[#9683] Automatic updating of Cassandra client (ycqlsh) internal meta…

…data cache.

Summary:
Implemented automatic internal cache update in case of an internal 'not found' error.

The cache updating is automatic & invisible.
To see when the cache is updated -  start the tool with `--debug` argument:
```
ycqlsh 127.0.0.3 --debug
```

Generic requests (like `DESC TABLES`, `DESC <keyspace>`) will NOT show updated information till e.g. the info will be updated via the `DESC <table>` request, which initiates the internal cache refreshing.
The new command line argument `--refresh_on_describe` (or `-r`) can be used to force the cache refreshing on every `DESC` command.
```
ycqlsh 127.0.0.3 --refresh_on_describe
```

The new function  `refresh_schema_metadata(self, fn_to_rerun, args, ex)` after the metadata refreshing must automatically rerun the function-caller: `fn_to_rerun(*args)`. If a recursive call detected, the exception will be raised (actually it's an old exception from the original implementation before the fix.) Automatic rerun of the caller helps too keep main part of the code unchanged.

Test Plan:
In terminal 1:
  CREATE KEYSPACE a;
  CREATE TABLE t (h INT PRIMARY KEY);
In terminal 2:
  SELECT * FROM a.t;
or
  INSERT INTO a.t (h) VALUES (1);
or
  DROP TABLE a.t;
or
  DESC a.t
or
  DESC a

Reviewers: mihnea, pjain

Reviewed By: pjain

Subscribers: yql

Differential Revision: https://phabricator.dev.yugabyte.com/D12972

bin/ycqlsh.py

@@ -175,7 +175,7 @@ def find_zip(libprefix):
 from cqlshlib import cql3handling, cqlhandling, pylexotron, sslhandling, cqlshhandling
 from cqlshlib.copyutil import ExportTask, ImportTask
 from cqlshlib.displaying import (ANSI_RESET, BLUE, COLUMN_NAME_COLORS, CYAN,
-                                 RED, WHITE, FormattedValue, colorme)
+                                 RED, WHITE, YELLOW, FormattedValue, colorme)
 from cqlshlib.formatting import (DEFAULT_DATE_FORMAT, DEFAULT_NANOTIME_FORMAT,
                                  DEFAULT_TIMESTAMP_FORMAT, CqlType, DateTimeFormat,
                                  format_by_type, formatter_for)
@@ -237,6 +237,8 @@ def find_zip(libprefix):
                   help='Specify the default request timeout in seconds (default: %default seconds).')
 parser.add_option("-t", "--tty", action='store_true', dest='tty',
                   help='Force tty mode (command prompt).')
+parser.add_option("-r", "--refresh_on_describe", action='store_true',
+                  help='Force refreshing of the schema metadata on DESCRIBE command.')
 
 optvalues = optparse.Values()
 (options, arguments) = parser.parse_args(sys.argv[1:], values=optvalues)
@@ -420,6 +422,7 @@ class Shell(cmd.Cmd):
     last_hist = None
     shunted_query_out = None
     use_paging = True
+    in_refresh_schema_metadata = False
 
     default_page_size = 100
 
@@ -439,7 +442,8 @@ def __init__(self, hostname, port, color=False,
                  single_statement=None,
                  request_timeout=DEFAULT_REQUEST_TIMEOUT_SECONDS,
                  protocol_version=DEFAULT_PROTOCOL_VERSION,
-                 connect_timeout=DEFAULT_CONNECT_TIMEOUT_SECONDS):
+                 connect_timeout=DEFAULT_CONNECT_TIMEOUT_SECONDS,
+                 refresh_on_describe=False):
         cmd.Cmd.__init__(self, completekey=completekey)
         self.hostname = hostname
         self.port = port
@@ -525,6 +529,8 @@ def __init__(self, hostname, port, color=False,
         self.statement_error = False
         self.single_statement = single_statement
 
+        self.refresh_on_describe = refresh_on_describe
+
     @property
     def is_using_utf8(self):
         # utf8 encodings from https://docs.python.org/{2,3}/library/codecs.html
@@ -538,6 +544,23 @@ def check_windows_encoding(self):
                           "If you experience encoding problems, change your console"
                           " codepage with 'chcp 65001' before starting ycqlsh.\n".format(self.encoding))
 
