mdbx: provide additional info via mdbx_env_info_ex().

Change-Id: Icfc751da73f090833800ad5429a9b296b4e34700

mdbx.h

@@ -1606,6 +1606,31 @@ typedef struct MDBX_envinfo {
   uint32_t mi_numreaders;   /* max reader slots used in the environment */
   uint32_t mi_dxb_pagesize; /* database pagesize */
   uint32_t mi_sys_pagesize; /* system pagesize */
+
+  uint64_t
+      mi_bootid[2]; /* A mostly unique ID that is regenerated on each boot.
+                       As such it can be used to identify the local
+                       machine's current boot. MDBX uses such when open
+                       the database to determine whether rollback required
+                       to the last steady sync point or not. I.e. if current
+                       bootid is differ from the value within a database then
+                       the system was rebooted and all changes since last steady
+                       sync must be reverted for data integrity. Zeros mean that
+                       no relevant information is available from the system. */
+  uint64_t mi_unsync_volume; /* bytes not explicitly synchronized to disk */
+  uint64_t mi_autosync_threshold;        /* current auto-sync threshold, see
+                                            mdbx_env_set_syncbytes(). */
+  uint32_t mi_since_sync_seconds16dot16; /* time since the last steady sync in
+                                            1/65536 of second */
+  uint32_t mi_autosync_period_seconds16dot16 /* current auto-sync period in
+                                                1/65536 of second, see
+                                                mdbx_env_set_syncperiod(). */
+      ;
+  uint32_t mi_since_reader_check_seconds16dot16; /* time since the last readers
+                                                    check in 1/65536 of second,
+                                                    see mdbx_reader_check(). */
+  uint32_t mi_mode; /* current environment mode, the same as
+                       mdbx_env_get_flags() returns. */
 } MDBX_envinfo;
 
 /* Return information about the MDBX environment.

src/elements/core.c

@@ -13027,12 +13027,14 @@ int __cold mdbx_env_info_ex(const MDBX_env *env, const MDBX_txn *txn,
     env = txn->mt_env;
   }
 
-  if (unlikely(bytes != sizeof(MDBX_envinfo)))
+  const size_t size_before_bootid = offsetof(MDBX_envinfo, mi_bootid);
+  if (unlikely(bytes != sizeof(MDBX_envinfo)) && bytes != size_before_bootid)
     return MDBX_EINVAL;
 
   const MDBX_meta *const meta0 = METAPAGE(env, 0);
   const MDBX_meta *const meta1 = METAPAGE(env, 1);
   const MDBX_meta *const meta2 = METAPAGE(env, 2);
+  pgno_t unsynced_pages;
   while (1) {
     if (unlikely(env->me_flags & MDBX_FATAL_ERROR))
       return MDBX_PANIC;
@@ -13063,6 +13065,8 @@ int __cold mdbx_env_info_ex(const MDBX_env *env, const MDBX_txn *txn,
     arg->mi_geo.upper = pgno2bytes(env, txn_meta->mm_geo.upper);
     arg->mi_geo.shrink = pgno2bytes(env, txn_meta->mm_geo.shrink);
     arg->mi_geo.grow = pgno2bytes(env, txn_meta->mm_geo.grow);
+    unsynced_pages = *env->me_unsynced_pages +
+                     (*env->me_meta_sync_txnid != (uint32_t)arg->mi_last_pgno);
 
     arg->mi_mapsize = env->me_mapsize;
     mdbx_compiler_barrier();
@@ -13082,15 +13086,32 @@ int __cold mdbx_env_info_ex(const MDBX_env *env, const MDBX_txn *txn,
   arg->mi_dxb_pagesize = env->me_psize;
   arg->mi_sys_pagesize = env->me_os_psize;
 
+  const MDBX_lockinfo *const lck = env->me_lck;
+  if (likely(bytes > size_before_bootid)) {
+    arg->mi_unsync_volume = pgno2bytes(env, unsynced_pages);
+    const uint64_t monotime_now = mdbx_osal_monotime();
+    arg->mi_since_sync_seconds16dot16 =
+        mdbx_osal_monotime_to_16dot16(monotime_now - *env->me_sync_timestamp);
+    arg->mi_since_reader_check_seconds16dot16 =
+        lck ? mdbx_osal_monotime_to_16dot16(monotime_now -
+                                            lck->mti_reader_check_timestamp)
+            : 0;
+    arg->mi_autosync_threshold = pgno2bytes(env, *env->me_autosync_threshold);
+    arg->mi_autosync_period_seconds16dot16 =
+        mdbx_osal_monotime_to_16dot16(*env->me_autosync_period);
+    arg->mi_bootid[0] = lck ? lck->mti_bootid[0] : 0;
+    arg->mi_bootid[1] = lck ? lck->mti_bootid[1] : 0;
+    arg->mi_mode = lck ? lck->mti_envmode : env->me_flags;
+  }
+
   arg->mi_self_latter_reader_txnid = arg->mi_latter_reader_txnid = 0;
-  if (env->me_lck) {
-    MDBX_reader *rlt = env->me_lck->mti_readers;
+  if (lck) {
     arg->mi_self_latter_reader_txnid = arg->mi_latter_reader_txnid =
         arg->mi_recent_txnid;
     for (unsigned i = 0; i < arg->mi_numreaders; ++i) {
-      const uint32_t pid = rlt[i].mr_pid;
+      const uint32_t pid = lck->mti_readers[i].mr_pid;
       if (pid) {
-        const txnid_t txnid = safe64_read(&rlt[i].mr_txnid);
+        const txnid_t txnid = safe64_read(&lck->mti_readers[i].mr_txnid);
         if (arg->mi_latter_reader_txnid > txnid)
           arg->mi_latter_reader_txnid = txnid;
         if (pid == env->me_pid && arg->mi_self_latter_reader_txnid > txnid)

src/elements/internals.h

@@ -535,8 +535,12 @@ typedef struct MDBX_lockinfo {
   /* Marker to distinguish uniqueness of DB/CLK.*/
   volatile uint64_t mti_bait_uniqueness;
 
-  /* the hash of /proc/sys/kernel/random/boot_id or analogue */
-  volatile uint64_t mti_boot_id;
+  /* The analogue /proc/sys/kernel/random/boot_id or similar to determine
+   * whether the system was rebooted after the last use of the database files.
+   * If there was no reboot, but there is no need to rollback to the last
+   * steady sync point. Zeros mean that no relevant information is available
+   * from the system. */
+  volatile uint64_t mti_bootid[2];
 
   alignas(MDBX_CACHELINE_SIZE) /* cacheline ---------------------------------*/
 #ifdef MDBX_OSAL_LOCK