Log Architecture & Structural Overview

The Caddy Web Server Structured JSON Log Parser is an essential telemetry stream within the Web Servers & Reverse Proxies ecosystem. Parse Caddy 2 structured JSON access logs with automatic TLS status, status codes, and duration float metrics.

This schema defines a structure of 12 extracted attributes, including 3 numeric metrics and 9 string dimensions. In production observability architectures, these tokens provide high-cardinality indexing keys for telemetry pipelines before shipping to storage backends such as ClickHouse, Elasticsearch, Amazon S3, or Datadog.

Raw Telemetry Ingestion Profile

A typical raw event line for caddy-structured-json averages 244 bytes across 12 tokens. Modern collectors such as Fluent Bit and Vector require zero-backtracking regular expressions to avoid CPU spikes during traffic surges.

Extracted Field Schema & Data Types

The transpiled Grok pattern extracts the following schema fields from each raw event line. Data collectors cast these values according to the typed mappings below.

Field Name	Inferred Type	Description & Collector Semantics
level	string	Log severity level.
ts	float	Unix epoch seconds with millisecond float.
logger	string	Subsystem logger identifier.
msg	string	Log message summary.
remote_ip	string	Client IP.
remote_port	string	Client port.
proto	string	Protocol negotiated.
method	string	HTTP method.
host	string	Host header.
uri	string	Requested URI.
status	integer	HTTP status code.
duration	float	Execution duration in seconds.

Common Regex Traps & Production Edge Cases

Engineers frequently encounter ingestion failures or pipeline drops due to subtle variations in real-world event logs. Watch out for these verified pitfalls:

1Caddy 2 logs timestamps as decimal epoch seconds (e.g. 1695734400.123). Multiply by 1000 for milliseconds.

2HTTP/3 protocol appears as 'HTTP/3.0' or 'h3'.

Production Collector Setup & Configurations

Pre-configured parser definitions ready to be dropped into your infrastructure repository.

Fluent Bit (parsers.conf)

Format: regex

# ==============================================================================
# Fluent Bit Parser Configuration (parsers.conf)
# ==============================================================================
[PARSER]
    Name        logpipeline_parser
    Format      regex
    Regex       ^\{"level":"(?<level>\b\w+\b)","ts":(?<ts>(?:(?:(?:[+-]?(?:[0-9]+(?:\.[0-9]+)?|\.[0-9]+))))),"logger":"(?<logger>\S+)","msg":"(?<msg>.*?)","request":\{"remote_ip":"(?<remote_ip>(?:(?:(?:(?:[0-9A-Fa-f]{1,4}:){7}[0-9A-Fa-f]{1,4}|(?:[0-9A-Fa-f]{1,4}:){1,7}:|(?:[0-9A-Fa-f]{1,4}:){1,6}:[0-9A-Fa-f]{1,4}|(?:[0-9A-Fa-f]{1,4}:){1,5}(?::[0-9A-Fa-f]{1,4}){1,2}|(?:[0-9A-Fa-f]{1,4}:){1,4}(?::[0-9A-Fa-f]{1,4}){1,3}|(?:[0-9A-Fa-f]{1,4}:){1,3}(?::[0-9A-Fa-f]{1,4}){1,4}|(?:[0-9A-Fa-f]{1,4}:){1,2}(?::[0-9A-Fa-f]{1,4}){1,5}|[0-9A-Fa-f]{1,4}:(?:(?::[0-9A-Fa-f]{1,4}){1,6})|:(?:(?::[0-9A-Fa-f]{1,4}){1,7}|:)|fe80:(?::[0-9A-Fa-f]{0,4}){0,4}%[0-9a-zA-Z]+|::(?:ffff(?::0{1,4})?:)?(?:(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])\.){3}(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])|(?:[0-9A-Fa-f]{1,4}:){1,4}:(?:(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])\.){3}(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])))|(?:(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?))))","remote_port":"(?<remote_port>(?:[+-]?(?:[0-9]+)))","proto":"(?<proto>\S+)","method":"(?<method>\b\w+\b)","host":"(?<host>\b(?:[0-9A-Za-z][0-9A-Za-z-]{0,62})(?:\.(?:[0-9A-Za-z][0-9A-Za-z-]{0,62}))*(?:\.?|\b))","uri":"(?<uri>\S+)"\},"status":(?<status>(?:[+-]?(?:[0-9]+))),"duration":(?<duration>(?:(?:(?:[+-]?(?:[0-9]+(?:\.[0-9]+)?|\.[0-9]+)))))\}$
    Time_Key    timestamp
    Time_Format %Y-%m-%dT%H:%M:%S%z
    Types       ts:float status:integer duration:float

