On Mar 27, 2012 4:17 PM, david@lang.hm wrote:
On Tue, 27 Mar 2012, William Heinbockel wrote:
On Tue, Mar 27, 2012 at 3:18 PM, david@lang.hm wrote:
I posted some of this at the bottom of a long message yesterday that
nobody
replied to, so I broke it out to a separate thread
The traditional syslog interface has been a write-only interface, with
the
only feedback being that the write could block.
With the new formats and new syslog replacement library, does there
need to
be some rethinking of this interface?
JSON can be pushed through the traditional syslog interface with no
changes
(which is one of the attractions of using JSON), but when we support additional formats, especially ones with type information, we need to
have a
way to tell what format to use when writing the log.
I don't think this is right approach. The end goal is to support structured log messages. The first step is to introduce the capability to sent structured events via existing capabilities (read: JSON over Syslog)
The next steps would be the ELAPI/selog API that would introduce a new logging interface, probably maintaining at least minimal compatibility with the syslog daemon (not the syslog API or syslog protocol). This would allow us to define and support more feature-rich log protocols and other features.
But does this mean that unless applications are re-written, they will
never send structured logs at all?
There are only two ways to have applications log with structured data: 1. Update the app to send name-value pairs 2. Use something like patterndb to convert the unstructured data
If the app wants to leverage structured data, they will already have to make some updates. We just offer them a choice to either use the minimal umberlog interface or convert to a more full featured one.
I see there being value in having the cee-syslog replacement library that
sends the metadata structured around the existing unstructured log data. It's not as good as a full structured log, but it's a lot better than the existing situation.
This could be done by configuring things in the openlog call, but that requries changes to every application.
I think it would be better to have the serialization format be
determined
automatically by the library if possible.
One way to do this is to have a handshake.
When a app opens /dev/log, the syslog server sends a capabilities
message.
The client can ignore this message and send traditional formatted syslog data to the server
Or, the client can read the capabilities message and then pick which supported format (potentially with compression options) to use to send
data
to the server.
This approach lets the format be anything that the library supports,
under
the control of the sysadmin of the system (by configuring what
capabilities
the syslog daemon advertises) without the application programmer
needing to
know anything about these formats.
thoughts?
Let's not get ahead of ourselves and try to shoehorn a solution into existing/legacy capabilities. We should approach this as a two-pronged solution:
- Backwards-compatible structured log implementation that works with
the syslog API and syslog protocol (this is umberlog). This should be as minimal and compatible as possible. I commend Gergely on his implementation
- Implement a new event API frontend and improved logging
capabilities. This should be able to work with syslogd, but does not have any requirements to be able to work with the existing syslog API, syslog protocol, /dev/log, etc.
Adding a new application API to generate more structured logs is a good
idea. But why do we need to create a completely new interface between the logging library and syslog instead of extending the existing interface?
You don't know what you are going to break and you restrict yourself to the limitations of the current interface. It is not that I am against it, just if we want to improve it it might be best to redo it entirely.
Also, remember that there is more than just syslog and user apps as potential customers. There is also the kernel, klogd, and auditd.
William Heinbockel