Adding upstream version 2.4.38.upstream/2.4.38upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 992 insertions, 0 deletions

diff --git a/modules/database/mod_dbd.c b/modules/database/mod_dbd.c
new file mode 100644
index 0000000..7212665
--- /dev/null
+++ b/modules/database/mod_dbd.c
@@ -0,0 +1,992 @@
+/* Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/* Overview of what this is and does:
+ * http://www.apache.org/~niq/dbd.html
+ * or
+ * http://apache.webthing.com/database/
+ */
+
+#include "apr_reslist.h"
+#include "apr_strings.h"
+#include "apr_hash.h"
+#include "apr_tables.h"
+#include "apr_lib.h"
+#include "apr_dbd.h"
+
+#define APR_WANT_MEMFUNC
+#define APR_WANT_STRFUNC
+#include "apr_want.h"
+
+#include "http_protocol.h"
+#include "http_config.h"
+#include "http_log.h"
+#include "http_request.h"
+#include "mod_dbd.h"
+
+extern module AP_MODULE_DECLARE_DATA dbd_module;
+
+APR_IMPLEMENT_OPTIONAL_HOOK_RUN_ALL(dbd, DBD, apr_status_t, post_connect,
+                                    (apr_pool_t *pool, dbd_cfg_t *cfg,
+                                    ap_dbd_t *dbd),
+                                    (pool, cfg, dbd), OK, DECLINED)
+
+/************ svr cfg: manage db connection pool ****************/
+
+#define NMIN_SET     0x1
+#define NKEEP_SET    0x2
+#define NMAX_SET     0x4
+#define EXPTIME_SET  0x8
+
+typedef struct dbd_group_t dbd_group_t;
+
+struct dbd_group_t {
+    dbd_cfg_t *cfg;
+    dbd_group_t *next;
+    apr_pool_t *pool;
+#if APR_HAS_THREADS
+    apr_thread_mutex_t *mutex;
+    apr_reslist_t *reslist;
+    int destroyed;
+#else
+    ap_dbd_t *rec;
+#endif
+};
+
+typedef struct {
+    dbd_cfg_t *cfg;
+    dbd_group_t *group;
+} svr_cfg;
+
+typedef enum { cmd_name, cmd_params, cmd_persist,
+               cmd_min, cmd_keep, cmd_max, cmd_exp
+} cmd_parts;
+
+static apr_pool_t *config_pool;
+static dbd_group_t *group_list;
+
+/* a default DBDriver value that'll generate meaningful error messages */
+static const char *const no_dbdriver = "[DBDriver unset]";
+
+/* A default nmin of >0 will help with generating meaningful
+ * startup error messages if the database is down.
+ */
+#define DEFAULT_NMIN 1
+#define DEFAULT_NKEEP 2
+#define DEFAULT_NMAX 10
+#define DEFAULT_EXPTIME 300
+
+#define DEFAULT_SQL_INIT_ARRAY_SIZE 5
+
+static void *create_dbd_config(apr_pool_t *pool, server_rec *s)
+{
+    svr_cfg *svr = apr_pcalloc(pool, sizeof(svr_cfg));
+    dbd_cfg_t *cfg = svr->cfg = apr_pcalloc(pool, sizeof(dbd_cfg_t));
+
+    cfg->server = s;
+    cfg->name = no_dbdriver; /* to generate meaningful error messages */
+    cfg->params = ""; /* don't risk segfault on misconfiguration */
+    cfg->persist = -1;
+#if APR_HAS_THREADS
+    cfg->nmin = DEFAULT_NMIN;
+    cfg->nkeep = DEFAULT_NKEEP;
+    cfg->nmax = DEFAULT_NMAX;
+    cfg->exptime = DEFAULT_EXPTIME;
+#endif
+    cfg->queries = apr_hash_make(pool);
+    cfg->init_queries = apr_array_make(pool, DEFAULT_SQL_INIT_ARRAY_SIZE,
+                                       sizeof(const char *));
+
+    return svr;
+}
+
+static void *merge_dbd_config(apr_pool_t *pool, void *basev, void *addv)
+{
+    dbd_cfg_t *base = ((svr_cfg*) basev)->cfg;
+    dbd_cfg_t *add = ((svr_cfg*) addv)->cfg;
+    svr_cfg *svr = apr_pcalloc(pool, sizeof(svr_cfg));
+    dbd_cfg_t *new = svr->cfg = apr_pcalloc(pool, sizeof(dbd_cfg_t));
+
+    new->server = add->server;
+    new->name = (add->name != no_dbdriver) ? add->name : base->name;
+    new->params = strcmp(add->params, "") ? add->params : base->params;
+    new->persist = (add->persist != -1) ? add->persist : base->persist;
+#if APR_HAS_THREADS
+    new->nmin = (add->set&NMIN_SET) ? add->nmin : base->nmin;
+    new->nkeep = (add->set&NKEEP_SET) ? add->nkeep : base->nkeep;
+    new->nmax = (add->set&NMAX_SET) ? add->nmax : base->nmax;
