[PATCH v2 04/10] box: don't use box_checkpoint_is_in_progress outside box.cc

[Vladimir Davydov <vdavydov.dev@gmail.com>]

We only use box_checkpoint_is_in_progress in SIGUSR1 signal handler to
print a warning in case checkpointing cannot be started, because it's
already done by another fiber. Actually, it's not necessary to use it
there - instead we can simply log the error returned by box_checkpoint,
which will be self-explaining ER_CHECKPOINT_IN_PROGRESS in this case.
So let's make box_checkpoint_is_in_progress private to box.cc - this
will simplify moving the checkpoint daemon to the gc module.

While we are at it, remove the unused snapshot_version declaration.
---
 src/box/box.cc | 12 ++++++++----
 src/box/box.h  |  5 -----
 src/main.cc    | 21 +++++++++++++++------
 3 files changed, 23 insertions(+), 15 deletions(-)

diff --git a/src/box/box.cc b/src/box/box.cc
index 036769a9..d146ec16 100644
--- a/src/box/box.cc
+++ b/src/box/box.cc
@@ -87,10 +87,14 @@ static void title(const char *new_status)
 	systemd_snotify("STATUS=%s", status);
 }
 
-bool box_checkpoint_is_in_progress = false;
 const struct vclock *box_vclock = &replicaset.vclock;
 
 /**
+ * Set if there's a fiber performing box_checkpoint() right now.
+ */
+static bool checkpoint_is_in_progress;
+
+/**
  * Set if backup is in progress, i.e. box_backup_start() was
  * called but box_backup_stop() hasn't been yet.
  */
@@ -2182,11 +2186,11 @@ box_checkpoint()
 	if (! is_box_configured)
 		return 0;
 	int rc = 0;
-	if (box_checkpoint_is_in_progress) {
+	if (checkpoint_is_in_progress) {
 		diag_set(ClientError, ER_CHECKPOINT_IN_PROGRESS);
 		return -1;
 	}
-	box_checkpoint_is_in_progress = true;
+	checkpoint_is_in_progress = true;
 	/* create checkpoint files */
 	latch_lock(&schema_lock);
 	if ((rc = engine_begin_checkpoint()))
@@ -2206,7 +2210,7 @@ end:
 		engine_abort_checkpoint();
 
 	latch_unlock(&schema_lock);
-	box_checkpoint_is_in_progress = false;
+	checkpoint_is_in_progress = false;
 
 	/*
 	 * Wait for background garbage collection that might
diff --git a/src/box/box.h b/src/box/box.h
index 7712c192..6de0691d 100644
--- a/src/box/box.h
+++ b/src/box/box.h
@@ -124,11 +124,6 @@ box_wait_ro(bool ro, double timeout);
 void
 box_set_orphan(bool orphan);
 
-/** True if snapshot is in progress. */
-extern bool box_checkpoint_is_in_progress;
-/** Incremented with each next snapshot. */
-extern uint32_t snapshot_version;
-
 /**
  * Iterate over all spaces and save them to the
  * snapshot file.
diff --git a/src/main.cc b/src/main.cc
index 6fb0e479..993355ac 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -96,18 +96,27 @@ tarantool_uptime(void)
 }
 
 /**
-* Create a checkpoint from signal handler (SIGUSR1)
-*/
+ * Create a checkpoint from signal handler (SIGUSR1)
+ */
+static int
+sig_checkpoint_f(va_list ap)
+{
+	(void)ap;
+	if (box_checkpoint() != 0)
+		diag_log();
+	return 0;
+}
+
 static void
 sig_checkpoint(ev_loop * /* loop */, struct ev_signal * /* w */,
 	     int /* revents */)
 {
-	if (box_checkpoint_is_in_progress) {
-		say_warn("Checkpoint is already in progress,"
-			" the signal is ignored");
+	struct fiber *f = fiber_new("checkpoint", sig_checkpoint_f);
+	if (f == NULL) {
+		say_warn("failed to allocate checkpoint fiber");
 		return;
 	}
-	fiber_start(fiber_new_xc("checkpoint", (fiber_func)box_checkpoint));
+	fiber_wakeup(f);
 }
 
 static void
-- 
2.11.0