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awk

Executes an AWK program on messages. This processor is very powerful as it offers a range of custom functions for querying and mutating message contents and metadata.

# Common config fields, showing default values
label: ""
awk:
codec: text
program: BEGIN { x = 0 } { print $0, x; x++ }

Works by feeding message contents as the program input based on a chosen codec and replaces the contents of each message with the result. If the result is empty (nothing is printed by the program) then the original message contents remain unchanged.

Comes with a wide range of custom functions for accessing message metadata, json fields, printing logs, etc. These functions can be overridden by functions within the program.

Check out the examples section in order to see how this processor can be used.

This processor uses GoAWK, in order to understand the differences in how the program works you can read more about it here.

Fields

codec

A codec defines how messages should be inserted into the AWK program as variables. The codec does not change which custom Benthos functions are available. The text codec is the closest to a typical AWK use case.

Type: string
Default: "text"
Options: none, text, json.

program

An AWK program to execute

Type: string
Default: "BEGIN { x = 0 } { print $0, x; x++ }"

parts

An optional array of message indexes of a batch that the processor should apply to. If left empty all messages are processed. This field is only applicable when batching messages at the input level.

Indexes can be negative, and if so the part will be selected from the end counting backwards starting from -1.

Type: array
Default: []

Examples

Because AWK is a full programming language it's much easier to map documents and perform arithmetic with it than with other Benthos processors. For example, if we were expecting documents of the form:

{"doc":{"val1":5,"val2":10},"id":"1","type":"add"}
{"doc":{"val1":5,"val2":10},"id":"2","type":"multiply"}

And we wished to perform the arithmetic specified in the type field, on the values val1 and val2 and, finally, map the result into the document, giving us the following resulting documents:

{"doc":{"result":15,"val1":5,"val2":10},"id":"1","type":"add"}
{"doc":{"result":50,"val1":5,"val2":10},"id":"2","type":"multiply"}

We can do that with the following:

pipeline:
processors:
- awk:
program: |
function map_add_vals() {
json_set_int("doc.result", json_get("doc.val1") + json_get("doc.val2"));
}
function map_multiply_vals() {
json_set_int("doc.result", json_get("doc.val1") * json_get("doc.val2"));
}
function map_unknown(type) {
json_set("error","unknown document type");
print_log("Document type not recognised: " type, "ERROR");
}
{
type = json_get("type");
if (type == "add")
map_add_vals();
else if (type == "multiply")
map_multiply_vals();
else
map_unknown(type);
}

Codecs

The chosen codec determines how the contents of the message are fed into the program. Codecs only impact the input string and variables initialised for your program, they do not change the range of custom functions available.

none

An empty string is fed into the program. Functions can still be used in order to extract and mutate metadata and message contents.

This is useful for when your program only uses functions and doesn't need the full text of the message to be parsed by the program, as it is significantly faster.

text

The full contents of the message are fed into the program as a string, allowing you to reference tokenised segments of the message with variables ($0, $1, etc). Custom functions can still be used with this codec.

This is the default codec as it behaves most similar to typical usage of the awk command line tool.

json

An empty string is fed into the program, and variables are automatically initialised before execution of your program by walking the flattened JSON structure. Each value is converted into a variable by taking its full path, e.g. the object:

{
"foo": {
"bar": {
"value": 10
},
"created_at": "2018-12-18T11:57:32"
}
}

Would result in the following variable declarations:

foo_bar_value = 10
foo_created_at = "2018-12-18T11:57:32"

Custom functions can also still be used with this codec.

AWK Functions

json_get

Signature: json_get(path)

Attempts to find a JSON value in the input message payload by a dot separated path and returns it as a string.

json_set

Signature: json_set(path, value)

Attempts to set a JSON value in the input message payload identified by a dot separated path, the value argument will be interpreted as a string.

In order to set non-string values use one of the following typed varieties:

  • json_set_int(path, value)
  • json_set_float(path, value)
  • json_set_bool(path, value)

json_append

Signature: json_append(path, value)

Attempts to append a value to an array identified by a dot separated path. If the target does not exist it will be created. If the target exists but is not already an array then it will be converted into one, with its original contents set to the first element of the array.

