\brief checks the existence of a node in zookeeper.
\param zh the zookeeper handle obtained by a call to \ref zookeeper_init
\param path the name of the node. Expressed as a file name with slashes
separating ancestors of the node.
\param watch if nonzero, a watch will be set at the server to notify the
client if the node changes. The watch will be set even if the node does not
exist. This allows clients to watch for nodes to appear.
\param completion the routine to invoke when the request completes. The completion
will be triggered with one of the following codes passed in as the rc argument:
ZOK operation completed successfully
ZNONODE the node does not exist.
ZNOAUTH the client does not have permission.
\param data the data that will be passed to the completion routine when the
function completes.
\return ZOK on success or one of the following errcodes on failure:
ZBADARGUMENTS - invalid input parameters
ZINVALIDSTATE - zhandle state is either ZOO_SESSION_EXPIRED_STATE or ZOO_AUTH_FAILED_STATE
ZMARSHALLINGERROR - failed to marshall a request; possibly, out of memory
\brief checks the existence of a node in zookeeper.
\param zh the zookeeper handle obtained by a call to \ref zookeeper_init \param path the name of the node. Expressed as a file name with slashes separating ancestors of the node. \param watch if nonzero, a watch will be set at the server to notify the client if the node changes. The watch will be set even if the node does not exist. This allows clients to watch for nodes to appear. \param completion the routine to invoke when the request completes. The completion will be triggered with one of the following codes passed in as the rc argument: ZOK operation completed successfully ZNONODE the node does not exist. ZNOAUTH the client does not have permission. \param data the data that will be passed to the completion routine when the function completes. \return ZOK on success or one of the following errcodes on failure: ZBADARGUMENTS - invalid input parameters ZINVALIDSTATE - zhandle state is either ZOO_SESSION_EXPIRED_STATE or ZOO_AUTH_FAILED_STATE ZMARSHALLINGERROR - failed to marshall a request; possibly, out of memory