Fix: consumerd: slow metadata push slows down application registration

[lttng-tools.git] / src / common / consumer / consumer.h

/*
 * Copyright (C) 2011 EfficiOS Inc.
 * Copyright (C) 2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 * Copyright (C) 2012 David Goulet <dgoulet@efficios.com>
 * Copyright (C) 2018 Jérémie Galarneau <jeremie.galarneau@efficios.com>
 *
 * SPDX-License-Identifier: GPL-2.0-only
 *
 */

#ifndef LIB_CONSUMER_H
#define LIB_CONSUMER_H

#include <limits.h>
#include <poll.h>
#include <stdint.h>
#include <unistd.h>
#include <urcu/list.h>

#include <lttng/lttng.h>

#include <common/hashtable/hashtable.h>
#include <common/compat/fcntl.h>
#include <common/uuid.h>
#include <common/sessiond-comm/sessiond-comm.h>
#include <common/pipe.h>
#include <common/index/ctf-index.h>
#include <common/trace-chunk-registry.h>
#include <common/credentials.h>
#include <common/buffer-view.h>
#include <common/dynamic-array.h>
#include <common/waiter.h>

struct lttng_consumer_local_data;

/* Commands for consumer */
enum lttng_consumer_command {
        LTTNG_CONSUMER_ADD_CHANNEL,
        LTTNG_CONSUMER_ADD_STREAM,
        /* pause, delete, active depending on fd state */
        LTTNG_CONSUMER_UPDATE_STREAM,
        /* inform the consumer to quit when all fd has hang up */
        LTTNG_CONSUMER_STOP,    /* deprecated */
        LTTNG_CONSUMER_ADD_RELAYD_SOCKET,
        /* Inform the consumer to kill a specific relayd connection */
        LTTNG_CONSUMER_DESTROY_RELAYD,
        /* Return to the sessiond if there is data pending for a session */
        LTTNG_CONSUMER_DATA_PENDING,
        /* Consumer creates a channel and returns it to sessiond. */
        LTTNG_CONSUMER_ASK_CHANNEL_CREATION,
        LTTNG_CONSUMER_GET_CHANNEL,
        LTTNG_CONSUMER_DESTROY_CHANNEL,
        LTTNG_CONSUMER_PUSH_METADATA,
        LTTNG_CONSUMER_CLOSE_METADATA,
        LTTNG_CONSUMER_SETUP_METADATA,
        LTTNG_CONSUMER_FLUSH_CHANNEL,
        LTTNG_CONSUMER_SNAPSHOT_CHANNEL,
        LTTNG_CONSUMER_SNAPSHOT_METADATA,
        LTTNG_CONSUMER_STREAMS_SENT,
        LTTNG_CONSUMER_DISCARDED_EVENTS,
        LTTNG_CONSUMER_LOST_PACKETS,
        LTTNG_CONSUMER_CLEAR_QUIESCENT_CHANNEL,
        LTTNG_CONSUMER_SET_CHANNEL_MONITOR_PIPE,
        LTTNG_CONSUMER_ROTATE_CHANNEL,
        LTTNG_CONSUMER_INIT,
        LTTNG_CONSUMER_CREATE_TRACE_CHUNK,
        LTTNG_CONSUMER_CLOSE_TRACE_CHUNK,
        LTTNG_CONSUMER_TRACE_CHUNK_EXISTS,
        LTTNG_CONSUMER_CLEAR_CHANNEL,
        LTTNG_CONSUMER_OPEN_CHANNEL_PACKETS,
};

enum lttng_consumer_type {
        LTTNG_CONSUMER_UNKNOWN = 0,
        LTTNG_CONSUMER_KERNEL,
        LTTNG_CONSUMER64_UST,
        LTTNG_CONSUMER32_UST,
};

enum consumer_endpoint_status {
        CONSUMER_ENDPOINT_ACTIVE,
        CONSUMER_ENDPOINT_INACTIVE,
};

enum consumer_channel_output {
        CONSUMER_CHANNEL_MMAP   = 0,
        CONSUMER_CHANNEL_SPLICE = 1,
};

enum consumer_channel_type {
        CONSUMER_CHANNEL_TYPE_METADATA  = 0,
        CONSUMER_CHANNEL_TYPE_DATA      = 1,
};

enum sync_metadata_status {
        SYNC_METADATA_STATUS_NEW_DATA,
        SYNC_METADATA_STATUS_NO_DATA,
        SYNC_METADATA_STATUS_ERROR,
};

extern struct lttng_consumer_global_data the_consumer_data;

struct stream_list {
        struct cds_list_head head;
        unsigned int count;
};

