line five, 216 07:44.360 --> 07:46.800 if we remove line five and hit enter, 217 07:46.800 --> 07:48.680 suddenly that problem has been fixed. 218 07:48.680 --> 07:51.200 And if we resolve the problem here of the unknown tag, 219 07:51.200 --> 07:53.080 remove that, suddenly once again, 220 07:53.080 --> 07:55.240 the YAML document is valid. 221 07:55.240 --> 07:56.840 Definitely, I would encourage you to make use 222 07:56.840 --> 07:58.000 of these YAML tools. 223 07:58.000 --> 07:59.760 It's going to make your life much, much easier 224 07:59.760 --> 08:02.360 because whilst YAML is very human readable, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 224 07:59.760 --> 08:02.360 because whilst YAML is very human readable, 225 08:02.360 --> 08:04.800 it is notoriously easy to make a mistake 226 08:04.800 --> 08:05.720 in a YAML document 227 08:05.720 --> 08:08.360 because of the whites based sensitivity 228 08:08.360 --> 08:10.880 and the emphasis on indentation levels.