Mojo Log service and a thread-safe client library.

mojo/services/log/interfaces/log.mojom

Index: mojo/services/log/interfaces/log.mojom
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+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+module mojo.log;
+
+import "log/interfaces/entry.mojom";
+
+// A log interface provides a way to do log source-code-level message entries. 

[viettrungluu, 2015/11/20 23:21:51]

I'd just say:

"An interface for logging, e.g., to the system log service."

(The source of the log messages can be anything, so saying anything about
"source code" is deceptive.)

[vardhan, 2015/12/02 00:06:14]

Done.

+// For example, this could be log messages generated from calling MOJO_LOG() in
+// C++.
+// TODO(vardhan):  How do we "globally silence" log entries issued by many

[viettrungluu, 2015/11/20 23:21:51]

What do you mean "silence"?

[vardhan, 2015/12/02 00:06:14]

(discussed offline)

This TODO is basically trying to address the need to control whatever is
displaying log messages to only display ERROR logs msgs, for example.  But this
control should not be related to this Log interface.

+// consumers of this interface?  Should |Log| provide controls for log levels?

[viettrungluu, 2015/11/20 23:21:51]

The answer to your second question is "no". In particular, what's the point?

If the client doesn't want the log service to do anything with a message, then
it can simply not send it.

[vardhan, 2015/12/02 00:06:13]

(discussed offline; see above)

+// or should clients register a "LogClientController" with this interface, and

[viettrungluu, 2015/11/20 23:21:51]

The answer to your third question is "maybe".

But the only utility of it would be to reduce the number of log messages
actually sent. The log service is free to filter/ignore/display log messages as
it desires, regardless of what the client thinks.

[vardhan, 2015/12/02 00:06:13]

(discussed offline; see above)

+// |Log| will control their log levels?
+[ServiceName="mojo::log::Log"]
+interface Log {
+  AddEntry(Entry entry);
+};