/* Stub. */
struct consumer_metadata_cache;

struct lttng_consumer_channel {
        /* Is the channel published in the channel hash tables? */
        bool is_published;
        /*
         * Was the channel deleted (logically) and waiting to be reclaimed?
         * If this flag is set, no modification that is not cleaned-up by the
         * RCU reclamation callback should be made
         */
        bool is_deleted;
        /* HT node used for consumer_data.channel_ht */
        struct lttng_ht_node_u64 node;
        /* HT node used for consumer_data.channels_by_session_id_ht */
        struct lttng_ht_node_u64 channels_by_session_id_ht_node;
        /* Indexed key. Incremented value in the consumer. */
        uint64_t key;
        /* Number of streams referencing this channel */
        int refcount;
        /* Tracing session id on the session daemon side. */
        uint64_t session_id;
        /* Current trace chunk of the session in which this channel exists. */
        struct lttng_trace_chunk *trace_chunk;
        /*
         * Session id when requesting metadata to the session daemon for
         * a session with per-PID buffers.
         */
        uint64_t session_id_per_pid;
        /*
         * In the case of local streams, this field contains the channel's
         * output path; a path relative to the session's output path.
         *   e.g. ust/uid/1000/64-bit
         *
         * In the case of remote streams, the contents of this field depends
         * on the version of the relay daemon peer. For 2.11+ peers, the
         * contents are the same as in the local case. However, for legacy
         * peers, this contains a path of the form:
         *   /hostname/session_path/ust/uid/1000/64-bit
         */
        char pathname[PATH_MAX];
        /* Channel name. */
        char name[LTTNG_SYMBOL_NAME_LEN];
        /* Relayd id of the channel. -1ULL if it does not apply. */
        uint64_t relayd_id;
        /*
         * Number of streams NOT initialized yet. This is used in order to not
         * delete this channel if streams are getting initialized.
         */
        unsigned int nb_init_stream_left;
        /* Output type (mmap or splice). */
        enum consumer_channel_output output;
        /* Channel type for stream */
        enum consumer_channel_type type;

        /* For UST */
        uid_t ust_app_uid;      /* Application UID. */
        struct lttng_ust_ctl_consumer_channel *uchan;
        unsigned char uuid[LTTNG_UUID_STR_LEN];
        /*
         * Temporary stream list used to store the streams once created and waiting
         * to be sent to the session daemon by receiving the
         * LTTNG_CONSUMER_GET_CHANNEL.
         */
        struct stream_list streams;

        /*
         * Set if the channel is metadata. We keep a reference to the stream
         * because we have to flush data once pushed by the session daemon. For a
         * regular channel, this is always set to NULL.
         */
        struct lttng_consumer_stream *metadata_stream;

        /* for UST */
        int wait_fd;
        /* Node within channel thread ht */
        struct lttng_ht_node_u64 wait_fd_node;

        /* Metadata cache is metadata channel */
        struct consumer_metadata_cache *metadata_cache;

        /*
         * Wait queue awaiting updates to metadata stream's flushed position.
         */
        struct lttng_wait_queue metadata_pushed_wait_queue;

        /* For UST metadata periodical flush */
        int switch_timer_enabled;
        timer_t switch_timer;
        int switch_timer_error;

        /* For the live mode */
        int live_timer_enabled;
        timer_t live_timer;
        int live_timer_error;
        /* Channel is part of a live session ? */
        bool is_live;

        /* For channel monitoring timer. */
        int monitor_timer_enabled;
        timer_t monitor_timer;

        /* On-disk circular buffer */
        uint64_t tracefile_size;
        uint64_t tracefile_count;
        /*
         * Monitor or not the streams of this channel meaning this indicates if the
         * streams should be sent to the data/metadata thread or added to the no
         * monitor list of the channel.
         */
        unsigned int monitor;

        /*
         * Channel lock.
         *
         * This lock protects against concurrent update of channel.
         *
         * This is nested INSIDE the consumer data lock.
         * This is nested OUTSIDE the channel timer lock.
         * This is nested OUTSIDE the metadata cache lock.
         * This is nested OUTSIDE stream lock.
         * This is nested OUTSIDE consumer_relayd_sock_pair lock.
         */
        pthread_mutex_t lock;

        /*
         * Channel teardown lock.
         *
         * This lock protect against teardown of channel. It is _never_
         * taken by the timer handler.
         *
         * This is nested INSIDE the consumer data lock.
         * This is nested INSIDE the channel lock.
         * This is nested OUTSIDE the metadata cache lock.
         * This is nested OUTSIDE stream lock.
         * This is nested OUTSIDE consumer_relayd_sock_pair lock.
         */
        pthread_mutex_t timer_lock;

        /* Timer value in usec for live streaming. */
        unsigned int live_timer_interval;

        int *stream_fds;
        int nr_stream_fds;
        char root_shm_path[PATH_MAX];
        char shm_path[PATH_MAX];
        /* Only set for UST channels. */
        LTTNG_OPTIONAL(struct lttng_credentials) buffer_credentials;
        /* Total number of discarded events for that channel. */
        uint64_t discarded_events;
        /* Total number of missed packets due to overwriting (overwrite). */
        uint64_t lost_packets;

        bool streams_sent_to_relayd;
};

struct stream_subbuffer {
        union {
                /*
                 * CONSUMER_CHANNEL_SPLICE
                 * No ownership assumed.
                 */
                int fd;
                /* CONSUMER_CHANNEL_MMAP */
                struct lttng_buffer_view buffer;
        } buffer;
        union {
                /*
                 * Common members are fine to access through either
                 * union entries (as per C11, Common Initial Sequence).
                 */
                struct {
                        unsigned long subbuf_size;
                        unsigned long padded_subbuf_size;
                        uint64_t version;
                        /*
                         * Left unset when unsupported.
                         *
                         * Indicates that this is the last sub-buffer of
                         * a series of sub-buffer that makes-up a coherent
                         * (parseable) unit of metadata.
                         */
                        LTTNG_OPTIONAL(bool) coherent;
                } metadata;
                struct {
                        unsigned long subbuf_size;
                        unsigned long padded_subbuf_size;
                        uint64_t packet_size;
                        uint64_t content_size;
                        uint64_t timestamp_begin;
                        uint64_t timestamp_end;
                        uint64_t events_discarded;
                        /* Left unset when unsupported. */
                        LTTNG_OPTIONAL(uint64_t) sequence_number;
                        uint64_t stream_id;
                        /* Left unset when unsupported. */
                        LTTNG_OPTIONAL(uint64_t) stream_instance_id;
                } data;
        } info;
};

enum get_next_subbuffer_status {
        GET_NEXT_SUBBUFFER_STATUS_OK,
        GET_NEXT_SUBBUFFER_STATUS_NO_DATA,
        GET_NEXT_SUBBUFFER_STATUS_ERROR,
};

/*
 * Perform any operation required to acknowledge
 * the wake-up of a consumer stream (e.g. consume a byte on a wake-up pipe).
 *
 * Stream and channel locks are acquired during this call.
 */
typedef int (*on_wake_up_cb)(struct lttng_consumer_stream *);

/*
 * Perform any operation required before a consumer stream is put
 * to sleep before awaiting a data availability notification.
 *
 * Stream and channel locks are acquired during this call.
 */
typedef int (*on_sleep_cb)(struct lttng_consumer_stream *,
                struct lttng_consumer_local_data *);

/*
 * Acquire the subbuffer at the current 'consumed' position.
 *
 * Stream and channel locks are acquired during this call.
 */
typedef enum get_next_subbuffer_status (*get_next_subbuffer_cb)(
                struct lttng_consumer_stream *, struct stream_subbuffer *);

/*
 * Populate the stream_subbuffer's info member. The info to populate
 * depends on the type (metadata/data) of the stream.
 *
 * Stream and channel locks are acquired during this call.
 */
typedef int (*extract_subbuffer_info_cb)(
                struct lttng_consumer_stream *, struct stream_subbuffer *);

/*
 * Invoked after a subbuffer's info has been filled.
 *
 * Stream and channel locks are acquired during this call.
 */
typedef int (*pre_consume_subbuffer_cb)(struct lttng_consumer_stream *,
                const struct stream_subbuffer *);

/*
 * Consume subbuffer contents.
 *
 * Stream and channel locks are acquired during this call.
 */
typedef ssize_t (*consume_subbuffer_cb)(struct lttng_consumer_local_data *,
                struct lttng_consumer_stream *,
                const struct stream_subbuffer *);

/*
 * Release the current subbuffer and advance the 'consumed' position by
 * one subbuffer.
 *
 * Stream and channel locks are acquired during this call.
 */
typedef int (*put_next_subbuffer_cb)(struct lttng_consumer_stream *,
                struct stream_subbuffer *);

/*
 * Invoked after consuming a subbuffer.
 *
 * Stream and channel locks are acquired during this call.
 */
typedef int (*post_consume_cb)(struct lttng_consumer_stream *,
                const struct stream_subbuffer *,
                struct lttng_consumer_local_data *);

/*
 * Send a live beacon if no data is available.
 *
 * Stream and channel locks are acquired during this call.
 */
typedef int (*send_live_beacon_cb)(struct lttng_consumer_stream *);

/*
 * Lock the stream and channel locks and any other stream-type specific
 * lock that need to be acquired during the processing of an
 * availability notification.
 */
typedef void (*lock_cb)(struct lttng_consumer_stream *);

/*
 * Unlock the stream and channel locks and any other stream-type specific
 * lock before sleeping until the next availability notification.
 *
 * Stream and channel locks are acquired during this call.
 */
typedef void (*unlock_cb)(struct lttng_consumer_stream *);

