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From James Peach <jpe...@apache.org>
Subject Re: git commit: Doc: Plugin identity and related logging tags.
Date Fri, 06 Jun 2014 04:11:17 GMT
On Jun 5, 2014, at 6:52 PM, amc@apache.org wrote:

> Repository: trafficserver
> Updated Branches:
>  refs/heads/master caf514b25 -> 13843023a
> 
> 
> Doc: Plugin identity and related logging tags.
> 
> 
> Project: http://git-wip-us.apache.org/repos/asf/trafficserver/repo
> Commit: http://git-wip-us.apache.org/repos/asf/trafficserver/commit/13843023
> Tree: http://git-wip-us.apache.org/repos/asf/trafficserver/tree/13843023
> Diff: http://git-wip-us.apache.org/repos/asf/trafficserver/diff/13843023
> 
> Branch: refs/heads/master
> Commit: 13843023a1eb45f9ee85b5df24a350eafc92db11
> Parents: caf514b
> Author: Alan M. Carroll <amc@network-geographics.com>
> Authored: Thu Jun 5 16:30:10 2014 -0700
> Committer: Alan M. Carroll <amc@network-geographics.com>
> Committed: Thu Jun 5 18:51:49 2014 -0700
> 
> ----------------------------------------------------------------------
> doc/admin/event-logging-formats.en.rst          | 10 ++++
> .../api/TSHttpConnectWithPluginId.en.rst        | 56 ++++++++++++++++++++
> 2 files changed, 66 insertions(+)
> ----------------------------------------------------------------------
> 
> 
> http://git-wip-us.apache.org/repos/asf/trafficserver/blob/13843023/doc/admin/event-logging-formats.en.rst
> ----------------------------------------------------------------------
> diff --git a/doc/admin/event-logging-formats.en.rst b/doc/admin/event-logging-formats.en.rst
> index 751ec35..81557f3 100644
> --- a/doc/admin/event-logging-formats.en.rst
> +++ b/doc/admin/event-logging-formats.en.rst
> @@ -220,6 +220,16 @@ The following list describes Traffic Server custom logging fields.
> ``phr``
>     The proxy hierarchy route; the route Traffic Server used to retrieve
>     the object.
> +    
> +.. _piid:
> +    
> +``piid``
> +   The plugin ID for the transaction. This is set for plugin driven transactions via
:c:func:`TSHttpConnectWithPluginId`.
> +
> +.. _pitag:
> +
> +``pitag``
> +   The plugin tag for the transaction. This is set for plugin driven transactions via
:c:func:`TSHttpConnectWithPluginId`.

Nice!

> 
> ``pqbl``
>     The proxy request transfer length; the body length in Traffic
> 
> http://git-wip-us.apache.org/repos/asf/trafficserver/blob/13843023/doc/reference/api/TSHttpConnectWithPluginId.en.rst
> ----------------------------------------------------------------------
> diff --git a/doc/reference/api/TSHttpConnectWithPluginId.en.rst b/doc/reference/api/TSHttpConnectWithPluginId.en.rst
> new file mode 100644
> index 0000000..2ddc7aa
> --- /dev/null
> +++ b/doc/reference/api/TSHttpConnectWithPluginId.en.rst
> @@ -0,0 +1,56 @@
> +.. Licensed to the Apache Software Foundation (ASF) under one or more
> +   contributor license agreements.  See the NOTICE file distributed
> +   with this work for additional information regarding copyright
> +   ownership.  The ASF licenses this file to you under the Apache
> +   License, Version 2.0 (the "License"); you may not use this file
> +   except in compliance with the License.  You may obtain a copy of
> +   the License at
> +
> +      http://www.apache.org/licenses/LICENSE-2.0
> +
> +   Unless required by applicable law or agreed to in writing, software
> +   distributed under the License is distributed on an "AS IS" BASIS,
> +   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
> +   implied.  See the License for the specific language governing
> +   permissions and limitations under the License.
> +
> +
> +TSHttpConnectWithPluginID
> +=========================
> +
> +Allows the plugin to initiate an http connection. This will tag the HTTP state machine
with extra data that can be accessed by the logging interface. The connection is treated as
an HTTP transaction as if it came from a client.
> +
> +
> +Synopsis
> +--------
> +
> +`#include <ts/ts.h>`
> +
> +.. c:function:: TSVConn TSHttpConnectWithPluginId(sockaddr const *addr, char const*
tag, int64_t id)
> +
> +
> +Description
> +-----------
> +
> +This call attempts to create an HTTP state machine and a virtual connection to that
state machine. This is more efficient than using :c:func:`TSNetConnect` because it avoids
using the operating system stack via the loopback interface.
> +
> +*addr*
> +   This is the network address of the target of the connection. This includes the port
which should be stored in the :c:type:`sockaddr` structure.

The correct syntax for referring to function arguments is :c:arg:`foo`

> +
> +*tag*
> +   This is a tag that is passed through to the HTTP state machine. It must be a persistent
string that has a lifetime longer than the connection. It is accessible via the log field
:ref:`pitag <pitag>`. This is intended as a class or type identifier that is consistent
across all connections for this plugin. In effect, the name of the plugin. This can be ``NULL``.

:data:`NULL`

> +
> +*id*
> +   This is a numeric identifier that is passed through to the HTTP state machine. It
is accessible via the log field :ref:`piid <piid>`. This is intended as a connection
identifier and should be distinct for every call to ``TSHttpConnectWithPluginID``.

:c:func:`TSHttpConnectWithPluginID`

> The easiest mechanism is to define a plugin global value and increment it for each connection.
The value ``0`` is reserved to mean "not set" and can be used as a default if this functionality
is not needed.
> +
> +The virtual connection returned as the ``TSCVonn``

:type:`TSVConn`

> is API equivalent to a network virtual connection both to the plugin and to internal
mechanisms. Data is read and written to the connection (and thence to the target system) by
reading and writing on this virtual connection.
> +
> +.. note:: This function only opens the connection - to drive the transaction an actual
HTTP request must be sent and the HTTP response handled. The transaction is handled as a standard
HTTP transaction and all of the standard configuration options and plugins will operate on
it.
> +
> +The combination of tag and id is intended to enable correlation in log post processing.
The tag identifies the connection as related to the plugin and the id can be used in conjuction
with plugin generated logs to correlate the log records.
> +
> +This should also be useful for debugging by tagging not just the HTTP state machine
but also the plugin's virtual connections (which are of type ``PluginVC``)

PluginVC is an internal type not visible in the API. I think it's better to omit any mention
of it here.

> with data that be correlated with the source plugin.
> +
> +.. topic:: Example

Examples
========


> +
> +   The SPDY plugin uses this to correlate client sessions with SPDY streams. Each client
connection is assigned a distinct numeric identifier. This is passed as the *id* to ``TSHttpConnectWithPluginId``.

Well, there is not SPDY plugin, and there is no code that actually uses TSHttpConnectWithPluginId,
so maybe this is not the best example. The "literalinclude" directive is useful for pasting
actual code example in here, see TSHttpIsInternalRequest for an example.

> The *tag* is selected to be the NPN string for the client session protocol, e.g. "spdy/3"
or "spdy/3.1". Log post processing can then count the number of connections for the various
supported protocols and the number of SPDY virtual streams for each real client connection
to Traffic Server.

We invariably close with a See also section, which should at least refer to :manpage:`TSAPI(3ts)`

J


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