Fix: relayd: handle consumerd crashes without leak

[lttng-tools.git] / src / bin / lttng-relayd / index.c

/*
 * Copyright (C) 2013 - Julien Desfossez <jdesfossez@efficios.com>
 *                      David Goulet <dgoulet@efficios.com>
 *               2015 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License, version 2 only, as
 * published by the Free Software Foundation.
 *
 * 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., 51
 * Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#define _GNU_SOURCE
#define _LGPL_SOURCE
#include <assert.h>

#include <common/common.h>
#include <common/utils.h>

#include "lttng-relayd.h"
#include "stream.h"
#include "index.h"

/*
 * Allocate a new relay index object. Pass the stream in which it is
 * contained as parameter. The sequence number will be used as the hash
 * table key.
 *
 * Called with stream mutex held.
 * Return allocated object or else NULL on error.
 */
static struct relay_index *relay_index_create(struct relay_stream *stream,
		uint64_t net_seq_num)
{
	struct relay_index *index;

	DBG2("Creating relay index for stream id %" PRIu64 " and seqnum %" PRIu64,
			stream->stream_handle, net_seq_num);

	index = zmalloc(sizeof(*index));
	if (!index) {
		PERROR("Relay index zmalloc");
		goto end;
	}
	if (!stream_get(stream)) {
		ERR("Cannot get stream");
		free(index);
		index = NULL;
		goto end;
	}
	index->stream = stream;

	lttng_ht_node_init_u64(&index->index_n, net_seq_num);
	pthread_mutex_init(&index->lock, NULL);
	pthread_mutex_init(&index->reflock, NULL);
	urcu_ref_init(&index->ref);

end:
	return index;
}

/*
 * Add unique relay index to the given hash table. In case of a collision, the
 * already existing object is put in the given _index variable.
 *
 * RCU read side lock MUST be acquired.
 */
static struct relay_index *relay_index_add_unique(struct relay_stream *stream,
		struct relay_index *index)
{
	struct cds_lfht_node *node_ptr;
	struct relay_index *_index;

	DBG2("Adding relay index with stream id %" PRIu64 " and seqnum %" PRIu64,
			stream->stream_handle, index->index_n.key);

	node_ptr = cds_lfht_add_unique(stream->indexes_ht->ht,
			stream->indexes_ht->hash_fct(&index->index_n, lttng_ht_seed),
			stream->indexes_ht->match_fct, &index->index_n,
			&index->index_n.node);
	if (node_ptr != &index->index_n.node) {
		_index = caa_container_of(node_ptr, struct relay_index,
				index_n.node);
	} else {
		_index = NULL;
	}
	return _index;
}

/*
 * Should be called with RCU read-side lock held.
 */
static bool relay_index_get(struct relay_index *index)
{
	bool has_ref = false;

	DBG2("index get for stream id %" PRIu64 " and seqnum %" PRIu64 " refcount %d",
			index->stream->stream_handle, index->index_n.key,
			(int) index->ref.refcount);

	/* Confirm that the index refcount has not reached 0. */
	pthread_mutex_lock(&index->reflock);
	if (index->ref.refcount != 0) {
		has_ref = true;
		urcu_ref_get(&index->ref);
	}
	pthread_mutex_unlock(&index->reflock);

	return has_ref;
}

/*
 * Get a relayd index in within the given stream, or create it if not
 * present.
 *
 * Called with stream mutex held.
 * Return index object or else NULL on error.
 */
struct relay_index *relay_index_get_by_id_or_create(struct relay_stream *stream,
		 uint64_t net_seq_num)
{
	struct lttng_ht_node_u64 *node;
	struct lttng_ht_iter iter;
	struct relay_index *index = NULL;

	DBG3("Finding index for stream id %" PRIu64 " and seq_num %" PRIu64,
			stream->stream_handle, net_seq_num);

	rcu_read_lock();
	lttng_ht_lookup(stream->indexes_ht, &net_seq_num, &iter);
	node = lttng_ht_iter_get_node_u64(&iter);
	if (node) {
		index = caa_container_of(node, struct relay_index, index_n);
	} else {
		struct relay_index *oldindex;

		index = relay_index_create(stream, net_seq_num);
		if (!index) {
			ERR("Cannot create index for stream id %" PRIu64 " and seq_num %" PRIu64,
				index->stream->stream_handle, net_seq_num);
			goto end;
		}
		oldindex = relay_index_add_unique(stream, index);
		if (oldindex) {
			/* Added concurrently, keep old. */
			relay_index_put(index);
			index = oldindex;
			if (!relay_index_get(index)) {
				index = NULL;
			}
		} else {
			stream->indexes_in_flight++;
			index->in_hash_table = true;
		}
	}
end:
	rcu_read_unlock();
	DBG2("Index %sfound or created in HT for stream ID %" PRIu64 " and seqnum %" PRIu64,
			(index == NULL) ? "NOT " : "", index->stream->stream_handle, net_seq_num);
	return index;
}

int relay_index_set_fd(struct relay_index *index, struct stream_fd *index_fd,
		uint64_t data_offset)
{
	int ret = 0;

	pthread_mutex_lock(&index->lock);
	if (index->index_fd) {
		ret = -1;
		goto end;
	}
	stream_fd_get(index_fd);
	index->index_fd = index_fd;
	index->index_data.offset = data_offset;
end:
	pthread_mutex_unlock(&index->lock);
	return ret;
}

