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/* Copyright (c) 2004-2018 Dovecot authors, see the included COPYING file */
#include "lib.h"
#include "array.h"
#include "hash.h"
#include "sql-api-private.h"
#include "sql-db-cache.h"
#define SQL_DB_CACHE_CONTEXT(obj) \
MODULE_CONTEXT_REQUIRE(obj, sql_db_cache_module)
struct sql_db_cache_context {
union sql_db_module_context module_ctx;
struct sql_db *prev, *next; /* These are set while refcount=0 */
struct sql_db_cache *cache;
int refcount;
char *key;
void (*orig_deinit)(struct sql_db *db);
};
struct sql_db_cache {
HASH_TABLE(char *, struct sql_db *) dbs;
unsigned int unused_count, max_unused_connections;
struct sql_db *unused_tail, *unused_head;
};
static MODULE_CONTEXT_DEFINE_INIT(sql_db_cache_module, &sql_db_module_register);
static void sql_db_cache_db_unref(struct sql_db *db)
{
struct sql_db_cache_context *ctx = SQL_DB_CACHE_CONTEXT(db);
struct sql_db_cache_context *head_ctx;
if (--ctx->refcount > 0)
return;
i_assert(db->refcount == 2);
ctx->cache->unused_count++;
if (ctx->cache->unused_tail == NULL)
ctx->cache->unused_tail = db;
else {
head_ctx = SQL_DB_CACHE_CONTEXT(ctx->cache->unused_head);
head_ctx->next = db;
}
ctx->prev = ctx->cache->unused_head;
ctx->cache->unused_head = db;
}
static void sql_db_cache_unlink(struct sql_db_cache_context *ctx)
{
struct sql_db_cache_context *prev_ctx, *next_ctx;
i_assert(ctx->refcount == 0);
if (ctx->prev == NULL)
ctx->cache->unused_tail = ctx->next;
else {
prev_ctx = SQL_DB_CACHE_CONTEXT(ctx->prev);
prev_ctx->next = ctx->next;
}
if (ctx->next == NULL)
ctx->cache->unused_head = ctx->prev;
else {
next_ctx = SQL_DB_CACHE_CONTEXT(ctx->next);
next_ctx->prev = ctx->prev;
}
ctx->cache->unused_count--;
}
static void sql_db_cache_free_tail(struct sql_db_cache *cache)
{
struct sql_db *db;
struct sql_db_cache_context *ctx;
db = cache->unused_tail;
i_assert(db->refcount == 1);
ctx = SQL_DB_CACHE_CONTEXT(db);
sql_db_cache_unlink(ctx);
hash_table_remove(cache->dbs, ctx->key);
i_free(ctx->key);
i_free(ctx);
db->v.unref = NULL;
sql_unref(&db);
}
static void sql_db_cache_drop_oldest(struct sql_db_cache *cache)
{
while (cache->unused_count >= cache->max_unused_connections)
sql_db_cache_free_tail(cache);
}
int sql_db_cache_new(struct sql_db_cache *cache, const struct sql_settings *set,
struct sql_db **db_r, const char **error_r)
{
struct sql_db_cache_context *ctx;
struct sql_db *db;
char *key;
key = i_strdup_printf("%s\t%s", set->driver, set->connect_string);
db = hash_table_lookup(cache->dbs, key);
if (db != NULL) {
ctx = SQL_DB_CACHE_CONTEXT(db);
if (ctx->refcount == 0) {
sql_db_cache_unlink(ctx);
ctx->prev = ctx->next = NULL;
}
i_free(key);
} else {
sql_db_cache_drop_oldest(cache);
if (sql_init_full(set, &db, error_r) < 0) {
i_free(key);
return -1;
}
ctx = i_new(struct sql_db_cache_context, 1);
ctx->cache = cache;
ctx->key = key;
ctx->orig_deinit = db->v.deinit;
db->v.unref = sql_db_cache_db_unref;
MODULE_CONTEXT_SET(db, sql_db_cache_module, ctx);
hash_table_insert(cache->dbs, ctx->key, db);
}
ctx->refcount++;
sql_ref(db);
*db_r = db;
return 0;
}
struct sql_db_cache *sql_db_cache_init(unsigned int max_unused_connections)
{
struct sql_db_cache *cache;
cache = i_new(struct sql_db_cache, 1);
hash_table_create(&cache->dbs, default_pool, 0, str_hash, strcmp);
cache->max_unused_connections = max_unused_connections;
return cache;
}
void sql_db_cache_deinit(struct sql_db_cache **_cache)
{
struct sql_db_cache *cache = *_cache;
*_cache = NULL;
while (cache->unused_tail != NULL)
sql_db_cache_free_tail(cache);
hash_table_destroy(&cache->dbs);
i_free(cache);
}
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