+    def internal_refresh_schema_metadata(self):
+        if self.debug:
+            self.printerr("Refreshing schema metadata cache...", color=YELLOW)
+        self.conn.refresh_schema_metadata(-1)
+
+    def refresh_schema_metadata(self, fn_to_rerun, args, ex):
+        if self.in_refresh_schema_metadata:
+            raise ex
+
+        self.internal_refresh_schema_metadata()
+
+        try:
+            self.in_refresh_schema_metadata = True
+            return fn_to_rerun(*args)
+        finally:
+            self.in_refresh_schema_metadata = False
+
     def set_expanded_cql_version(self, ver):
         ver, vertuple = full_cql_version(ver)
         self.cql_version = ver
@@ -647,7 +670,8 @@ def get_usertype_layout(self, ksname, typename):
         try:
             user_type = ks_meta.user_types[typename]
         except KeyError:
-            raise UserTypeNotFound("User type %r not found" % typename)
+            return self.refresh_schema_metadata(self.get_usertype_layout, (ksname, typename),
+                UserTypeNotFound("User type %r not found" % typename))
 
         return list(zip(user_type.field_names, user_type.field_types))
 
@@ -671,7 +695,8 @@ def get_partitioner(self):
 
     def get_keyspace_meta(self, ksname):
         if ksname not in self.conn.metadata.keyspaces:
-            raise KeyspaceNotFound('Keyspace %r not found.' % ksname)
+            return self.refresh_schema_metadata(self.get_keyspace_meta, (ksname,),
+                KeyspaceNotFound('Keyspace %r not found.' % ksname))
         return self.conn.metadata.keyspaces[ksname]
 
     def get_keyspaces(self):
@@ -690,7 +715,8 @@ def get_table_meta(self, ksname, tablename):
             if ksname == 'system_auth' and tablename in ['roles', 'role_permissions']:
                 self.get_fake_auth_table_meta(ksname, tablename)
             else:
-                raise ColumnFamilyNotFound("Column family %r not found" % tablename)
+                return self.refresh_schema_metadata(self.get_table_meta, (ksname, tablename),
+                    ColumnFamilyNotFound("Column family %r not found" % tablename))
         else:
             return ksmeta.tables[tablename]
 
@@ -711,15 +737,17 @@ def get_fake_auth_table_meta(self, ksname, tablename):
             table_meta.columns['resource'] = ColumnMetadata(table_meta, 'resource', cassandra.cqltypes.UTF8Type)
             table_meta.columns['permission'] = ColumnMetadata(table_meta, 'permission', cassandra.cqltypes.UTF8Type)
         else:
-            raise ColumnFamilyNotFound("Column family %r not found" % tablename)
+            return self.refresh_schema_metadata(self.get_fake_auth_table_meta, (ksname, tablename),
+                ColumnFamilyNotFound("Column family %r not found" % tablename))
 
     def get_index_meta(self, ksname, idxname):
         if ksname is None:
             ksname = self.current_keyspace
         ksmeta = self.get_keyspace_meta(ksname)
 
         if idxname not in ksmeta.indexes:
-            raise IndexNotFound("Index %r not found" % idxname)
+            return self.refresh_schema_metadata(self.get_index_meta, (ksname, idxname),
+                IndexNotFound("Index %r not found" % idxname))
 
         return ksmeta.indexes[idxname]
 
@@ -729,15 +757,17 @@ def get_view_meta(self, ksname, viewname):
         ksmeta = self.get_keyspace_meta(ksname)
 
         if viewname not in ksmeta.views:
-            raise MaterializedViewNotFound("Materialized view %r not found" % viewname)
+            return self.refresh_schema_metadata(self.get_view_meta, (ksname, viewname),
+                MaterializedViewNotFound("Materialized view %r not found" % viewname))
         return ksmeta.views[viewname]
 
     def get_object_meta(self, ks, name):
         if name is None:
             if ks and ks in self.conn.metadata.keyspaces:
                 return self.conn.metadata.keyspaces[ks]
             elif self.current_keyspace is None:
-                raise ObjectNotFound("%r not found in keyspaces" % (ks))
+                return self.refresh_schema_metadata(self.get_object_meta, (ks, name),
+                    ObjectNotFound("%r not found in keyspaces" % (ks)))
             else:
                 name = ks
                 ks = self.current_keyspace
@@ -754,7 +784,8 @@ def get_object_meta(self, ks, name):
         elif name in ksmeta.views:
             return ksmeta.views[name]
 
