Hello Julien,

I applied the mysql+pymysql change you suggested but with the same result, gnocchi-metricd was running for almos 30 minutes before segfaulting again. The gnocchi-metricd.log file shows:

(...)
2016-01-14 15:24:47.765 31023 DEBUG gnocchi.service [-] ******************************************************************************** log_opt_values /usr/local/lib/python2.7/dist-packages/oslo_config/cfg.py:2343
2016-01-14 15:25:02.653 2114 DEBUG oslo_db.sqlalchemy.engines [-] MySQL server mode set to STRICT_TRANS_TABLES,STRICT_ALL_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,TRADITIONAL,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION _check_effective_sql_mode /usr/local/lib/python2.7/dist-packages/oslo_db/sqlalchemy/engines.py:256
2016-01-14 15:25:02.654 2115 DEBUG oslo_db.sqlalchemy.engines [-] MySQL server mode set to STRICT_TRANS_TABLES,STRICT_ALL_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,TRADITIONAL,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION _check_effective_sql_mode /usr/local/lib/python2.7/dist-packages/oslo_db/sqlalchemy/engines.py:256
2016-01-14 15:25:02.658 2114 DEBUG gnocchi.storage [-] Processing new and to delete measures process_background_tasks /usr/local/lib/python2.7/dist-packages/gnocchi/storage/__init__.py:171
2016-01-14 15:25:02.658 2115 DEBUG gnocchi.storage [-] Processing new and to delete measures process_background_tasks /usr/local/lib/python2.7/dist-packages/gnocchi/storage/__init__.py:171
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage [-] Unexpected error during measures processing
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage Traceback (most recent call last):
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage   File "/usr/local/lib/python2.7/dist-packages/gnocchi/storage/__init__.py", line 173, in process_background_tasks
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage     self.process_measures(index, sync)
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage   File "/usr/local/lib/python2.7/dist-packages/gnocchi/storage/_carbonara.py", line 159, in process_measures
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage     metrics = indexer.get_metrics(metrics_to_process)
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage   File "/usr/local/lib/python2.7/dist-packages/gnocchi/indexer/sqlalchemy.py", line 148, in get_metrics
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage     metrics = list(query.all())
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/query.py", line 2584, in all
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage     return list(self)
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/query.py", line 2732, in __iter__
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage     return self._execute_and_instances(context)
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/query.py", line 2747, in _execute_and_instances
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage     result = conn.execute(querycontext.statement, self._params)
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 914, in execute
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage     return meth(self, multiparams, params)
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/elements.py", line 323, in _execute_on_connection
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage     return connection._execute_clauseelement(self, multiparams, params)
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 1003, in _execute_clauseelement
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage     inline=len(distilled_params) > 1)
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage   File "<string>", line 1, in <lambda>
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/elements.py", line 494, in compile
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage     return self._compiler(dialect, bind=bind, **kw)
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/elements.py", line 500, in _compiler
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage     return dialect.statement_compiler(dialect, self, **kw)
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/compiler.py", line 392, in __init__
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage     Compiled.__init__(self, dialect, statement, **kwargs)
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/compiler.py", line 190, in __init__
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage     self.string = self.process(self.statement, **compile_kwargs)
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/compiler.py", line 213, in process
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage     return obj._compiler_dispatch(self, **kwargs)
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/visitors.py", line 81, in _compiler_dispatch
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage     return meth(self, **kw)
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/compiler.py", line 1602, in visit_select
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage     text, select, inner_columns, froms, byfrom, kwargs)
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/compiler.py", line 1699, in _compose_select_body
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage     t = select._whereclause._compiler_dispatch(self, **kwargs)
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/visitors.py", line 93, in _compiler_dispatch
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage     return meth(self, **kw)
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/compiler.py", line 745, in visit_clauselist
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage     for c in clauselist.clauses)
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/compiler.py", line 742, in <genexpr>
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage     s for s in
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/compiler.py", line 745, in <genexpr>
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage     for c in clauselist.clauses)
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/visitors.py", line 93, in _compiler_dispatch
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage     return meth(self, **kw)
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/compiler.py", line 921, in visit_binary
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage     return self._generate_generic_binary(binary, opstring, **kw)
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/compiler.py", line 938, in _generate_generic_binary
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage     binary.right._compiler_dispatch(self, **kw)
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/visitors.py", line 93, in _compiler_dispatch
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage     return meth(self, **kw)
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/compiler.py", line 524, in visit_grouping
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage     return "(" + grouping.element._compiler_dispatch(self, **kwargs) + ")"
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/visitors.py", line 93, in _compiler_dispatch
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage     return meth(self, **kw)
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/compiler.py", line 745, in visit_clauselist
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage     for c in clauselist.clauses)
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/compiler.py", line 742, in <genexpr>
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage     s for s in
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/compiler.py", line 745, in <genexpr>
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage     for c in clauselist.clauses)
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/visitors.py", line 93, in _compiler_dispatch
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage     return meth(self, **kw)
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/compiler.py", line 1091, in visit_bindparam
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage     self.binds[bindparam.key] = self.binds[name] = bindparam
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage MemoryError
2016-01-14 15:52:10.018 2115 ERROR gnocchi.storage 
2016-01-14 15:52:11.810 2115 DEBUG gnocchi.storage [-] Expunging deleted metrics process_background_tasks /usr/local/lib/python2.7/dist-packages/gnocchi/storage/__init__.py:179
2016-01-14 15:52:12.567 2115 DEBUG gnocchi.storage [-] Processing new and to delete measures process_background_tasks /usr/local/lib/python2.7/dist-packages/gnocchi/storage/__init__.py:171

Is 16GB of RAM too little? Should I try to distribute metricd among several hosts?

Thanks, regards.