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Quick start

Introduction​

This document provides an overview of the New Tracing System's functionality, configuration, and modes of operation. The system has been designed to offer flexible and efficient monitoring of Cardano nodes through trace forwarding and hierarchical trace message handling.

Functionality Split between Node and Tracer​

The new system separates monitoring responsibilities between the Cardano Node and the Cardano Tracer services. This modular approach ensures the node focuses on core operations, while cardano-tracer manages logging, monitoring, and external communication.

Introducing Trace Forwarding​

Trace forwarding enables seamless transmission of trace data and metrics from nodes to a centralized tracer service. This feature simplifies remote monitoring and supports scenarios where multiple nodes are monitored by a single cardano-tracer instance.

Hierarchical Namespaces for Trace Messages​

To streamline configuration, the system now uses hierarchical namespaces for trace messages instead of directly referencing tracers. This change improves manageability and aligns trace configuration with logical groupings.

Modes of Operation​

The new tracing system supports several modes of operation to suit different deployment scenarios:

  • Without Forwarding (No Metrics): The node operates independently and writes trace messages to stdout. Metrics are not provided and would have to be built manually from observing stdout.

  • One Node, One Cardano Tracer (Local Socket): The tracer connects to a single node over a local socket. Trace output and metrics are forwarded to the tracer, and are available according to its configuration.

  • One Tracer, Many Nodes (Socket Connection, possibly via SSH Tunnel): A single tracer connects to multiple nodes over socket connections, either locally on the same host, or remotely through secure SSH tunnels.

Two-Part Configuration​

The configuration for the new tracing system is distributed across two key components:

  1. Node Configuration File

    • Specifies the settings required to enable and manage trace forwarding from the node to the tracer.
    • Includes parameters such as:
      • Enabling the new tracing system.
      • Defining trace message filtering and granularity.
      • Additional details about trace forwarding.

  2. Cardano Tracer Configuration File

    • Configures the tracer service itself with settings such as:
      • Communication endpoints (e.g., socket paths).
      • Logging formats and destinations.
      • Metrics, and where to query them (e.g., HTTP ports for EKG or Prometheus).
      • Directories for log storage and rotation.

These configurations work together to ensure efficient communication between the node and the tracer, providing a flexible and robust monitoring setup.

Configuration and use of Cardano Tracer​

cardano-tracer is a key component of the new tracing infrastructure. It operates as a standalone service that consumes trace messages from cardano-node, processes them, and provides outputs for monitoring and analysis.

Key Features:

  • Logging to File or System Services: Write logs in JSON format for machine processing or as text for human readability.
  • Metrics Exposure: Provides EKG and Prometheus metrics endpoints for system monitoring.

Below is an example of configuring a simple use case: a node and cardano-tracer running on the same machine.

Step 1: Transport from Node to Tracer​

Add the following option to the Cardano node's CLI arguments:

--tracer-socket-path-connect /tmp/forwarder.sock

This instructs the node to forward trace messages to cardano-tracer via the specified socket path. The system only supports its own transport layer, the 'forwarding protocol'.

Step 2: Build and Run cardano-tracer​

Build and run cardano-tracer using either cabal or nix. Below are examples for both methods.

Using Cabal:

cabal build cardano-tracer && cabal install cardano-tracer --installdir=PATH_TO_DIR --overwrite-policy=always
cd PATH_TO_DIR
./cardano-tracer --config PATH_TO_CONFIG

Using Nix:

nix build github://github.com/IntersectMBO/cardano-node#cardano-tracer
./result/bin/cardano-tracer --config PATH_TO_CONFIG

Replace PATH_TO_CONFIG with the path to your cardano-tracer configuration file (see next step).

Step 3: Minimal Example Configuration​

Below is an example configuration for a single-node-to-single-tracer setup. The system's forwarding protocol encodes the network magic, so it is mandatory to provide one. Both ends of trace forwarding require the same magic; the example uses the one for mainnet:

Minimal Example:

networkMagic: 764824073
network:
  tag: AcceptAt
  contents: "/tmp/forwarder.sock"
logging:
- logRoot: "/tmp/cardano-tracer-logs"
  logMode: FileMode
  logFormat: ForMachine
  • network: Specifies the socket path for communication between the node and the tracer.
  • logging: Configures logs to be written to the /tmp/cardano-tracer-logs directory in JSON format.

Step 4: Running the Setup​

Starting with Node 10.2, the new tracing system is chosen by default. On previous versions, it can be explicitly enabled in the config by setting UseTraceDispatcher: true.

Go through the adjustments for your Node configuration file (next chapter). When this is done, and cardano-tracer is running, start the Node. It will establish a connection to cardano-tracer and begin forwarding trace messages. The tracer will process these messages and generate logs in the specified directory (/tmp/cardano-tracer-logs).

Advanced Configuration​

For more complex setups, such as monitoring multiple nodes or exposing metrics via Prometheus, additional configuration examples are available. Please refer to the Cardano Tracer Documentation for detailed guidance on advanced setups and use cases.

Node-side configuration of new tracing​

Node-side configuration of new tracing: TraceOptions​

The new tracing system uses namespaces for configuration values, enabling fine-grained control down to individual messages. More specific configuration values will override general ones, allowing for a flexible hierarchical setup. The values are provided in the new TraceOptions object in the node configuration file, which we'll further inspect here:

1. Specify Message Severity Filter​

Define the severity level of messages you want to be included in trace output. More specific namespaces override general ones.

Example:

# Default: show messages of severity Notice or higher
"":
  severity: Notice

# ChainDB messages: show starting from severity Info
ChainDB:
  severity: Info

To suppress all messages pertaining to a namespace, use the severity level Silence.

For a map of the entire namespace of trace messages, please refer to the Cardano Trace Documentation.

