# UDF

> The functions for projection processors. 

  ## Function of content

- [Asn Lookup](#asn-lookup)
- [Base64 Decode](#base64-decode)
- [Base64 Encode](#base64-encode)
- [Current Unix Timestamp](#current-unix-timestamp)
- [Domain](#domain)
- [Drop](#drop)
- [Eval](#eval)
- [Flatten](#flatten)
- [From Unix Timestamp](#from-unix-timestamp)
- [Generate String Array](#generate-string-array)
- [GeoIP Lookup](#geoip-lookup)
- [JSON Extract](#json-extract)
- [Path Combine](#path-combine)
- [Rename](#rename)
- [Snowflake ID](#snowflake-id)
- [String Joiner](#string-joiner)
- [Unix Timestamp Converter](#unix-timestamp-converter)

## Description

Scalar UDF(User Defined Function) is used to extend the functions of projection processor. The UDF is a part of the processing pipeline. It can be used in the pre-processing pipeline, processing pipeline, and post-processing pipeline.

## UDF Definition

A UDF includes the following parts: name, event(processing data), context, evaluate function, open function, and close function.
- name: Function name, with uppercase words separated by underscores, used for function registration.
- event: The data to be processed. It is organized in a Map<String, Object> structure.
- context: Function context, used to store the state of the function. Including the following parameters:
- `filter`: Filter expression, string type. It is used to filter events that need to processed by the function. The expression is written in Aviator expression language. For example, `event.server_ip == '.
- `lookup_fields`: The fields that need to be used as lookup keys. It is an array of string type. For example, `['server_ip', 'client_ip']`.
- `output_fields`: The fields are used to append the result to the event. It is an array of string type. For example, `['server_ip', 'client_ip']`. If the field already exists in the event, the value will be overwritten.
- `parameters`: Custom parameters. It is a Map<String, Object> type.
- evaluate function: The function to process the event. It is a function that returns a Map<String, Object> type.
- open function: Initialize the resources used by the function.
- close function: Release the resources used by the function.

## Functions

Function define common parameters: `filter`, `lookup_fields`, `output_fields`, `parameters`, and will return a Map<String, Object> value of the event.
``` FUNCTION_NAME(filter, lookup_fields, output_fields[, parameters])```

### Asn Lookup

Asn lookup function is used to lookup the asn information by ip address. You need to host the `.mmdb` database file from Knowledge Base Repository.

```ASN_LOOKUP(filter, lookup_fields, output_fields[, parameters])```
- filter: optional
- lookup_fields: required
- output_fields: required
- parameters: required
  - kb_name: required. The name of the knowledge base.
  - option: required. Now only support `IP_TO_ASN`.

Example:

```yaml
- function: ASN_LOOKUP
  lookup_fields: [client_ip]
  output_fields: [client_asn]
  parameters:
    kb_name: tsg_ip_asn
    option: IP_TO_ASN
```

### Base64 Decode

Base64 decode function is used to decode the base64 encoded string.

```BASE64_DECODE_TO_STRING(filter, output_fields[, parameters])```
- filter: optional
- lookup_fields: not required
- output_fields: required
- parameters: required
  - value_field: `<String>` required.
  - charset_field:`<String>` optional. Default is `UTF-8`.

Example:

```yaml
- function: BASE64_DECODE_TO_STRING
  output_fields: [mail_attachment_name]
  parameters:
    value_field: mail_attachment_name
    charset_field: mail_attachment_name_charset
```

### Base64 Encode

Base64 encode function is commonly used to encode the binary data to base64 string. Especially when that data need to be stored and transferred over media that are designed to deal with text. This encoding helps to ensure that the data remains intact without modification during transport.

```BASE64_ENCODE_TO_STRING(filter, output_fields[, parameters])```
- filter: optional
- lookup_fields: not required
- output_fields: required
- parameters: required
  - value_field: `<String>` required.

Example:

```yaml
- function: BASE64_ENCODE_TO_STRING
  output_fields: [packet]
  parameters:
    value_field: packet
```

### Current Unix Timestamp

Current unix timestamp function is used to get the current unix timestamp.

```CURRENT_UNIX_TIMESTAMP(output_fields[, parameters])```  
- filter: not required
- lookup_fields: not required
- output_fields: required
- parameters: optional
  - precision: `<String>` optional. Default is `seconds`. Enum: `milliseconds`, `seconds`.

Example:

```yaml
- function: CURRENT_UNIX_TIMESTAMP
  output_fields: [recv_time]
  parameters:
    precision: seconds
```

### Domain

Domain function is used to extract the domain from the url.

