Once a plugin process is started, go-plugin will redirect the stdout and
stderr stream through a grpc service and provide those streams to the
client. This is rarely used, as it is prone to failing with races
because those same file descriptors are needed for the initial handshake
and logging setup, but data may be accidentally sent to these
nonetheless.
The usual culprits are stray `fmt.Print` usage where logging was
intended, or the configuration of a logger after the os.Stderr file
descriptor was replaced by go-plugin. These situations are very hard for
provider developers to debug since the data is discarded entirely.
While there may be improvements to be made in the go-plugin package to
configure this behavior, in the meantime we can add a simple monitoring
io.Writer to the streams which will surface th data as warnings in the
logs instead of writing it to `io.Discard`
This is not currently a supported interface, but we plan to release
tool(s) that consume parts of it that are more dependable later,
separately from Terraform CLI itself.
Create a logger that will record any apparent crash output for later
processing.
If the cli command returns with a non-zero exit status, check for any
recorded crashes and add those to the output.
Now that hclog can independently set levels on related loggers, we can
separate the log levels for different subsystems in terraform.
This adds the new environment variables, `TF_LOG_CORE` and
`TF_LOG_PROVIDER`, which each take the same set of log level arguments,
and only applies to logs from that subsystem. This means that setting
`TF_LOG_CORE=level` will not show logs from providers, and
`TF_LOG_PROVIDER=level` will not show logs from core. The behavior of
`TF_LOG` alone does not change.
While it is not necessarily needed since the default is to disable logs,
there is also a new level argument of `off`, which reflects the
associated level in hclog.
Use a separate log sink to always capture trace logs for the panicwrap
handler to write out in a crash log.
This requires creating a log file in the outer process and passing that
path to the child process to log to.
Use a single log writer instance for all std library logging.
Setup the std log writer in the logging package, and remove boilerplate
from test packages.
James Bardin