+    new->exptime = (add->set&EXPTIME_SET) ? add->exptime : base->exptime;
+#endif
+    new->queries = apr_hash_overlay(pool, add->queries, base->queries);
+    new->init_queries = apr_array_append(pool, add->init_queries,
+                                         base->init_queries);
+
+    return svr;
+}
+
+static void ap_dbd_sql_init(server_rec *s, const char *query)
+{
+    svr_cfg *svr;
+    const char **arr_item;
+
+    svr = ap_get_module_config(s->module_config, &dbd_module);
+    if (!svr) {
+         /* some modules may call from within config directive handlers, and
+          * if these are called in a server context that contains no mod_dbd
+          * config directives, then we have to create our own server config
+          */
+         svr = create_dbd_config(config_pool, s);
+         ap_set_module_config(s->module_config, &dbd_module, svr);
+    }
+
+    if (query) {
+        arr_item = apr_array_push(svr->cfg->init_queries);
+        *arr_item = query;
+    }
+}
+
+static const char *dbd_param(cmd_parms *cmd, void *dconf, const char *val)
+{
+    apr_status_t rv;
+    const apr_dbd_driver_t *driver = NULL;
+    svr_cfg *svr = ap_get_module_config(cmd->server->module_config,
+                                        &dbd_module);
+    dbd_cfg_t *cfg = svr->cfg;
+
+    switch ((long) cmd->info) {
+    case cmd_name:
+        cfg->name = val;
+        /* loading the driver involves once-only dlloading that is
+         * best done at server startup.  This also guarantees that
+         * we won't return an error later.
+         */
+        rv = apr_dbd_get_driver(cmd->pool, cfg->name, &driver);
+        if (APR_STATUS_IS_ENOTIMPL(rv)) {
+            return apr_psprintf(cmd->pool, "No driver for %s", cfg->name);
+        }
+        else if (APR_STATUS_IS_EDSOOPEN(rv)) {
+            return apr_psprintf(cmd->pool,
+#ifdef NETWARE
+                                "Can't load driver file dbd%s.nlm",
+#else
+                                "Can't load driver file apr_dbd_%s.so",
+#endif
+                                cfg->name);
+        }
+        else if (APR_STATUS_IS_ESYMNOTFOUND(rv)) {
+            return apr_psprintf(cmd->pool,
+                                "Failed to load driver apr_dbd_%s_driver",
+                                cfg->name);
+        }
+        break;
+    case cmd_params:
+        cfg->params = val;
+        break;
+    }
+
+    return NULL;
+}
+
+#if APR_HAS_THREADS
+static const char *dbd_param_int(cmd_parms *cmd, void *dconf, const char *val)
+{
+    svr_cfg *svr = ap_get_module_config(cmd->server->module_config,
+                                        &dbd_module);
+    dbd_cfg_t *cfg = svr->cfg;
+    const char *p;
+
+    for (p = val; *p; ++p) {
+        if (!apr_isdigit(*p)) {
+            return "Argument must be numeric!";
+        }
+    }
+
+    switch ((long) cmd->info) {
+    case cmd_min:
+        cfg->nmin = atoi(val);
+        cfg->set |= NMIN_SET;
+        break;
+    case cmd_keep:
+        cfg->nkeep = atoi(val);
+        cfg->set |= NKEEP_SET;
+        break;
+    case cmd_max:
+        cfg->nmax = atoi(val);
+        cfg->set |= NMAX_SET;
+        break;
+    case cmd_exp:
+        cfg->exptime = atoi(val);
+        cfg->set |= EXPTIME_SET;
+        break;
+    }
+
+    return NULL;
+}
+#endif
+
+static const char *dbd_param_flag(cmd_parms *cmd, void *dconf, int flag)
+{
+    svr_cfg *svr = ap_get_module_config(cmd->server->module_config,
+                                        &dbd_module);
+
+    switch ((long) cmd->info) {
+    case cmd_persist:
+        svr->cfg->persist = flag;
+        break;
+    }
+
+    return NULL;
+}
+
+static const char *dbd_prepare(cmd_parms *cmd, void *dconf, const char *query,
+                               const char *label)
+{
+    if (!label) {
+        label = query;
