diff options
Diffstat (limited to 'lib/stdlib/doc/src/supervisor.xml')
| -rw-r--r-- | lib/stdlib/doc/src/supervisor.xml | 75 |
1 files changed, 52 insertions, 23 deletions
diff --git a/lib/stdlib/doc/src/supervisor.xml b/lib/stdlib/doc/src/supervisor.xml index ec607d6e4c..cddb55e5c5 100644 --- a/lib/stdlib/doc/src/supervisor.xml +++ b/lib/stdlib/doc/src/supervisor.xml @@ -93,6 +93,10 @@ instead the child specification identifier is used, <c>terminate_child/2</c> will return <c>{error,simple_one_for_one}</c>.</p> + <p>Because a <c>simple_one_for_one</c> supervisor could have many + children, it shuts them all down at same time. So, order in which they + are stopped is not defined. For the same reason, it could have an + overhead with regards to the <c>Shutdown</c> strategy.</p> </item> </list> <p>To prevent a supervisor from getting into an infinite loop of @@ -154,7 +158,7 @@ child_spec() = {Id,StartFunc,Restart,Shutdown,Type,Modules} death causes the temporary process to be terminated) and a <c>transient</c> child process should be restarted only if it terminates abnormally, i.e. with another exit reason - than <c>normal</c>.</p> + than <c>normal</c>, <c>shutdown</c> or <c>{shutdown,Term}</c>.</p> </item> <item> <p><c>Shutdown</c> defines how a child process should be @@ -169,7 +173,15 @@ child_spec() = {Id,StartFunc,Restart,Shutdown,Type,Modules} <c>exit(Child,kill)</c>.</p> <p>If the child process is another supervisor, <c>Shutdown</c> should be set to <c>infinity</c> to give the subtree ample - time to shutdown.</p> + time to shutdown. It is also allowed to set it to <c>infinity</c>, + if the child process is a worker.</p> + <warning> + <p>Be careful by setting the <c>Shutdown</c> strategy to + <c>infinity</c> when the child process is a worker. Because, in this + situation, the termination of the supervision tree depends on the + child process, it must be implemented in a safe way and its cleanup + procedure must always return.</p> + </warning> <p><em>Important note on simple-one-for-one supervisors:</em> The dynamically created child processes of a simple-one-for-one supervisor are not explicitly killed, @@ -343,14 +355,23 @@ child_spec() = {Id,StartFunc,Restart,Shutdown,Type,Modules} <desc> <p>Tells the supervisor <c><anno>SupRef</anno></c> to terminate the given child.</p> + <p>If the supervisor is not <c>simple_one_for_one</c>, - <c><anno>Id</anno></c> must be the child specification identifier. The - process, if there is one, is terminated but the child - specification is kept by the supervisor. The child process - may later be restarted by the supervisor. The child process - can also be restarted explicitly by calling + <c><anno>Id</anno></c> must be the child specification + identifier. The process, if there is one, is terminated and, + unless it is a temporary child, the child specification is + kept by the supervisor. The child process may later be + restarted by the supervisor. The child process can also be + restarted explicitly by calling <c>restart_child/2</c>. Use <c>delete_child/2</c> to remove the child specification.</p> + + <p>If the child is temporary, the child specification is deleted as + soon as the process terminates. This means + that <c>delete_child/2</c> has no meaning + and <c>restart_child/2</c> can not be used for these + children.</p> + <p>If the supervisor is <c>simple_one_for_one</c>, <c><anno>Id</anno></c> must be the child process' <c>pid()</c>. I the specified process is alive, but is not a child of the given @@ -387,26 +408,34 @@ child_spec() = {Id,StartFunc,Restart,Shutdown,Type,Modules} <name name="restart_child" arity="2"/> <fsummary>Restart a terminated child process belonging to a supervisor.</fsummary> <desc> - <p>Tells the supervisor <c><anno>SupRef</anno></c> to restart a child process - corresponding to the child specification identified by - <c><anno>Id</anno></c>. The child specification must exist and - the corresponding child process must not be running.</p> - <p>See <seealso marker="#SupRef"><c>start_child/2</c></seealso> for a description of - <c>SupRef</c>.</p> - <p>If the child specification identified by <c><anno>Id</anno></c> does not - exist, the function returns <c>{error,not_found}</c>. If - the child specification exists but the corresponding process - is already running, the function returns + <p>Tells the supervisor <c><anno>SupRef</anno></c> to restart + a child process corresponding to the child specification + identified by <c><anno>Id</anno></c>. The child + specification must exist and the corresponding child process + must not be running.</p> + <p>Note that for temporary children, the child specification + is automatically deleted when the child terminates, and thus + it is not possible to restart such children.</p> + <p>See <seealso marker="#SupRef"><c>start_child/2</c></seealso> + for a description of <c>SupRef</c>.</p> + <p>If the child specification identified + by <c><anno>Id</anno></c> does not exist, the function + returns <c>{error,not_found}</c>. If the child specification + exists but the corresponding process is already running, the + function returns <c>{error,running}</c>.</p> - <p>If the child process start function returns <c>{ok,<anno>Child</anno>}</c> - or <c>{ok,<anno>Child</anno>,<anno>Info</anno>}</c>, the pid is added to the supervisor - and the function returns the same value.</p> + <p>If the child process start function + returns <c>{ok,<anno>Child</anno>}</c> + or <c>{ok,<anno>Child</anno>,<anno>Info</anno>}</c>, the pid + is added to the supervisor and the function returns the same + value.</p> <p>If the child process start function returns <c>ignore</c>, the pid remains set to <c>undefined</c> and the function returns <c>{ok,undefined}</c>.</p> - <p>If the child process start function returns an error tuple or - an erroneous value, or if it fails, the function returns - <c>{error,<anno>Error</anno>}</c> where <c><anno>Error</anno></c> is a term containing + <p>If the child process start function returns an error tuple + or an erroneous value, or if it fails, the function returns + <c>{error,<anno>Error</anno>}</c> + where <c><anno>Error</anno></c> is a term containing information about the error.</p> </desc> </func> |