-        raise ObjectNotFound("%r not found in keyspace %r" % (name, ks))
+        return self.refresh_schema_metadata(self.get_object_meta, (ks, name),
+            ObjectNotFound("%r not found in keyspace %r" % (name, ks)))
 
     def get_usertypes_meta(self):
         data = self.session.execute("select * from system.schema_usertypes")
@@ -1005,7 +1036,8 @@ def parse_for_select_meta(self, query_string):
             try:
                 return self.get_view_meta(ks, name)
             except MaterializedViewNotFound:
-                raise ObjectNotFound("%r not found in keyspace %r" % (name, ks))
+                return self.refresh_schema_metadata(self.parse_for_select_meta, (query_string,),
+                    ObjectNotFound("%r not found in keyspace %r" % (name, ks)))
 
     def parse_for_update_meta(self, query_string):
         try:
@@ -1321,7 +1353,8 @@ def describe_function(self, ksname, functionname):
         ksmeta = self.get_keyspace_meta(ksname)
         functions = [f for f in list(ksmeta.functions.values()) if f.name == functionname]
         if len(functions) == 0:
-            raise FunctionNotFound("User defined function %r not found" % functionname)
+            return self.refresh_schema_metadata(self.describe_function, (ksname, functionname),
+                FunctionNotFound("User defined function %r not found" % functionname))
         print("\n\n".join(func.export_as_string() for func in functions))
         print('')
 
@@ -1346,7 +1379,8 @@ def describe_aggregate(self, ksname, aggregatename):
         ksmeta = self.get_keyspace_meta(ksname)
         aggregates = [f for f in list(ksmeta.aggregates.values()) if f.name == aggregatename]
         if len(aggregates) == 0:
-            raise FunctionNotFound("User defined aggregate %r not found" % aggregatename)
+            return self.refresh_schema_metadata(self.describe_aggregate, (ksname, aggregatename),
+                FunctionNotFound("User defined aggregate %r not found" % aggregatename))
         print("\n\n".join(aggr.export_as_string() for aggr in aggregates))
         print('')
 
@@ -1372,7 +1406,8 @@ def describe_usertype(self, ksname, typename):
         try:
             usertype = ksmeta.user_types[typename]
         except KeyError:
-            raise UserTypeNotFound("User type %r not found" % typename)
+            return self.refresh_schema_metadata(self.describe_usertype, (ksname, typename),
+                UserTypeNotFound("User type %r not found" % typename))
         print(usertype.export_as_string())
 
     def _columnize_unicode(self, name_list, quote=False):
@@ -1498,6 +1533,9 @@ def do_describe(self, parsed):
           where object can be either a keyspace or a table or an index or a materialized
           view (in this order).
   """
+        if self.refresh_on_describe:
+            self.internal_refresh_schema_metadata()
+
         what = parsed.matched[1][1].lower()
         if what == 'functions':
             self.describe_functions(self.current_keyspace)
@@ -1747,7 +1785,8 @@ def do_source(self, parsed):
                          display_timezone=self.display_timezone,
                          max_trace_wait=self.max_trace_wait, ssl=self.ssl,
                          request_timeout=self.session.default_timeout,
-                         connect_timeout=self.conn.connect_timeout)
+                         connect_timeout=self.conn.connect_timeout,
+                         refresh_on_describe=self.refresh_on_describe)
         subshell.cmdloop()
         f.close()
 
@@ -2217,6 +2256,7 @@ def read_options(cmdlineargs, environment):
     optvalues.max_trace_wait = option_with_default(configs.getfloat, 'tracing', 'max_trace_wait',
                                                    DEFAULT_MAX_TRACE_WAIT)
     optvalues.timezone = option_with_default(configs.get, 'ui', 'timezone', None)
+    optvalues.refresh_on_describe = option_with_default(configs.getboolean, 'ui', 'refresh_on_describe', False)
 
     optvalues.debug = False
     optvalues.file = None
@@ -2390,7 +2430,8 @@ def main(options, hostname, port):
                       single_statement=options.execute,
                       request_timeout=options.request_timeout,
                       connect_timeout=options.connect_timeout,
-                      encoding=options.encoding)
+                      encoding=options.encoding,
+                      refresh_on_describe=options.refresh_on_describe)
     except KeyboardInterrupt:
         sys.exit('Connection aborted.')
     except CQL_ERRORS as e: