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Posted to commits@mesos.apache.org by vi...@apache.org on 2014/02/11 20:30:53 UTC
[3/5] git commit: Made Group's state transitions monotonic except
when expiration occurs,
in which case it is reset to the initial state (DISCONNECTED).
Made Group's state transitions monotonic except when expiration occurs,
in which case it is reset to the initial state (DISCONNECTED).
- Reconnecting does not reset the state to CONNECTING now. The steps
the group has taken to set up the group are remembered (thus not
redone) across reconnections.
- Improved comments on state transitions.
- Added the DISCONNECTED state back for the parity between Group and
ZooKeeperStorage.
Review: https://reviews.apache.org/r/17858
Project: http://git-wip-us.apache.org/repos/asf/mesos/repo
Commit: http://git-wip-us.apache.org/repos/asf/mesos/commit/9ad3c042
Tree: http://git-wip-us.apache.org/repos/asf/mesos/tree/9ad3c042
Diff: http://git-wip-us.apache.org/repos/asf/mesos/diff/9ad3c042
Branch: refs/heads/master
Commit: 9ad3c042cf35dc1685502bd31fdb2a6e4a62e3e8
Parents: 44508c2
Author: Jiang Yan Xu <ya...@jxu.me>
Authored: Tue Feb 11 11:18:21 2014 -0800
Committer: Vinod Kone <vi...@twitter.com>
Committed: Tue Feb 11 11:18:21 2014 -0800
----------------------------------------------------------------------
src/zookeeper/group.cpp | 62 +++++++++++++++++++++++++++++++++-----------
src/zookeeper/group.hpp | 12 ++++++++-
2 files changed, 58 insertions(+), 16 deletions(-)
----------------------------------------------------------------------
http://git-wip-us.apache.org/repos/asf/mesos/blob/9ad3c042/src/zookeeper/group.cpp
----------------------------------------------------------------------
diff --git a/src/zookeeper/group.cpp b/src/zookeeper/group.cpp
index a61a384..793763e 100644
--- a/src/zookeeper/group.cpp
+++ b/src/zookeeper/group.cpp
@@ -82,7 +82,7 @@ GroupProcess::GroupProcess(
: ZOO_OPEN_ACL_UNSAFE),
watcher(NULL),
zk(NULL),
- state(CONNECTING),
+ state(DISCONNECTED),
retrying(false)
{}
@@ -101,7 +101,7 @@ GroupProcess::GroupProcess(
: ZOO_OPEN_ACL_UNSAFE),
watcher(NULL),
zk(NULL),
- state(CONNECTING),
+ state(DISCONNECTED),
retrying(false)
{}
@@ -310,7 +310,22 @@ void GroupProcess::connected(bool reconnect)
LOG(INFO) << "Group process (" << self() << ") "
<< (reconnect ? "reconnected" : "connected") << " to ZooKeeper";
- state = CONNECTED;
+ if (!reconnect) {
+ // This is the first time the ZooKeeper client connects to
+ // ZooKeeper service. (It could be also the first time for the
+ // group or after session expiration which causes a new ZooKeeper
+ // client instance to be created.)
+ CHECK_EQ(state, CONNECTING);
+ state = CONNECTED;
+ } else {
+ // This means we are reconnecting within the same ZooKeeper
+ // session. We could have completed authenticate() or create()
+ // before we lost the connection (thus the state can be the any
+ // of the following three) so 'sync()' below will check the state
+ // and only execute necessary operations accordingly.
+ CHECK(state == CONNECTED || state == AUTHENTICATED || state == READY)
+ << state;
+ }
// Cancel and cleanup the reconnect timer (if necessary).
if (timer.isSome()) {
@@ -399,7 +414,10 @@ void GroupProcess::reconnecting()
LOG(INFO) << "Lost connection to ZooKeeper, attempting to reconnect ...";
- state = CONNECTING;
+ // Set 'retrying' to false to prevent retry() from executing sync()
+ // before the group reconnects to ZooKeeper. The group will sync
+ // with ZooKeeper after it is connected.
