Logging from a Scala Agent

The Scala SDK provides golem.wasi.Logging — a typed facade over wasi:logging/logging with convenience methods for each log level and an optional context parameter.

Quick Start

Import and use the Logging object directly — no initialization needed:


import golem.wasi.Logging
 
Logging.info("order created: " + orderId)
Logging.debug("processing item: " + itemId)
Logging.warn("retry attempt " + attempt + " for request " + reqId)
Logging.error("failed to connect: " + err.getMessage)

Log Levels

Method	WASI Level	Use for
`Logging.trace(msg)`	trace	Fine-grained control flow
`Logging.debug(msg)`	debug	Debugging information
`Logging.info(msg)`	info	Monitoring, normal operations
`Logging.warn(msg)`	warn	Hazardous situations
`Logging.error(msg)`	error	Serious errors
`Logging.critical(msg)`	critical	Fatal errors

Context Strings

Every method accepts an optional context parameter (defaults to ""). Use it to scope log entries to a subsystem or request:


Logging.info("connected to database", context = "db")
Logging.debug(s"query took ${ms}ms", context = "db/query")
Logging.error(s"timeout after ${retries} retries", context = "http-client")

For the lowest-level API, call Logging.log directly:


Logging.log(Logging.Level.Critical, "shutdown", "system is shutting down")

Using `println` / `System.err.println`

Standard output and error also work and are captured by Golem:


println("stdout message")
System.err.println("stderr message")

These appear in golem agent stream output but lack log levels and context. Prefer Logging.* methods for structured, filterable logging.

Viewing Logs

Stream live agent output:


golem agent stream '<agent-id>'

Or during an invocation:


golem agent invoke '<agent-id>' '<method>' [args]

Key Points

No setup needed — golem.wasi.Logging is available from golem-scala-core which is already in the project dependencies
All methods map directly to the wasi:logging/logging WASI interface
Context strings help group and filter log entries by subsystem
Logs are recorded in the oplog and visible via golem agent stream and golem agent invoke
Logging is a side effect — during replay (crash recovery), log calls from replayed operations are skipped