+        query = "";
+    }
+
+    ap_dbd_prepare(cmd->server, query, label);
+
+    return NULL;
+}
+
+static const char *dbd_init_sql(cmd_parms *cmd, void *dconf, const char *query)
+{
+    if (!query || *query == '\n') {
+        return "You should specify SQL statement";
+    }
+
+    ap_dbd_sql_init(cmd->server, query);
+
+    return NULL;
+}
+
+static const command_rec dbd_cmds[] = {
+    AP_INIT_TAKE1("DBDriver", dbd_param, (void*)cmd_name, RSRC_CONF,
+                  "SQL Driver"),
+    AP_INIT_TAKE1("DBDParams", dbd_param, (void*)cmd_params, RSRC_CONF,
+                  "SQL Driver Params"),
+    AP_INIT_FLAG("DBDPersist", dbd_param_flag, (void*)cmd_persist, RSRC_CONF,
+                 "Use persistent connection/pool"),
+    AP_INIT_TAKE12("DBDPrepareSQL", dbd_prepare, NULL, RSRC_CONF,
+                   "SQL statement to prepare (or nothing, to override "
+                   "statement inherited from main server) and label"),
+    AP_INIT_TAKE1("DBDInitSQL", dbd_init_sql, NULL, RSRC_CONF,
+                   "SQL statement to be executed after connection is created"),
+#if APR_HAS_THREADS
+    AP_INIT_TAKE1("DBDMin", dbd_param_int, (void*)cmd_min, RSRC_CONF,
+                  "Minimum number of connections"),
+    /* XXX: note that mod_proxy calls this "smax" */
+    AP_INIT_TAKE1("DBDKeep", dbd_param_int, (void*)cmd_keep, RSRC_CONF,
+                  "Maximum number of sustained connections"),
+    AP_INIT_TAKE1("DBDMax", dbd_param_int, (void*)cmd_max, RSRC_CONF,
+                  "Maximum number of connections"),
+    /* XXX: note that mod_proxy calls this "ttl" (time to live) */
+    AP_INIT_TAKE1("DBDExptime", dbd_param_int, (void*)cmd_exp, RSRC_CONF,
+                  "Keepalive time for idle connections"),
+#endif
+    {NULL}
+};
+
+static int dbd_pre_config(apr_pool_t *pconf, apr_pool_t *plog,
+                          apr_pool_t *ptemp)
+{
+   config_pool = pconf;
+   group_list = NULL;
+   return OK;
+}
+
+DBD_DECLARE_NONSTD(void) ap_dbd_prepare(server_rec *s, const char *query,
+                                        const char *label)
+{
+    svr_cfg *svr;
+
+    svr = ap_get_module_config(s->module_config, &dbd_module);
+    if (!svr) {
+         /* some modules may call from within config directive handlers, and
+          * if these are called in a server context that contains no mod_dbd
+          * config directives, then we have to create our own server config
+          */
+         svr = create_dbd_config(config_pool, s);
+         ap_set_module_config(s->module_config, &dbd_module, svr);
+    }
+
+    if (apr_hash_get(svr->cfg->queries, label, APR_HASH_KEY_STRING)
+        && strcmp(query, "")) {
+        ap_log_error(APLOG_MARK, APLOG_WARNING, 0, s, APLOGNO(02653)
+                     "conflicting SQL statements with label %s", label);
+    }
+
+    apr_hash_set(svr->cfg->queries, label, APR_HASH_KEY_STRING, query);
+}
+
+typedef struct {
+    const char *label, *query;
+} dbd_query_t;
+
+static int dbd_post_config(apr_pool_t *pconf, apr_pool_t *plog,
+                           apr_pool_t *ptemp, server_rec *s)
+{
+    server_rec *sp;
+    apr_array_header_t *add_queries = apr_array_make(ptemp, 10,
+                                                     sizeof(dbd_query_t));
+
+    for (sp = s; sp; sp = sp->next) {
+        svr_cfg *svr = ap_get_module_config(sp->module_config, &dbd_module);
+        dbd_cfg_t *cfg = svr->cfg;
+        apr_hash_index_t *hi_first = apr_hash_first(ptemp, cfg->queries);
+        dbd_group_t *group;
+
+        /* dbd_setup in 2.2.3 and under was causing spurious error messages
+         * when dbd isn't configured.  We can stop that with a quick check here
+         * together with a similar check in ap_dbd_open (where being
+         * unconfigured is a genuine error that must be reported).
