README.md in fluent-plugin-geoip-0.4.0 vs README.md in fluent-plugin-geoip-0.5.0.beta

@@ -14,13 +14,15 @@
 
 before use, install dependent library as:
 
 ```bash
 # for RHEL/CentOS
+$ sudo yum group install "Development Tools"
 $ sudo yum install geoip-devel --enablerepo=epel
 
 # for Ubuntu/Debian
+$ sudo apt-get install build-essential
 $ sudo apt-get install libgeoip-dev
 ```
 
 ## Installation
 
@@ -65,10 +67,13 @@
 
   # Settings for tag
   remove_tag_prefix access.
   tag               geoip.${tag}
 
+  # To avoid get stacktrace error with `[null, null]` array for elasticsearch.
+  skip_adding_null_record  true
+
   # Set log_level for fluentd-v0.10.43 or earlier (default: warn)
   log_level         info
 
   # Set buffering time (default: 0s)
   flush_interval    1s
@@ -106,16 +111,19 @@
   
     # lat lon as string
     # ex. "37.4192008972168,-122.05740356445312"
     location_string      ${latitude["host"]},${longitude["host"]}
     
-    # lat lon as array (it is useful for Kibana's bettermap.)
+    # GeoJSON (lat lon as array) is useful for Kibana's bettermap.
     # ex. [-122.05740356445312, 37.4192008972168]
     location_array       [${longitude["host"]},${latitude["host"]}]
   </record>
   remove_tag_prefix      access.
   tag                    geoip.${tag}
+
+  # To avoid get stacktrace error with `[null, null]` array for elasticsearch.
+  skip_adding_null_record  true
 </match>
 ```
 
 On the case of using td-agent2 (v1-config), it have to quote `{ ... }` or `[ ... ]` block with quotation like below.
 
@@ -128,10 +136,11 @@
     location_string      ${latitude["host"]},${longitude["host"]}
     location_array       '[${longitude["host"]},${latitude["host"]}]'
   </record>
   remove_tag_prefix      access.
   tag                    geoip.${tag}
+  skip_adding_null_record  true
 </match>
 ```
 
 ## Tutorial
 
@@ -180,28 +189,38 @@
 For more details of geoip data format is described at the page below in section `GeoIP City Edition CSV Database Fields`.<br />
 http://dev.maxmind.com/geoip/legacy/csv/
 
 ## Placeholders
 
-Provides these placeholders for adding field of geolocate results.
+Provides these placeholders for adding field of geolocate results.<br />
+For more example of geolocating, you can try these websites like [Geo IP Address View](http://www.geoipview.com/) or [View my IP information](http://www.geoiptool.com/en/).
 
-* ${city[lookup_field]}
-* ${latitude[lookup_field]}
-* ${longitude[lookup_field]}
-* ${country_code3[lookup_field]}
-* ${country_code[lookup_field]}
-* ${country_name[lookup_field]}
-* ${dma_code[lookup_field]}
-* ${area_code[lookup_field]}
-* ${region[lookup_field]}
+| placeholder attributes         | output example    | type         | note |
+|--------------------------------|-------------------|--------------|------|
+| ${city[lookup_field]}          | "Ithaca"          | varchar(255) |  -   |
+| ${latitude[lookup_field]}      | 42.4277992248535  | decimal      |  -   |
+| ${longitude[lookup_field]}     | -76.4981994628906 | decimal      |  -   |
+| ${country_code3[lookup_field]} | "USA"             | varchar(3)   |  -   |
+| ${country_code[lookup_field]}  | "US"              | varchar(2)   | A two-character ISO 3166-1 country code      |
+| ${country_name[lookup_field]}  | "United States"   | varchar(50)  |  -   |
+| ${dma_code[lookup_field]}      | 555               | unsigned int | **only for US**  |
+| ${area_code[lookup_field]}     | 607               | char(3)      | **only for US**  |
+| ${region[lookup_field]}        | "NY"              | char(2)      | A two character ISO-3166-2 or FIPS 10-4 code |
 
+Further more specification available at http://dev.maxmind.com/geoip/legacy/csv/#GeoIP_City_Edition_CSV_Database_Fields
+
 ## Parameters
 
 * `include_tag_key` (default: false)
 * `tag_key`
 
 Add original tag name into filtered record using SetTagKeyMixin.<br />
 Further details are written at http://docs.fluentd.org/articles/in_exec
+
+* `skip_adding_null_record` (default: false)
+
+Skip adding geoip fields when this valaues to `true`.
+On the case of getting nothing of GeoIP info (such as local IP), it will output the original record without changing anything.
 
 * `remove_tag_prefix`
 * `remove_tag_suffix`
 * `add_tag_prefix`
 * `add_tag_suffix`