src/common/consumer/consumer-metadata-cache.h

   1 /*
   2  * Copyright (C) 2013 Julien Desfossez <jdesfossez@efficios.com>
   3  * Copyright (C) 2013 David Goulet <dgoulet@efficios.com>
   4  *
   5  * SPDX-License-Identifier: GPL-2.0-only
   6  *
   7  */
   8
   9 #ifndef CONSUMER_METADATA_CACHE_H
  10 #define CONSUMER_METADATA_CACHE_H
  11
  12 #include <common/consumer/consumer.h>
  13
  14 enum consumer_metadata_cache_write_status {
  15         CONSUMER_METADATA_CACHE_WRITE_STATUS_ERROR = -1,
  16         /*
  17          * New metadata content was appended to the cache successfully.
  18          * Previously available content remains valid.
  19          */
  20         CONSUMER_METADATA_CACHE_WRITE_STATUS_APPENDED_CONTENT = 0,
  21         /*
  22          * The new content pushed to the cache invalidated the content that
  23          * was already present. The contents of the cache should be re-read.
  24          */
  25         CONSUMER_METADATA_CACHE_WRITE_STATUS_INVALIDATED,
  26         /*
  27          * A metadata cache write can simply overwrite an already existing
  28          * section of the cache (and it should be a write-through with identical
  29          * data). From the caller's standpoint, there is no change to the state
  30          * of the cache.
  31          */
  32         CONSUMER_METADATA_CACHE_WRITE_STATUS_NO_CHANGE,
  33 };
  34
  35 struct consumer_metadata_cache {
  36         char *data;
  37         uint64_t cache_alloc_size;
  38         /*
  39          * Current version of the metadata cache.
  40          */
  41         uint64_t version;
  42         /*
  43          * The upper-limit of data written inside the buffer.
  44          *
  45          * With the total_bytes_written it allows us to keep track of when the
  46          * cache contains contiguous metadata ready to be sent to the RB.
  47          * All cached data is contiguous.
  48          */
  49         uint64_t max_offset;
  50         /*
  51          * Lock to update the metadata cache and push into the ring_buffer
  52          * (ustctl_write_metadata_to_channel).
  53          *
  54          * This is nested INSIDE the consumer_data lock.
  55          */
  56         pthread_mutex_t lock;
  57 };
  58
  59 enum consumer_metadata_cache_write_status
  60 consumer_metadata_cache_write(struct consumer_metadata_cache *cache,
  61                 unsigned int offset, unsigned int len, uint64_t version,
  62                 const char *data);
  63 int consumer_metadata_cache_allocate(struct lttng_consumer_channel *channel);
  64 void consumer_metadata_cache_destroy(struct lttng_consumer_channel *channel);
  65 int consumer_metadata_cache_flushed(struct lttng_consumer_channel *channel,
  66                 uint64_t offset, int timer);
  67
  68 #endif /* CONSUMER_METADATA_CACHE_H */