src/bin/lttng-relayd/viewer-session.hpp

   1 #ifndef _VIEWER_SESSION_H
   2 #define _VIEWER_SESSION_H
   3
   4 /*
   5  * Copyright (C) 2013 Julien Desfossez <jdesfossez@efficios.com>
   6  * Copyright (C) 2013 David Goulet <dgoulet@efficios.com>
   7  * Copyright (C) 2015 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   8  *
   9  * SPDX-License-Identifier: GPL-2.0-only
  10  *
  11  */
  12
  13 #include <limits.h>
  14 #include <inttypes.h>
  15 #include <pthread.h>
  16 #include <urcu/list.h>
  17 #include <urcu/ref.h>
  18
  19 #include <common/hashtable/hashtable.hpp>
  20 #include <common/trace-chunk.hpp>
  21
  22 #include "session.hpp"
  23 #include "lttng-viewer-abi.hpp"
  24
  25 struct relay_viewer_session {
  26         /*
  27          * Session list. Updates are protected by the session_list_lock.
  28          * Traversals are protected by RCU.
  29          * This list limits the design to having the sessions in at most
  30          * one viewer session.
  31          */
  32         struct cds_list_head session_list;      /* RCU list. */
  33         pthread_mutex_t session_list_lock;      /* Protects list updates. */
  34         /*
  35          * The viewer session's current trace chunk is initially set, when
  36          * a viewer attaches to the viewer session, to a copy the corresponding
  37          * relay_session's current trace chunk.
  38          *
  39          * A live session always attempts to "catch-up" to the newest available
  40          * trace chunk. This means that when a viewer reaches the end of a
  41          * trace chunk, the viewer session may not transition to the "next" one:
  42          * it jumps to the most recent trace chunk available (the one being
  43          * produced by the relay_session). Hence, if the producer performs
  44          * multiple rotations before a viewer completes the consumption of a
  45          * trace chunk, it will skip over those "intermediary" trace chunks.
  46          *
  47          * A viewer session updates its current trace chunk when:
  48          *   1) new viewer streams are created,
  49          *   2) a new index is requested,
  50          *   3) metadata is requested.
  51          *
  52          * Hence, as a general principle, the viewer session will reference the
  53          * most recent trace chunk available _even if its streams do not point to
  54          * it_. It indicates which trace chunk viewer streams should transition
  55          * to when the end of their current trace chunk is reached.
  56          *
  57          * Note that a viewer session's trace chunk points to the session's
  58          * output directory. The sub-directories in which the various stream files
  59          * are created are considered as being a part of their name.
  60          */
  61         struct lttng_trace_chunk *current_trace_chunk;
  62 };
  63
  64 struct relay_viewer_session *viewer_session_create(void);
  65 void viewer_session_destroy(struct relay_viewer_session *vsession);
  66 void viewer_session_close(struct relay_viewer_session *vsession);
  67
  68 enum lttng_viewer_attach_return_code viewer_session_attach(
  69                 struct relay_viewer_session *vsession,
  70                 struct relay_session *session);
  71 int viewer_session_is_attached(struct relay_viewer_session *vsession,
  72                 struct relay_session *session);
  73 void viewer_session_close_one_session(struct relay_viewer_session *vsession,
  74                 struct relay_session *session);
  75 int viewer_session_set_trace_chunk_copy(struct relay_viewer_session *vsession,
  76                 struct lttng_trace_chunk *relay_session_trace_chunk);
  77
  78 #endif /* _VIEWER_SESSION_H */