Host Troubleshooting

Host troubleshooting largely revolves around checking host logs and determining the issue from there. With wasmCloud we aim to log relevant information so that you can diagnose the source of the problem.

The primary wasmCloud host runtime is the wasmcloud-otp host, and this is what you’ll be using if you’re running the host from the release tarball or with the wasmcloud_host docker image. The Javascript host has different log messages and it’s recommended to create an issue here if you are running into errors in the browser.

The wasmCloud host logs include the following:

  1. Logs from the host runtime
  2. Logs from capability providers that emit to stdout
  3. Logs from actors that utilize the wasmcloud:builtin:logging capability

Finding the logs (release tarball)

If you followed the installation guide then you likely started the host by running a command like ./bin/wasmcloud_host start or ./bin/wasmcloud_host daemon. In the same directory where you unpacked the tarball you’ll be able to find the logs in ./tmp/log/erlang.log.X, where X starts at 1 and will increment monotonically as the log file grows too large.

If you take a look at the top of one of these logfiles (using head for example on Unix systems) you’ll see something like:

=====
===== LOGGING STARTED Tue Jan 18 16:15:11 EST 2022
=====
Erlang/OTP 24 [erts-12.0.3] [source] [64-bit] [smp:10:10] [ds:10:10:10] [async-threads:1]

16:15:22.532 [info] Wrote "./host_config.json"
16:15:22.549 [info] Wrote "/my/user/.wash/host_config.json"
16:15:22.549 [info] Connecting to control interface NATS without authentication
16:15:22.549 [info] Connecting to lattice rpc NATS without authentication

The Erlang/OTP line is useful for submitting issues, but what you’re likely interested in is the end of the log file where logs are being constantly appended. This is where you’ll want to look for any errors.

Finding the logs (docker)

If you followed the installation with docker guide, then you’ll be running the wasmCloud host inside of a Docker container. It’s fairly simple to get the logs from here.

First, find the name of the wasmCloud host container:

docker ps -a --format "table {{.Image}}\t{{.Names}}"
IMAGE                             NAMES
wasmcloud/wasmcloud_host:latest   tmp-wasmcloud-1
registry:2.7                      tmp-registry-1
redis:6.2                         tmp-redis-1
nats:2.7.2-alpine                 tmp-nats-1

Then, attach your terminal to the logs of that container (in this case, tmp-wasmcloud-1):

$ docker logs -f tmp-wasmcloud-1
15:51:06.582 [info] Wrote "./host_config.json"
15:51:06.582 [info] Wrote "/root/.wash/host_config.json"
15:51:06.582 [info] Connecting to control interface NATS without authentication
15:51:06.582 [info] Connecting to lattice rpc NATS without authentication
15:51:06.582 [info] Starting wasmCloud OTP Host Runtime v0.52.1
...

Changing log level

At the time of writing this, the main wasmCloud host runtime is an Elixir/OTP application and actors and providers both are written in Rust. Both of these components have adjustable log levels.

Elixir + Actors

Elixir supports log levels of error, warn, info, and debug. In order to change the log level you’ll need to use the integrated Elixir terminal using one of the methods below. Because actors log through the host runtime, this will also affect their log level.

When you launch your host, do so with the integrated terminal attached. In the wasmcloud_host directory:

iex -S mix phx.server

Then you can set the log level in the iex terminal

Logger.configure(level: :debug)

As mentioned above, you can replace debug with info, warn, or error.

Use the following command to attach to the Elixir integrated terminal

./bin/wasmcloud_host remote

Then use the Logger module to configure the log level

Logger.configure(level: :debug)

As mentioned above, you can replace debug with info, warn, or error. You are now free to quit out of the console by inputting CTRL+c twice.

Use the docker CLI to exec into your container:

docker exec -it <your_container_id> /opt/app/bin/wasmcloud_host remote

Then use the Logger module to configure the log level

Logger.configure(level: :debug)

As mentioned above, you can replace debug with info, warn, or error. You are now free to quit out of the console by inputting CTRL+c twice.

Rust Capability Providers

Changing the log level for capability providers requires setting the RUST_LOG environment variable.

You can either export the RUST_LOG=<log_level> environment variable in the same terminal that you launch the host, or you can use the integrated Elixir terminal to change the verbosity at runtime. Refer to the steps in the above section to connect to the integrated terminal, and then run the following command to set the environment variable:

System.put_env("RUST_LOG", "debug")

Rust supports log levels of error, warn, info, debug, and trace, and you can replace the second argument in the function above with any of those levels.