#Query discipline

How to compose efficient agent-events queries. Hard rule: structured filters first, FTS only as residual.

For the JSON shape of the Function payload (including the selections multi-value filter mechanism), see:

• <repo>/docs/netdata-ai/skills/query-netdata-cloud/query-logs.md ("Multi-value field selections" section)

This doc covers agent-events-specific guidance: which AE_* fields to put in selections, how to compose them, and the anti-patterns to avoid.

#The hard rule

selections (structured, indexable)  -->  query (FTS, residual narrower)

NEVER FTS-first on agent-events. The namespace can hold 40k-200k records / day; a bare query over a wide window full-scans the dataset.

#What to put in selections

Always include at least one of these fields (always present on every record per <repo>/src/daemon/status-file.c:967-976):

• AE_AGENT_HEALTH -- crash class. Filter to crash-* values to drop healthy records.
• AE_EXIT_CAUSE -- exit reason (26 distinct values; pick the ones you want).
• AE_AGENT_VERSION -- producing agent version (regression slicing; pair with the auto-version filter).
• AE_FATAL_SIGNAL_CODE -- empty / non-empty discriminates signal crashes from deliberate fatals / graceful exits.

For more specific triage:

• AE_FATAL_FUNCTION / AE_FATAL_FILENAME -- localize to a function or source file.
• AE_HOST_ARCHITECTURE -- arch-specific bugs.
• AE_OS_FAMILY / AE_OS_TYPE -- distro / OS-specific.
• AE_AGENT_PROFILE_0 -- standalone / parent / child / iot.
• AE_AGENT_KUBERNETES -- k8s-specific.
• AE_AGENT_INSTALL_TYPE -- packaging-specific.
• AE_AGENT_ACLK -- cloud-claimed vs not.

See AE_FIELDS.md for the full field map and which values each enum supports.

#Worked examples

#Example 1: index-friendly crash slice

Find recent signal crashes on stable v2.10.x and the latest 2 nightlies:

{
  "after":  -86400,
  "before": 0,
  "last":   500,
  "__logs_sources": "agent-events",
  "selections": {
    "AE_AGENT_HEALTH":  ["crash-first", "crash-loop", "crash-repeated", "crash-entered"],
    "AE_AGENT_VERSION": ["v2.10.0", "v2.10.0-135-nightly", "v2.10.0-130-nightly"]
  },
  "facets": ["AE_FATAL_SIGNAL_CODE", "AE_FATAL_FUNCTION", "AE_HOST_ARCHITECTURE"]
}

The selections cuts to ~hundreds-to-low-thousands of records via the facet index; facets on top groups by the dimensions of interest. No FTS needed.

#Example 2: index-friendly + FTS narrower

Find recent crashes whose stack trace mentions a specific function:

{
  "after":  -86400,
  "before": 0,
  "last":   200,
  "__logs_sources": "agent-events",
  "selections": {
    "AE_AGENT_HEALTH":  ["crash-first", "crash-loop", "crash-repeated", "crash-entered"]
  },
  "query": "rrdcontext_release"
}

selections cuts to crashes only; query does FTS over the already-sliced subset for the substring match. This is the right composition: structured first, FTS narrows.

If you can express the function name as a selections value on AE_FATAL_FUNCTION, prefer that:

{
  "after":  -86400,
  "before": 0,
  "last":   200,
  "__logs_sources": "agent-events",
  "selections": {
    "AE_FATAL_FUNCTION": ["rrdcontext_release"]
  }
}

This is even faster (pure indexed, no FTS).

#Example 3: regression spotter

Compare crash counts across versions:

{
  "after":  -86400,
  "before": 0,
  "last":   1,
  "__logs_sources": "agent-events",
  "selections": {
    "AE_AGENT_HEALTH": ["crash-first", "crash-loop", "crash-repeated", "crash-entered"]
  },
  "facets": ["AE_AGENT_VERSION"],
  "histogram": "AE_AGENT_VERSION"
}

last: 1 because we only need the facet counts, not the rows. The histogram + facets give the per-version distribution.

#Example 4: rare-crash investigation (wider window)

Looking for a known rare crash signature (1-per-few-days):

{
  "after":  -604800,
  "before": 0,
  "last":   500,
  "__logs_sources": "agent-events",
  "selections": {
    "AE_FATAL_SIGNAL_CODE": ["SIGSEGV/SEGV_MAPERR"],
    "AE_FATAL_FUNCTION":    ["specific_function"]
  }
}

7-day window is acceptable here because the selections cuts to specific signal+function -- a sharp index-resolved slice that returns small results regardless of window width.

#Anti-patterns

#Bare FTS over wide window (BAD)

{
  "after":  -604800,
  "before": 0,
  "__logs_sources": "agent-events",
  "query": "SIGSEGV"
}

A 7-day FTS over the full namespace. Slow. ALWAYS pair with at least one structured selections field.

#FTS for things that should be selections (BAD)

{
  "query": "SIGSEGV"
}

SIGSEGV/... is a value in the AE_FATAL_SIGNAL_CODE field. Use:

{
  "selections": {
    "AE_FATAL_SIGNAL_CODE": ["SIGSEGV/SEGV_MAPERR", "SIGSEGV/SEGV_ACCERR", "SIGSEGV/SEGV_BNDERR", "SIGSEGV/SEGV_PKUERR"]
  }
}

#Naive equality on = only (BAD when you want OR)

The selections mechanism gives you OR-of-values for free. Don't run multiple queries to OR results client-side; put the values in the array.

#Wide window without version filter (BAD when noisy)

If 40-200k events / day are reported on stable releases, a 30-day window without AE_AGENT_VERSION filter returns millions of records, most from old versions whose bugs are already fixed. Always pair wide windows with a version slice.

#Discovery first, then query

Use info=true to discover what fields and values the agent currently exposes:

{ "info": true, "__logs_sources": "agent-events" }

Or use last: 1 + a facet to enumerate values:

{
  "after": -86400, "before": 0, "last": 1,
  "__logs_sources": "agent-events",
  "facets": ["AE_AGENT_VERSION"]
}

Then build the real query using the discovered values in selections.

#Combining facets + selections

facets (the array of field names you want grouped in the response) and selections (the structured filter) are independent. Common pattern: filter narrowly with selections, then facets over the narrow result to see per-field breakdowns.

{
  "selections": {
    "AE_AGENT_HEALTH":  ["crash-loop"],
    "AE_AGENT_VERSION": ["v2.10.0"]
  },
  "facets": ["AE_FATAL_FUNCTION", "AE_HOST_ARCHITECTURE", "AE_OS_FAMILY"]
}

This filters to "crash-loop on v2.10.0", then shows the distribution by function, architecture, and OS in the result facets.

#Quick checklist

Before sending any query, verify:

1. __logs_sources is set to "agent-events" (the journal namespace -- hardcoded constant, NOT the value of ${AGENT_EVENTS_HOSTNAME}).
2. selections contains at least ONE always-present field (AE_AGENT_HEALTH, AE_EXIT_CAUSE, AE_AGENT_VERSION).
3. Time window matches the use case (24h default, 7d for rare crashes).
4. If you used query for FTS, you have a structured selections slice in front of it.
5. last is set sensibly (200-500 for triage; 1 if you only want facet counts).