Fluent Bit stream processor uses common SQL to perform record queries. The following section describe the features available and examples of it.
Statements
You can find the detailed query language syntax in BNF form here. The following section will be a brief introduction on how to write SQL queries for Fluent Bit stream processing.
SELECT Statement
Synopsis
Description
Select keys from records coming from a stream or records matching a specific Tag pattern. Note that a simple SELECT statement not associated from a stream creation will send the results to the standard output interface (stdout), useful for debugging purposes.
The query allows filtering the results by applying a condition using WHERE statement. We will explain WINDOW and GROUP BY statements later in aggregation functions section.
Examples
Select all keys from records coming from a stream called apache:
Select code key from records which Tag starts with apache.:
Since the TAG selector allows the use of wildcards, we put the value between single quotes.
CREATE STREAM Statement
Synopsis
Description
Create a new stream of data using the results from the SELECT statement. New stream created can be optionally re-ingested back into Fluent Bit pipeline if the property Tag is set in the WITH statement.
Examples
Create a new stream called hello from stream called apache:
Create a new stream called hello for all records which original Tag starts with apache:
Aggregation Functions
Aggregation functions are used in results_statement on the keys, allowing to perform data calculation on groups of records. Group of records that aggregation functions apply on are determined by WINDOW keyword. When WINDOW is not specified, aggregation functions apply on the current buffer of records received, which may have non-deterministic number of elements. Aggregation functions can be applied on records in a window of a specific time interval (see the syntax of WINDOW in select statement).
Fluent Bit streaming currently supports tumbling window, which is non-overlapping window type. That means, a window of size 5 seconds performs aggregation computations on records over a 5-second interval, and then starts new calculations for the next interval.
In addition, the syntax support GROUP BY statement, which groups the results by the one or more keys, when they have the same values.
AVG
Synopsis
Description
Calculates the average of request sizes in POST requests.
COUNT
Synopsis
Description
Count the number of records in 5 second windows group by host IP addresses.
MIN
Synopsis
Description
Gets the minimum value of a key in a set of records.
MAX
Synopsis
Description
Gets the maximum value of a key in a set of records.
SUM
Synopsis
Description
Calculates the sum of all values of key in a set of records.
Time Functions
Time functions adds a new key into the record with timing data
NOW
Synopsis
Description
Add system time using format: %Y-%m-%d %H:%M:%S. Output example: 2019-03-09 21:36:05.
UNIX_TIMESTAMP
Synopsis
Description
Add current Unix timestamp to the record. Output example: 1552196165 .
Record Functions
Record functions append new keys to the record using values from the record context.
RECORD_TAG
Synopsis
Description
Append Tag string associated to the record as a new key.
RECORD_TIME
Synopsis
WHERE Condition
Similar to conventional SQL statements, WHERE condition is supported in Fluent Bit query language. The language supports conditions over keys and subkeys, for instance:
It is possible to check the existence of a key in the record using record-specific function @record.contains:
And to check if the value of a key is/is not NULL:
Description
Append a new key with the record Timestamp in double format: seconds.nanoseconds. Output example: 1552196165.705683 .
SELECT results_statement
FROM STREAM:stream_name | TAG:match_rule
[WINDOW TUMBLING (integer SECOND)]
[WHERE condition]
[GROUP BY groupby]
SELECT * FROM STREAM:apache;
SELECT code AS http_status FROM TAG:'apache.*';
CREATE STREAM stream_name
[WITH (property_name=value, [...])]
AS select_statement
CREATE STREAM hello AS SELECT * FROM STREAM:apache;
CREATE STREAM hello AS SELECT * FROM TAG:'apache.*';
SELECT AVG(size) FROM STREAM:apache WHERE method = 'POST' ;
SELECT host, COUNT(*) FROM STREAM:apache WINDOW TUMBLING (5 SECOND) GROUP BY host;
SELECT MIN(key) FROM STREAM:apache;
SELECT MIN(key) FROM STREAM:apache;
SELECT SUM(key) FROM STREAM:apache;
SELECT NOW() FROM STREAM:apache;
SELECT UNIX_TIMESTAMP() FROM STREAM:apache;
SELECT RECORD_TAG() FROM STREAM:apache;
SELECT RECORD_TIME() FROM STREAM:apache;
SELECT AVG(size) FROM STREAM:apache WHERE method = 'POST' AND status = 200;
SELECT MAX(key) FROM STREAM:apache WHERE @record.contains(key);
SELECT MAX(key) FROM STREAM:apache WHERE key IS NULL;
SELECT * FROM STREAM:apache WHERE user IS NOT NULL;