Emit multiline telemetry from DaemonSet heartbeat

[suyadav1]

Problem

Multiline configuration telemetry (multilineEnabled, multilineLanguages) is silently dropped when the LOGS_AND_EVENTS_ONLY profile is enabled, so we have no visibility into multiline usage for clusters running that profile.

Root cause

The multiline dimensions are emitted from two places today, and neither runs in LOGS_AND_EVENTS_ONLY mode:

Emitter	Plugin / channel	Why it doesn't fire in LOGS_AND_EVENTS_ONLY
source/plugins/ruby/CAdvisorMetricsAPIClient.rb (lines 306-311)	fluentd cAdvisor heartbeat → customMetrics	fluentd is skipped entirely in this profile (kubernetes/linux/main.sh ~lines 1202-1211)
source/plugins/go/input/lib/cadvisor.go (lines 1068-1070)	fluent-bit perf input → customEvents (cAdvisor heartbeat)	only loaded when AZMON_RESOURCE_OPTIMIZATION_ENABLED=true (gated in build/common/installer/scripts/fluent-bit-conf-customizer.rb line 75)

The DaemonSet heartbeat (ContainerLogDaemonSetHeartbeatEvent) emitted from source/plugins/go/src/telemetry.go is the one telemetry path that always runs in the DS, including under LOGS_AND_EVENTS_ONLY. It already carries the logsAndEventsOnly dimension but did not include the multiline fields.

Fix

Add multilineEnabled and multilineLanguages to the DaemonSet heartbeat in telemetry.go, right next to the existing logsAndEventsOnly dimension.

azmonMultilineEnabled := os.Getenv("AZMON_MULTILINE_ENABLED")
if azmonMultilineEnabled != "" {
    telemetryDimensions["multilineEnabled"] = azmonMultilineEnabled
    azmonMultilineLanguages := os.Getenv("AZMON_MULTILINE_LANGUAGES")
    if azmonMultilineLanguages != "" {
        telemetryDimensions["multilineLanguages"] = azmonMultilineLanguages
    }
}

Precedent

Commit aa3098b14 (PR #1212, "move LOGS_AND_EVENTS_ONLY telemetry to DS") used the same approach to surface the logsAndEventsOnly dimension. The duplication between the cAdvisor heartbeat and the DS heartbeat also matches the existing nflEnabled pattern (emitted in both cadvisor.go and telemetry.go).

Why we keep the existing emit sites

• They publish to a different App Insights table (customMetrics via the cAdvisor heartbeat vs customEvents via the DS heartbeat), so they do not double-count.
• The Ruby and Go cAdvisor sites are mutually exclusive (one runs with fluentd, the other only when resource optimization is enabled).
• Removing them would be a behavior change for the non-LOGS_AND_EVENTS_ONLY paths and is out of scope for this fix.

Validation

• go build ./... from source/plugins/go/src is clean.
• No behavior change for non-LOGS_AND_EVENTS_ONLY modes; the multiline dimensions will simply also be present on the DS heartbeat.

Follow-up (not in this PR)

A broader audit identified other log-related fields with the same gap in LOGS_AND_EVENTS_ONLY (e.g. clusterstdoutlogs, clusterstderrlogs, containerLogsRoute, metadataEnabled, etc.). Happy to fix those in a separate PR if desired.

[rashmichandrashekar]

can this be special characters and does ingestion work for all characters? any validation needeD?