support filtering on a specific unit

[jsirianni]

Description of Changes

Add optional parameter for filtering on a given service

Resolves #227

Please check that the PR fulfills these requirements

• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)
• Add a changelog entry (for non-trivial bug fixes / features)
• CI passes

[djaglowski]

Log Files	Logs / Second	CPU Avg (%)	CPU Avg Δ (%)	Memory Avg (MB)	Memory Avg Δ (MB)
1	1000	1.4310281	-0.051741958	128.12271	+0.34186554
1	5000	5.2759776	+0.120788574	138.50108	+4.7649536
1	10000	9.965653	-0.051650047	143.75189	-0.09805298
1	50000	53.277325	+0	178.72737	+0
1	100000	101.20083	-16.198303	239.06358	+0.098739624
10	100	1.7759361	-0.1896857	136.78395	+3.8502197
10	500	5.844952	-0.034337997	141.65234	-2.2586212
10	1000	11.551987	-0.43094444	148.0128	+3.09227
10	5000	59.61834	+3.262394	178.87782	-5.090393
10	10000	115.91292	+5.9741898	222.9348	-0.45529175

[codecov]

Codecov Report

Merging #403 (c5f6efb) into master (33d1551) will decrease coverage by 0.02%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #403      +/-   ##
==========================================
- Coverage   73.07%   73.05%   -0.02%     
==========================================
  Files         124      124              
  Lines        8055     8057       +2     
==========================================
  Hits         5886     5886              
- Misses       1668     1669       +1     
- Partials      501      502       +1     

Impacted Files	Coverage Δ
operator/builtin/input/journald/journald.go	56.59% <0.00%> (-0.89%)	⬇️

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[djaglowski]

There was a similar PR on otel-log-collection, which has a couple improvements upon this design: https://github.com/open-telemetry/opentelemetry-log-collection/pull/252/files

In short:

• allow multiple units to be specified in a single operator
• also allow priority to be specified as a filter (orthogonal feature but follows same pattern)

[djaglowski]

Suggested change

	- Journald input: Opetioanl `unit` parameter for filtering [PR 403](https://github.com/observIQ/stanza/pull/403)
	- Journald input: Optional `unit` parameter for filtering [PR 403](https://github.com/observIQ/stanza/pull/403)

[jsirianni]

There was a similar PR on otel-log-collection, which has a couple improvements upon this design: https://github.com/open-telemetry/opentelemetry-log-collection/pull/252/files

In short:

• allow multiple units to be specified in a single operator
• also allow priority to be specified as a filter (orthogonal feature but follows same pattern)

Good point, closing in favor of OTEL.