ovsdb-tool: Convert clustered db to standalone db.

Add support in ovsdb-tool for migrating clustered dbs to standalone dbs.
E.g. usage to migrate nb/sb db to standalone db from raft:
ovsdb-tool cluster-to-standalone ovnnb_db.db ovnnb_db_cluster.db

Acked-by: Han Zhou <hzhou8@ebay.com>
Signed-off-by: Aliasgar Ginwala <aginwala@ebay.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>

Documentation/ref/ovsdb.7.rst

@@ -514,6 +514,9 @@ standalone database from the contents of a running clustered database.
 When the cluster is down and cannot be revived, ``ovsdb-client backup`` will
 not work.
 
+Use ``ovsdb-tool cluster-to-standalone`` to convert clustered database to
+standalone database when the cluster is down and cannot be revived.
+
 Upgrading or Downgrading a Database
 -----------------------------------
 

NEWS

@@ -52,6 +52,9 @@ v2.12.0 - 03 Sep 2019
        quickly after a brief disconnection, saving bandwidth and CPU time.
        See section 4.1.15 of ovsdb-server(7) for details of related OVSDB
        protocol extension.
+     * Support to convert from cluster database to standalone database is now
+       available when clustered is down and cannot be revived using ovsdb-tool
+       . Check "Database Migration Commands" in ovsdb-tool man section.
    - OVN:
      * IPAM/MACAM:
        - select IPAM mac_prefix in a random manner if not provided by the user

ovsdb/ovsdb-tool.1.in

@@ -146,6 +146,14 @@ avoid this possibility, specify \fB\-\-cid=\fIuuid\fR, where
 \fIuuid\fR is the cluster ID of the cluster to join, as printed by
 \fBovsdb\-tool get\-cid\fR.
 .
+.SS "Database Migration Commands"
+This commands will convert cluster database to standalone database.
+.
+.IP "\fBcluster\-to\-standalone\fI db clusterdb"
+Use this command to convert to standalone database from clustered database
+when the cluster is down and cannot be revived. It creates new standalone
+\fIdb\fR file from the given cluster \fIdb\fR file.
+.
 .SS "Version Management Commands"
 .so ovsdb/ovsdb-schemas.man
 .PP

ovsdb/ovsdb-tool.c

@@ -173,6 +173,9 @@ usage(void)
            "  compare-versions A OP B  compare OVSDB schema version numbers\n"
            "  query [DB] TRNS         execute read-only transaction on DB\n"
            "  transact [DB] TRNS      execute read/write transaction on DB\n"
+           "  cluster-to-standalone DB DB    Convert clustered DB to\n"
+           "      standalone DB when cluster is down and cannot be\n"
+           "        revived\n"
            "  [-m]... show-log [DB]   print DB's log entries\n"
            "The default DB is %s.\n"
            "The default SCHEMA is %s.\n",
@@ -942,6 +945,55 @@ print_raft_record(const struct raft_record *r,
     }
 }
 
+static void
+raft_header_to_standalone_log(const struct raft_header *h,
+                              struct ovsdb_log *db_log_data)
+{
+    if (h->snap_index) {
+        if (!h->snap.data || json_array(h->snap.data)->n != 2) {
+        ovs_fatal(0, "Incorrect raft header data array length");
+        }
+
+        struct json *schema_json = json_array(h->snap.data)->elems[0];
+        if (schema_json->type != JSON_NULL) {
+            struct ovsdb_schema *schema;
+            check_ovsdb_error(ovsdb_schema_from_json(schema_json, &schema));
+            ovsdb_schema_destroy(schema);
+            check_ovsdb_error(ovsdb_log_write_and_free(db_log_data,
+                                                       schema_json));
+        }
+
+        struct json *data_json = json_array(h->snap.data)->elems[1];
+        if (!data_json || data_json->type != JSON_OBJECT) {
+            ovs_fatal(0, "Invalid raft header data");
+        }
+        if (data_json->type != JSON_NULL) {
+            check_ovsdb_error(ovsdb_log_write_and_free(db_log_data,
+                                                       data_json));
+        }
+    }
+}
+
+static void
+raft_record_to_standalone_log(const struct raft_record *r,
+                              struct ovsdb_log *db_log_data)
+{
+    if (r->type == RAFT_REC_ENTRY) {
+        if (!r->entry.data) {
+            return;
+        }
+        if (json_array(r->entry.data)->n != 2) {
+            ovs_fatal(0, "Incorrect raft record array length");
+        }
+
+        struct json *data_json = json_array(r->entry.data)->elems[1];
+        if (data_json->type != JSON_NULL) {
+            check_ovsdb_error(ovsdb_log_write_and_free(db_log_data,
+                                                       data_json));
+        }
+    }
+}
+
 static void
 do_show_log_cluster(struct ovsdb_log *log)
 {
@@ -1511,6 +1563,51 @@ do_compare_versions(struct ovs_cmdl_context *ctx)
     exit(result ? 0 : 2);
 }
 