+ retrying = false;
// ZooKeeper won't tell us of a session expiration until we
// reconnect, which could occur much much later than the session was
@@ -447,6 +465,9 @@ void GroupProcess::expired()
return;
}
+ // Cancel the retries. Group will sync() after it reconnects to ZK.
+ retrying = false;
+
// Cancel and cleanup the reconnect timer (if necessary).
if (timer.isSome()) {
Timer::cancel(timer.get());
@@ -482,12 +503,14 @@ void GroupProcess::expired()
// then. We could imagine doing this for owned memberships too, but
// for now we proactively cancel them above.
- state = CONNECTING;
+ state = DISCONNECTED;
delete CHECK_NOTNULL(zk);
delete CHECK_NOTNULL(watcher);
watcher = new ProcessWatcher<GroupProcess>(self());
zk = new ZooKeeper(servers, timeout, watcher);
+
+ state = CONNECTING;
}
@@ -754,9 +777,12 @@ Try<bool> GroupProcess::sync()
<< pending.joins.size() << ", " << pending.cancels.size() << ", "
<< pending.datas.size() << ")";
- CHECK_NE(state, CONNECTING);
+ // The state may be CONNECTED or AUTHENTICATED if Group setup has
+ // not finished.
+ CHECK(state == CONNECTED || state == AUTHENTICATED || state == READY)
+ << state;
- // Authenticate with ZK if not already created.
+ // Authenticate with ZK if not already authenticated.
if (state == CONNECTED) {
Try<bool> authenticated = authenticate();
if (authenticated.isError() || !authenticated.get()) {
@@ -840,18 +866,21 @@ Try<bool> GroupProcess::sync()
void GroupProcess::retry(const Duration& duration)
{
- CHECK(retrying);
+ if (!retrying) {
+ // Retry could be cancelled before it is scheduled.
+ return;
+ }
+
+ // We cancel the retries when the group aborts and when its ZK
+ // session expires so 'retrying' should be false in the condition
+ // check above.
+ CHECK(error.isNone());
+ CHECK(state == CONNECTED || state == CONNECTING || state == READY)
+ << state;
// Will reset it to true if another retry is necessary.
retrying = false;
- if (error.isSome() || state == CONNECTING) {
- // The delayed retry can be invoked while group has aborted or
- // is trying to (re)connect to ZK. In this case we directly
- // return and we will sync when group is connected to ZK.
- return;
- }
-
Try<bool> synced = sync();
if (synced.isError()) {
@@ -873,6 +902,9 @@ void GroupProcess::abort(const string& message)
LOG(ERROR) << "Group aborting: " << message;
+ // Cancel the retries.
+ retrying = false;
+
fail(&pending.joins, message);
fail(&pending.cancels, message);
fail(&pending.datas, message);
http://git-wip-us.apache.org/repos/asf/mesos/blob/9ad3c042/src/zookeeper/group.hpp
----------------------------------------------------------------------
diff --git a/src/zookeeper/group.hpp b/src/zookeeper/group.hpp
index e51ebb2..d1ead38 100644
--- a/src/zookeeper/group.hpp
+++ b/src/zookeeper/group.hpp
@@ -246,7 +246,17 @@ private:
Watcher* watcher;
ZooKeeper* zk;
- enum State { // Group connection state.
+ // Group connection state.
+ // Normal state transitions:
+ // DISCONNECTED -> CONNECTING -> CONNECTED -> AUTHENTICATED
+ // -> READY.
+ // Reconnection does not change the current state and the state is
+ // only reset to DISCONNECTED after session expiration. Therefore
+ // the client's "progress" in setting up the group is preserved
+ // across reconnections. This means authenticate() and create() are
+ // only successfully executed once in one ZooKeeper session.
+ enum State {
+ DISCONNECTED, // The initial state.
CONNECTING, // ZooKeeper connecting.
CONNECTED, // ZooKeeper connected but before group setup.
AUTHENTICATED, // ZooKeeper connected and authenticated.