upstream: Improve error message for misconfigured HTTP_PROXY variable

[lecaros]

Added specific messages for errors inside the function flb_utils_proxy_url_split().
Removed the call to flb_errno() since errors are displayed by flb_utils_proxy_url_split.

Fixes #9327

---

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

• Example configuration file for the change
  Config for repro from error message for misconfigured http_proxy is misleading #9327.

Fluent Bit v3.2.0
* Copyright (C) 2015-2024 The Fluent Bit Authors
* Fluent Bit is a CNCF sub-project under the umbrella of Fluentd
* https://fluentbit.io

______ _                  _    ______ _ _           _____  __  
|  ___| |                | |   | ___ (_) |         |____ |/  | 
| |_  | |_   _  ___ _ __ | |_  | |_/ /_| |_  __   __   / /`| | 
|  _| | | | | |/ _ \ '_ \| __| | ___ \ | __| \ \ / /   \ \ | | 
| |   | | |_| |  __/ | | | |_  | |_/ / | |_   \ V /.___/ /_| |_
\_|   |_|\__,_|\___|_| |_|\__| \____/|_|\__|   \_/ \____(_)___/

[2024/09/02 14:51:40] [ info] Configuration:
[2024/09/02 14:51:40] [ info]  flush time     | 1.000000 seconds
[2024/09/02 14:51:40] [ info]  grace          | 5 seconds
[2024/09/02 14:51:40] [ info]  daemon         | 0
[2024/09/02 14:51:40] [ info] ___________
[2024/09/02 14:51:40] [ info]  inputs:
[2024/09/02 14:51:40] [ info]      dummy
[2024/09/02 14:51:40] [ info] ___________
[2024/09/02 14:51:40] [ info]  filters:
[2024/09/02 14:51:40] [ info] ___________
[2024/09/02 14:51:40] [ info]  outputs:
[2024/09/02 14:51:40] [ info]      stdout.0
[2024/09/02 14:51:40] [ info]      http.1
[2024/09/02 14:51:40] [ info] ___________
[2024/09/02 14:51:40] [ info]  collectors:
[2024/09/02 14:51:40] [ info] [fluent bit] version=3.2.0, commit=c69a6dfe9b, pid=1711
[2024/09/02 14:51:40] [debug] [engine] coroutine stack size: 36864 bytes (36.0K)
[2024/09/02 14:51:40] [ info] [storage] ver=1.1.6, type=memory, sync=normal, checksum=off, max_chunks_up=128
[2024/09/02 14:51:40] [ info] [cmetrics] version=0.9.5
[2024/09/02 14:51:40] [ info] [ctraces ] version=0.5.5
[2024/09/02 14:51:40] [ info] [input:dummy:dummy.0] initializing
[2024/09/02 14:51:40] [ info] [input:dummy:dummy.0] storage_strategy='memory' (memory only)
[2024/09/02 14:51:40] [debug] [dummy:dummy.0] created event channels: read=21 write=22
[2024/09/02 14:51:40] [debug] [stdout:stdout.0] created event channels: read=23 write=24
[2024/09/02 14:51:40] [debug] [http:http.1] created event channels: read=30 write=31
[2024/09/02 14:51:40] [ info] [input] pausing dummy.0
[2024/09/02 14:51:40] [debug] [upstream] config->http_proxy: hostname.domain.tld
[2024/09/02 14:51:40] [ info] [output:stdout:stdout.0] worker #0 started
[2024/09/02 14:51:40] [error] HTTP_PROXY variable must be set in the form of 'http://[username:password@]host:port'
[2024/09/02 14:51:40] [error] [output] failed to initialize 'http' plugin
[2024/09/02 14:51:40] [ info] [output:stdout:stdout.0] thread worker #0 stopping...
[2024/09/02 14:51:40] [error] [engine] output initialization failed
[2024/09/02 14:51:40] [ info] [output:stdout:stdout.0] thread worker #0 stopped

• 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

Current documentation is correct.

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.

[edsiper]

@lecaros thanks for this PR.

please change the commit prefix here:

• upstream: remove call to flb_errno(). The error is displayed by flb_utils_proxy_url_split()
• flb_utils: improve error messaging inside the flb_utils_proxy_url_split()
• flb_utils: fix typos

flb_utils needs to be changed to utils

[lecaros]

Thanks @edsiper
Changes done.

[edsiper]

note: this PR was done against master, we need one for branch 3.1