+         */
+        if (cfg->name == no_dbdriver || !cfg->persist) {
+            continue;
+        }
+
+        for (group = group_list; group; group = group->next) {
+            dbd_cfg_t *group_cfg = group->cfg;
+            apr_hash_index_t *hi;
+            int group_ok = 1;
+
+            if (strcmp(cfg->name, group_cfg->name)
+                || strcmp(cfg->params, group_cfg->params)) {
+                continue;
+            }
+
+#if APR_HAS_THREADS
+            if (cfg->nmin != group_cfg->nmin
+                || cfg->nkeep != group_cfg->nkeep
+                || cfg->nmax != group_cfg->nmax
+                || cfg->exptime != group_cfg->exptime) {
+                continue;
+            }
+#endif
+
+            add_queries->nelts = 0;
+
+            for (hi = hi_first; hi; hi = apr_hash_next(hi)) {
+                const char *label, *query;
+                const char *group_query;
+
+                apr_hash_this(hi, (void*) &label, NULL, (void*) &query);
+
+                group_query = apr_hash_get(group_cfg->queries, label,
+                                           APR_HASH_KEY_STRING);
+
+                if (!group_query) {
+                    dbd_query_t *add_query = apr_array_push(add_queries);
+
+                    add_query->label = label;
+                    add_query->query = query;
+                }
+                else if (strcmp(query, group_query)) {
+                    group_ok = 0;
+                    break;
+                }
+            }
+
+            if (group_ok) {
+                int i;
+
+                for (i = 0; i < add_queries->nelts; ++i) {
+                    dbd_query_t *add_query = ((dbd_query_t*) add_queries->elts)
+                                             + i;
+
+                    apr_hash_set(group_cfg->queries, add_query->label,
+                                 APR_HASH_KEY_STRING, add_query->query);
+                }
+
+                svr->group = group;
+                break;
+            }
+        }
+
+        if (!svr->group) {
+            svr->group = group = apr_pcalloc(pconf, sizeof(dbd_group_t));
+
+            group->cfg = cfg;
+
+            group->next = group_list;
+            group_list = group;
+        }
+    }
+
+    return OK;
+}
+
+static apr_status_t dbd_prepared_init(apr_pool_t *pool, dbd_cfg_t *cfg,
+                                      ap_dbd_t *rec)
+{
+    apr_hash_index_t *hi;
+
+    rec->prepared = apr_hash_make(pool);
+
+    for (hi = apr_hash_first(pool, cfg->queries); hi;
+         hi = apr_hash_next(hi)) {
+        const char *label, *query;
+        apr_dbd_prepared_t *stmt;
+
+        apr_hash_this(hi, (void*) &label, NULL, (void*) &query);
+
+        if (!strcmp(query, "")) {
+            continue;
+        }
+
+        stmt = NULL;
+        if (apr_dbd_prepare(rec->driver, pool, rec->handle, query,
+                            label, &stmt)) {
+            return APR_EGENERAL;
+        }
+        else {
+            apr_hash_set(rec->prepared, label, APR_HASH_KEY_STRING, stmt);
+        }
+    }
+
+    return APR_SUCCESS;
+}
+
+static apr_status_t dbd_init_sql_init(apr_pool_t *pool, dbd_cfg_t *cfg,
+                                      ap_dbd_t *rec)
+{
+    int i;
+    apr_status_t rv = APR_SUCCESS;
+
+    for (i = 0; i < cfg->init_queries->nelts; i++) {
+        int nrows;
+        char **query_p;
+
+        query_p = (char **)cfg->init_queries->elts + i;
+
+        if (apr_dbd_query(rec->driver, rec->handle, &nrows, *query_p)) {
+            rv = APR_EGENERAL;
+            break;
+        }
+    }
+
+    return rv;
+}
+
+static apr_status_t dbd_close(void *data)
+{
+    ap_dbd_t *rec = data;
+
+    return apr_dbd_close(rec->driver, rec->handle);
+}
+
+#if APR_HAS_THREADS
+static apr_status_t dbd_destruct(void *data, void *params, apr_pool_t *pool)
+{
+    dbd_group_t *group = params;
+
+    if (!group->destroyed) {
+        ap_dbd_t *rec = data;
+
+        apr_pool_destroy(rec->pool);
+    }
+
+    return APR_SUCCESS;
+}
+#endif
+
+/* an apr_reslist_constructor for SQL connections
+ * Also use this for opening in non-reslist modes, since it gives
+ * us all the error-handling in one place.
