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Here is the second and updated version after Yannick comments.
- v0.2: 07/08/0212
* Change lttng_create_session_addr to lttng_create_session_url
* Describe URL string format
* Add set_consumer_url examples
* Add the HOP option to the set_consumer_url function
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
* Change lttng_create_session_addr to lttng_create_session_url
* Describe URL string format
* Add set_consumer_url examples
* Add the HOP option to the set_consumer_url function
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 change deprecates
the old API function and adds a new one.
Current and will be deprecated:
--> lttng_create_session(const char *name, const char *path);
Proposed:
--> lttng_create_session_url(const char *name, const char *url,
int
enable_consumer);
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
The PATH section is the destination path on the _remote_ host where the trace
data will be written. For example:
* net://hostname/foo/bar
Results in writing the trace data in $USER/lttng-traces/foo/bar where
"$USER/lttng-traces" is the default output directory set by the lttng-relayd.
It is possible to change this option.
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]
Finally, the enable_consumer option will disable the use of the consumer for
the tracing session. This will be useful with the upcoming snapshot feature.
The motivation behind this flag is to offer the same options as the
enable-consumer command where you can only set the URI for the consumer and not
enable it.
Note that the hop feature CAN NOT be used with this function call since only
one URL can be define here.
[*] Consumer:
The 2.2+ roadmap will implement the concept of hop for network streaming. This
hop is basically a proxy daemon which will relay the information to a final
destination. It is possible to define as many hops as you want but once the
final destination is set, it's not possible anymore.
Current and will be deprecated:
--> lttng_set_consumer_uri(...)
Proposed:
--> lttng_set_consumer_url(struct lttng_handle *handle,
const char *url, enum lttng_url_type type);
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.
The _type_ argument is the URL type where the possibilities are:
enum lttng_url_type {
LTTNG_URL_DST, /* Final destination */
LTTNG_URL_HOP, /* HOP destination */
};
Example:
set_consumer_url(handle, "net://42.42.42.2", LTTNG_URL_HOP);
set_consumer_url(handle, "net://42.42.42.3", LTTNG_URL_HOP);
set_consumer_url(handle, "net://42.42.42.42", LTTNG_URL_DST);
With all this, the lttng_uri data structure will not be exposed to the public
API and the user command line interface.
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