# ==============================================================================
# Fluent Bit Pipeline Filter (fluent-bit.conf)
# ==============================================================================
[FILTER]
    Name         parser
    Match        *
    Key_Name     log
    Parser       logpipeline_parser
    Reserve_Data On

Vector.dev (Remap VRL)

parse_regex!

# ==============================================================================
# Vector.dev Remap Language (VRL) Transform
# Use inside a 'remap' transform in vector.yaml
# ==============================================================================
.parsed, err = parse_regex(.message, r'^\{"level":"(?<level>\b\w+\b)","ts":(?<ts>(?:(?:(?:[+-]?(?:[0-9]+(?:\.[0-9]+)?|\.[0-9]+))))),"logger":"(?<logger>\S+)","msg":"(?<msg>.*?)","request":\{"remote_ip":"(?<remote_ip>(?:(?:(?:(?:[0-9A-Fa-f]{1,4}:){7}[0-9A-Fa-f]{1,4}|(?:[0-9A-Fa-f]{1,4}:){1,7}:|(?:[0-9A-Fa-f]{1,4}:){1,6}:[0-9A-Fa-f]{1,4}|(?:[0-9A-Fa-f]{1,4}:){1,5}(?::[0-9A-Fa-f]{1,4}){1,2}|(?:[0-9A-Fa-f]{1,4}:){1,4}(?::[0-9A-Fa-f]{1,4}){1,3}|(?:[0-9A-Fa-f]{1,4}:){1,3}(?::[0-9A-Fa-f]{1,4}){1,4}|(?:[0-9A-Fa-f]{1,4}:){1,2}(?::[0-9A-Fa-f]{1,4}){1,5}|[0-9A-Fa-f]{1,4}:(?:(?::[0-9A-Fa-f]{1,4}){1,6})|:(?:(?::[0-9A-Fa-f]{1,4}){1,7}|:)|fe80:(?::[0-9A-Fa-f]{0,4}){0,4}%[0-9a-zA-Z]+|::(?:ffff(?::0{1,4})?:)?(?:(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])\.){3}(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])|(?:[0-9A-Fa-f]{1,4}:){1,4}:(?:(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])\.){3}(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])))|(?:(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?))))","remote_port":"(?<remote_port>(?:[+-]?(?:[0-9]+)))","proto":"(?<proto>\S+)","method":"(?<method>\b\w+\b)","host":"(?<host>\b(?:[0-9A-Za-z][0-9A-Za-z-]{0,62})(?:\.(?:[0-9A-Za-z][0-9A-Za-z-]{0,62}))*(?:\.?|\b))","uri":"(?<uri>\S+)"\},"status":(?<status>(?:[+-]?(?:[0-9]+))),"duration":(?<duration>(?:(?:(?:[+-]?(?:[0-9]+(?:\.[0-9]+)?|\.[0-9]+)))))\}$')

if err == null {
    . = merge(., .parsed)
    del(.parsed)

