Structuring Modes

LTS provides five log structuring modes: regular expressions, JSON, delimiter, Nginx, and structuring template. You can make your choice flexibly.

Regular Expressions

If you choose regular expressions, fields are extracted based on your defined regular expressions.

Select a typical log event as the sample.
- Click Select from existing log events, select a log event, and click OK. You can select different time ranges to filter logs.
- Click Paste from Clipboard to copy the cut log content to the sample log box.
  There are three types of time range: relative time from now, relative time from last, and specified time. Select a time range as required.
  - From now: queries log data generated in a time range that ends with the current time, such as the previous 1, 5, or 15 minutes. For example, if the current time is 19:20:31 and 1 hour is selected as the relative time from now, the charts on the dashboard display the log data that is generated from 18:20:31 to 19:20:31.
  - From last: queries log data generated in a time range that ends with the current time, such as the previous 1 or 15 minutes. For example, if the current time is 19:20:31 and 1 hour is selected as the relative time from last, the charts on the dashboard display the log data that is generated from 18:00:00 to 19:00:00.
  - Specified: queries log data that is generated in a specified time range.

Extract fields. Extracted fields are shown with their example values. You can extract fields in two ways:
- Auto generate: Select the log content you want to extract as a field in the sample log event. In the dialog box displayed, set the field name. The name must start with a letter and contain only letters and digits. Then click Add.
  Figure 1 Selecting a field
- Manually enter: Enter a regular expression in the text box and click Extract Field. A regular expression may contain multiple capturing groups, which group strings with parentheses. There are three types of capturing groups:
  - (exp): Capturing groups are numbered by counting their opening parentheses from left to right. The numbering starts with 1.
  - (?<name>exp): named capturing group. It captures text that matches exp into the group name. The group name must start with a letter and contain only letters and digits. A group is recalled by group name or number.
  - (?:exp): non-capturing group. It captures text that matches exp, but it is not named or numbered and cannot be recalled.
- When you select manually enter, the regular expression can contain up to 5000 characters. You do not have to name capturing groups when writing the regular expression. When you click Extract Field, those unnamed groups will be named as field1, field2, field3, and so on.
Click Save. The type of extracted fields cannot be changed after the structuring is complete.

JSON

If you choose JSON, JSON logs are split into key-value pairs.

Select a typical log event as the sample. Click Select from existing log events, select a log event, or enter a log event in the text box, and click OK. You can select different time ranges to filter logs.
There are three types of time range: relative time from now, relative time from last, and specified time. Select a time range as required.
- From now: queries log data generated in a time range that ends with the current time, such as the previous 1, 5, or 15 minutes. For example, if the current time is 19:20:31 and 1 hour is selected as the relative time from now, the charts on the dashboard display the log data that is generated from 18:20:31 to 19:20:31.
- From last: queries log data generated in a time range that ends with the current time, such as the previous 1 or 15 minutes. For example, if the current time is 19:20:31 and 1 hour is selected as the relative time from last, the charts on the dashboard display the log data that is generated from 18:00:00 to 19:00:00.
- Specified: queries log data that is generated in a specified time range.

Extract fields. Extract fields from the log event. Extracted fields are shown with their example values.

Click Intelligent Extraction. Take the following log event as an example.

Enter the log event in the text box.
```
{"a1": "a1", "b1": "b1", "c1": "c1", "d1": "d1"}
```
- The float data type has seven digit precision.
- If a value contains more than seven valid digits, the extracted content is incorrect, which affects visualization and quick analysis. In this case, you are advised to change the field type to string.
Check and edit the fields if needed. For details about rules for configuring extracted fields, see Setting Log Structuring Fields.
Click Save. The type of extracted fields cannot be changed after the structuring is complete.

Delimiter

Logs can be parsed by delimiters, such as commas (,), spaces, or other special characters.