/*
 * Assert that the stream and channel lock and any other stream type specific
 * lock that need to be acquired during the processing of a read_subbuffer
 * operation is acquired.
 */
typedef void (*assert_locked_cb)(struct lttng_consumer_stream *);

/*
 * Invoked when a subbuffer's metadata version does not match the last
 * known metadata version.
 *
 * Stream and channel locks are acquired during this call.
 */
typedef void (*reset_metadata_cb)(struct lttng_consumer_stream *);

/*
 * Internal representation of the streams, sessiond_key is used to identify
 * uniquely a stream.
 */
struct lttng_consumer_stream {
        /* HT node used by the data_ht and metadata_ht */
        struct lttng_ht_node_u64 node;
        /* stream indexed per channel key node */
        struct lttng_ht_node_u64 node_channel_id;
        /* HT node used in consumer_data.stream_list_ht */
        struct lttng_ht_node_u64 node_session_id;
        /*
         * List used by channels to reference streams that are not yet globally
         * visible.
         */
        struct cds_list_head send_node;
        /* Pointer to associated channel. */
        struct lttng_consumer_channel *chan;
        /*
         * Current trace chunk. Holds a reference to the trace chunk.
         * `chunk` can be NULL when a stream is not associated to a chunk, e.g.
         * when it was created in the context of a no-output session.
         */
        struct lttng_trace_chunk *trace_chunk;

        /* Key by which the stream is indexed for 'node'. */
        uint64_t key;
        /*
         * File descriptor of the data output file. This can be either a file or a
         * socket fd for relayd streaming.
         */
        int out_fd; /* output file to write the data */
        /* Write position in the output file descriptor */
        off_t out_fd_offset;
        /* Amount of bytes written to the output */
        uint64_t output_written;
        int shm_fd_is_copy;
        int data_read;
        int hangup_flush_done;

        /*
         * Whether the stream is in a "complete" state (e.g. it does not have a
         * partially written sub-buffer.
         *
         * Initialized to "false" on stream creation (first packet is empty).
         *
         * The various transitions of the quiescent state are:
         *     - On "start" tracing: set to false, since the stream is not
         *       "complete".
         *     - On "stop" tracing: if !quiescent -> flush FINAL (update
         *       timestamp_end), and set to true; the stream has entered a
         *       complete/quiescent state.
         *     - On "destroy" or stream/application hang-up: if !quiescent ->
         *       flush FINAL, and set to true.
         *
         * NOTE: Update and read are protected by the stream lock.
         */
        bool quiescent;

        /*
         * True if the sequence number is not available (lttng-modules < 2.8).
         */
        bool sequence_number_unavailable;

        /*
         * metadata_timer_lock protects flags waiting_on_metadata and
         * missed_metadata_flush.
         */
        pthread_mutex_t metadata_timer_lock;
        /*
         * Flag set when awaiting metadata to be pushed. Used in the
         * timer thread to skip waiting on the stream (and stream lock) to
         * ensure we can proceed to flushing metadata in live mode.
         */
        bool waiting_on_metadata;
        /* Raised when a timer misses a metadata flush. */
        bool missed_metadata_flush;

        enum lttng_event_output output;
        /* Maximum subbuffer size (in bytes). */
        unsigned long max_sb_size;

        /*
         * Still used by the kernel for MMAP output. For UST, the ustctl getter is
         * used for the mmap base and offset.
         */
        void *mmap_base;
        unsigned long mmap_len;

        /* For UST */

        int wait_fd;
        /* Network sequence number. Indicating on which relayd socket it goes. */
        uint64_t net_seq_idx;
        /*
         * Indicate if this stream was successfully sent to a relayd. This is set
         * after the refcount of the relayd is incremented and is checked when the
         * stream is closed before decrementing the refcount in order to avoid an
         * unbalanced state.
         */
        unsigned int sent_to_relayd;