    # Type coercions
    .ts = to_float!(.ts)
    .status = to_int!(.status)
    .duration = to_float!(.duration)

} else {
    log("LogPipeline parsing warning: " + err, level: "warn")
}

# ==============================================================================
# vector.yaml Pipeline Component
# ==============================================================================
transforms:
  parse_logs:
    type: remap
    inputs: ["source_logs"]
    source: |
      .parsed, err = parse_regex(.message, r'^\{"level":"(?<level>\b\w+\b)","ts":(?<ts>(?:(?:(?:[+-]?(?:[0-9]+(?:\.[0-9]+)?|\.[0-9]+))))),"logger":"(?<logger>\S+)","msg":"(?<msg>.*?)","request":\{"remote_ip":"(?<remote_ip>(?:(?:(?:(?:[0-9A-Fa-f]{1,4}:){7}[0-9A-Fa-f]{1,4}|(?:[0-9A-Fa-f]{1,4}:){1,7}:|(?:[0-9A-Fa-f]{1,4}:){1,6}:[0-9A-Fa-f]{1,4}|(?:[0-9A-Fa-f]{1,4}:){1,5}(?::[0-9A-Fa-f]{1,4}){1,2}|(?:[0-9A-Fa-f]{1,4}:){1,4}(?::[0-9A-Fa-f]{1,4}){1,3}|(?:[0-9A-Fa-f]{1,4}:){1,3}(?::[0-9A-Fa-f]{1,4}){1,4}|(?:[0-9A-Fa-f]{1,4}:){1,2}(?::[0-9A-Fa-f]{1,4}){1,5}|[0-9A-Fa-f]{1,4}:(?:(?::[0-9A-Fa-f]{1,4}){1,6})|:(?:(?::[0-9A-Fa-f]{1,4}){1,7}|:)|fe80:(?::[0-9A-Fa-f]{0,4}){0,4}%[0-9a-zA-Z]+|::(?:ffff(?::0{1,4})?:)?(?:(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])\.){3}(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])|(?:[0-9A-Fa-f]{1,4}:){1,4}:(?:(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])\.){3}(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])))|(?:(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?))))","remote_port":"(?<remote_port>(?:[+-]?(?:[0-9]+)))","proto":"(?<proto>\S+)","method":"(?<method>\b\w+\b)","host":"(?<host>\b(?:[0-9A-Za-z][0-9A-Za-z-]{0,62})(?:\.(?:[0-9A-Za-z][0-9A-Za-z-]{0,62}))*(?:\.?|\b))","uri":"(?<uri>\S+)"\},"status":(?<status>(?:[+-]?(?:[0-9]+))),"duration":(?<duration>(?:(?:(?:[+-]?(?:[0-9]+(?:\.[0-9]+)?|\.[0-9]+)))))\}$')
      if err == null {
        . = merge(., .parsed)
        del(.parsed)
      }

Datadog Log Pipeline Grok Parser

match_rules

# ==============================================================================
# Datadog Log Processing Pipeline Grok Parser
# Navigate to: Logs -> Configuration -> Pipelines -> Add Processor -> Grok Parser
# ==============================================================================

# Match Rule:
rule \{"level":"%{WORD:level}","ts":%{NUMBER:ts},"logger":"%{NOTSPACE:logger}","msg":"%{DATA:msg}","request":\{"remote_ip":"%{IP:remote_ip}","remote_port":"%{INT:remote_port}","proto":"%{NOTSPACE:proto}","method":"%{WORD:method}","host":"%{HOSTNAME:host}","uri":"%{NOTSPACE:uri}"\},"status":%{INT:status},"duration":%{NUMBER:duration}\}

