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docs: internals/sessions: minor fixes

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Dan Frost 2014-11-26 12:49:53 +00:00
parent dbb365baca
commit 2ad884abee
1 changed files with 5 additions and 5 deletions
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website/source/docs/internals/sessions.html.markdown
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@ -64,9 +64,9 @@ systems to be built that require an operator to intervene in the
case of a failure, but preclude the possibility of a split-brain. case of a failure, but preclude the possibility of a split-brain.
The final nuance is that sessions may provide a `lock-delay`. This The final nuance is that sessions may provide a `lock-delay`. This
is a time duration, between 0 and 60 second. When a session invalidation is a time duration, between 0 and 60 seconds. When a session invalidation
takes place, Consul prevents any of the previously held locks from takes place, Consul prevents any of the previously held locks from
being re-acquired for the `lock-delay` interval; this is a safe guard being re-acquired for the `lock-delay` interval; this is a safeguard
inspired by Google's Chubby. The purpose of this delay is to allow inspired by Google's Chubby. The purpose of this delay is to allow
the potentially still live leader to detect the invalidation and stop the potentially still live leader to detect the invalidation and stop
processing requests that may lead to inconsistent state. While not a processing requests that may lead to inconsistent state. While not a
@ -79,7 +79,7 @@ mechanism by providing a zero delay value.
Integration between the Key/Value store and sessions are the primary Integration between the Key/Value store and sessions are the primary
place where sessions are used. A session must be created prior to use, place where sessions are used. A session must be created prior to use,
and is then referred to by it's ID. and is then referred to by its ID.
The Key/Value API is extended to support an `acquire` and `release` operation. The Key/Value API is extended to support an `acquire` and `release` operation.
The `acquire` operation acts like a Check-And-Set operation, except it The `acquire` operation acts like a Check-And-Set operation, except it
@ -93,7 +93,7 @@ since the request will fail if given an invalid session. A critical note is
that the lock can be released without being the creator of the session. that the lock can be released without being the creator of the session.
This is by design, as it allows operators to intervene and force terminate This is by design, as it allows operators to intervene and force terminate
a session if necessary. As mentioned above, a session invalidation will also a session if necessary. As mentioned above, a session invalidation will also
cause all held locks to be released. When a lock is released, the `LockIndex`, cause all held locks to be released. When a lock is released, the `LockIndex`
does not change, however the `Session` is cleared and the `ModifyIndex` increments. does not change, however the `Session` is cleared and the `ModifyIndex` increments.
These semantics (heavily borrowed from Chubby), allow the tuple of (Key, LockIndex, Session) These semantics (heavily borrowed from Chubby), allow the tuple of (Key, LockIndex, Session)
@ -103,7 +103,7 @@ is incremented on each `acquire`, even if the same session re-acquires a lock,
the `sequencer` will be able to detect a stale request. Similarly, if a session is the `sequencer` will be able to detect a stale request. Similarly, if a session is
invalided, the Session corresponding to the given `LockIndex` will be blank. invalided, the Session corresponding to the given `LockIndex` will be blank.
To make clear, this locking system is purely *advisory*. There is no enforcement To be clear, this locking system is purely *advisory*. There is no enforcement
that clients must acquire a lock to perform any operation. Any client can that clients must acquire a lock to perform any operation. Any client can
read, write, and delete a key without owning the corresponding lock. It is not read, write, and delete a key without owning the corresponding lock. It is not
the goal of Consul to protect against misbehaving clients. the goal of Consul to protect against misbehaving clients.