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https://issues.apache.org/jira/browse/COUCHDB-2975?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15211933#comment-15211933
]
Nick Vatamaniuc commented on COUCHDB-2975:
------------------------------------------
Noticed transient mode does not clean up child specs after it is done. Even if
exit is normal. The intent behind that is to let users restart children.
>From erlang docs saw this {{If the child is temporary, the child specification
>is deleted as soon as the process terminates. This means that delete_child/2
>has no meaning, and restart_child/2 can not be used for these children.}}
However in our code sometimes we explicitly delete child:
{code}
cancel_replication({BaseId, Extension}) ->
...
case supervisor:terminate_child(couch_replicator_job_sup, FullRepId) of
ok ->
...
case supervisor:delete_child(couch_replicator_job_sup, FullRepId) of
ok ->
{ok, {cancelled, ?l2b(FullRepId)}};
...
{code}
That would make it seem as if supervisor auto-deleted the child spec in some
cases. To test that it doesn't start a normal replication (not a continuous
one) and then after it is finished inspect the state of
{{couch_replicator_job_sup}}.
An example of state from supervisor after 10 replication have finished on a
cluster:
{code}
{state,
{local,couch_replicator_job_sup},
one_for_one,
[{child,undefined,"ac35738f5003c02b6780116fdf04b524",
{gen_server,start_link,
[couch_replicator,
{rep,
{"ac35738f5003c02b6780116fdf04b524",[]},
{httpdb,"http://adm:pass@localhost:5984/rdyno_src_0001/";,
nil,
[{"Accept","application/json"},
{"User-Agent","CouchDB-Replicator/5fa9098"}],
200000,
[{socket_options,[{keepalive,true},{nodelay,false}]}],
1,250,nil,1},
{httpdb,"http://adm:pass@localhost:5984/rdyno_tgt_0009/";,
nil,
[{"Accept","application/json"},
{"User-Agent","CouchDB-Replicator/5fa9098"}],
200000,
[{socket_options,[{keepalive,true},{nodelay,false}]}],
1,250,nil,1},
[{checkpoint_interval,5000},
{connection_timeout,200000},
{continuous,false},
{http_connections,1},
{retries,1},
{socket_options,[{keepalive,true},{nodelay,false}]},
{use_checkpoints,true},
{worker_batch_size,500},
{worker_processes,1}],
{user_ctx,null,[],undefined},
db,nil,
<<"rdyno_0001"...(15 B)>>,
<<"shards/a00"...(47 B)>>},
[{timeout,200000}]]},
transient,250,worker,
[couch_replicator]},
{child,undefined,"6c48c1ab7a6e3ed5e3d4415ced912e4a",
{gen_server,start_link,
[couch_replicator,
{rep,
{"6c48c1ab7a6e3ed5e3d4415ced912e4a",[]},
{httpdb,"http://adm:pass@localhost:5984/rdyno_src_0001/";,
nil,
[{"Accept","application/json"},
{"User-Agent","CouchDB-Replicator/5fa9098"}],
200000,
[{socket_options,[{keepalive,true},{nodelay,false}]}],
1,250,nil,1},
{httpdb,"http://adm:pass@localhost:5984/rdyno_tgt_0002/";,
nil,
[{"Accept","application/json"},
{"User-Agent","CouchDB-Replicator/5fa9098"}],
200000,
[{socket_options,[{keepalive,true},{nodelay,false}]}],
1,250,nil,1},
[{checkpoint_interval,5000},
{connection_timeout,200000},
{continuous,false},
{http_connections,1},
{retries,1},
{socket_options,[{keepalive,true},{nodelay,false}]},
{use_checkpoints,true},
{worker_batch_size,500},
{worker_processes,1}],
{user_ctx,null,[],undefined},
db,nil,
<<"rdyno_0001"...(15 B)>>,
<<"shards/200"...(47 B)>>},
[{timeout,200000}]]},
transient,250,worker,
[couch_replicator]}],
undefined,100,1,[],couch_replicator_job_sup,[]}
{code}
> Automatically restart replication jobs if they crash
> ----------------------------------------------------
>
> Key: COUCHDB-2975
> URL: https://issues.apache.org/jira/browse/COUCHDB-2975
> Project: CouchDB
> Issue Type: Improvement
> Components: Replication
> Reporter: Robert Newson
>
> We currently use the temporary restart strategy for replication jobs, which
> means if they crash they are not restarted.
> Instead, let's use the transient restart strategy, ensuring they are
> restarted on abnormal termination, while still allowing these tasks to end
> successfully on completion or cancellation.
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