2. Specify Message Detail Level​

Configure the detail level for the messages to control the amount of information rendered for each message.

Example:

"":
  severity: Notice
  detail: DNormal
  • Supported detail levels:
    • DMinimal: minimal message verbosity
    • DNormal: default verbosity
    • DDetailed: extended message verbosity
    • DMaximum: be extremely verbose - only recommended for development or debugging

Note: Trace messages might choose to not support every detail level in their implementation - or only one; the highest matching detail level will then be chosen for rendering.

3. Specify Message Frequency Limiters​

Use frequency limiters to control how often messages are displayed. This replaces the old 'eliding tracers' functionality.

Example:

ChainDB.AddBlockEvent.AddedBlockToQueue:
  # Show a maximum of 2 messages per second
  maxFrequency: 2.0

Setting maxFrequency: 0.0 disables frequency limiting - which is the default.

4. Specify backends for trace data​

Define the backends that will be enabled inside the Node to process trace data.

Example:

"":
  severity: Notice
  detail: DNormal
  backends:
    - Stdout MachineFormat
    - EKGBackend
    - Forwarder
  • Writing to standard output (only one can be used):
    • Stdout MachineFormat: in JSON format
    • Stdout HumanFormatColoured: in color-coded text format
    • Stdout HumanFormatUncoloured: in plain text format
  • EKGBackend: Forwards metrics to cardano-tracer
  • Forwarder: Forwards trace messages to cardano-tracer

Note: For standard output, trace messages that do not implement a text format might be displayed as JSON.

Note: Please make sure to enable the Forwarder backend if and only if you intend to consume the trace ouput with a running cardano-tracer instance. In case of unreliable forwarding connections, the Node generously buffers traces that have not been consumed; and though the buffer is bounded, you will experience permanently increased RAM usage if traces are never consumed at all.

Note: Metrics, although being based on trace data, are independent of trace messages. This means, you can receive all metrics with cardano-tracer even when you don't forward the corresponding trace messages. This also means, all metrics will be available even if their corresponding trace messages are filtered out or silenced in your configuration.

Node-side configuration of new tracing: other fields​

In addition to providing a TraceOptions entry, the new tracing system introduces additional configuration values in the node configuration file:

  • TraceOptionNodeName: (string) This is used by cardano-tracer as the base for creating logging subdirectories and URL paths to query metrics. By default, the hostname is chosen.
  • TraceOptionMetricsPrefix: (string) Adds a prefix to all metrics names. For increased compatibility with names in the old system, you could use "cardano.node.metrics.".
  • UseTraceDispatcher: (boolean) Enables / disables the new tracing system

Configuration formats and fallback​

Configurations can be written in both JSON and YAML. The examples in this document are provided in YAML for readability.

A full example of a mainnet node config file utilizing various settings for the new tracing system can be found here: mainnet-config-new-tracing.json

There's a sensible fallback configuration hard-coded inside a Haskell module of the Node: Cardano.Node.Tracing.DefaultTraceConfig. It is important to state the TraceOptions from this fallback will be used if and only if the TraceOptions object in your Node configuration is empty.

Old Tracing and New Tracing​

The old tracing system is slated for decommissioning but will coexist with the new tracing system during a transitional grace period of approximately 3 to 6 months. During this time, both systems will remain part of the default cardano-node build, ensuring compatibility and easing the migration process.

Switching Between Tracing Systems​

  • To enable the new tracing system, set the Node's configuration value UseTraceDispatcher: true.
  • To continue using the old tracing system, you need to explicitly set UseTraceDispatcher: false on Node 10.2 and onwards.

Deprecation of the kind field in trace messages​

Certain legacy features will be deprecated to simplify and unify the tracing infrastructure. Specifically:

  • The kind field will be deprecated and removed when decomissioning the old tracing system.
  • We strongly recommend using namespaces (provided in the new ns field; see below) instead for any analysis tools or automations involving traces.

You're set!​

Feedback and Reporting​

Your feedback is invaluable during this transition. Please help us improve the system by reporting any regressions, issues or difficulties integrating with existing automations while using the new tracing infrastructure.

Developers only: developing new tracers during transition time​

During the transition from old to new tracing system, we recommend the following best practices for developing tracers:

  1. Avoid Using Strictness Annotations for Trace types Trace messages are either discarded immediately or quickly converted into another format for processing. They are never stored for long durations. Using strictness annotations can make the code less efficient without adding any tangible benefits. Additionally, strictness annotations do not align well with the prototype requirements for messages in the new framework.

  2. Prioritize Developing New Tracers Focus on developing new tracers first and then map them to the old tracers. This approach ensures compatibility while future-proofing your work, as the new tracers will remain in use after the old system is decommissioned. You can find numerous examples in cardano-nodes source code in module Cardano.Node.Tracing.Tracers.

  3. Leverage Expertise If you have questions or need reviews for your tracers, reach out to the Performance & Tracing Team.

  4. kind Fields As described above, keep in mind the kind field will be removed eventually; please rely on namespaces when analysing trace messages.

Documentation and References​

To support users, administrators and developers, the following documentation provides comprehensive insights into trace messages, metrics, and data points:

  • Trace Messages and Default Configuration: This periodically regenerated document catalogs all trace messages, metrics, and data points in cardano-node. It also illustrates how these messages are handled with the current default configuration: Cardano Trace Documentation

  • Trace-Dispatcher Library: This document describes the underlying library powering the new tracing system. It provides details about its design, flexibility, and efficiency: trace-dispatcher: Efficient, Simple, and Flexible Program Tracing

  • Cardano Tracer: For information about the cardano-tracer service, which facilitates logging and monitoring, refer to its dedicated documentation: Cardano Tracer Documentation