The value argument will be interpreted as a string. In order to append non-string values use one of the following typed varieties:

  • json_append_int(path, value)
  • json_append_float(path, value)
  • json_append_bool(path, value)

json_delete

Signature: json_delete(path)

Attempts to delete a JSON field from the input message payload identified by a dot separated path.

json_length

Signature: json_length(path)

Returns the size of the string or array value of JSON field from the input message payload identified by a dot separated path.

If the target field does not exist, or is not a string or array type, then zero is returned. In order to explicitly check the type of a field use json_type.

json_type

Signature: json_type(path)

Returns the type of a JSON field from the input message payload identified by a dot separated path.

Possible values are: "string", "int", "float", "bool", "undefined", "null", "array", "object".

create_json_object

Signature: create_json_object(key1, val1, key2, val2, ...)

Generates a valid JSON object of key value pair arguments. The arguments are variadic, meaning any number of pairs can be listed. The value will always resolve to a string regardless of the value type. E.g. the following call:

create_json_object("a", "1", "b", 2, "c", "3")

Would result in this string:

{"a":"1","b":"2","c":"3"}

create_json_array

Signature: create_json_array(val1, val2, ...)

Generates a valid JSON array of value arguments. The arguments are variadic, meaning any number of values can be listed. The value will always resolve to a string regardless of the value type. E.g. the following call:

create_json_array("1", 2, "3")

Would result in this string:

["1","2","3"]

metadata_set

Signature: metadata_set(key, value)

Set a metadata key for the message to a value. The value will always resolve to a string regardless of the value type.

metadata_get

Signature: metadata_get(key) string

Get the value of a metadata key from the message.

timestamp_unix

Signature: timestamp_unix() int

Returns the current unix timestamp (the number of seconds since 01-01-1970).

timestamp_unix

Signature: timestamp_unix(date) int

Attempts to parse a date string by detecting its format and returns the equivalent unix timestamp (the number of seconds since 01-01-1970).

timestamp_unix

Signature: timestamp_unix(date, format) int

Attempts to parse a date string according to a format and returns the equivalent unix timestamp (the number of seconds since 01-01-1970).

The format is defined by showing how the reference time, defined to be Mon Jan 2 15:04:05 -0700 MST 2006 would be displayed if it were the value.

timestamp_unix_nano

Signature: timestamp_unix_nano() int

Returns the current unix timestamp in nanoseconds (the number of nanoseconds since 01-01-1970).

timestamp_unix_nano

Signature: timestamp_unix_nano(date) int

Attempts to parse a date string by detecting its format and returns the equivalent unix timestamp in nanoseconds (the number of nanoseconds since 01-01-1970).

timestamp_unix_nano

Signature: timestamp_unix_nano(date, format) int

Attempts to parse a date string according to a format and returns the equivalent unix timestamp in nanoseconds (the number of nanoseconds since 01-01-1970).

The format is defined by showing how the reference time, defined to be Mon Jan 2 15:04:05 -0700 MST 2006 would be displayed if it were the value.

timestamp_format

Signature: timestamp_format(unix, format) string

Formats a unix timestamp. The format is defined by showing how the reference time, defined to be Mon Jan 2 15:04:05 -0700 MST 2006 would be displayed if it were the value.

The format is optional, and if omitted RFC3339 (2006-01-02T15:04:05Z07:00) will be used.

timestamp_format_nano

Signature: timestamp_format_nano(unixNano, format) string

Formats a unix timestamp in nanoseconds. The format is defined by showing how the reference time, defined to be Mon Jan 2 15:04:05 -0700 MST 2006 would be displayed if it were the value.

The format is optional, and if omitted RFC3339 (2006-01-02T15:04:05Z07:00) will be used.

Signature: print_log(message, level)

Prints a Benthos log message at a particular log level. The log level is optional, and if omitted the level INFO will be used.