Callbacks on receive and update FD

[lttng-tools.git] / include / lttng / lttng-kconsumerd.h

/*
 * Copyright (C) 2011 - Julien Desfossez <julien.desfossez@polymtl.ca>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; only version 2
 * of the License.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

#ifndef _LTTNG_KCONSUMERD_H
#define _LTTNG_KCONSUMERD_H

#include <limits.h>
#include <lttng/lttng.h>

/*
 * When the receiving thread dies, we need to have a way to make the polling
 * thread exit eventually. If all FDs hang up (normal case when the
 * ltt-sessiond stops), we can exit cleanly, but if there is a problem and for
 * whatever reason some FDs remain open, the consumer should still exit
 * eventually.
 *
 * If the timeout is reached, it means that during this period no events
 * occurred on the FDs so we need to force an exit. This case should not happen
 * but it is a safety to ensure we won't block the consumer indefinitely.
 *
 * The value of 2 seconds is an arbitrary choice.
 */
#define LTTNG_KCONSUMERD_POLL_GRACE_PERIOD 2000

/* Commands for kconsumerd */
enum lttng_kconsumerd_command {
	ADD_STREAM,
	UPDATE_STREAM, /* pause, delete, active depending on fd state */
	STOP, /* inform the kconsumerd to quit when all fd has hang up */
};

/* State of each fd in consumerd */
enum lttng_kconsumerd_fd_state {
	ACTIVE_FD,
	PAUSE_FD,
	DELETE_FD,
};

struct lttng_kconsumerd_fd_list {
	struct cds_list_head head;
};

/*
 * Internal representation of the FDs, sessiond_fd is used to identify uniquely
 * a fd
 */
struct lttng_kconsumerd_fd {
	struct cds_list_head list;
	int sessiond_fd; /* used to identify uniquely a fd with sessiond */
	int consumerd_fd; /* fd to consume */
	int out_fd; /* output file to write the data */
	off_t out_fd_offset; /* write position in the output file descriptor */
	char path_name[PATH_MAX]; /* tracefile name */
	enum lttng_kconsumerd_fd_state state;
	unsigned long max_sb_size; /* the subbuffer size for this channel */
	void *mmap_base;
	size_t mmap_len;
	enum lttng_event_output output; /* splice or mmap */
};

/*
 * Kernel consumer local data to the program.
 */
struct lttng_kconsumerd_local_data {
	/* function to call when data is available on a buffer */
	int (*on_buffer_ready)(struct lttng_kconsumerd_fd *kconsumerd_fd);
	/*
	 * function to call when we receive a new fd, it receives a
	 * newly allocated kconsumerd_fd, depending on the return code
	 * of this function, the new FD will be handled by the
	 * application or the library.
	 *
	 * Returns:
	 *    > 0 (success, FD is kept by application)
	 *   == 0 (success, FD is left to library)
	 *    < 0 (error)
	 */
	int (*on_recv_fd)(struct lttng_kconsumerd_fd *kconsumerd_fd);
	/*
	 * function to call when a FD is getting updated by the session
	 * daemon, this function receives the FD as seen by the session
	 * daemon (sessiond_fd) and the new state, depending on the
	 * return code of this function the update of state for the FD
	 * is handled by the application or the library.
	 *
	 * Returns:
	 *    > 0 (success, FD is kept by application)
	 *   == 0 (success, FD is left to library)
	 *    < 0 (error)
	 */
	int (*on_update_fd)(int sessiond_fd, uint32_t state);
	/* socket to communicate errors with sessiond */
	int kconsumerd_error_socket;
	/* socket to exchange commands with sessiond */
	char *kconsumerd_command_sock_path;
	/* communication with splice */
	int kconsumerd_thread_pipe[2];
	/* pipe to wake the poll thread when necessary */
	int kconsumerd_poll_pipe[2];
	/* to let the signal handler wake up the fd receiver thread */
	int kconsumerd_should_quit[2];
};

/*
 * Initialise the necessary environnement:
 * - create a new context
 * - create the poll_pipe
 * - create the should_quit pipe (for signal handler)
 * - create the thread pipe (for splice)
 *
 * Takes the function pointers to the on_buffer_ready, on_recv_fd, and
 * on_update_fd callbacks.
 *
 * Returns a pointer to the new context or NULL on error.
 */
extern struct lttng_kconsumerd_local_data *lttng_kconsumerd_create(
		int (*buffer_ready)(struct lttng_kconsumerd_fd *kconsumerd_fd),
		int (*recv_fd)(struct lttng_kconsumerd_fd *kconsumerd_fd),
		int (*update_fd)(int sessiond_fd, uint32_t state));

/*
 * Close all fds associated with the instance and free the context.
 */
extern void lttng_kconsumerd_destroy(struct lttng_kconsumerd_local_data *ctx);

/*
 * Mmap the ring buffer, read it and write the data to the tracefile.
 *
 * Returns the number of bytes written.
 */
extern int lttng_kconsumerd_on_read_subbuffer_mmap(
		struct lttng_kconsumerd_local_data *ctx,
		struct lttng_kconsumerd_fd *kconsumerd_fd, unsigned long len);

/*
 * Splice the data from the ring buffer to the tracefile.
 *
 * Returns the number of bytes spliced.
 */
extern int lttng_kconsumerd_on_read_subbuffer_splice(
		struct lttng_kconsumerd_local_data *ctx,
		struct lttng_kconsumerd_fd *kconsumerd_fd, unsigned long len);

/*
 * Take a snapshot for a specific fd
 *
 * Returns 0 on success, < 0 on error
 */
int lttng_kconsumerd_take_snapshot(struct lttng_kconsumerd_local_data *ctx,
        struct lttng_kconsumerd_fd *kconsumerd_fd);

/*
 * Get the produced position
 *
 * Returns 0 on success, < 0 on error
 */
int lttng_kconsumerd_get_produced_snapshot(
        struct lttng_kconsumerd_local_data *ctx,
        struct lttng_kconsumerd_fd *kconsumerd_fd,
        unsigned long *pos);

/*
 * Send return code to session daemon.
 *
 * Returns the return code of sendmsg : the number of bytes transmitted or -1
 * on error.
 */
extern int lttng_kconsumerd_send_error(
		struct lttng_kconsumerd_local_data *ctx, int cmd);

/*
 * Poll on the should_quit pipe and the command socket return -1 on error and
 * should exit, 0 if data is available on the command socket.
 */
extern int lttng_kconsumerd_poll_socket(struct pollfd *kconsumerd_sockpoll);

/*
 * This thread polls the fds in the ltt_fd_list to consume the data and write
 * it to tracefile if necessary.
 */
extern void *lttng_kconsumerd_thread_poll_fds(void *data);

/*
 * This thread listens on the consumerd socket and receives the file
 * descriptors from ltt-sessiond.
 */
extern void *lttng_kconsumerd_thread_receive_fds(void *data);

/*
 * Called from signal handler to ensure a clean exit.
 */
extern void lttng_kconsumerd_should_exit(
		struct lttng_kconsumerd_local_data *ctx);

/*
 * Cleanup the daemon's socket on exit.
 */
extern void lttng_kconsumerd_cleanup(void);

/*
 * Set the error socket for communication with a session daemon.
 */
extern void lttng_kconsumerd_set_error_sock(
		struct lttng_kconsumerd_local_data *ctx, int sock);

/*
 * Set the command socket path for communication with a session daemon.
 */
extern void lttng_kconsumerd_set_command_sock_path(
		struct lttng_kconsumerd_local_data *ctx, char *sock);

#endif /* _LTTNG_KCONSUMERD_H */