        /* Identify if the stream is the metadata */
        unsigned int metadata_flag;
        /*
         * Last known metadata version, reset the metadata file in case
         * of change.
         */
        uint64_t metadata_version;
        /* Used when the stream is set for network streaming */
        uint64_t relayd_stream_id;
        /*
         * When sending a stream packet to a relayd, this number is used to track
         * the packet sent by the consumer and seen by the relayd. When sending the
         * data header to the relayd, this number is sent and if the transmission
         * was successful, it is incremented.
         *
         * Even if the full data is not fully transmitted it won't matter since
         * only two possible error can happen after that where either the relayd
         * died or a read error is detected on the stream making this value useless
         * after that.
         *
         * This value SHOULD be read/updated atomically or with the lock acquired.
         */
        uint64_t next_net_seq_num;
        /*
         * Lock to use the stream FDs since they are used between threads.
         *
         * This is nested INSIDE the consumer_data lock.
         * This is nested INSIDE the channel lock.
         * This is nested INSIDE the channel timer lock.
         * This is nested OUTSIDE the metadata cache lock.
         * This is nested OUTSIDE consumer_relayd_sock_pair lock.
         */
        pthread_mutex_t lock;
        /* Tracing session id */
        uint64_t session_id;
        /*
         * Indicates if the stream end point is still active or not (network
         * streaming or local file system). The thread "owning" the stream is
         * handling this status and can be notified of a state change through the
         * consumer data appropriate pipe.
         */
        enum consumer_endpoint_status endpoint_status;
        /* Stream name. Format is: <channel_name>_<cpu_number> */
        char name[LTTNG_SYMBOL_NAME_LEN];
        /* Internal state of libustctl. */
        struct lttng_ust_ctl_consumer_stream *ustream;
        /* On-disk circular buffer */
        uint64_t tracefile_size_current;
        uint64_t tracefile_count_current;
        /*
         * Monitor or not the streams of this channel meaning this indicates if the
         * streams should be sent to the data/metadata thread or added to the no
         * monitor list of the channel.
         */
        unsigned int monitor;
        /*
         * Indicate if the stream is globally visible meaning that it has been
         * added to the multiple hash tables. If *not* set, NO lock should be
         * acquired in the destroy path.
         */
        unsigned int globally_visible;
        /*
         * Pipe to wake up the metadata poll thread when the UST metadata
         * cache is updated.
         */
        int ust_metadata_poll_pipe[2];
        /*
         * How much metadata was read from the metadata cache and sent
         * to the channel.
         */
        uint64_t ust_metadata_pushed;
        /*
         * Copy of the last discarded event value to detect the overflow of
         * the counter.
         */
        uint64_t last_discarded_events;
        /* Copy of the sequence number of the last packet extracted. */
        uint64_t last_sequence_number;
        /*
         * Index file object of the index file for this stream.
         */
        struct lttng_index_file *index_file;

        /*
         * Local pipe to extract data when using splice.
         */
        int splice_pipe[2];

        /*
         * Rendez-vous point between data and metadata stream in live mode.
         */
        pthread_cond_t metadata_rdv;
        pthread_mutex_t metadata_rdv_lock;

        /*
         * rotate_position represents the packet sequence number of the last
         * packet which belongs to the current trace chunk prior to the rotation.
         * When that position is reached, this tracefile can be closed and a
         * new one is created in channel_read_only_attributes.path.
         */
        uint64_t rotate_position;

        /* Whether or not a packet was opened during the current trace chunk. */
        bool opened_packet_in_current_trace_chunk;

        /*
         * Read-only copies of channel values. We cannot safely access the
         * channel from a stream, so we need to have a local copy of these
         * fields in the stream object. These fields should be removed from
         * the stream objects when we introduce refcounting.
         */
        struct {
                uint64_t tracefile_size;
        } channel_read_only_attributes;

        /*
         * Flag to inform the data or metadata thread that a stream is
         * ready to be rotated.
         */
        bool rotate_ready;

        /* Indicate if the stream still has some data to be read. */
        unsigned int has_data:1;
        /*
         * Inform the consumer or relay to reset the metadata
         * file before writing in it (regeneration).
         */
        unsigned int reset_metadata_flag:1;
        struct {
                /*
                 * Invoked in the order of declaration.
                 * See callback type definitions.
                 */
                lock_cb lock;
                on_wake_up_cb on_wake_up;
                get_next_subbuffer_cb get_next_subbuffer;
                extract_subbuffer_info_cb extract_subbuffer_info;
                pre_consume_subbuffer_cb pre_consume_subbuffer;
                reset_metadata_cb reset_metadata;
                consume_subbuffer_cb consume_subbuffer;
                put_next_subbuffer_cb put_next_subbuffer;
                struct lttng_dynamic_array post_consume_cbs;
                send_live_beacon_cb send_live_beacon;
                on_sleep_cb on_sleep;
                unlock_cb unlock;
                assert_locked_cb assert_locked;
        } read_subbuffer_ops;
        struct metadata_bucket *metadata_bucket;
};

/*
 * Internal representation of a relayd socket pair.
 */
struct consumer_relayd_sock_pair {
        /* Network sequence number. */
        uint64_t net_seq_idx;
        /* Number of stream associated with this relayd */
        int refcount;

        /*
         * This flag indicates whether or not we should destroy this object. The
         * destruction should ONLY occurs when this flag is set and the refcount is
         * set to zero.
         */
        unsigned int destroy_flag;

