LTTng address API proposal v3

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After a discussion with Mathieu and Yannick, here is some big changes.

I hope I did not forget anything important.

Cheers!
David
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RFC - LTTng address API proposal

Author: David Goulet <[email protected]>

Contributors:
* Mathieu Desnoyers <[email protected]>
* Yannick Brosseau <[email protected]>

Version:
- v0.1: 31/07/2012
* Initial proposal
- v0.2: 07/08/0212
* Remove lttng_create_session_addr
* Describe URL string format
* Add set_consumer_url examples

Introduction
-----------------

This document proposes the use of string URLs to the command line interface and API which will deprecate a function and propose new ones.

The purpose of this proposal is to support network streaming using URL string format that you can find in proposal doc/proposals/0003-network.consumer.txt, remove the lttng_uri structure from the API and integrate the URL string to the API.

API
-----------------

In order NOT to expose the new lttng_uri structure used to identify trace location for lttng consumer, the public API will only use string address where it will be converted in a lttng_uri and sent to the session daemon.

[*] Create session:

With the introduction of the enable-consumer command used for network streaming, the create session command has been modified so the user could define a consumer location either on the network or local with the command.

This does NOT change the current API call but rather simply rename _path_ to _url_ and how it is used in the lttng-ctl library.

Call changed from:
--> lttng_create_session(const char *name, const char *path);

To:
--> lttng_create_session(const char *name, const char *url);

The _name_ argument is the session name and _url_ is a string representing the URL specified by the user which is define like so:

PROTO://[HOSTNAME|IP][:PORT][/PATH]

The proto supported at this stage are (6 means IPv6):

* net, net6, tcp, tcp6, file

If the proto is NOT recognized, the string is considered to be a simple path on the local filesystem.

The PATH section is the destination path on the _remote_ host where the trace data will be written with the <target_hostname> append after.

The relayd
defines a default location

if none is given using the -o, --output option. This default is at:

* $USER/lttng-traces

For example, this URL results in writing the trace data in "$USER/lttng-traces/<target_hostname>/foo/bar".

* net://hostname/foo/bar

The PATH part can not be bigger than PATH_MAX (define in limits.h) which is 4096 bytes at the time of this proposal. Moreover, "../" is ignored and removed. For instance, using "net://localhost/../../" will set the path to the default one.

The <net(6)> protocol has a special case where the user can input two ports respectively being the control and data port.

* net://[HOSTNAME|IP][:CTRL_PORT][:DATA_PORT][/PATH]

If _url_ is not NULL, the lttng_create_session will use two API calls.

1) lttng_set_consumer_url(handle, url);
2) lttng_enable_consumer(handle);

If _url_ is NULL, then NO consumer is created for this tracing session and subsequent calls are needed to set up a consumer (i.e lttng_enable_consumer and lttng_set_consumer_url).

[*] Consumer:

This call is simply renamed.

From:
--> lttng_set_consumer_uri(...)

To:
--> lttng_set_consumer_url(struct lttng_handle *handle,

				const char *url);

For both functions (consumer and create), the _url_ will be parsed into a lttng_uri in the liblttng-ctl and sent to the session daemon.

Example:

	lttng_set_consumer_url(handle, "net://42.42.42.2");

With all this, the lttng_uri data structure will NOT be exposed to the public API and the user command line interface.

_______________________________________________
lttng-dev mailing list
[email protected]
http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev

* David Goulet ([email protected]) wrote: After a discussion with Mathieu and Yannick, here is some big changes.

I hope I did not forget anything important.

Cheers! David

Quoted 54 lines

RFC - LTTng address API proposal

Author: David Goulet <[email protected]>

Contributors: * Mathieu Desnoyers <[email protected]> * Yannick Brosseau <[email protected]>

Version: - v0.1: 31/07/2012 * Initial proposal - v0.2:
07/08/0212 * Remove lttng_create_session_addr * Describe URL string format * Add set_consumer_url examples

Introduction -----------------

This document proposes the use of string URLs to the command line interface and API which will deprecate a function and propose new ones.

The purpose of this proposal is to support network streaming using URL string format that you can find in proposal doc/proposals/0003-network.consumer.txt, remove the lttng_uri structure from the API and integrate the URL string to the API.

API -----------------

In order NOT to expose the new lttng_uri structure used to identify trace location for lttng consumer, the public API will only use string address where it will be converted in a lttng_uri and sent to the session daemon.

[*] Create session:

With the introduction of the enable-consumer command used for network streaming, the create session command has been modified so the user could define a consumer location either on the network or local with the command.

This does NOT change the current API call but rather simply rename _path_ to _url_ and how it is used in the lttng-ctl library.