+ */
+static apr_status_t dbd_construct(void **data_ptr,
+                                  void *params, apr_pool_t *pool)
+{
+    dbd_group_t *group = params;
+    dbd_cfg_t *cfg = group->cfg;
+    apr_pool_t *rec_pool, *prepared_pool;
+    ap_dbd_t *rec;
+    apr_status_t rv;
+    const char *err = "";
+
+    rv = apr_pool_create(&rec_pool, pool);
+    if (rv != APR_SUCCESS) {
+        ap_log_error(APLOG_MARK, APLOG_CRIT, rv, cfg->server, APLOGNO(00624)
+                     "Failed to create memory pool");
+        return rv;
+    }
+
+    rec = apr_pcalloc(rec_pool, sizeof(ap_dbd_t));
+
+    rec->pool = rec_pool;
+
+    /* The driver is loaded at config time now, so this just checks a hash.
+     * If that changes, the driver DSO could be registered to unload against
+     * our pool, which is probably not what we want.  Error checking isn't
+     * necessary now, but in case that changes in the future ...
+     */
+    rv = apr_dbd_get_driver(rec->pool, cfg->name, &rec->driver);
+    if (rv != APR_SUCCESS) {
+        if (APR_STATUS_IS_ENOTIMPL(rv)) {
+            ap_log_error(APLOG_MARK, APLOG_ERR, rv, cfg->server, APLOGNO(00625)
+                         "driver for %s not available", cfg->name);
+        }
+        else if (APR_STATUS_IS_EDSOOPEN(rv)) {
+            ap_log_error(APLOG_MARK, APLOG_ERR, rv, cfg->server, APLOGNO(00626)
+                         "can't find driver for %s", cfg->name);
+        }
+        else if (APR_STATUS_IS_ESYMNOTFOUND(rv)) {
+            ap_log_error(APLOG_MARK, APLOG_ERR, rv, cfg->server, APLOGNO(00627)
+                         "driver for %s is invalid or corrupted",
+                         cfg->name);
+        }
+        else {
+            ap_log_error(APLOG_MARK, APLOG_ERR, rv, cfg->server, APLOGNO(00628)
+                         "mod_dbd not compatible with APR in get_driver");
+        }
+        apr_pool_destroy(rec->pool);
+        return rv;
+    }
+
+    rv = apr_dbd_open_ex(rec->driver, rec->pool, cfg->params, &rec->handle, &err);
+    if (rv != APR_SUCCESS) {
+        switch (rv) {
+        case APR_EGENERAL:
+            ap_log_error(APLOG_MARK, APLOG_ERR, rv, cfg->server, APLOGNO(00629)
+                         "Can't connect to %s: %s", cfg->name, err);
+            break;
+        default:
+            ap_log_error(APLOG_MARK, APLOG_ERR, rv, cfg->server, APLOGNO(00630)
+                         "mod_dbd not compatible with APR in open");
+            break;
+        }
+
+        apr_pool_destroy(rec->pool);
+        return rv;
+    }
+
+    apr_pool_cleanup_register(rec->pool, rec, dbd_close,
+                              apr_pool_cleanup_null);
+
+    /* we use a sub-pool for the prepared statements for each connection so
+     * that they will be cleaned up first, before the connection is closed
+     */
+    rv = apr_pool_create(&prepared_pool, rec->pool);
+    if (rv != APR_SUCCESS) {
+        ap_log_error(APLOG_MARK, APLOG_CRIT, rv, cfg->server, APLOGNO(00631)
+                     "Failed to create memory pool");
+
+        apr_pool_destroy(rec->pool);
+        return rv;
+    }
+
+    rv = dbd_prepared_init(prepared_pool, cfg, rec);
+    if (rv != APR_SUCCESS) {
+        const char *errmsg = apr_dbd_error(rec->driver, rec->handle, rv);
+        ap_log_error(APLOG_MARK, APLOG_ERR, rv, cfg->server, APLOGNO(00632)
+                     "failed to prepare SQL statements: %s",
+                     (errmsg ? errmsg : "[???]"));
+
+        apr_pool_destroy(rec->pool);
+        return rv;
+    }
+
+    dbd_run_post_connect(prepared_pool, cfg, rec);
+
+    *data_ptr = rec;
+
+    return APR_SUCCESS;
+}
+
+#if APR_HAS_THREADS
+static apr_status_t dbd_destroy(void *data)
+{
+    dbd_group_t *group = data;
+
+    group->destroyed = 1;
+
+    return APR_SUCCESS;
+}
+
+static apr_status_t dbd_setup(server_rec *s, dbd_group_t *group)
+{
+    dbd_cfg_t *cfg = group->cfg;
+    apr_status_t rv;
+
+    /* We create the reslist using a sub-pool of the pool passed to our
+     * child_init hook.  No other threads can be here because we're
+     * either in the child_init phase or dbd_setup_lock() acquired our mutex.
