2013/11/29 Liu Yuan <namei.unix at gmail.com> > On Fri, Nov 29, 2013 at 06:35:11PM +0800, Robin Dong wrote: > > The patch title need updated, e.g, as "sheep/cluster: introduce > distributed lock" > > > Implement the distributed lock by zookeeper (refer: > http://zookeeper.apache.org/doc/trunk/recipes.html) > > The routine is: > > 1. create a seq-ephemeral znode in lock directory (use lock-id > as dir name) > > 2. get smallest file path as owner of the lock; the other thread > wait on a pthread_mutex_t > > 3. if owner of the lock release it (or the owner is killed by > accident), zookeeper will > > trigger zk_watch() which will wake up all waiting threads to > compete new owner of the lock > > > > We add ->local_lock for dist_mutex to avoid many threads in one sheepdog > daemon to create too many files > > in a lock directory. > > What exactly kind of scenario does this handle? It would be great if you > can > show us any use case or clear problem this ->local_lock solves. Unless > there is > a definite use case, I think we should avoid pre-mature optimization. > > > > > v2 --> v3: > > 1. change cluster interface to init_lock()/lock()/unlock() > > 2. change 'struct zk_mutex' to 'struct cluster_lock' > > 3. add empty implementation to local/corosync > > > > v1 --> v2: > > move code from sheep/http/lock.c into sheep/cluster/zookeeper.c > using cluster framework > > > > Signed-off-by: Robin Dong <sanbai at taobao.com> > > --- > > sheep/cluster.h | 25 ++++++++ > > sheep/cluster/corosync.c | 16 +++++ > > sheep/cluster/local.c | 16 +++++ > > sheep/cluster/zookeeper.c | 140 > ++++++++++++++++++++++++++++++++++++++++++++- > > 4 files changed, 196 insertions(+), 1 deletions(-) > > > > diff --git a/sheep/cluster.h b/sheep/cluster.h > > index 81b5ae4..260573c 100644 > > --- a/sheep/cluster.h > > +++ b/sheep/cluster.h > > @@ -23,6 +23,13 @@ > > #include "sheep.h" > > #include "config.h" > > > > +struct cluster_lock { > > + uint32_t id; /* id of this mutex */ > > + pthread_mutex_t wait; > > + pthread_mutex_t local_lock; > > + char ephemeral_path[MAX_NODE_STR_LEN]; > > +}; > > I suppose cluster_lock will be used throughout the sheep daemon, so this > should be declared in include/sheep.h > > > /* > > * maximum payload size sent in ->notify and ->unblock, it should be > large > > * enough to support COROSYNC_MAX_NODES * struct sd_node > > @@ -109,6 +116,24 @@ struct cluster_driver { > > int (*unblock)(void *msg, size_t msg_len); > > > > /* > > + * Init a distributed mutually exclusive lock to avoid race > condition > > + * when using swift interface to add/delete/list object. > > + * > > + * Returns SD_RES_XXX > > + */ > > 'swift stuff' should be removed from the comment. And I think you'd better > describe id in the comment too. > > > > > + int (*init_lock)(struct cluster_lock *lock, uint32_t id); > > uint32_t is supposed to be a per vdi lock, right? I am wondering if can > solve the > following case: > > (AG) Allocation Group > > vdi: AG1, AG2, AG3 ... > > Every AG need a lock to allow concurrent allocation and deallocation in > the vdi > so your lock can't hanlde it right? > > What about extend it as uint64_t, then we can use 'vdi + lock_id' to solve > the > above case. > > > > + /* > > + * Get the distributed lock. > > Better as "Acquire the distributed lock" and we need more comment on a bit > how > it works, I'd suggest man pthread_mutex_lock as a reference. > > > + * > > + * It will never return if it can't acquire the lock. > > + */ > > > > + void (*lock)(struct cluster_lock *lock); > > + > > + /* Release the distributed lock. */ > > Ditto > > > + void (*unlock)(struct cluster_lock *lock); > > + > > + /* > > * Update the specific node in the driver's private copy of nodes > > * > > * Returns SD_RES_XXX > > diff --git a/sheep/cluster/corosync.c b/sheep/cluster/corosync.c > > index ea4421b..35c95d3 100644 > > --- a/sheep/cluster/corosync.c > > +++ b/sheep/cluster/corosync.c > > @@ -774,6 +774,19 @@ again: > > return 0; > > } > > > > +static int corosync_init_lock(struct cluster_lock *dlock, uint32_t id) > > +{ > > + return -1; > > +} > > + > > +static void corosync_lock(struct cluster_lock *dlock) > > +{ > > +} > > + > > +static void corosync_unlock(struct cluster_lock *dlock) > > +{ > > +} > > + > > static int corosync_update_node(struct sd_node *node) > > { > > struct cpg_node cnode = this_node; > > @@ -794,6 +807,9 @@ static struct cluster_driver cdrv_corosync = { > > .notify = corosync_notify, > > .block = corosync_block, > > .unblock = corosync_unblock, > > + .init_lock = corosync_init_lock, > > + .lock = corosync_lock, > > + .unlock = corosync_unlock, > > .update_node = corosync_update_node, > > }; > > > > diff --git a/sheep/cluster/local.c b/sheep/cluster/local.c > > index b8cbb5c..d71cd20 100644 > > --- a/sheep/cluster/local.c > > +++ b/sheep/cluster/local.c > > @@ -547,6 +547,19 @@ static int local_init(const char *option) > > return 0; > > } > > > > +static int local_init_lock(struct cluster_lock *dlock, uint32_t id) > > +{ > > + return -1; > > +} > > + > > +static void local_lock(struct cluster_lock *dlock) > > +{ > > +} > > + > > +static void local_unlock(struct cluster_lock *dlock) > > +{ > > +} > > + > > static int local_update_node(struct sd_node *node) > > { > > struct local_node lnode = this_node; > > @@ -566,6 +579,9 @@ static struct cluster_driver cdrv_local = { > > .notify = local_notify, > > .block = local_block, > > .unblock = local_unblock, > > + .init_lock = local_init_lock, > > + .lock = local_lock, > > + .unlock = local_unlock, > > .update_node = local_update_node, > > }; > > > > diff --git a/sheep/cluster/zookeeper.c b/sheep/cluster/zookeeper.c > > index fa89c46..fc6c207 100644 > > --- a/sheep/cluster/zookeeper.c > > +++ b/sheep/cluster/zookeeper.c > > @@ -30,6 +30,21 @@ > > #define QUEUE_ZNODE BASE_ZNODE "/queue" > > #define MEMBER_ZNODE BASE_ZNODE "/member" > > #define MASTER_ZNONE BASE_ZNODE "/master" > > +#define LOCK_ZNODE BASE_ZNODE "/lock" > > + > > +#define MAX_MUTEX_NR 4096 > > +#define WAIT_TIME 1 /* second */ > > + > > +static struct cluster_lock **dlock_array; > > + > > +/* > > + * Wait a while when create, delete or get_children fail on > > + * zookeeper lock so it will not print too much loop log > > + */ > > +static void zk_wait(void) > > +{ > > + sleep(WAIT_TIME); > > +} > > > > /* iterate child znodes */ > > #define FOR_EACH_ZNODE(parent, path, strs) \ > > @@ -506,6 +521,7 @@ static void zk_watcher(zhandle_t *zh, int type, int > state, const char *path, > > { > > struct zk_node znode; > > char str[MAX_NODE_STR_LEN], *p; > > + uint32_t lock_id; > > int ret; > > > > if (type == ZOO_SESSION_EVENT && state == > ZOO_EXPIRED_SESSION_STATE) { > > @@ -528,6 +544,14 @@ static void zk_watcher(zhandle_t *zh, int type, int > state, const char *path, > > } else if (type == ZOO_DELETED_EVENT) { > > struct zk_node *n; > > > > + /* process distributed lock */ > > + ret = sscanf(path, LOCK_ZNODE "/%u/%s", &lock_id, str); > > + if (ret == 2 && lock_id < MAX_MUTEX_NR && > > + dlock_array && dlock_array[lock_id]) { > > + > pthread_mutex_unlock(&(dlock_array[lock_id]->wait)); > > + sd_debug("release lock %u %s", lock_id, str); > > + } > > + > > ret = sscanf(path, MASTER_ZNONE "/%s", str); > > if (ret == 1) { > > zk_compete_master(); > > @@ -1058,6 +1082,108 @@ kick_block_event: > > kick_block_event(); > > } > > > > +static int zk_init_lock(struct cluster_lock *dlock, uint32_t id) > > +{ > > + int rc; > > + char path[MAX_NODE_STR_LEN]; > > + > > + if (id > MAX_MUTEX_NR) { > > + sd_err("lock-id is too large!"); > > + rc = -1; > > + goto err; > > + } > > + > > + dlock_array[id] = dlock; > > + dlock->id = id; > > + snprintf(path, MAX_NODE_STR_LEN, LOCK_ZNODE "/%u", dlock->id); > > + rc = zk_init_node(path); > > + if (rc) > > + goto err; > > + > > + rc = pthread_mutex_init(&dlock->wait, NULL); > > + if (rc) { > > + sd_err("failed to init dlock->wait"); > > + goto err; > > + } > > + > > + rc = pthread_mutex_init(&dlock->local_lock, NULL); > > + if (rc) { > > + sd_err("failed to init dlock->local_lock"); > > + goto err; > > + } > > + > > + return 0; > > +err: > > + dlock_array[id] = NULL; > > + return rc; > > +} > > + > > +static void zk_lock(struct cluster_lock *dlock) > > +{ > > + int flags = ZOO_SEQUENCE | ZOO_EPHEMERAL; > > + int rc, len = MAX_NODE_STR_LEN; > > + char *my_path; > > + char parent[MAX_NODE_STR_LEN]; > > + char lowest_seq_path[MAX_NODE_STR_LEN]; > > + char owner_name[MAX_NODE_STR_LEN]; > > + > > + /* > > + * if many threads use locks with same id, we should use > > + * ->local_lock to avoid the only zookeeper handler to > > + * create many seq-ephemeral files. > > + */ > > + pthread_mutex_lock(&dlock->local_lock); > > + > > + my_path = dlock->ephemeral_path; > > + > > + /* compete owner of lock is just like zk_compete_master() */ > > Though this is not relevent to this patch, I am wondering if > zk_compete_master > can make use of your proposed lock? > zk_compete_master() could return without success, but zk_lock() will return only when it has acquired the lock. So the routine of the two function is very different. And, I have used zk_get_least_seq() as the common code of the two functions. > > Thanks > Yuan > -- -- Best Regard Robin Dong -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.wpkg.org/pipermail/sheepdog/attachments/20131201/881b9293/attachment.html> |