Merge pull request #6818 from chu11/issue6814_flux_kvs_sync

flux-kvs: support sync command

Author: mergify[bot]

doc/man1/flux-kvs.rst

@@ -21,6 +21,7 @@ SYNOPSIS
 | **flux** **kvs** **getroot**
 | **flux** **kvs** **version**
 | **flux** **kvs** **wait** *version*
+| **flux** **kvs** **sync**
 
 | **flux** **kvs** **namespace** **create** [*-o owner*] *name...*
 | **flux** **kvs** **namespace** **remove** *name...*
@@ -435,6 +436,16 @@ Block until the KVS version reaches *version* or greater. A simple form
 of synchronization between peers is: node A puts a value, commits it,
 reads version, sends version to node B. Node B waits for version, gets value.
 
+sync
+----
+
+.. program:: flux kvs sync
+
+Flush pending content and checkpoints to disk to ensure data persists
+across a Flux instance crash.  This command is identical to the
+:command:`flux kvs put` :option:`--sync` option, but does not require
+any data to be written.
+
 namespace create
 ----------------
 

src/cmd/flux-kvs.c

@@ -47,6 +47,7 @@ int cmd_move (optparse_t *p, int argc, char **argv);
 int cmd_dir (optparse_t *p, int argc, char **argv);
 int cmd_ls (optparse_t *p, int argc, char **argv);
 int cmd_getroot (optparse_t *p, int argc, char **argv);
+int cmd_sync (optparse_t *p, int argc, char **argv);
 int cmd_eventlog (optparse_t *p, int argc, char **argv);
 
 static int get_window_width (optparse_t *p, int fd);
@@ -373,6 +374,13 @@ static struct optparse_subcommand subcommands[] = {
       0,
       getroot_opts
     },
+    { "sync",
+      NULL,
+      "sync content and checkpoint to disk",
+      cmd_sync,
+      0,
+      NULL
+    },
     { "eventlog",
       NULL,
       "Manipulate a KVS eventlog",
@@ -1828,6 +1836,37 @@ int cmd_getroot (optparse_t *p, int argc, char **argv)
     return (0);
 }
 
+/* We could call kvs_checkpoint_commit() for syncing, however we
+ * choose to go with FLUX_KVS_SYNC and an empty transaction.  That way
+ * this "transaction" goes into the same queue as other KVS
+ * transactions and syncs after all previously submitted KVS
+ * transactions.  In contrast, kvs_checkpoint_commit() operates
+ * outside of the KVS transaction queue.
+ */
+int cmd_sync (optparse_t *p, int argc, char **argv)
+{
+    flux_t *h;
+    int optindex = optparse_option_index (p);
+    flux_kvs_txn_t *txn;
+    flux_future_t *f;
+
+    if (optindex != argc) {
+        optparse_print_usage (p);
+        exit (1);
+    }
+    if (!(h = flux_open (NULL, 0)))
+        log_err_exit ("flux_open");
+    if (!(txn = flux_kvs_txn_create ()))
+        log_err_exit ("flux_kvs_txn_create");
+    if (!(f = flux_kvs_commit (h, NULL, FLUX_KVS_SYNC, txn))
+        || flux_future_get (f, NULL) < 0)
+        log_err_exit ("flux_kvs_commit");
+    flux_future_destroy (f);
+    flux_kvs_txn_destroy (txn);
+    flux_close (h);
+    return (0);
+}
+
 /* combine 'argv' elements into one space-separated string (caller must free).
  * assumes 'argv' is NULL terminated.
  */

t/t1010-kvs-commit-sync.t

@@ -33,7 +33,7 @@ test_expect_success 'kvs: no checkpoint of kvs-primary should exist yet' '
         test_must_fail checkpoint_get kvs-primary
 '
 
-test_expect_success 'kvs: put some data to kvs and sync it' '
+test_expect_success 'kvs: put some data to kvs and sync it (flux kvs put)' '
         flux kvs put --blobref --sync c=3 > syncblob.out
 '
 
@@ -46,6 +46,16 @@ test_expect_success 'kvs: checkpoint of kvs-primary should match rootref' '
         test_cmp syncblob.out checkpoint.out
 '
 
+test_expect_success 'kvs: put some data to kvs and sync it (flux kvs sync)' '
+        flux kvs put --blobref d=4 > syncblob2.out &&
+        flux kvs sync
+'
+
+test_expect_success 'kvs: checkpoint of kvs-primary should match rootref' '
+        checkpoint_get kvs-primary | jq -r .value.rootref > checkpoint2.out &&
+        test_cmp syncblob2.out checkpoint2.out
+'
+
 test_expect_success 'kvs: sync fails against non-primary namespace' '
         flux kvs namespace create ${TESTNAMESPACE} &&
         flux kvs put --namespace=${TESTNAMESPACE} a=10 &&

t/t2816-fsck-cmd.t

@@ -29,8 +29,8 @@ test_expect_success 'create some kvs content' '
 '
 # N.B. startlog commands in rc scripts normally ensures a checkpoint
 # exists but we do this just to be extra sure
-test_expect_success 'call --sync to ensure we have checkpointed' '
-	flux kvs put --sync dir.sync=foo
+test_expect_success 'call sync to ensure we have checkpointed' '
+	flux kvs sync
 '
 test_expect_success 'save some treeobjs for later' '
 	flux kvs get --treeobj dir.b > dirb.out &&