+     * No other threads will use this sub-pool after this, except via
+     * reslist calls, which have an internal mutex.
+     *
+     * We need to short-circuit the cleanup registered internally by
+     * apr_reslist_create().  We do this by registering dbd_destroy()
+     * as a cleanup afterwards, so that it will run before the reslist's
+     * internal cleanup.
+     *
+     * If we didn't do this, then we could free memory twice when the pool
+     * was destroyed.  When apr_pool_destroy() runs, it first destroys all
+     * all the per-connection sub-pools created in dbd_construct(), and
+     * then it runs the reslist's cleanup.  The cleanup calls dbd_destruct()
+     * on each resource, which would then attempt to destroy the sub-pools
+     * a second time.
+     */
+    rv = apr_reslist_create(&group->reslist,
+                            cfg->nmin, cfg->nkeep, cfg->nmax,
+                            apr_time_from_sec(cfg->exptime),
+                            dbd_construct, dbd_destruct, group,
+                            group->pool);
+    if (rv != APR_SUCCESS) {
+        ap_log_error(APLOG_MARK, APLOG_ERR, rv, s, APLOGNO(00633)
+                     "failed to initialise");
+        return rv;
+    }
+
+    apr_pool_cleanup_register(group->pool, group, dbd_destroy,
+                              apr_pool_cleanup_null);
+
+    return APR_SUCCESS;
+}
+#endif
+
+static apr_status_t dbd_setup_init(apr_pool_t *pool, server_rec *s)
+{
+    dbd_group_t *group;
+    apr_status_t rv = APR_SUCCESS;
+
+    for (group = group_list; group; group = group->next) {
+        apr_status_t rv2;
+
+        rv2 = apr_pool_create(&group->pool, pool);
+        if (rv2 != APR_SUCCESS) {
+            ap_log_error(APLOG_MARK, APLOG_CRIT, rv2, s, APLOGNO(00634)
+                         "Failed to create reslist cleanup memory pool");
+            return rv2;
+        }
+
+#if APR_HAS_THREADS
+        rv2 = dbd_setup(s, group);
+        if (rv2 == APR_SUCCESS) {
+            continue;
+        }
+        else if (rv == APR_SUCCESS) {
+            rv = rv2;
+        }
+
+        /* we failed, so create a mutex so that subsequent competing callers
+         * to ap_dbd_open can serialize themselves while they retry
+         */
+        rv2 = apr_thread_mutex_create(&group->mutex,
+                                      APR_THREAD_MUTEX_DEFAULT, pool);
+        if (rv2 != APR_SUCCESS) {
+             ap_log_error(APLOG_MARK, APLOG_CRIT, rv2, s, APLOGNO(00635)
+                          "Failed to create thread mutex");
+             return rv2;
+        }
+#endif
+    }
+
+    return rv;
+}
+
+static void dbd_child_init(apr_pool_t *p, server_rec *s)
+{
+  apr_status_t rv = dbd_setup_init(p, s);
+  if (rv) {
+    ap_log_error(APLOG_MARK, APLOG_CRIT, rv, s, APLOGNO(00636)
+                 "child init failed!");
+  }
+}
+
+#if APR_HAS_THREADS
+static apr_status_t dbd_setup_lock(server_rec *s, dbd_group_t *group)
+{
+    apr_status_t rv = APR_SUCCESS, rv2;
+
+    /* several threads could be here at the same time, all trying to
+     * initialize the reslist because dbd_setup_init failed to do so
+     */
+    if (!group->mutex) {
+        /* we already logged an error when the mutex couldn't be created */
+        return APR_EGENERAL;
+    }
+
+    rv2 = apr_thread_mutex_lock(group->mutex);
+    if (rv2 != APR_SUCCESS) {
+        ap_log_error(APLOG_MARK, APLOG_ERR, rv2, s, APLOGNO(00637)
+                     "Failed to acquire thread mutex");
+        return rv2;
+    }
+
+    if (!group->reslist) {
+        rv = dbd_setup(s, group);
+    }
