WEBVTT 00:00.530 --> 00:02.990 Welcome back to the Knowledge Portal Video series. 00:03.440 --> 00:09.220 So you might hear a lot of cracker busting up in the background throughout the video. 00:09.230 --> 00:14.950 So it is Diwali today and a lot of crackers are bursting up. 00:14.960 --> 00:18.400 So happy Diwali to you all. 00:18.410 --> 00:21.080 So most of you will be watching this video later. 00:21.080 --> 00:26.180 So consider this as a futuristic message for the upcoming years. 00:27.440 --> 00:34.850 So coming back to the topic we have already discussed about the engine access log and how can we configure 00:34.850 --> 00:37.850 our own custom access log directives? 00:38.570 --> 00:45.020 Now there is a second type of log called as error log, which are very information as very informational. 00:45.020 --> 00:48.920 As far as this debugging issues are concerned. 00:49.610 --> 01:00.080 Now there are a lot of level of error logs which starts from emergency to debug, so there is no mention 01:00.180 --> 01:05.190 on what exactly each of this level of logging means. 01:05.190 --> 01:09.000 So Enginex documentation does not have that officially. 01:09.210 --> 01:15.480 So if you really want to know the exact difference, then you have to dig in through the source code 01:15.510 --> 01:18.600 to see what exactly each one of them is doing. 01:18.840 --> 01:25.560 But we will try to understand on or have an overview on what exactly this does. 01:27.630 --> 01:33.210 So let's go back to the Nginx configuration file. 01:35.370 --> 01:41.580 And here we have something called as error log directive, followed by the path in which the log to 01:41.580 --> 01:42.240 be stored. 01:43.440 --> 01:51.450 Now, as far as error log is concerned, it is very important to know that Nginx does not allow us to 01:51.450 --> 01:55.680 have the flexibility that we had with access log. 01:56.340 --> 02:00.360 That same amount of flexibility is not available for error log. 02:00.870 --> 02:06.990 So as far as error log is concerned, you cannot have any other format in which the logs will be stored. 02:06.990 --> 02:11.460 So the format is predefined and you cannot change that. 02:11.730 --> 02:19.710 The only thing that you can change maybe is the level of logging and the file in which the error log 02:19.710 --> 02:20.340 will be stored. 02:20.880 --> 02:22.320 And this is it. 02:23.520 --> 02:30.780 So let me clear the log files before we start so it will become much more better. 02:34.230 --> 02:36.720 Okay, I'll clear the access log as well. 02:39.060 --> 02:44.820 So let's open up the browser and before that let's do a tail. 02:50.720 --> 02:52.430 I'll remove the example dot log. 02:52.580 --> 02:56.660 We had configured this in the access log. 02:57.920 --> 02:59.390 Time and. 03:02.520 --> 03:02.850 Example. 03:02.940 --> 03:03.450 Dot log. 03:03.660 --> 03:10.110 Okay, let's do a tail on the logs. 03:13.970 --> 03:17.960 Okay, so currently you see the access log is empty and error log is empty. 03:18.140 --> 03:25.970 So let's open up the browser and let's create some logs specifically in the error logs. 03:25.970 --> 03:32.150 So I'll say example.com slash something which is non-existent if I press enter. 03:32.450 --> 03:35.030 And now you see an error log is generated. 03:36.170 --> 03:41.220 So let's try to understand on what can be the predetermined format for it. 03:41.240 --> 03:44.120 So the first thing is the timestamp. 03:44.120 --> 03:51.650 So this is the timestamp of the request which resulted in an error. 03:51.740 --> 03:54.590 Now this is a log level, which is error. 03:54.590 --> 03:58.550 So we have already seen that there are various types of log level. 03:58.550 --> 04:07.610 Now this log level is considered as type error followed by the log level is the process ID. 04:07.820 --> 04:16.110 Now, this process ID is the ID of the worker process, which handled this particular request. 04:19.260 --> 04:22.770 Followed by the process ID, you can see hash zero. 04:22.800 --> 04:31.860 Now, this hash zero basically means it is single threaded, so this will always remain zero because 04:31.860 --> 04:36.510 Nginx is a single threaded followed by. 04:36.540 --> 04:44.910 There is a open call for this particular file example which is not there. 04:44.910 --> 04:50.460 So it is already saying that no such file or directory followed by it is also saying the IP address 04:50.460 --> 04:52.620 of the client and the host name. 04:54.300 --> 05:00.030 So this is an overview about how an error log looks like. 05:00.060 --> 05:06.660 So as we've already discussed, that there are various types of logging, so this is of type error. 05:06.690 --> 05:12.650 Now if we go above, there are many things like emergency alert or critical. 05:12.660 --> 05:21.300 So emergency basically deals with, let's say, some kind of error in the enginex configuration due 05:21.300 --> 05:24.030 to which Nginx itself will not start. 05:24.750 --> 05:32.160 So those kind of very critical logs are termed as emergency. 05:32.610 --> 05:37.770 So let's look into what an emergency log might look like. 05:39.210 --> 05:49.560 So let's open nginx.conf and let's say we make some error in the configuration file itself. 05:49.890 --> 05:55.470 And if I try to do reload, you see Nginx itself has failed. 05:57.370 --> 06:05.800 Now, if we go into the log file here, it says this is emergency because this deals with Nginx itself 06:05.800 --> 06:07.470 not starting at all. 06:07.480 --> 06:14.950 So if Nginx itself does not start, that means if there are multiple websites within nginx all will 06:14.950 --> 06:15.970 stop working. 06:15.970 --> 06:20.650 So those type of logs are categorized as emergency. 06:21.310 --> 06:26.890 Now there is also something called as debug logs which actually provides a huge deal of information 06:26.890 --> 06:28.420 within the log files. 06:28.540 --> 06:36.790 Now debug logs by default are not enabled and you have to compile Nginx manually if you want to enable 06:36.790 --> 06:38.380 the debug log directives. 06:38.590 --> 06:43.630 So this is a short video about what a error log looks like. 06:43.750 --> 06:52.090 So as we cannot configure our own format for error log, there is not much thing that we can have in 06:52.090 --> 06:58.310 this video, so I hope this basic concept has been informative for you and I'd like to thank you for 06:58.310 --> 06:58.700 viewing.