        /*
         * Mutex protecting the control socket to avoid out of order packets
         * between threads sending data to the relayd. Since metadata data is sent
         * over that socket, at least two sendmsg() are needed (header + data)
         * creating a race for packets to overlap between threads using it.
         *
         * This is nested INSIDE the consumer_data lock.
         * This is nested INSIDE the stream lock.
         */
        pthread_mutex_t ctrl_sock_mutex;

        /* Control socket. Command and metadata are passed over it */
        struct lttcomm_relayd_sock control_sock;

        /*
         * We don't need a mutex at this point since we only splice or write single
         * large chunk of data with a header appended at the begining. Moreover,
         * this socket is for now only used in a single thread.
         */
        struct lttcomm_relayd_sock data_sock;
        struct lttng_ht_node_u64 node;

        /* Session id on both sides for the sockets. */
        uint64_t relayd_session_id;
        uint64_t sessiond_session_id;
        struct lttng_consumer_local_data *ctx;
};

/*
 * UST consumer local data to the program. One or more instance per
 * process.
 */
struct lttng_consumer_local_data {
        /*
         * Function to call when data is available on a buffer.
         * Returns the number of bytes read, or negative error value.
         */
        ssize_t (*on_buffer_ready)(struct lttng_consumer_stream *stream,
                        struct lttng_consumer_local_data *ctx,
                        bool locked_by_caller);
        /*
         * function to call when we receive a new channel, it receives a
         * newly allocated channel, depending on the return code of this
         * function, the new channel 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_channel)(struct lttng_consumer_channel *channel);
        /*
         * function to call when we receive a new stream, it receives a
         * newly allocated stream, depending on the return code of this
         * function, the new stream 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_stream)(struct lttng_consumer_stream *stream);
        /*
         * function to call when a stream is getting updated by the session
         * daemon, this function receives the sessiond key and the new
         * state, depending on the return code of this function the
         * update of state for the stream 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_stream)(uint64_t sessiond_key, uint32_t state);
        enum lttng_consumer_type type;
        /* socket to communicate errors with sessiond */
        int consumer_error_socket;
        /* socket to ask metadata to sessiond. */
        int consumer_metadata_socket;
        /*
         * Protect consumer_metadata_socket.
         *
         * This is nested OUTSIDE the metadata cache lock.
         */
        pthread_mutex_t metadata_socket_lock;
        /* socket to exchange commands with sessiond */
        char *consumer_command_sock_path;
        /* communication with splice */
        int consumer_channel_pipe[2];
        /* Data stream poll thread pipe. To transfer data stream to the thread */
        struct lttng_pipe *consumer_data_pipe;

        /*
         * Data thread use that pipe to catch wakeup from read subbuffer that
         * detects that there is still data to be read for the stream encountered.
         * Before doing so, the stream is flagged to indicate that there is still
         * data to be read.
         *
         * Both pipes (read/write) are owned and used inside the data thread.
         */
        struct lttng_pipe *consumer_wakeup_pipe;
        /* Indicate if the wakeup thread has been notified. */
        unsigned int has_wakeup:1;

        /* to let the signal handler wake up the fd receiver thread */
        int consumer_should_quit[2];
        /* Metadata poll thread pipe. Transfer metadata stream to it */
        struct lttng_pipe *consumer_metadata_pipe;
        /*
         * Pipe used by the channel monitoring timers to provide state samples
         * to the session daemon (write-only).
         */
        int channel_monitor_pipe;
        LTTNG_OPTIONAL(lttng_uuid) sessiond_uuid;
};

/*
 * Library-level data. One instance per process.
 */
struct lttng_consumer_global_data {
        /*
         * At this time, this lock is used to ensure coherence between the count
         * and number of element in the hash table. It's also a protection for
         * concurrent read/write between threads.
         *
         * This is nested OUTSIDE the stream lock.
         * This is nested OUTSIDE the consumer_relayd_sock_pair lock.
         */
        pthread_mutex_t lock;

        /*
         * Number of streams in the data stream hash table declared outside.
         * Protected by consumer_data.lock.
         */
        int stream_count;

        /* Channel hash table protected by consumer_data.lock. */
        struct lttng_ht *channel_ht;
        /* Channel hash table indexed by session id. */
        struct lttng_ht *channels_by_session_id_ht;
        /*
         * Flag specifying if the local array of FDs needs update in the
         * poll function. Protected by consumer_data.lock.
         */
        unsigned int need_update;
        enum lttng_consumer_type type;

        /*
         * Relayd socket(s) hashtable indexed by network sequence number. Each
         * stream has an index which associate the right relayd socket to use.
         */
        struct lttng_ht *relayd_ht;

        /*
         * This hash table contains all streams (metadata and data) indexed by
         * session id. In other words, the ht is indexed by session id and each
         * bucket contains the list of associated streams.
         *
         * This HT uses the "node_session_id" of the consumer stream.
         */
        struct lttng_ht *stream_list_ht;

