Logging

Obelisk provides two mechanisms for logging from WASM components: the structured obelisk:log interface and stdout/stderr stream forwarding.

obelisk:log Interface

The preferred way to emit log messages is through the obelisk:log/log@1.0.0 WIT interface. It is available to all component types: activities, workflows, and webhook endpoints.

The interface provides five log levels:

package obelisk:log@1.0.0;

interface log {
    trace: func(message: string);
    debug: func(message: string);
    info: func(message: string);
    warn: func(message: string);
    error: func(message: string);
}

Usage in WIT

Import the interface in your component's WIT world:

package my:component;

world my-world {
    import obelisk:log/log@1.0.0;
    // ... other imports and exports
}

Alternatively, generate the WIT support files using the CLI:

obelisk generate wit-support <COMPONENT_TYPE> <OUTPUT_DIRECTORY>

Usage in Rust

use obelisk::log::log;

log::info("Processing request");
log::debug(&format!("Input: {input:?}"));
log::error("Something went wrong");

Each message is a string, so use format! for dynamic content.

stdout/stderr Forwarding

Activities and webhook endpoints can also produce output via stdout and stderr (e.g., println! in Rust). This byte-stream output can be forwarded to the database or to the server's console.

Workflows do not support stdout/stderr forwarding — use obelisk:log instead.

Forwarding is controlled per component in the TOML configuration:

[[activity_wasm]]
name = "my_activity"
location = "my_activity.wasm"
forward_stdout = "db"      # One of "none"|"stdout"|"stderr"|"db". Default: "db"
forward_stderr = "db"      # One of "none"|"stdout"|"stderr"|"db". Default: "db"

Persistent Log Storage

Both obelisk:log messages and forwarded stdout/stderr streams can be stored in the database. Stored logs can be retrieved via the WebAPI. Export OBELISK_API_TOKEN as described in Authentication first:

curl 127.1:5005/v1/executions/<EXECUTION_ID>/logs -H 'Accept: text/plain' \
  -H "Authorization: Bearer $OBELISK_API_TOKEN"

Logs are also visible in the Web UI on the execution detail page.

logs_store_min_level

The logs_store_min_level setting controls the minimum log level of obelisk:log messages that are persisted to the database. It can be configured per component:

[[activity_wasm]]
name = "my_activity"
location = "my_activity.wasm"
logs_store_min_level = "debug"  # One of "off"|"trace"|"debug"|"info"|"warn"|"error"

The default is "debug", which stores all messages at debug level and above. Set to "off" to disable log persistence entirely, or to "info" to reduce storage in high-throughput scenarios.

This setting applies to all component types: [[activity_wasm]], [[workflow]], and [[webhook_endpoint]].

Comparison