Flow Purge Telemetry

The Flow Purge telemetry is emitted when a tracked flow is removed from the engine, typically after normal connection closure (TCP), inactivity timeout, or internal purge conditions. It captures final flow counters and end-state details at the point the flow leaves active tracking.

Use this record for post-session analysis, accounting, and flow lifecycle validation. Comparing purge records with periodic flow_stats updates helps explain why sessions ended and whether termination behavior aligns with network expectations.

Requirements

Flow Purge telemetry was introduced in the Core Plugin in version 1.0.20. To begin streaming the telemetry:

Install and configure the Netify Agent
Install and configure a Sink Plugin for receiving the telemetry
Install and configure the Core Plugin and add stream-flows to types

Source: Core Plugin
Plugin Release: 1.0.20

Attributes

type

string

Telemetry record type. Always flow_purge.

interface

string

Interface name associated with the purged flow.

internal

boolean

Indicates whether the flow is internal to the local network context.

reason

string

Purge reason reported by the engine.

Values

closed expired

flow

object

Container for final per-flow statistics at purge time.

flow.detection_packets

integer

Number of packets used for application/protocol detection.

flow.digest

string

Current flow digest identifier.

flow.digest_prev

array[string]

List of previous digest identifiers associated with the flow.

flow.last_seen_at

integer

Timestamp in Unix epoch milliseconds when the flow was last observed.

flow.local_bytes

integer

Bytes sent from the local endpoint.

flow.local_packets

integer

Packets sent from the local endpoint.

flow.local_rate

integer

Final local transmit rate for the flow.

flow.other_bytes

integer

Bytes sent from the remote endpoint.

flow.other_packets

integer

Packets sent from the remote endpoint.

flow.other_rate

integer

Final remote transmit rate for the flow.

flow.tcp

object

TCP health and error counters for TCP flows.

flow.tcp.resets

integer

Count of observed TCP reset packets for the flow.

flow.tcp.retrans

integer

Count of observed TCP retransmissions for the flow.

flow.tcp.seq_errors

integer

Count of TCP sequence anomalies for the flow.

flow.total_bytes

integer

Total bytes seen for the flow in both directions.

flow.total_packets

integer

Total packets seen for the flow in both directions.

Flow Purge Attributes - Example

{
  "flow": {
    "detection_packets": 12,
    "digest": "fb69e87ed3b...",
    "digest_prev": [
      "d7fddd35cc27..."
    ],
    "last_seen_at": 1772665905392,
    "local_bytes": 0,
    "local_packets": 0,
    "local_rate": 387,
    "other_bytes": 0,
    "other_packets": 0,
    "other_rate": 300,
    "tcp": {
      "resets": 0,
      "retrans": 0,
      "seq_errors": 0
    },
    "total_bytes": 13968,
    "total_packets": 51
  },
  "interface": "wlp3s0",
  "internal": true,
  "reason": "closed",
  "type": "flow_purge"
}