StatsD and CollectD serve fundamentally different purposes in the monitoring ecosystem:

• CollectD is a metrics collection daemon focused on system-level statistics (CPU, memory, disk I/O)
• StatsD is a metrics aggregation service designed for application-level instrumentation

In production environments, they often work together:

# Typical data flow:
[Application] --custom metrics--> [StatsD]
[Server] --system metrics--> [CollectD]
[CollectD] --optional forwarding--> [StatsD]
[StatsD] --> [TimeSeries DB like Graphite]

Pattern 1: CollectD as Source for StatsD

LoadPlugin write_graphite
<Plugin write_graphite>
  <Node "statsd">
    Host "statsd.example.com"
    Port "8125"
    Protocol "udp"
    Prefix "collectd."
  </Node>
</Plugin>

Pattern 2: StatsD as Aggregation Layer

// Node.js application sending metrics
const StatsD = require('node-statsd');
const client = new StatsD({
  host: 'statsd.example.com',
  prefix: 'app.'
});

client.increment('user.login');

The hybrid approach makes sense when you need:

• System-level monitoring via CollectD (disk space, network traffic)
• Application business metrics via StatsD (API calls, user actions)
• Unified visualization in dashboards

Example Grafana query showing both sources:

aliasByNode(
  group(
    stats_counts.app.*.login,
    collectd.*.memory.free
  ),
  2
)

StatsD and CollectD serve complementary roles in the monitoring ecosystem. While both handle metrics collection, they operate at different layers:

• CollectD: Primarily a data collection agent that gathers system-level metrics (CPU, memory, disk I/O) directly from hosts
• StatsD: Functions as a metrics aggregation service that receives, processes, and forwards metrics from various sources

# CollectD Architecture
Host -> CollectD (collection) -> Time-series DB (e.g., Graphite, InfluxDB)

# StatsD Architecture
Application -> StatsD (aggregation) -> Backend (e.g., Graphite, Prometheus)

They can work together in these common deployment scenarios:

1. Direct Collection:

   # CollectD config to send metrics to StatsD
   LoadPlugin write_graphite
   <Plugin write_graphite>
     <Node "statsd">
       Host "statsd.example.com"
       Port "8125"
       Protocol "udp"
     </Node>
   </Plugin>
   

2. Sidecar Pattern:

   # Docker compose example
   services:
     collectd:
       image: collectd:latest
       volumes:
         - ./collectd.conf:/etc/collectd/collectd.conf
     statsd:
       image: statsd/statsd
       ports:
         - "8125:8125/udp"
   

Here's how to configure CollectD to filter metrics before sending to StatsD:

LoadPlugin match_regex
LoadPlugin target_set

<Chain "PreCache">
  <Rule "filter_system_metrics">
    <Match regex>
      Plugin "^cpu|memory|disk$"
    </Match>
    <Target set>
      MetaData "target_type" "statsd"
    </Target>
  </Rule>
</Chain>