WEBVTT 00:04.510 --> 00:10.210 In this new section of the course we'll cover some useful modules and directives outside of the fundamental 00:10.240 --> 00:12.040 engine configuration. 00:12.280 --> 00:18.190 And with the overall focus of the Course leaning toward Web servers a good starting point is configuring 00:18.190 --> 00:20.050 expires headers. 00:20.050 --> 00:25.540 Now if you're not familiar with expires headers they're essentially a response header informing the 00:25.540 --> 00:30.380 client or browser how long it can cached that response for. 00:30.430 --> 00:37.780 So for example let's say we have an image or more specifically a photo on our website that photo data 00:37.820 --> 00:43.810 isn't realistically going to change all that often meaning we can tell the browser to cache a copy of 00:43.810 --> 00:46.560 the photo for a relatively long time. 00:46.720 --> 00:53.860 And in doing so avoid any future requests for that photo drastically improving Web site load times and 00:53.950 --> 00:58.660 often overlooked a reduction in requests to our server. 00:58.660 --> 01:03.460 Another resource like a style sheet however which could very well change more frequently. 01:03.460 --> 01:08.230 We could say to a shorter time but still have the browser cache it none the less. 01:08.560 --> 01:14.320 Over to the configuration file as we lifted before and first thing I'll do is clean up some of these 01:14.320 --> 01:19.270 directives from the previous lesson then before we can figure out a way expires. 01:19.270 --> 01:25.540 Let's also as part of this lesson see how to set a generic response header in this thumb. 01:25.540 --> 01:27.310 Don't be in G location. 01:27.310 --> 01:35.830 I'll use the built in add header directive with the first argument being the header name my header and 01:35.830 --> 01:36.520 the second. 01:36.550 --> 01:37.720 The header value. 01:37.930 --> 01:39.610 Hello world. 01:39.610 --> 01:44.780 Save this reload the configuration and now to test this. 01:44.800 --> 01:51.290 We can make a cold request to thump or be in G with the flag for headers. 01:51.310 --> 01:56.090 I'll paste that you are L. enter and there we have it in the response headers. 01:56.140 --> 01:58.470 My header said to Hello World. 01:58.780 --> 02:05.020 So knowing how to said headers we can configure this location as a typical static resource by first 02:05.020 --> 02:12.940 setting the cache control header to public telling the receiving client that this resource or response 02:13.270 --> 02:15.510 can be cached in any way. 02:15.670 --> 02:18.970 Then the pragma header also to public. 02:18.970 --> 02:26.020 Essentially just an older version of this cache control header then else relate it but equally important 02:26.020 --> 02:34.550 header vary meaning the content of this response can vary with the value being xcept encoding. 02:34.570 --> 02:40.000 This is something we'll cover in more depth in the next lesson but essentially saying the response can 02:40.000 --> 02:44.890 vary based on the value of the request header except encoding. 02:45.190 --> 02:48.850 And finally to set the expires head up on this response. 02:48.850 --> 02:53.640 Engine X provides us a very convenient directive called expires. 02:53.650 --> 02:58.980 We could of course have said this header manually but there would be no logical way of setting a duration 02:59.020 --> 03:02.860 as the expires hid his value which needs to be a date. 03:02.890 --> 03:10.870 So with this expires directive we can simply sit a standard engine X duration for example 60 M which 03:10.870 --> 03:19.040 is 60 Minutes the same unit notations we used with the time out directives or 1 h for one hour. 03:19.360 --> 03:20.200 Or finally. 03:20.200 --> 03:22.400 In this case one m. 03:22.450 --> 03:25.270 Which in uppercase form is month. 03:25.420 --> 03:28.890 With this now you can see better why sit in an actual date. 03:28.900 --> 03:29.890 Wouldn't work. 03:30.070 --> 03:34.800 Let's say you sit in expires header using the ADD header directive with a date 1. 03:34.830 --> 03:40.990 Our way in the future that date would change in the configuration meaning in our time that date would 03:40.990 --> 03:43.820 be in the past whereas with this directive. 03:43.840 --> 03:47.500 Engine X sends the expires head of value as a date. 03:47.500 --> 03:51.070 This amount of time in the future for every request. 03:51.660 --> 03:55.290 Save this so we can test it reload. 03:55.470 --> 04:02.670 Make that same call request again and this time we get an expires header with the date set to exactly 04:02.670 --> 04:09.210 one month ahead of this recording including those additional headers we said and another cache control 04:09.210 --> 04:12.270 header added by the expires directive. 04:12.480 --> 04:13.780 Max h. 04:13.800 --> 04:19.650 With this being the number of seconds in 30 days or one month as we set it. 04:20.040 --> 04:26.160 This is essentially all this to configuring expires headers and given these new headers a browser will 04:26.160 --> 04:33.420 now cache this thumb or PRNG image locally meaning on the user's machine for this amount of time before 04:33.420 --> 04:39.570 requesting it from our server again before we finish up however let's see what a more typical location 04:39.570 --> 04:42.930 for such static resources might look like. 04:42.990 --> 04:49.920 First up I'll change this to be a case insensitive regular expression match looking to any request ending 04:49.920 --> 04:51.180 with an extension. 04:51.180 --> 04:55.380 So dot C S S J S J. 04:55.380 --> 04:59.150 B G or j peg or P E N G. 04:59.220 --> 05:03.350 You can of course add a bunch more year but this is the general idea. 05:03.690 --> 05:10.810 And not forgetting access underscore log off unless you really want to log each and every request. 05:11.010 --> 05:19.920 Save this reload the configuration and this time given that new location try style dotsie SS instead. 05:20.890 --> 05:24.570 Which now responds with those exact same expires headers. 05:24.880 --> 05:28.890 A simple but incredibly valuable addition to any Web server.