        /*
         * This HT uses the "node_channel_id" of the consumer stream.
         */
        struct lttng_ht *stream_per_chan_id_ht;

        /*
         * Trace chunk registry indexed by (session_id, chunk_id).
         */
        struct lttng_trace_chunk_registry *chunk_registry;
};

/*
 * Set to nonzero when the consumer is exiting. Updated by signal
 * handler and thread exit, read by threads.
 */
extern int consumer_quit;

/*
 * Set to nonzero when the consumer is exiting. Updated by signal
 * handler and thread exit, read by threads.
 */
extern int consumer_quit;

/* Flag used to temporarily pause data consumption from testpoints. */
extern int data_consumption_paused;

/* Return a human-readable consumer type string that is suitable for logging. */
static inline
const char *lttng_consumer_type_str(enum lttng_consumer_type type)
{
        switch (type) {
        case LTTNG_CONSUMER_UNKNOWN:
                return "unknown";
        case LTTNG_CONSUMER_KERNEL:
                return "kernel";
        case LTTNG_CONSUMER32_UST:
                return "32-bit user space";
        case LTTNG_CONSUMER64_UST:
                return "64-bit user space";
        default:
                abort();
        }
}

/*
 * Init consumer data structures.
 */
int lttng_consumer_init(void);

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

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

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

/*
 * Called from signal handler to ensure a clean exit.
 */
void lttng_consumer_should_exit(struct lttng_consumer_local_data *ctx);

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

/*
 * 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
 */
int lttng_consumer_poll_socket(struct pollfd *kconsumer_sockpoll);

/*
 * Copy the fields from the channel that need to be accessed (read-only)
 * directly from the stream.
 */
void consumer_stream_update_channel_attributes(
                struct lttng_consumer_stream *stream,
                struct lttng_consumer_channel *channel);

struct lttng_consumer_stream *consumer_allocate_stream(
                struct lttng_consumer_channel *channel,
                uint64_t channel_key,
                uint64_t stream_key,
                const char *channel_name,
                uint64_t relayd_id,
                uint64_t session_id,
                struct lttng_trace_chunk *trace_chunk,
                int cpu,
                int *alloc_ret,
                enum consumer_channel_type type,
                unsigned int monitor);
struct lttng_consumer_channel *consumer_allocate_channel(uint64_t key,
                uint64_t session_id,
                const uint64_t *chunk_id,
                const char *pathname,
                const char *name,
                uint64_t relayd_id,
                enum lttng_event_output output,
                uint64_t tracefile_size,
                uint64_t tracefile_count,
                uint64_t session_id_per_pid,
                unsigned int monitor,
                unsigned int live_timer_interval,
                bool is_in_live_session,
                const char *root_shm_path,
                const char *shm_path);
void consumer_del_stream(struct lttng_consumer_stream *stream,
                struct lttng_ht *ht);
void consumer_del_metadata_stream(struct lttng_consumer_stream *stream,
                struct lttng_ht *ht);
int consumer_add_channel(struct lttng_consumer_channel *channel,
                struct lttng_consumer_local_data *ctx);
void consumer_del_channel(struct lttng_consumer_channel *channel);

/* lttng-relayd consumer command */
struct consumer_relayd_sock_pair *consumer_find_relayd(uint64_t key);
int consumer_send_relayd_stream(struct lttng_consumer_stream *stream, char *path);
int consumer_send_relayd_streams_sent(uint64_t net_seq_idx);
void close_relayd_stream(struct lttng_consumer_stream *stream);
struct lttng_consumer_channel *consumer_find_channel(uint64_t key);
int consumer_handle_stream_before_relayd(struct lttng_consumer_stream *stream,
                size_t data_size);
void consumer_steal_stream_key(int key, struct lttng_ht *ht);

struct lttng_consumer_local_data *lttng_consumer_create(
                enum lttng_consumer_type type,
                ssize_t (*buffer_ready)(struct lttng_consumer_stream *stream,
                        struct lttng_consumer_local_data *ctx,
                        bool locked_by_caller),
                int (*recv_channel)(struct lttng_consumer_channel *channel),
                int (*recv_stream)(struct lttng_consumer_stream *stream),
                int (*update_stream)(uint64_t sessiond_key, uint32_t state));
void lttng_consumer_destroy(struct lttng_consumer_local_data *ctx);
ssize_t lttng_consumer_on_read_subbuffer_mmap(
                struct lttng_consumer_stream *stream,
                const struct lttng_buffer_view *buffer,
                unsigned long padding);
ssize_t lttng_consumer_on_read_subbuffer_splice(
                struct lttng_consumer_local_data *ctx,
                struct lttng_consumer_stream *stream, unsigned long len,
                unsigned long padding);
int lttng_consumer_sample_snapshot_positions(struct lttng_consumer_stream *stream);
int lttng_consumer_take_snapshot(struct lttng_consumer_stream *stream);
int lttng_consumer_get_produced_snapshot(struct lttng_consumer_stream *stream,
                unsigned long *pos);
int lttng_consumer_get_consumed_snapshot(struct lttng_consumer_stream *stream,
                unsigned long *pos);
int lttng_ustconsumer_get_wakeup_fd(struct lttng_consumer_stream *stream);
int lttng_ustconsumer_close_wakeup_fd(struct lttng_consumer_stream *stream);
void *consumer_thread_metadata_poll(void *data);
void *consumer_thread_data_poll(void *data);
void *consumer_thread_sessiond_poll(void *data);
void *consumer_thread_channel_poll(void *data);
int lttng_consumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                int sock, struct pollfd *consumer_sockpoll);

