in_dummy: Add interval settings.

[franciscovalentecastro]

This PR adds new interval_sec and interval_nsec settings to the in_dummy input plugin. This settings enable to set an arbitrary time interval in which to generate dummy logs. When interval_sec/nsec is set correctly, the rate configuration is ignored.
Documentation update in fluent/fluent-bit-docs#1239.

Configuration

[INPUT]
    Name          dummy
    Dummy         {"message": "custom dummy"}
    Interval_sec  1
    Interval_nsec 500000000
    Rate          0

[OUTPUT]
    Name   stdout
    Match  *

Output Log

With this config a log message is generated every 1.5 seconds).

./fluent-bit -c fluent-bit.conf
Fluent Bit v2.2.0
* Copyright (C) 2015-2023 The Fluent Bit Authors
* Fluent Bit is a CNCF sub-project under the umbrella of Fluentd
* https://fluentbit.io

[2023/10/27 18:06:56] [ info] [fluent bit] version=2.2.0, commit=785f45a16d, pid=1533032
[2023/10/27 18:06:56] [ info] [storage] ver=1.5.1, type=memory, sync=normal, checksum=off, max_chunks_up=128
[2023/10/27 18:06:56] [ info] [cmetrics] version=0.6.3
[2023/10/27 18:06:56] [ info] [ctraces ] version=0.3.1
[2023/10/27 18:06:56] [ info] [input:dummy:dummy.0] initializing
[2023/10/27 18:06:56] [ info] [input:dummy:dummy.0] storage_strategy='memory' (memory only)
[2023/10/27 18:06:56] [ info] [sp] stream processor started
[2023/10/27 18:06:56] [ info] [output:stdout:stdout.0] worker #0 started
[0] dummy.0: [[1698430017.644439396, {}], {"message"=>"custom dummy"}]
[0] dummy.0: [[1698430019.144370981, {}], {"message"=>"custom dummy"}]
[0] dummy.0: [[1698430020.644434995, {}], {"message"=>"custom dummy"}]
[0] dummy.0: [[1698430022.144357678, {}], {"message"=>"custom dummy"}]
^C[2023/10/27 18:07:03] [engine] caught signal (SIGINT)
[2023/10/27 18:07:03] [ warn] [engine] service will shutdown in max 5 seconds
[2023/10/27 18:07:03] [ info] [input] pausing dummy.0
[2023/10/27 18:07:03] [ info] [engine] service has stopped (0 pending tasks)
[2023/10/27 18:07:03] [ info] [input] pausing dummy.0
[2023/10/27 18:07:03] [ info] [output:stdout:stdout.0] thread worker #0 stopping...
[2023/10/27 18:07:03] [ info] [output:stdout:stdout.0] thread worker #0 stopped

Valgrind Output

valgrind --leak-check=yes ./fluent-bit   --config ./fluent-bit.conf
==1533023== Memcheck, a memory error detector
==1533023== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==1533023== Using Valgrind-3.16.1 and LibVEX; rerun with -h for copyright info
==1533023== Command: ./fluent-bit --config ./fluent-bit.conf
==1533023==
Fluent Bit v2.2.0
* Copyright (C) 2015-2023 The Fluent Bit Authors
* Fluent Bit is a CNCF sub-project under the umbrella of Fluentd
* https://fluentbit.io

[2023/10/27 18:06:01] [ info] [fluent bit] version=2.2.0, commit=785f45a16d, pid=1533023
[2023/10/27 18:06:01] [ info] [storage] ver=1.5.1, type=memory, sync=normal, checksum=off, max_chunks_up=128
[2023/10/27 18:06:01] [ info] [cmetrics] version=0.6.3
[2023/10/27 18:06:01] [ info] [ctraces ] version=0.3.1
[2023/10/27 18:06:01] [ info] [input:dummy:dummy.0] initializing
[2023/10/27 18:06:01] [ info] [input:dummy:dummy.0] storage_strategy='memory' (memory only)
[2023/10/27 18:06:01] [ info] [sp] stream processor started
[2023/10/27 18:06:01] [ info] [output:stdout:stdout.0] worker #0 started
[0] dummy.0: [[1698429961.660134534, {}], {"message"=>"custom dummy"}]
[0] dummy.0: [[1698429963.144432977, {}], {"message"=>"custom dummy"}]
[0] dummy.0: [[1698429964.644634450, {}], {"message"=>"custom dummy"}]
[0] dummy.0: [[1698429966.144556969, {}], {"message"=>"custom dummy"}]
^C[2023/10/27 18:06:07] [engine] caught signal (SIGINT)
[2023/10/27 18:06:07] [ warn] [engine] service will shutdown in max 5 seconds
[2023/10/27 18:06:07] [ info] [input] pausing dummy.0
[2023/10/27 18:06:07] [ info] [engine] service has stopped (0 pending tasks)
[2023/10/27 18:06:07] [ info] [input] pausing dummy.0
[2023/10/27 18:06:07] [ info] [output:stdout:stdout.0] thread worker #0 stopping...
[2023/10/27 18:06:07] [ info] [output:stdout:stdout.0] thread worker #0 stopped
==1533023==
==1533023== HEAP SUMMARY:
==1533023==     in use at exit: 0 bytes in 0 blocks
==1533023==   total heap usage: 1,716 allocs, 1,716 frees, 1,779,752 bytes allocated
==1533023==
==1533023== All heap blocks were freed -- no leaks are possible
==1533023==
==1533023== For lists of detected and suppressed errors, rerun with: -s
==1533023== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

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Testing
Before we can approve your change; please submit the following in a comment:

• Example configuration file for the change
• Debug log output from testing the change

• Attached Valgrind output that shows no leaks or memory corruption was found

If this is a change to packaging of containers or native binaries then please confirm it works for all targets.

• Run local packaging test showing all targets (including any new ones) build.
• Set ok-package-test label to test for all targets (requires maintainer to do).

Documentation

• Documentation required for this feature

Backporting

• Backport to latest stable release.

---

Fluent Bit is licensed under Apache 2.0, by submitting this pull request I understand that this code will be released under the terms of that license.

[braydonk]

Realized after talking offline that we should add some tests for this to in_simple_systems.c

[nokute78]

@franciscovalentecastro Thank you! LGTM.

[braydonk]

Those MacOS test failures look unrelated to this PR.

[braydonk]

Thanks @nokute78!

tests/runtime/in_simple_systems.c doesn't have a listing in CODEOWNERS (would that make sense for it to be you?)

This means I think we need approval from one of the default folks. @edsiper @leonardo-albertovich if you are able to.