1
00:00:06,570 --> 00:00:09,980
- In this video, we are going
to explore the use of blocks.

2
00:00:09,980 --> 00:00:11,340
So what is a block?

3
00:00:11,340 --> 00:00:12,660
Well, the block is a electrical group

4
00:00:12,660 --> 00:00:15,300
of tasks and blocks are convenient

5
00:00:15,300 --> 00:00:18,290
because you can use them to
control how tasks are executed

6
00:00:18,290 --> 00:00:19,650
in an easy way.

7
00:00:19,650 --> 00:00:23,030
If you want a web statement
to apply to multiple tasks

8
00:00:23,030 --> 00:00:24,680
that's where blocks are coming in

9
00:00:25,970 --> 00:00:29,930
blocks can also be used in
error condition handling.

10
00:00:29,930 --> 00:00:32,870
So you can use block to
define the main tasks to run.

11
00:00:32,870 --> 00:00:35,780
And then you'll use rescue
to define tasks that run.

12
00:00:35,780 --> 00:00:38,780
If tasks that are defined
in the block are failing

13
00:00:38,780 --> 00:00:42,750
and you use always to define
tasks that will run regardless

14
00:00:42,750 --> 00:00:46,410
of success or failure of
block and ratio tasks.

15
00:00:46,410 --> 00:00:48,110
So that makes a block can be used

16
00:00:48,110 --> 00:00:50,650
like an if then else statement

17
00:00:50,650 --> 00:00:53,950
you should notice that items
cannot be used on blocks.

18
00:00:53,950 --> 00:00:55,447
That's an inconvenience.

19
00:00:55,447 --> 00:00:58,690
Do remember it when you
start working with blocks

20
00:00:58,690 --> 00:00:59,890
let's go check this out.

21
00:01:01,530 --> 00:01:04,113
So in our first example,

22
00:01:05,468 --> 00:01:07,710
this is a very simple example.

23
00:01:07,710 --> 00:01:09,490
And in the simple example, we are running

24
00:01:09,490 --> 00:01:13,340
against all hosts and we have a block.

25
00:01:13,340 --> 00:01:15,868
As you can see the play.

26
00:01:15,868 --> 00:01:18,416
Heather starts with tasks.

27
00:01:18,416 --> 00:01:22,796
Then before you start
actually specifying the tasks

28
00:01:22,796 --> 00:01:26,350
there is this block section
and below the block section

29
00:01:26,350 --> 00:01:28,200
as child elements through the block

30
00:01:28,200 --> 00:01:30,677
you'll find the actual tasks

31
00:01:30,677 --> 00:01:33,380
the tasks themselves are
not very interesting.

32
00:01:33,380 --> 00:01:36,910
It's just installing
and running a service.

33
00:01:36,910 --> 00:01:38,745
The interesting part is that the

34
00:01:38,745 --> 00:01:41,490
when statement applies
to the entire block.

35
00:01:41,490 --> 00:01:44,300
so when Ansible distribution is Rocky

36
00:01:44,300 --> 00:01:45,770
that is how it's going to work.

37
00:01:45,770 --> 00:01:48,253
Then the entire block
is going to be executed.

38
00:01:50,051 --> 00:01:53,267
So Ansible playbook on blocks dot YML.

39
00:01:59,440 --> 00:02:02,620
It's showing us that
everything is working now.

40
00:02:02,620 --> 00:02:05,470
Let's also prove the negative.

41
00:02:05,470 --> 00:02:08,210
That is something that I
would like to advise you.

42
00:02:08,210 --> 00:02:11,697
Anyway, if you write a
playbook to do something

43
00:02:11,697 --> 00:02:13,560
then it's nice to see

44
00:02:13,560 --> 00:02:16,580
that the playbook is actually
doing what you expected to do

45
00:02:16,580 --> 00:02:19,730
but you should also test
the opposite, meaning

46
00:02:19,730 --> 00:02:21,790
that you should make
sure that the playbook is

47
00:02:21,790 --> 00:02:26,056
not doing it when the
condition is not true.

48
00:02:26,056 --> 00:02:30,416
So in my configuration where
I only have Rocky machines

49
00:02:30,416 --> 00:02:33,430
well, it's easy to put anything else.

50
00:02:33,430 --> 00:02:34,640
And there we can see skipping

51
00:02:34,640 --> 00:02:37,520
and skipping and that's
exactly what we needed.

52
00:02:37,520 --> 00:02:40,730
Those second example is blocks 2 dot YML

53
00:02:41,930 --> 00:02:43,560
is a little bit more complex.

54
00:02:43,560 --> 00:02:44,393
So what do we see?

55
00:02:44,393 --> 00:02:47,860
We see a block, a rescue, and an always.

56
00:02:47,860 --> 00:02:49,910
So block is what we want to do.

57
00:02:49,910 --> 00:02:52,170
If the block tasks don't work

58
00:02:52,170 --> 00:02:54,850
we are going to execute the rescue tasks.

59
00:02:54,850 --> 00:02:59,060
And always we are going to
learn this specific command.

60
00:02:59,060 --> 00:03:00,637
I've kept it simple by
using the command module.

61
00:03:00,637 --> 00:03:04,092
So the command module is
a removing a file command

62
00:03:04,092 --> 00:03:06,978
usr bin RM var www.

63
00:03:06,978 --> 00:03:09,500
Then it is creating a file

64
00:03:09,500 --> 00:03:13,300
and then it is writing a
message to, to the logs.

65
00:03:13,300 --> 00:03:15,568
It said, is this best practice?