Call changed from: --> lttng_create_session(const char *name, const char *path);

To: --> lttng_create_session(const char *name, const char *url);

The _name_ argument is the session name and _url_ is a string representing the URL specified by the user which is define like so:

PROTO://[HOSTNAME|IP][:PORT][/PATH]

The proto supported at this stage are (6 means IPv6):

Quoted 4 lines

* net, net6, tcp, tcp6, file

If the proto is NOT recognized, the string is considered to be a simple path on the local filesystem.

you could specify that it is a path relative to the process CWD (unless it starts with a /).

Quoted 5 lines

The PATH section is the destination path on the _remote_ host where the trace data will be written with the <target_hostname> append after.

The last sentence is not clear (after reading it 2-3 times, it's still not obvious what it explains).

Simply saying that the PATH is relative to a subdirectory "hostname", under the remote relayd "virtual" root directory, might be enough.

Quoted 2 lines

The relayd defines a default location

... for its virtual root directory...

Quoted 19 lines

if none is given using the -o, --output option. This default is at:

* $USER/lttng-traces

For example, this URL results in writing the trace data in "$USER/lttng-traces/<target_hostname>/foo/bar".

* net://hostname/foo/bar

The PATH part can not be bigger than PATH_MAX (define in limits.h) which is 4096 bytes at the time of this proposal. Moreover, "../" is ignored and removed. For instance, using "net://localhost/../../" will set the path to the default one.

The <net(6)> protocol has a special case where the user can input two ports respectively being the control and data port.

Quoted 4 lines

* net://[HOSTNAME|IP][:CTRL_PORT][:DATA_PORT][/PATH]

If _url_ is not NULL, the lttng_create_session will use two API calls.

If _url_ is not NULL, in addition to creating the session, the lttng_create_session will use the two following API calls:

Quoted 27 lines

1) lttng_set_consumer_url(handle, url); 2)
lttng_enable_consumer(handle);

If _url_ is NULL, then NO consumer is created for this tracing session and subsequent calls are needed to set up a consumer (i.e lttng_enable_consumer and lttng_set_consumer_url).

[*] Consumer:

This call is simply renamed.

From: --> lttng_set_consumer_uri(...)

To: --> lttng_set_consumer_url(struct lttng_handle *handle, const char *url);

For both functions (consumer and create), the _url_ will be parsed into a lttng_uri in the liblttng-ctl and sent to the session daemon.

Example:

lttng_set_consumer_url(handle, "net://42.42.42.2");

Quoted 2 lines

With all this, the lttng_uri data structure will NOT be exposed to the public API and the user command line interface.

The rest looks good!

Thanks,

Mathieu

Quoted 3 lines

_______________________________________________ lttng-dev mailing list [email protected]
http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev

After a discussion with Mathieu and Yannick, here is some big changes.

I hope I did not forget anything important.

Cheers! David

This body part will be downloaded on demand.

ADDENDUM:

The set_consumer_url() call needs an extra arguments since we can both set the CONTROL or STREAM path using this call (the stream type).

So, I would like to propose a change:

From:
lttng_set_consumer_url(struct lttng_handle *handle, const char *url);

To:
lttng_set_consumer_url(struct lttng_handle *handle, const char *url, enum lttng_url_stream_type stype);

With:
enum lttng_url_stream_type {
LTTNG_STREAM_CONTROL,
LTTNG_STREAM_DATA,
LTTNG_STREAM_ALL,
};

An _url_ argument with "net://localhost" for instance implies LTTNG_STREAM_ALL as a type however with "tcp://", we have to specify it.

The second possible idea is to add specialize calls like:

set_consumer_control_url()
set_consumer_stream_url()

Quoted 20 lines

ADDENDUM:

The set_consumer_url() call needs an extra arguments since we can both set the CONTROL or STREAM path using this call (the stream type).

So, I would like to propose a change:

From: lttng_set_consumer_url(struct lttng_handle *handle, const char *url);

To: lttng_set_consumer_url(struct lttng_handle *handle, const char *url, enum lttng_url_stream_type stype);

With: enum lttng_url_stream_type { LTTNG_STREAM_CONTROL, LTTNG_STREAM_DATA, LTTNG_STREAM_ALL, };

An _url_ argument with "net://localhost" for instance implies LTTNG_STREAM_ALL as a type however with "tcp://", we have to specify it.

Quoted 3 lines

The second possible idea is to add specialize calls like:

set_consumer_control_url() set_consumer_stream_url()

Just brainstorming: lttng_set_consumer_url(struct lttng_handle *handle, const char *control_url, const char *data_url)

Yannick

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