```DOMAIN(filter, lookup_fields, output_fields[, parameters])```  
- filter: optional
- lookup_fields: required. Support more than one fields. All fields will be processed from left to right, and the result will be overwritten if the field processed value is not null.
- output_fields: required
- parameters: required
  - option: `<String>` required. Enum: `TOP_LEVEL_DOMAIN`, `FIRST_SIGNIFICANT_SUBDOMAIN`.

#### Option

- `TOP_LEVEL_DOMAIN` is used to extract the top level domain from the url. For example, `www.abc.com` will be extracted to `com`.
- `FIRST_SIGNIFICANT_SUBDOMAIN` is used to extract the first significant subdomain from the url. For example, `www.abc.com` will be extracted to `abc.com`.

Example:

```yaml
- function: DOMAIN
  lookup_fields: [http_host, ssl_sni, quic_sni] 
  output_fields: [server_domain]
  parameters:
    option: FIRST_SIGNIFICANT_SUBDOMAIN
```

### Drop

Drop function is used to filter the event. If the filter expression is true, the event will be dropped. Otherwise, the event will be passed to downstream.

```DROP(filter)```
- filter: required
- lookup_fields: not required
- output_fields: not required
- parameters: not required

Example:

```yaml
- function: DROP
  filter:  event.server_ip == '4.4.4.4'
```

### Eval

Eval function is used to adds or removes fields from events by evaluating an value expression.

```EVAL(filter, output_fields[, parameters])```
- filter: optional
- lookup_fields: not required
- output_fields: required
- parameters: required
  - value_expression: `<String>` required. Enter a value expression to set the field’s value – this can be a constant.

Example 1:
Add a field `ingestion_time` with value `recv_time`:

```yaml
- function: EVAL
  output_fields: [ingestion_time]
  parameters:
    value_expression: recv_time
```

Example 2:
If the value of `direction` is `69`, the value of `internal_ip` will be `client_ip`, otherwise the value of `internal_ip` will be `server_ip`.

```yaml
- function: EVAL
  output_fields: [internal_ip]
  parameters:
    value_expression: 'direction=69 ? client_ip : server_ip'
```

### Flatten

Flatten the fields of nested structure to the top level. The new fields name are named using the field name prefixed with the names of the struct fields to reach it, separated by dots as default.

```FLATTEN(filter, lookup_fields, output_fields[, parameters])```
- filter: optional
- lookup_fields: optional
- output_fields: not required
- parameters: optional
  - prefix: `<String>` optional. Prefix string for flattened field names. Default is empty.
  - depth: `<Integer>` optional. Number representing the nested levels to consider for flattening. Minimum 1. Default is `5`.
  - delimiter: `<String>` optional. The string used to join nested keys Default is `.`.
  - json_string_keys: `<Array>` optional. The keys of the json string fields. It indicates keys that contain JSON strings and should be parsed and flattened. Default is empty.

Example 1:

Flatten the nested structure of fields and tags in Metrics. If lookup_fields is empty, flatten all nested structures.

```yaml
- function: FLATTEN
  lookup_fields: [tags,fields]
```

Example 2:

Flatten the nested structure of the session record field `encapsulation` (JSON String format), add the prefix `tunnels`, specify the nesting depth as `3`, and use an dot "." as the delimiter.

```yaml
- function: FLATTEN
  lookup_fields: [encapsulation]
  parameters:
    prefix: tunnels
    depth: 3
    delimiter: .
    json_string_keys: [encapsulation]
```

Output:

```json
{
  "tunnels.encapsulation.ipv4.client_ip:": "192.168.11.12",
  "tunnels.encapsulation.ipv4.server_ip": "8.8.8.8"
}
```

### From Unix Timestamp

From unix timestamp function is used to convert the unix timestamp to date time string. The default time zone is UTC+0.

```FROM_UNIX_TIMESTAMP(filter, lookup_fields, output_fields[, parameters])```
- filter: optional
- lookup_fields: required
- output_fields: required
- parameters: optional
  - precision: `<String>` optional. Default is `seconds`. Enum: `milliseconds`, `seconds`.

#### Precision

- `milliseconds` is used to convert the unix timestamp to milliseconds date time string. For example, `1619712000` will be converted to `2021-04-30 00:00:00.000`.
- `seconds` is used to convert the unix timestamp to seconds date time string. For example, `1619712000` will be converted to `2021-04-30 00:00:00`.