66
00:03:15,568 --> 00:03:18,057
it's not let's change it.

67
00:03:18,057 --> 00:03:21,880
Why would we want to
use the command model?

68
00:03:21,880 --> 00:03:25,140
If you want to remove a file, I mean, file

69
00:03:26,780 --> 00:03:29,193
path or name if you want,

70
00:03:30,123 --> 00:03:34,440
var WW, HTML, index dot HTML,

71
00:03:35,780 --> 00:03:38,300
state absent

72
00:03:38,300 --> 00:03:40,360
that will remove it as well.

73
00:03:40,360 --> 00:03:43,870
And then we have this
other command to create.

74
00:03:43,870 --> 00:03:45,570
Get out of here.

75
00:03:45,570 --> 00:03:48,424
We are going to use file again

76
00:03:48,424 --> 00:03:53,424
and file is going to use the path.

77
00:03:54,010 --> 00:03:58,050
So the path is TMP rescue file

78
00:03:58,050 --> 00:04:03,050
and state touch touch will
make sure that it is created.

79
00:04:04,420 --> 00:04:06,540
If it does not yet exist.

80
00:04:06,540 --> 00:04:08,853
We only cannot really change the

81
00:04:08,853 --> 00:04:12,151
the logger command into an Ansible model.

82
00:04:12,151 --> 00:04:16,290
So I will keep this
logger command as it is.

83
00:04:16,290 --> 00:04:19,040
Sometimes command is unavoidable, but Hey

84
00:04:19,040 --> 00:04:20,370
it's a best practice.

85
00:04:20,370 --> 00:04:21,240
If you can

86
00:04:21,240 --> 00:04:26,240
you should avoid using
command or shell even worse.

87
00:04:27,090 --> 00:04:28,840
Let's go for Ansible playbook

88
00:04:28,840 --> 00:04:31,773
blocks 2 dot YML and
see how it is working.

89
00:04:33,600 --> 00:04:35,060
So what do we see?

90
00:04:35,060 --> 00:04:37,320
Well, it remove the file
back to the playbook,

91
00:04:37,320 --> 00:04:38,318
remove a file.

92
00:04:38,318 --> 00:04:40,140
That's what it needed to do.

93
00:04:40,140 --> 00:04:43,570
So the file at this point
is removed, which means

94
00:04:43,570 --> 00:04:47,432
that the rescue doesn't have to happen.

95
00:04:47,432 --> 00:04:49,763
Now I'm going to learn it again.

96
00:04:52,550 --> 00:04:56,310
Now we can see that removal a
file is giving an okay and Hey

97
00:04:56,310 --> 00:04:59,450
we don't see the rescue
and you know why we don't

98
00:04:59,450 --> 00:05:00,610
see the rescue?

99
00:05:00,610 --> 00:05:04,040
That is because of the nature of rescue

100
00:05:04,040 --> 00:05:06,175
rescue will earn tasks.

101
00:05:06,175 --> 00:05:10,650
If tasks that are defined
in the block are failing.

102
00:05:10,650 --> 00:05:13,470
We don't have a failure
on remove a file because

103
00:05:13,470 --> 00:05:15,946
of the item, potent
nature of the playbook.

104
00:05:15,946 --> 00:05:20,550
So you know what it happens
to be that using command.

105
00:05:20,550 --> 00:05:22,570
Wasn't such a bad idea.

106
00:05:22,570 --> 00:05:27,140
Anyway, so I am getting back to command

107
00:05:28,210 --> 00:05:31,540
and we are going to rewrite command.

108
00:05:31,540 --> 00:05:33,150
And what is this command?

109
00:05:33,150 --> 00:05:36,780
Well, the command is removing, right?

110
00:05:36,780 --> 00:05:41,130
So I'm using cmd RM var www and so on.

111
00:05:44,060 --> 00:05:47,730
And then we are running it again.

112
00:05:47,730 --> 00:05:49,733
So here we go, running it again.

113
00:05:50,970 --> 00:05:52,210
And this time, yay

114
00:05:52,210 --> 00:05:56,760
the command is failing and
the file is created now

115
00:05:56,760 --> 00:05:58,600
again, and this is an important thing.

116
00:05:58,600 --> 00:06:00,830
In fact, that I wanted you to be aware of.

117
00:06:00,830 --> 00:06:04,220
This is all about the item,
potent nature of Ansible.

118
00:06:04,220 --> 00:06:06,400
If you are using Ansible models

119
00:06:06,400 --> 00:06:09,770
most Ansible models are
item potent by nature.

120
00:06:09,770 --> 00:06:13,050
So they will just give an okay

121
00:06:13,050 --> 00:06:15,490
if no changes were were needed.

122
00:06:15,490 --> 00:06:16,630
If you have command

123
00:06:16,630 --> 00:06:20,970
and command is trying to remove
a file that doesn't exist

124
00:06:20,970 --> 00:06:24,680
then the command will give
you a non-zero return code

125
00:06:24,680 --> 00:06:26,440
which is what we see here.

126
00:06:26,440 --> 00:06:28,220
Return code one.

127
00:06:28,220 --> 00:06:30,620
That's obvious because the
command does not exist.

128
00:06:30,620 --> 00:06:32,000
That's a real failure.

129
00:06:32,000 --> 00:06:34,110
And that is why in this second attempt

130
00:06:34,110 --> 00:06:36,340
the rescue is going to be effective.

131
00:06:36,340 --> 00:06:38,453
And in the first attempt, it is not.