# Complete Datadog Pipeline Processor JSON:
{
  "type": "grok-parser",
  "name": "LogPipeline Grok Parser",
  "is_enabled": true,
  "source": "message",
  "samples": [],
  "grok": {
    "match_rules": "rule \\{\"level\":\"%{WORD:level}\",\"ts\":%{NUMBER:ts},\"logger\":\"%{NOTSPACE:logger}\",\"msg\":\"%{DATA:msg}\",\"request\":\\{\"remote_ip\":\"%{IP:remote_ip}\",\"remote_port\":\"%{INT:remote_port}\",\"proto\":\"%{NOTSPACE:proto}\",\"method\":\"%{WORD:method}\",\"host\":\"%{HOSTNAME:host}\",\"uri\":\"%{NOTSPACE:uri}\"\\},\"status\":%{INT:status},\"duration\":%{NUMBER:duration}\\}",
    "support_rules": ""
  }
}

# Target Fields Created:
# level (string), ts (float), logger (string), msg (string), remote_ip (string), remote_port (string), proto (string), method (string), host (string), uri (string), status (integer), duration (float)

OpenTelemetry Collector (transform processor)

regex_parser

# ==============================================================================
# OpenTelemetry Collector Configuration (otel-collector-config.yaml)
# Option 1: Filelog Receiver with regex_parser Operator
# ==============================================================================
receivers:
  filelog:
    include: [ /var/log/**/*.log ]
    start_at: beginning
    operators:
      - type: regex_parser
        id: logpipeline_regex_parser
        regex: '^\{"level":"(?<level>\b\w+\b)","ts":(?<ts>(?:(?:(?:[+-]?(?:[0-9]+(?:\.[0-9]+)?|\.[0-9]+))))),"logger":"(?<logger>\S+)","msg":"(?<msg>.*?)","request":\{"remote_ip":"(?<remote_ip>(?:(?:(?:(?:[0-9A-Fa-f]{1,4}:){7}[0-9A-Fa-f]{1,4}|(?:[0-9A-Fa-f]{1,4}:){1,7}:|(?:[0-9A-Fa-f]{1,4}:){1,6}:[0-9A-Fa-f]{1,4}|(?:[0-9A-Fa-f]{1,4}:){1,5}(?::[0-9A-Fa-f]{1,4}){1,2}|(?:[0-9A-Fa-f]{1,4}:){1,4}(?::[0-9A-Fa-f]{1,4}){1,3}|(?:[0-9A-Fa-f]{1,4}:){1,3}(?::[0-9A-Fa-f]{1,4}){1,4}|(?:[0-9A-Fa-f]{1,4}:){1,2}(?::[0-9A-Fa-f]{1,4}){1,5}|[0-9A-Fa-f]{1,4}:(?:(?::[0-9A-Fa-f]{1,4}){1,6})|:(?:(?::[0-9A-Fa-f]{1,4}){1,7}|:)|fe80:(?::[0-9A-Fa-f]{0,4}){0,4}%[0-9a-zA-Z]+|::(?:ffff(?::0{1,4})?:)?(?:(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])\.){3}(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])|(?:[0-9A-Fa-f]{1,4}:){1,4}:(?:(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])\.){3}(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])))|(?:(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?))))","remote_port":"(?<remote_port>(?:[+-]?(?:[0-9]+)))","proto":"(?<proto>\S+)","method":"(?<method>\b\w+\b)","host":"(?<host>\b(?:[0-9A-Za-z][0-9A-Za-z-]{0,62})(?:\.(?:[0-9A-Za-z][0-9A-Za-z-]{0,62}))*(?:\.?|\b))","uri":"(?<uri>\S+)"\},"status":(?<status>(?:[+-]?(?:[0-9]+))),"duration":(?<duration>(?:(?:(?:[+-]?(?:[0-9]+(?:\.[0-9]+)?|\.[0-9]+)))))\}$'
        timestamp:
          parse_from: attributes.timestamp
          layout: '%Y-%m-%dT%H:%M:%S%z'