Example:

```yaml
- function: FROM_UNIX_TIMESTAMP
  lookup_fields: [recv_time]
  output_fields: [recv_time_string]
  parameters:
    precision: seconds
```

### Generate String Array

Generate string array function is used to merge multiple fields into a string array. The merged field may be a string or a string array.

```GENERATE_STRING_ARRAY(filter, lookup_fields, output_fields)```
- filter: optional
- lookup_fields: required. more than one fields.
- output_fields: required
- parameters: not required

Example:

```yaml
- function: GENERATE_STRING_ARRAY
  lookup_fields: [http_host, ssl_sni, quic_sni] 
  output_fields: [server_domains]
```

### GeoIP Lookup

GeoIP lookup function is used to lookup the geoip information by ip address. You need to host the `.mmdb` database file from Knowledge Base Repository.

```GEOIP_LOOKUP(filter, lookup_fields, output_fields[, parameters])```  
- filter: optional
- lookup_fields: required
- output_fields: optional
- parameters: required
  - kb_name: `<String>` required. The name of the knowledge base.
  - option: `<String>` required. Enum: `IP_TO_COUNTRY`, `IP_TO_PROVINCE`, `IP_TO_CITY`, `IP_TO_SUBDIVISION_ADDR`, `IP_TO_DETAIL`, `IP_TO_LATLNG`, `IP_TO_PROVIDER`, `IP_TO_JSON`, `IP_TO_OBJECT`.
  - geolocation_field_mapping : `<Map<String, String>>` optional. The option is required when the option is `IP_TO_OBJECT`. The mapping of the geolocation fields. The key is the field name of the knowledge base , and the value is the field name of the event.
    - COUNTRY: `<String>` optional.
    - PROVINCE: `<String>` optional.
    - CITY: `<String>` optional.
    - LONGITUDE: `<String>` optional.
    - LATITUDE: `<String>` optional.
    - ISP: `<String>` optional.
    - ORGANIZATION: `<String>` optional.

#### Option

- `IP_TO_COUNTRY` is used to lookup the country or region information by ip address.
- `IP_TO_PROVINCE` is used to lookup the province or state information by ip address.
- `IP_TO_CITY` is used to lookup the city information by ip address.
- `IP_TO_SUBDIVISION_ADDR` is used to lookup the subdivision address information by ip address.
- `IP_TO_DETAIL` is used to lookup the above four levels of information by ip address. It separated by `.`.
- `IP_TO_LATLNG` is used to lookup the latitude and longitude information by ip address. It separated by `,`.
- `IP_TO_PROVIDER` is used to lookup the provider information by ip address.
- `IP_TO_JSON` is used to lookup the above information by ip address. The result is a json string.
- `IP_TO_OBJECT` is used to lookup the above information by ip address. The result is a `LocationResponse` object.

#### GeoLocation Field Mapping

- `COUNTRY` is used to map the country information to the event field.
- `PROVINCE` is used to map the province information to the event field.
- `CITY` is used to map the city information to the event field.
- `LONGITUDE` is used to map the longitude information to the event field.
- `LATITUDE` is used to map the latitude information to the event field.
- `ISP` is used to map the isp information to the event field.
- `ORGANIZATION` is used to map the organization information to the event field.

Example:

```yaml
- function: GEOIP_LOOKUP
  lookup_fields: [ client_ip ]
  output_fields: [ client_geolocation ]
  parameters:
    kb_name: tsg_ip_location
    option: IP_TO_DETAIL
```

```yaml
- function: GEOIP_LOOKUP
  lookup_fields: [ server_ip ]
  output_fields: []
  parameters:
    kb_name: tsg_ip_location
    option: IP_TO_OBJECT
    geolocation_field_mapping:
      COUNTRY: server_country
      PROVINCE: server_super_administrative_area
      CITY: server_administrative_area
```

### JSON Extract

JSON extract function is used to extract the value from json string.

```JSON_EXTRACT(filter, lookup_fields, output_fields[, parameters])```
- filter: optional
- lookup_fields: required
- output_fields: required
- parameters: required
  - value_expression: `<String>` required. The json path expression.

Example:

```yaml
- function: JSON_EXTRACT
  lookup_fields: [ device_tag ]
  output_fields: [ device_group ]
  parameters:
    value_expression: $.tags[?(@.tag=='device_group')][0].value
```

### Path Combine

Path combine function is used to combine the file path. The path value can be configuration parameter with prefix `props.` or a constant string.