Select a typical log event as the sample. Click Select from existing log events, select a log event, or enter a log event in the text box, and click OK. You can select different time ranges to filter logs.
There are three types of time range: relative time from now, relative time from last, and specified time. Select a time range as required.
- From now: queries log data generated in a time range that ends with the current time, such as the previous 1, 5, or 15 minutes. For example, if the current time is 19:20:31 and 1 hour is selected as the relative time from now, the charts on the dashboard display the log data that is generated from 18:20:31 to 19:20:31.
- From last: queries log data generated in a time range that ends with the current time, such as the previous 1 or 15 minutes. For example, if the current time is 19:20:31 and 1 hour is selected as the relative time from last, the charts on the dashboard display the log data that is generated from 18:00:00 to 19:00:00.
- Specified: queries log data that is generated in a specified time range.
Select or customize a delimiter.
- For invisible characters, enter hexadecimal characters starting with 0x. The length ranges from 0 to 4 characters. There are 32 invisible characters in total.
- For custom characters, enter 1 to 10 characters, each as an independent delimiter.
- For custom character string, enter 1 to 30 characters as one whole delimiter.

Extract fields. Extract fields from the log event. Extracted fields are shown with their example values.

Click Intelligent Extraction. Take the following log event as an example.

Enter the log event in the text box.
```
1 5f67944957444bd6bb4fe3b367de8f3d 1d515d18-1b36-47dc-a983-bd6512aed4bd 192.168.0.154 192.168.3.25 38929 53 17 1 96 1548752136 1548752736 ACCEPT OK
```
Figure 2 Intelligent extraction results

The float data type has seven digit precision.

If a value contains more than seven valid digits, the extracted content is incorrect, which affects visualization and quick analysis. In this case, you are advised to change the field type to string.

Check and edit the fields if needed. For details about rules for configuring extracted fields, see Setting Log Structuring Fields.
Click Save. The type of extracted fields cannot be changed after the structuring is complete.

Nginx

You can customize the format of access logs by the log_format command.

Select a typical log event as the sample. Click Select from existing log events, select a log event, or enter a log event in the text box, and click OK. You can select different time ranges to filter logs.
There are three types of time range: relative time from now, relative time from last, and specified time. Select a time range as required.
- From now: queries log data generated in a time range that ends with the current time, such as the previous 1, 5, or 15 minutes. For example, if the current time is 19:20:31 and 1 hour is selected as the relative time from now, the charts on the dashboard display the log data that is generated from 18:20:31 to 19:20:31.
- From last: queries log data generated in a time range that ends with the current time, such as the previous 1 or 15 minutes. For example, if the current time is 19:20:31 and 1 hour is selected as the relative time from last, the charts on the dashboard display the log data that is generated from 18:00:00 to 19:00:00.
- Specified: queries log data that is generated in a specified time range.
Define the Nginx log format. You can click Apply Default Nginx Log Format to apply the default format,

Figure 3 Defining the Nginx log format
In standard Nginx configuration files, the portion starting with log_format indicates the log configuration.

Log format
- Default Nginx log format:
```
log_format  main   '$remote_addr - $remote_user [$time_local] "$request" '
                            '$status $body_bytes_sent "$http_referer" '
                            '"$http_user_agent" "$http_x_forwarded_for"';
```
- You can also customize a format. The format must meet the following requirements:
  - Cannot be blank.
  - Must start with log_format and contain apostrophes (') and field names.
  - Can contain up to 5000 characters.
  - Must match the sample log event.
  - Any character except letters, digits, underscores (_), and hyphens (-) can be used to separate fields.
  - Must end with an apostrophe (') or an apostrophe plus a semicolon (";).

Extract fields. Extract fields from the log event. Extracted fields are shown with their example values.

Click Intelligent Extraction. Take the following log event as an example.

Enter the log event in the text box.
```
39.149.31.187 - - [12/Mar/2020:12:24:02 +0800] "GET / HTTP/1.1" 304 0 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/80.0.3987.132 Safari/537.36" "-"
```
Configure the following Nginx log format in step 2:
```
log_format  main   '$remote_addr - $remote_user [$time_local] "$request" '
                            '$status $body_bytes_sent "$http_referer" '
                            '"$http_user_agent" "$http_x_forwarded_for"';
```
- The float data type has seven digit precision.
- If a value contains more than seven valid digits, the extracted content is incorrect, which affects visualization and quick analysis. In this case, you are advised to change the field type to string.
Check and edit the fields if needed. For details about rules for configuring extracted fields, see Setting Log Structuring Fields.
Click Save. The type of extracted fields cannot be changed after the structuring is complete.