agent: Log ttrpc messages

The `ttrpc` crate uses the `log` crate for logging. But the agent uses
the `slog` crate. This means that currently, all `ttrpc` log messages
are being discarded.

Use the `slog-stdlog` create to redirect `log` crate logging calls into
`slog` so they are visible in the agents log output.

Fixes: #978.

Signed-off-by: James O. D. Hunt <james.o.hunt@intel.com>

src/agent/Cargo.lock

@@ -392,6 +392,7 @@ dependencies = [
  "signal-hook",
  "slog",
  "slog-scope",
+ "slog-stdlog",
  "tempfile",
  "ttrpc",
 ]
@@ -1077,6 +1078,17 @@ dependencies = [
  "slog",
 ]
 
+[[package]]
+name = "slog-stdlog"
+version = "4.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8228ab7302adbf4fcb37e66f3cda78003feb521e7fd9e3847ec117a7784d0f5a"
+dependencies = [
+ "log",
+ "slog",
+ "slog-scope",
+]
+
 [[package]]
 name = "smallvec"
 version = "1.4.2"

src/agent/Cargo.toml

@@ -27,6 +27,10 @@ regex = "1"
 #   (by stopping the compiler from removing log calls).
 slog = { version = "2.5.2", features = ["dynamic-keys", "max_level_trace", "release_max_level_info"] }
 slog-scope = "4.1.2"
+
+# Redirect ttrpc log calls
+slog-stdlog = "4.0.0"
+
 # for testing
 tempfile = "3.1.0"
 prometheus = { version = "0.9.0", features = ["process"] }

src/agent/src/main.rs

@@ -198,6 +198,9 @@ fn main() -> Result<()> {
     // which is required to satisfy the the lifetime constraints of the auto-generated gRPC code.
     let _guard = slog_scope::set_global_logger(logger.new(o!("subsystem" => "rpc")));
 
+    // Redirect ttrpc log calls to slog
+    let _log_guard = slog_stdlog::init()?;
+
     start_sandbox(&logger, &config, init_mode)?;
 
     let _ = log_handle.join();