```PATH_COMBINE(filter, lookup_fields, output_fields[, parameters])```
- filter: optional
- lookup_fields: required
- output_fields: required
- parameters: required
  - path: `<Array>` required.

Example:

```yaml
- function: PATH_COMBINE
  lookup_fields: [ packet_capture_file ]
  output_fields: [ packet_capture_file ]
  parameters:
    path: [ props.hos.path, props.hos.bucket.name.traffic_file, packet_capture_file ]
```

### Rename

Rename function is used to rename or reformat(e.g. by replacing character underscores with dots) the field name.

```RENAME(filter, lookup_fields, output_fields, parameters)```
- filter: optional
- lookup_fields: not required
- output_fields: not required
- parameters: required
  - parent_fields: `<Array>` optional. Specify fields whose children will inherit the Rename fields and Rename expression operations.
  - rename_fields: `Map<String, String>` required. The key  is the original field name, and the value is the new field name.
  - current_field_name: `<String>` required. The original field name.
  - new_field_name: `<String>` required. The new field name.
  - rename_expression: `<String>` optional. AviatorScript expression whose returned value will be used to rename fields.

```
A single Function can include both rename_fields (to rename specified field names) and rename_expression (to globally rename fields). However, the Rename fields strategy will execute first.
```

Example 1:

Remove the prefix "tags_" from the field names and rename the field "timestamp_ms" to "recv_time_ms".

```yaml
- function: RENAME
- parameters:
    rename_fields:
      - timestamp_ms: recv_time_ms
    rename_expression: key=string.replace_all(key,'tags_',''); return key;
     
```

Example 2:

Rename the field `client_ip` to `source_ip`, including the fields under the `encapsulation.ipv4` tunnel.

```yaml
- function: RENAME
- parameters:
    parent_fields: [encapsulation.ipv4]
    rename_fields:
      - client_ip: source_ip
     
```

Output: `source_ip:192.168.4.1, encapsulation.ipv4.source_ip:192.168.12.12`

### Snowflake ID

Snowflake ID function is used to generate the snowflake id. The snowflake id is a 64-bit integer. The snowflake id is composed of the following parts:
- 1 bit sign bit. The highest bit is 0.
- 39 bits timestamp. The maximum timestamp that can be represented using 39 bits is 2^39-1 or 549755813887, which comes out to be 17 years, 1 month, 7 days, 20 hours, 31 minutes and 35 seconds. That gives us 17 years with respect to a custom epoch.
- 13 bits machine id. 8 bits for the worker id and 5 bits for the datacenter id.
- 11 bits sequence number. The maximum sequence number is 2^11-1 or 2047, which means that a maximum of 2047 IDs can be generated in the same milliseconds in the same machine.

```SNOWFLAKE_ID(filter, output_fields[, parameters])```
- filter: optional
- lookup_fields: not required
- output_fields: required
- parameters: optional
  - data_center_id_num: `<Integer>` optional. Default is `0`, range is `0-31`.

Example:

```yaml
- function: SNOWFLAKE_ID
  output_fields: [log_id]
  parameters:
    data_center_id_num: 1
```

### String Joiner

String joiner function joins multiple string fields using a delimiter, prefix, and suffix.

```STRING_JOINER(filter, lookup_fields, output_fields[, parameters])```
- filter: optional
- lookup_fields: required. Support more than one fields.
- output_fields: required
- parameters: optional
  - delimiter: `<String>` optional. Default is `,`.
  - prefix: `<String>` optional. Default is empty string.
  - suffix: `<String>` optional. Default is empty string.

Example:

```yaml
- function: STRING_JOINER
  lookup_fields: [http_host, ssl_sni, quic_sni] 
  output_fields: [server_domains]
  parameters:
    delimiter: ','
    prefix: '['
    suffix: ']'
```

### Unix Timestamp Converter

Unix timestamp converter function is used to convert the unix timestamp precision.

```UNIX_TIMESTAMP_CONVERTER(filter, lookup_fields, output_fields[, parameters])```
- filter: optional
- lookup_fields: required
- output_fields: required
- parameters: required
  - precision: `<String>` required. Enum: `milliseconds`, `seconds`, `minutes`. The minutes precision is used to generate Unix timestamp, round it to the minute level, and output it in seconds format.
- Example:
_`__timestamp` Internal field, from source ingestion time or current unix timestamp.

```yaml
- function: UNIX_TIMESTAMP_CONVERTER
  lookup_fields: [__timestamp]
  output_fields: [recv_time]
  parameters:
    precision: seconds
```