Logs

Golem server logs

Every Golem service emits structured logs with with configurable format and level. The default configuration for our dockerized builds is to log to the container’s standard output using JSON format. Each service supports the same set of configuration keys controlling the logging behavior, which can be overwritten using environment variables.

The default log level and filtering can be configured using the RUST_LOG environment variable, as described in the tracing-subscriber crate’s documentation. The simplest way to use this environment variable is to set a global log level, for example RUST_LOG=debug.

The Golem specific config keys are the following:


[tracing]
console = false
dtor_friendly = false
file_name = "worker-executor.log"
file_truncate = true
 
[tracing.file]
ansi = false
compact = false
enabled = false
json = true
json_flatten = true
json_flatten_span = true
pretty = false
span_events_active = false
span_events_full = false
without_time = false
 
[tracing.stdout]
ansi = true
compact = false
enabled = true
json = false
json_flatten = true
json_flatten_span = true
pretty = false
span_events_active = false
span_events_full = false
without_time = false

Overwriting config

To overwrite any of the above config keys using environment variables, use the GOLEM_ prefix and the __ separator for levels. For example to disable logging to the standard output, and instead enable logging to a file, set the following two variables:


GOLEM_TRACING__FILE__ENABLED=true
GOLEM_TRACING__STDOUT__ENABLED=false

Configurable options

The top-level tracing block allows setting the file name and truncate behavior for file logging, as well as enabling connection to tokio-console.

For both file and stdout logging, a set of boolean flags control the format of the emitted log lines:

Flag	Description
`ansi`	Use ANSI colors for the output
`compact`	Use the compact formatter.
`enabled`	Enables logging to file or stdout
`json`	Use JSON logging
`json_flatten`	Flatten event metadata
`json_flatten_span`	Flatten nested span fields
`pretty`	Use the pretty formatter
`span_events_active`	Emit one event per enter/exit of a span
`span_events_full`	Emit one event at all points (new, enter, exit, drop)
`without_time`	Do not emit timestamps for the log entries

Golem agent logs

TypeScript

In TypeScript agents, use the standard console API to log messages. console.log writes to the agent’s standard output, console.error writes to standard error, while console.debug, console.info, console.warn, etc. write log entries with the corresponding log level.

Rust

In Rust agents, anything written to the agent’s standard output and error channels, for example with println! or eprintln!, is logged.

In addition to that it is possible to use the log function in the golem_rust::bindings::wasi::logging::logging module directly to write log entries with specific log levels:


use golem_rust::bindings::wasi::logging::logging;
 
logging::log(logging::Level::Info, "my_context", "my_message");

The recommended way is to use the log crate, which is initialized automatically by the Rust agent runtime:


log::info!("my_message");

Scala

In Scala agents, use the JavaScript console API through Scala.js to log messages. js.Dynamic.global.console.log(...) writes to the agent’s standard output, js.Dynamic.global.console.error(...) writes to standard error, while js.Dynamic.global.console.debug(...), js.Dynamic.global.console.info(...), etc. write log entries with the corresponding log level.


import scala.scalajs.js
 
js.Dynamic.global.console.info("my_message")

MoonBit

In MoonBit agents, use the Golem MoonBit SDK logging helpers to write log entries with specific log levels. Assuming golemcloud/golem_sdk/logging is imported as @logging:


@logging.info("my_message")

Getting agent logs

Agent logs (both stdout/err and WASI logging entries) are persisted for each agent, and they can be watched in live by using the connect API. There are two ways to connect to an agent:

Using golem
Using the connect WebSocket API To connect to an agent’s log with golem, use the golem agent stream command, or simply use golem agent invoke which streams logs by default. See the CLI documentation for more details.