+
+    rv2 = apr_thread_mutex_unlock(group->mutex);
+    if (rv2 != APR_SUCCESS) {
+        ap_log_error(APLOG_MARK, APLOG_ERR, rv2, s, APLOGNO(00638)
+                     "Failed to release thread mutex");
+        if (rv == APR_SUCCESS) {
+            rv = rv2;
+        }
+    }
+
+    return rv;
+}
+#endif
+
+/* Functions we export for modules to use:
+        - open acquires a connection from the pool (opens one if necessary)
+        - close releases it back in to the pool
+*/
+DBD_DECLARE_NONSTD(void) ap_dbd_close(server_rec *s, ap_dbd_t *rec)
+{
+    svr_cfg *svr = ap_get_module_config(s->module_config, &dbd_module);
+
+    if (!svr->cfg->persist) {
+        apr_pool_destroy(rec->pool);
+    }
+#if APR_HAS_THREADS
+    else {
+        apr_reslist_release(svr->group->reslist, rec);
+    }
+#endif
+}
+
+static apr_status_t dbd_check(apr_pool_t *pool, server_rec *s, ap_dbd_t *rec)
+{
+    svr_cfg *svr;
+    apr_status_t rv = apr_dbd_check_conn(rec->driver, pool, rec->handle);
+    const char *errmsg;
+
+    if ((rv == APR_SUCCESS) || (rv == APR_ENOTIMPL)) {
+        return APR_SUCCESS;
+    }
+
+    /* we don't have a driver-specific error code, so we'll just pass
+     * a "success" value and rely on the driver to ignore it
+     */
+    errmsg = apr_dbd_error(rec->driver, rec->handle, 0);
+    if (!errmsg) {
+        errmsg = "(unknown)";
+    }
+
+    svr = ap_get_module_config(s->module_config, &dbd_module);
+    ap_log_error(APLOG_MARK, APLOG_ERR, rv, s, APLOGNO(00639)
+                 "DBD [%s] Error: %s", svr->cfg->name, errmsg);
+    return rv;
+}
+
+DBD_DECLARE_NONSTD(ap_dbd_t*) ap_dbd_open(apr_pool_t *pool, server_rec *s)
+{
+    svr_cfg *svr = ap_get_module_config(s->module_config, &dbd_module);
+    dbd_group_t *group = svr->group;
+    dbd_cfg_t *cfg = svr->cfg;
+    ap_dbd_t *rec = NULL;
+#if APR_HAS_THREADS
+    apr_status_t rv;
+#endif
+
+    /* If nothing is configured, we shouldn't be here */
+    if (cfg->name == no_dbdriver) {
+        ap_log_error(APLOG_MARK, APLOG_ERR, 0, s, APLOGNO(02654)
+                     "not configured");
+        return NULL;
+    }
+
+    if (!cfg->persist) {
+        /* Return a once-only connection */
+        group = apr_pcalloc(pool, sizeof(dbd_group_t));
+
+        group->cfg = cfg;
+
+        dbd_construct((void*) &rec, group, pool);
+        return rec;
+    }
+
+#if APR_HAS_THREADS
+    if (!group->reslist) {
+        if (dbd_setup_lock(s, group) != APR_SUCCESS) {
+            return NULL;
+        }
+    }
+
+    rv = apr_reslist_acquire(group->reslist, (void*) &rec);
+    if (rv != APR_SUCCESS) {
+        ap_log_error(APLOG_MARK, APLOG_ERR, rv, s, APLOGNO(02655)
+                     "Failed to acquire DBD connection from pool!");
+        return NULL;
+    }
+
+    if (dbd_check(pool, s, rec) != APR_SUCCESS) {
+        apr_reslist_invalidate(group->reslist, rec);
+        return NULL;
+    }
+#else
+    /* If we have a persistent connection and it's good, we'll use it;
+     * since this is non-threaded, we can update without a mutex
+     */
+    rec = group->rec;
+    if (rec) {
+        if (dbd_check(pool, s, rec) != APR_SUCCESS) {
+            apr_pool_destroy(rec->pool);
+            rec = NULL;
+        }
+    }
+
+    /* We don't have a connection right now, so we'll open one */
+    if (!rec) {
+        dbd_construct((void*) &rec, group, group->pool);
+        group->rec = rec;
+    }
+#endif
+
+    return rec;
+}
+
+#if APR_HAS_THREADS
+typedef struct {
+    ap_dbd_t *rec;
+    apr_reslist_t *reslist;
+} dbd_acquire_t;
+
+static apr_status_t dbd_release(void *data)