+static void
+do_convert_to_standalone(struct ovsdb_log *log, struct ovsdb_log *db_log_data)
+{
+    for (unsigned int i = 0; ; i++) {
+        struct json *json;
+        check_ovsdb_error(ovsdb_log_read(log, &json));
+        if (!json) {
+            break;
+        }
+
+        if (i == 0) {
+            struct raft_header h;
+            check_ovsdb_error(raft_header_from_json(&h, json));
+            raft_header_to_standalone_log(&h, db_log_data);
+            raft_header_uninit(&h);
+        } else {
+            struct raft_record r;
+            check_ovsdb_error(raft_record_from_json(&r, json));
+            raft_record_to_standalone_log(&r, db_log_data);
+            raft_record_uninit(&r);
+        }
+    }
+}
+
+static void
+do_cluster_standalone(struct ovs_cmdl_context *ctx)
+{
+    const char *db_file_name = ctx->argv[1];
+    const char *cluster_db_file_name = ctx->argv[2];
+    struct ovsdb_log *log;
+    struct ovsdb_log *db_log_data;
+
+    check_ovsdb_error(ovsdb_log_open(cluster_db_file_name,
+                                     OVSDB_MAGIC"|"RAFT_MAGIC,
+                                     OVSDB_LOG_READ_ONLY, -1, &log));
+    check_ovsdb_error(ovsdb_log_open(db_file_name, OVSDB_MAGIC,
+                                     OVSDB_LOG_CREATE_EXCL, -1, &db_log_data));
+    if (strcmp(ovsdb_log_get_magic(log), RAFT_MAGIC) != 0) {
+        ovs_fatal(0, "Database is not clustered db.\n");
+    }
+    do_convert_to_standalone(log, db_log_data);
+    check_ovsdb_error(ovsdb_log_commit_block(db_log_data));
+    ovsdb_log_close(db_log_data);
+    ovsdb_log_close(log);
+}
 
 static void
 do_help(struct ovs_cmdl_context *ctx OVS_UNUSED)
@@ -1550,7 +1647,9 @@ static const struct ovs_cmdl_command all_commands[] = {
     { "compare-versions", "a op b", 3, 3, do_compare_versions, OVS_RO },
     { "help", NULL, 0, INT_MAX, do_help, OVS_RO },
     { "list-commands", NULL, 0, INT_MAX, do_list_commands, OVS_RO },
-    { NULL, NULL, 0, 0, NULL, OVS_RO },
+    { "cluster-to-standalone", "db clusterdb", 2, 2,
+    do_cluster_standalone, OVS_RW },
+    { NULL, NULL, 2, 2, NULL, OVS_RO },
 };
 
 static const struct ovs_cmdl_command *get_all_commands(void)

tests/ovsdb-tool.at

@@ -459,3 +459,41 @@ OVS_APP_EXIT_AND_WAIT([ovsdb-server])
 # Make sure that the clustered data matched the standalone data.
 AT_CHECK([cat dump2], [0], [expout])
 AT_CLEANUP
+
+AT_SETUP([ovsdb-tool convert-to-standalone])
+AT_KEYWORDS([ovsdb file positive])
+ordinal_schema > schema
+AT_CHECK([ovsdb-tool create-cluster db schema unix:s1.raft], [0], [stdout], [ignore])
+AT_CHECK([ovsdb-server --detach --no-chdir --pidfile --remote=punix:socket --log-file db >/dev/null 2>&1])
+for txn in m4_foreach([txn], [[[["ordinals",
+      {"op": "insert",
+       "table": "ordinals",
+       "row": {"number": 0, "name": "zero"}},
+      {"op": "insert",
+       "table": "ordinals",
+       "row": {"number": 1, "name": "one"}},
+      {"op": "insert",
+       "table": "ordinals",
+       "row": {"number": 2, "name": "two"}}]]]], ['txn' ]); do
+AT_CHECK([ovsdb-client transact unix:socket "$txn"], [0], [ignore], [ignore])
+done
+AT_CHECK([ovsdb-client transact unix:socket '[["ordinals"]]'], [0],
+         [ignore], [ignore])
+AT_CHECK([ovsdb-client dump unix:socket > clusterdump])
+AT_CHECK([ovs-appctl -t ovsdb-server -e exit], [0], [ignore], [ignore])
+
+# Convert to standalone database from clustered database.
+AT_CHECK(ovsdb-tool cluster-to-standalone db1 db)
+
+# Check its standalone db
+AT_CHECK([ovsdb-tool db-is-standalone db1])
+
+# Dump the standalone db data.
+AT_CHECK([ovsdb-server -vconsole:off -vfile -vvlog:off --detach --no-chdir --pidfile --log-file --remote=punix:db.sock db1])
+AT_CHECK([ovsdb_client_wait ordinals connected])
+AT_CHECK([ovsdb-client dump  > standalonedump])
+OVS_APP_EXIT_AND_WAIT([ovsdb-server])
+
+# Make sure both standalone and cluster db data matches.
+AT_CHECK([diff standalonedump clusterdump])
+AT_CLEANUP