ssize_t lttng_consumer_read_subbuffer(struct lttng_consumer_stream *stream,
                struct lttng_consumer_local_data *ctx,
                bool locked_by_caller);
int lttng_consumer_on_recv_stream(struct lttng_consumer_stream *stream);
void consumer_add_relayd_socket(uint64_t net_seq_idx,
                int sock_type,
                struct lttng_consumer_local_data *ctx,
                int sock,
                struct pollfd *consumer_sockpoll,
                uint64_t sessiond_id,
                uint64_t relayd_session_id,
                uint32_t relayd_version_major,
                uint32_t relayd_version_minor,
                enum lttcomm_sock_proto relayd_socket_protocol);
void consumer_flag_relayd_for_destroy(
                struct consumer_relayd_sock_pair *relayd);
int consumer_data_pending(uint64_t id);
int consumer_send_status_msg(int sock, int ret_code);
int consumer_send_status_channel(int sock,
                struct lttng_consumer_channel *channel);
void notify_thread_del_channel(struct lttng_consumer_local_data *ctx,
                uint64_t key);
void consumer_destroy_relayd(struct consumer_relayd_sock_pair *relayd);
unsigned long consumer_get_consume_start_pos(unsigned long consumed_pos,
                unsigned long produced_pos, uint64_t nb_packets_per_stream,
                uint64_t max_sb_size);
void consumer_add_data_stream(struct lttng_consumer_stream *stream);
void consumer_del_stream_for_data(struct lttng_consumer_stream *stream);
void consumer_add_metadata_stream(struct lttng_consumer_stream *stream);
void consumer_del_stream_for_metadata(struct lttng_consumer_stream *stream);
int consumer_create_index_file(struct lttng_consumer_stream *stream);
int lttng_consumer_rotate_channel(struct lttng_consumer_channel *channel,
                uint64_t key, uint64_t relayd_id, uint32_t metadata,
                struct lttng_consumer_local_data *ctx);
int lttng_consumer_stream_is_rotate_ready(struct lttng_consumer_stream *stream);
int lttng_consumer_rotate_stream(struct lttng_consumer_local_data *ctx,
                struct lttng_consumer_stream *stream);
int lttng_consumer_rotate_ready_streams(struct lttng_consumer_channel *channel,
                uint64_t key, struct lttng_consumer_local_data *ctx);
void lttng_consumer_reset_stream_rotate_state(struct lttng_consumer_stream *stream);
enum lttcomm_return_code lttng_consumer_create_trace_chunk(
                const uint64_t *relayd_id, uint64_t session_id,
                uint64_t chunk_id,
                time_t chunk_creation_timestamp,
                const char *chunk_override_name,
                const struct lttng_credentials *credentials,
                struct lttng_directory_handle *chunk_directory_handle);
enum lttcomm_return_code lttng_consumer_close_trace_chunk(
                const uint64_t *relayd_id, uint64_t session_id,
                uint64_t chunk_id, time_t chunk_close_timestamp,
                const enum lttng_trace_chunk_command_type *close_command,
                char *path);
enum lttcomm_return_code lttng_consumer_trace_chunk_exists(
                const uint64_t *relayd_id, uint64_t session_id,
                uint64_t chunk_id);
void lttng_consumer_cleanup_relayd(struct consumer_relayd_sock_pair *relayd);
enum lttcomm_return_code lttng_consumer_init_command(
                struct lttng_consumer_local_data *ctx,
                const lttng_uuid sessiond_uuid);
int lttng_consumer_clear_channel(struct lttng_consumer_channel *channel);
enum lttcomm_return_code lttng_consumer_open_channel_packets(
                struct lttng_consumer_channel *channel);
int consumer_metadata_wakeup_pipe(const struct lttng_consumer_channel *channel);
void lttng_consumer_sigbus_handle(void *addr);

#endif /* LIB_CONSUMER_H */