+{
+    dbd_acquire_t *acq = data;
+    apr_reslist_release(acq->reslist, acq->rec);
+    return APR_SUCCESS;
+}
+
+DBD_DECLARE_NONSTD(ap_dbd_t *) ap_dbd_acquire(request_rec *r)
+{
+    dbd_acquire_t *acq;
+
+    while (!ap_is_initial_req(r)) {
+        if (r->prev) {
+            r = r->prev;
+        }
+        else if (r->main) {
+            r = r->main;
+        }
+    }
+
+    acq = ap_get_module_config(r->request_config, &dbd_module);
+    if (!acq) {
+        acq = apr_palloc(r->pool, sizeof(dbd_acquire_t));
+        acq->rec = ap_dbd_open(r->pool, r->server);
+        if (acq->rec) {
+            svr_cfg *svr = ap_get_module_config(r->server->module_config,
+                                                &dbd_module);
+
+            ap_set_module_config(r->request_config, &dbd_module, acq);
+            if (svr->cfg->persist) {
+                acq->reslist = svr->group->reslist;
+                apr_pool_cleanup_register(r->pool, acq, dbd_release,
+                                          apr_pool_cleanup_null);
+            }
+        }
+    }
+
+    return acq->rec;
+}
+
+DBD_DECLARE_NONSTD(ap_dbd_t *) ap_dbd_cacquire(conn_rec *c)
+{
+    dbd_acquire_t *acq = ap_get_module_config(c->conn_config, &dbd_module);
+
+    if (!acq) {
+        acq = apr_palloc(c->pool, sizeof(dbd_acquire_t));
+        acq->rec = ap_dbd_open(c->pool, c->base_server);
+        if (acq->rec) {
+            svr_cfg *svr = ap_get_module_config(c->base_server->module_config,
+                                                &dbd_module);
+
+            ap_set_module_config(c->conn_config, &dbd_module, acq);
+            if (svr->cfg->persist) {
+                acq->reslist = svr->group->reslist;
+                apr_pool_cleanup_register(c->pool, acq, dbd_release,
+                                          apr_pool_cleanup_null);
+            }
+        }
+    }
+
+    return acq->rec;
+}
+#else
+DBD_DECLARE_NONSTD(ap_dbd_t *) ap_dbd_acquire(request_rec *r)
+{
+    ap_dbd_t *rec;
+
+    while (!ap_is_initial_req(r)) {
+        if (r->prev) {
+            r = r->prev;
+        }
+        else if (r->main) {
+            r = r->main;
+        }
+    }
+
+    rec = ap_get_module_config(r->request_config, &dbd_module);
+    if (!rec) {
+        rec = ap_dbd_open(r->pool, r->server);
+        if (rec) {
+            ap_set_module_config(r->request_config, &dbd_module, rec);
+        }
+    }
+
+    return rec;
+}
+
+DBD_DECLARE_NONSTD(ap_dbd_t *) ap_dbd_cacquire(conn_rec *c)
+{
+    ap_dbd_t *rec = ap_get_module_config(c->conn_config, &dbd_module);
+
+    if (!rec) {
+        rec = ap_dbd_open(c->pool, c->base_server);
+        if (rec) {
+            ap_set_module_config(c->conn_config, &dbd_module, rec);
+        }
+    }
+
+    return rec;
+}
+#endif
+
+static void dbd_hooks(apr_pool_t *pool)
+{
+    ap_hook_pre_config(dbd_pre_config, NULL, NULL, APR_HOOK_MIDDLE);
+    ap_hook_post_config(dbd_post_config, NULL, NULL, APR_HOOK_MIDDLE);
+    ap_hook_child_init(dbd_child_init, NULL, NULL, APR_HOOK_MIDDLE);
+
+    APR_REGISTER_OPTIONAL_FN(ap_dbd_prepare);
+    APR_REGISTER_OPTIONAL_FN(ap_dbd_open);
+    APR_REGISTER_OPTIONAL_FN(ap_dbd_close);
+    APR_REGISTER_OPTIONAL_FN(ap_dbd_acquire);
+    APR_REGISTER_OPTIONAL_FN(ap_dbd_cacquire);
+
+    APR_OPTIONAL_HOOK(dbd, post_connect, dbd_init_sql_init,
+                      NULL, NULL, APR_HOOK_MIDDLE);
+
+    apr_dbd_init(pool);
+}
+
+AP_DECLARE_MODULE(dbd) = {
+    STANDARD20_MODULE_STUFF,
+    NULL,
+    NULL,
+    create_dbd_config,
+    merge_dbd_config,
+    dbd_cmds,
+    dbd_hooks
+};
+