# ==============================================================================
# Option 2: Transform Processor (OTel Transformation Language - OTTL)
# ==============================================================================
processors:
  transform:
    error_mode: ignore
    log_statements:
      - context: log
        statements:
          - merge_maps(attributes, extract_patterns(body, "^\\{\"level\":\"(?<level>\\b\\w+\\b)\",\"ts\":(?<ts>(?:(?:(?:[+-]?(?:[0-9]+(?:\\.[0-9]+)?|\\.[0-9]+))))),\"logger\":\"(?<logger>\\S+)\",\"msg\":\"(?<msg>.*?)\",\"request\":\\{\"remote_ip\":\"(?<remote_ip>(?:(?:(?:(?:[0-9A-Fa-f]{1,4}:){7}[0-9A-Fa-f]{1,4}|(?:[0-9A-Fa-f]{1,4}:){1,7}:|(?:[0-9A-Fa-f]{1,4}:){1,6}:[0-9A-Fa-f]{1,4}|(?:[0-9A-Fa-f]{1,4}:){1,5}(?::[0-9A-Fa-f]{1,4}){1,2}|(?:[0-9A-Fa-f]{1,4}:){1,4}(?::[0-9A-Fa-f]{1,4}){1,3}|(?:[0-9A-Fa-f]{1,4}:){1,3}(?::[0-9A-Fa-f]{1,4}){1,4}|(?:[0-9A-Fa-f]{1,4}:){1,2}(?::[0-9A-Fa-f]{1,4}){1,5}|[0-9A-Fa-f]{1,4}:(?:(?::[0-9A-Fa-f]{1,4}){1,6})|:(?:(?::[0-9A-Fa-f]{1,4}){1,7}|:)|fe80:(?::[0-9A-Fa-f]{0,4}){0,4}%[0-9a-zA-Z]+|::(?:ffff(?::0{1,4})?:)?(?:(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])\\.){3}(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])|(?:[0-9A-Fa-f]{1,4}:){1,4}:(?:(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])\\.){3}(?:25[0-5]|(?:2[0-4]|1?[0-9])?[0-9])))|(?:(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?))))\",\"remote_port\":\"(?<remote_port>(?:[+-]?(?:[0-9]+)))\",\"proto\":\"(?<proto>\\S+)\",\"method\":\"(?<method>\\b\\w+\\b)\",\"host\":\"(?<host>\\b(?:[0-9A-Za-z][0-9A-Za-z-]{0,62})(?:\\.(?:[0-9A-Za-z][0-9A-Za-z-]{0,62}))*(?:\\.?|\\b))\",\"uri\":\"(?<uri>\\S+)\"\\},\"status\":(?<status>(?:[+-]?(?:[0-9]+))),\"duration\":(?<duration>(?:(?:(?:[+-]?(?:[0-9]+(?:\\.[0-9]+)?|\\.[0-9]+)))))\\}$"), "insert")

service:
  pipelines:
    logs:
      receivers: [filelog]
      processors: [transform]
      exporters: [otlp]

Logstash Filter Configuration

filter.grok

# ==============================================================================
# Logstash Pipeline Configuration (/etc/logstash/conf.d/logpipeline.conf)
# ==============================================================================
filter {
  grok {
    match => { "message" => "\{\"level\":\"%{WORD:level}\",\"ts\":%{NUMBER:ts:float},\"logger\":\"%{NOTSPACE:logger}\",\"msg\":\"%{DATA:msg}\",\"request\":\{\"remote_ip\":\"%{IP:remote_ip}\",\"remote_port\":\"%{INT:remote_port}\",\"proto\":\"%{NOTSPACE:proto}\",\"method\":\"%{WORD:method}\",\"host\":\"%{HOSTNAME:host}\",\"uri\":\"%{NOTSPACE:uri}\"\},\"status\":%{INT:status:integer},\"duration\":%{NUMBER:duration:float}\}" }
    tag_on_failure => [ "_grokparsefailure" ]
  }

  date {
    match => [ "timestamp", "ISO8601", "dd/MMM/yyyy:HH:mm:ss Z" ]
    target => "@timestamp"
    remove_field => [ "timestamp" ]
  }
}