int relay_index_set_data(struct relay_index *index,
                const struct ctf_packet_index *data)
{
	int ret = 0;

	pthread_mutex_lock(&index->lock);
	if (index->has_index_data) {
		ret = -1;
		goto end;
	}
	/* Set everything except data_offset. */
	index->index_data.packet_size = data->packet_size;
	index->index_data.content_size = data->content_size;
	index->index_data.timestamp_begin = data->timestamp_begin;
	index->index_data.timestamp_end = data->timestamp_end;
	index->index_data.events_discarded = data->events_discarded;
	index->index_data.stream_id = data->stream_id;
	index->has_index_data = true;
end:
	pthread_mutex_unlock(&index->lock);
	return ret;
}

static void index_destroy(struct relay_index *index)
{
	free(index);
}

static void index_destroy_rcu(struct rcu_head *rcu_head)
{
	struct relay_index *index =
		caa_container_of(rcu_head, struct relay_index, rcu_node);

	index_destroy(index);
}

/* Stream lock must be held by the caller. */
static void index_release(struct urcu_ref *ref)
{
	struct relay_index *index = caa_container_of(ref, struct relay_index, ref);
	struct relay_stream *stream = index->stream;
	int ret;
	struct lttng_ht_iter iter;

	if (index->index_fd) {
		stream_fd_put(index->index_fd);
		index->index_fd = NULL;
	}
	if (index->in_hash_table) {
		/* Delete index from hash table. */
		iter.iter.node = &index->index_n.node;
		ret = lttng_ht_del(stream->indexes_ht, &iter);
		assert(!ret);
		stream->indexes_in_flight--;
	}

	stream_put(index->stream);
	index->stream = NULL;

	call_rcu(&index->rcu_node, index_destroy_rcu);
}

/*
 * Called with stream mutex held.
 *
 * Stream lock must be held by the caller.
 */
void relay_index_put(struct relay_index *index)
{
	DBG2("index put for stream id %" PRIu64 " and seqnum %" PRIu64 " refcount %d",
			index->stream->stream_handle, index->index_n.key,
			(int) index->ref.refcount);
	/*
	 * Ensure existance of index->lock for index unlock.
	 */
	rcu_read_lock();
	/*
	 * Index lock ensures that concurrent test and update of stream
	 * ref is atomic.
	 */
	pthread_mutex_lock(&index->reflock);
	assert(index->ref.refcount != 0);
	urcu_ref_put(&index->ref, index_release);
	pthread_mutex_unlock(&index->reflock);
	rcu_read_unlock();
}

/*
 * Try to flush index to disk. Releases self-reference to index once
 * flush succeeds.
 *
 * Stream lock must be held by the caller.
 * Return 0 on successful flush, a negative value on error, or positive
 * value if no flush was performed.
 */
int relay_index_try_flush(struct relay_index *index)
{
	int ret = 1;
	bool flushed = false;
	int fd;

	pthread_mutex_lock(&index->lock);
	if (index->flushed) {
		goto skip;
	}
	/* Check if we are ready to flush. */
	if (!index->has_index_data || !index->index_fd) {
		goto skip;
	}
	fd = index->index_fd->fd;
	DBG2("Writing index for stream ID %" PRIu64 " and seq num %" PRIu64
			" on fd %d", index->stream->stream_handle,
			index->index_n.key, fd);
	flushed = true;
	index->flushed = true;
	ret = index_write(fd, &index->index_data, sizeof(index->index_data));
	if (ret == sizeof(index->index_data)) {
		ret = 0;
	} else {
		ret = -1;
	}
skip:
	pthread_mutex_unlock(&index->lock);

	if (flushed) {
		/* Put self-ref from index now that it has been flushed. */
		relay_index_put(index);
	}
	return ret;
}

/*
 * Close every relay index within a given stream, without flushing
 * them.
 */
void relay_index_close_all(struct relay_stream *stream)
{
	struct lttng_ht_iter iter;
	struct relay_index *index;

	rcu_read_lock();
	cds_lfht_for_each_entry(stream->indexes_ht->ht, &iter.iter,
			index, index_n.node) {
		/* Put self-ref from index. */
		relay_index_put(index);
	}
	rcu_read_unlock();
}

void relay_index_close_partial_fd(struct relay_stream *stream)
{
	struct lttng_ht_iter iter;
	struct relay_index *index;

	rcu_read_lock();
	cds_lfht_for_each_entry(stream->indexes_ht->ht, &iter.iter,
			index, index_n.node) {
		if (!index->index_fd) {
			continue;
		}
		/*
		 * Partial index has its index_fd: we have only
		 * received its info from the data socket.
		 * Put self-ref from index.
		 */
		relay_index_put(index);
	}
	rcu_read_unlock();
}

uint64_t relay_index_find_last(struct relay_stream *stream)
{
	struct lttng_ht_iter iter;
	struct relay_index *index;
	uint64_t net_seq_num = -1ULL;

	rcu_read_lock();
	cds_lfht_for_each_entry(stream->indexes_ht->ht, &iter.iter,
			index, index_n.node) {
		if (net_seq_num == -1ULL ||
				index->index_n.key > net_seq_num) {
			net_seq_num = index->index_n.key;
		}
	}
	rcu_read_unlock();
	return net_seq_num;
}