I'm building an erlang app in a docker container.
My data directory is connected as a docker volume.
I'm using:
application:set_env(mnesia, schema_location, disc),
and {disc_copies, Nodes}.
When I restart the app with:
docker-composer stop myapp && docker-composer up myapp
all works fine but when I turn it off completely with:
sudo systemctl restart docker
docker-composer up -d
Mnesia stops recognizing my data. The same is true when I restart my computer.
Basically (after this "hard" restart) Mnesia starts normally but when I try to read anything from it, I get an error:
{running_method,getTasksByProjectId}
terminate reason: {aborted,{no_exists,mtm_tasks}}
terminate reason: {{aborted,{no_exists,mtm_tasks}},
{gen_server,call,
[{global,tasks_da_serv},
{get_tasks_by_project_id,
"j1xvqric-2oj2q784xieccowg8880"}]}}
=ERROR REPORT==== 8-Jun-2017::10:29:04 ===
** Generic server tasks_da_serv terminating
** Last message in was {get_tasks_by_project_id,
"j1xvqric-2oj2q784xieccowg8880"}
** When Server state == {tasks_da_state}
** Reason for termination ==
** {{aborted,{no_exists,mtm_tasks}},
[{mnesia,wrap_trans,6,[{file,"mnesia.erl"},{line,404}]},
{tasks_logic,get_tasks_by_project_id,1,
[{file,"/release/_build/default/lib/tasks/src/tasks_logic.erl"},
{line,70}]},
{tasks_da_serv,handle_call,3,
[{file,"/release/_build/default/lib/tasks/src/tasks_da_serv.erl"},
{line,52}]},
{gen_server,try_handle_call,4,[{file,"gen_server.erl"},{line,615}]},
{gen_server,handle_msg,5,[{file,"gen_server.erl"},{line,647}]},
{proc_lib,init_p_do_apply,3,[{file,"proc_lib.erl"},{line,247}]}]}
Starting {global,tasks_da_serv} (<0.492.0>)
Starting {global,tasks_manager_serv} (<0.497.0>)
=ERROR REPORT==== 8-Jun-2017::10:29:04 ===
** Generic server tasks_manager_serv terminating
** Last message in was {{'basic.deliver',
<<"amq.ctag-pt-OySikx5BShVLRASvIPw">>,1,false,
<<>>,<<"tasks">>},
{amqp_msg,
{'P_basic',undefined,undefined,[],undefined,
undefined,undefined,undefined,undefined,
undefined,undefined,undefined,undefined,
undefined,undefined},
<<"{\"correlationId\":\"j3oa5b84-pcxn9ld6mswsck8kw48\",\"replyTo\":\"amq.gen-8h_kLqz4sHB-qjJ2cj8Y6w\",\"method\":\"getTasksByProjectId\",\"params\":{\"projectId\":\"j1xvqric-2oj2q784xieccowg8880\"}}">>}}
** When Server state == {tasks_manager_state,<0.481.0>,<0.490.0>}
** Reason for termination ==
** {{{aborted,{no_exists,mtm_tasks}},
{gen_server,call,
[{global,tasks_da_serv},
{get_tasks_by_project_id,"j1xvqric-2oj2q784xieccowg8880"}]}},
[{gen_server,call,2,[{file,"gen_server.erl"},{line,204}]},
{tasks_manager_logic,handle_message,2,
[{file,"/release/_build/default/lib/tasks/src/tasks_manager_logic.erl"},
{line,7}]},
{tasks_manager_serv,handle_info,2,
[{file,"/release/_build/default/lib/tasks/src/tasks_manager_serv.erl"},
{line,45}]},
{gen_server,try_dispatch,4,[{file,"gen_server.erl"},{line,601}]},
{gen_server,handle_msg,5,[{file,"gen_server.erl"},{line,667}]},
{proc_lib,init_p_do_apply,3,[{file,"proc_lib.erl"},{line,247}]}]}
At this point the only way to make it work again is to remove the data from the docker volume.
I have figured it out. The problem is that docker is assigning a custom hostnames to containers and Mnesia disc copy apparently is bound to hostname. Now I have fixed hostname in docker-compose.yaml file:
version: '2'
services:
myapp:
build: './myapp'
hostname: 'myapp'
volumes:
...
And now can restart it without loosing data.