static ngx_int_t
ngx_buffer_cache_init(ngx_shm_zone_t *shm_zone, void *data)
{
ngx_buffer_cache_sh_t *sh;
ngx_buffer_cache_t *ocache = data;
ngx_buffer_cache_t *cache;
u_char* p;
cache = shm_zone->data;
if (ocache)
{
cache->sh = ocache->sh;
cache->shpool = ocache->shpool;
return NGX_OK;
}
cache->shpool = (ngx_slab_pool_t *)shm_zone->shm.addr;
if (shm_zone->shm.exists)
{
cache->sh = cache->shpool->data;
return NGX_OK;
}
// start following the ngx_slab_pool_t that was allocated at the beginning of the chunk
p = shm_zone->shm.addr + sizeof(ngx_slab_pool_t);
// initialize the log context
cache->shpool->log_ctx = p;
p = ngx_sprintf(cache->shpool->log_ctx, " in buffer cache \"%V\"%Z", &shm_zone->shm.name);
// allocate the shared cache state
p = ngx_align_ptr(p, sizeof(void *));
sh = (ngx_buffer_cache_sh_t*)p;
p += sizeof(*sh);
cache->sh = sh;
cache->shpool->data = sh;
// initialize fixed cache fields
p = ngx_align_ptr(p, sizeof(void *));
sh->entries_start = (ngx_buffer_cache_entry_t*)p;
sh->buffers_end = shm_zone->shm.addr + shm_zone->shm.size;
sh->access_time = 0;
// reset the stats
ngx_memzero(&sh->stats, sizeof(sh->stats));
// reset the cache status
ngx_buffer_cache_reset(sh);
sh->reset = 0;
return NGX_OK;
}
ngx_flag_t
ngx_buffer_cache_store_gather(
ngx_buffer_cache_t* cache,
u_char* key,
ngx_str_t* buffers,
size_t buffer_count)
{
ngx_buffer_cache_entry_t* entry;
ngx_buffer_cache_sh_t *sh = cache->sh;
ngx_str_t* cur_buffer;
ngx_str_t* last_buffer;
size_t buffer_size;
uint32_t hash;
uint32_t evictions;
u_char* target_buffer;
hash = ngx_crc32_short(key, BUFFER_CACHE_KEY_SIZE);
ngx_shmtx_lock(&cache->shpool->mutex);
if (sh->reset)
{
// a previous store operation was killed in progress, need to reset the cache
// since the data structures may be corrupt. we can only reset the cache after
// the access time expires since other processes may still be reading from /
// writing to the cache
if (ngx_time() < sh->access_time + CACHE_LOCK_EXPIRATION)
{
ngx_shmtx_unlock(&cache->shpool->mutex);
return 0;
}
// reset the cache, leave the reset flag enabled
ngx_buffer_cache_reset(sh);
// update stats
sh->stats.reset++;
}
else
{
// remove expired entries
if (cache->expiration)
{
for (evictions = MAX_EVICTIONS_PER_STORE; evictions > 0; evictions--)
{
if (!ngx_buffer_cache_free_oldest_entry(sh, cache->expiration))
{
break;
}
}
}
// make sure the entry does not already exist
entry = ngx_buffer_cache_rbtree_lookup(&sh->rbtree, key, hash);
if (entry != NULL)
{
sh->stats.store_exists++;
ngx_shmtx_unlock(&cache->shpool->mutex);
return 0;
}
// enable the reset flag before we start making any changes
sh->reset = 1;
}
// allocate a new entry
entry = ngx_buffer_cache_get_free_entry(sh);
if (entry == NULL)
{
goto error;
}
// calculate the buffer size
last_buffer = buffers + buffer_count;
buffer_size = 0;
for (cur_buffer = buffers; cur_buffer < last_buffer; cur_buffer++)
{
buffer_size += cur_buffer->len;
}
// allocate a buffer to hold the data
target_buffer = ngx_buffer_cache_get_free_buffer(sh, buffer_size);
if (target_buffer == NULL)
{
goto error;
}
// initialize the entry
entry->state = CES_ALLOCATED;
entry->node.key = hash;
memcpy(entry->key, key, BUFFER_CACHE_KEY_SIZE);
entry->start_offset = target_buffer;
entry->buffer_size = buffer_size;
// update the write position
sh->buffers_write = target_buffer;
// move from free_queue to used_queue
ngx_queue_remove(&entry->queue_node);
ngx_queue_insert_tail(&sh->used_queue, &entry->queue_node);
// insert to rbtree
ngx_rbtree_insert(&sh->rbtree, &entry->node);
// update stats
sh->stats.store_ok++;
sh->stats.store_bytes += buffer_size;
// Note: the memcpy is performed after releasing the lock to avoid holding the lock for a long time
// setting the access time of the entry and cache prevents it from being freed
sh->access_time = entry->access_time = ngx_time();
entry->write_time = ngx_time();
sh->reset = 0;
ngx_shmtx_unlock(&cache->shpool->mutex);
for (cur_buffer = buffers; cur_buffer < last_buffer; cur_buffer++)
{
target_buffer = ngx_copy(target_buffer, cur_buffer->data, cur_buffer->len);
}
// Note: no need to obtain the lock since state is ngx_atomic_t
entry->state = CES_READY;
return 1;
error:
sh->stats.store_err++;
sh->reset = 0;
ngx_shmtx_unlock(&cache->shpool->mutex);
return 0;
}
