Make sure that we are at least using 16 workers for sync, otherwise
multiply the current sync worker count by 2.
Finally, this patch also logs the duration of the time it takes to
transfer all the messages from the server.
Revise syncing work distribution. Sync time can be reduced by up to 50%.
Rework the sync so that it pipelines better with bigger batch counts at
each stage. We now use 3 separate stages: Download, Updates and Sync.
The Download stage downloads messages in maxBatchSize intervals using
1.5x syncWorkers. Once the current batch has finished downloading it's
forwarded to the Updates stage and we proceed to download the next
batch.
The Update stage converts everything into gluon updates and prepares a
collection of noops that the sync stage can wait on for termination.
Finally the sync stage waits until the updates have been applied in
Gluon so that the vault information can be updated. We allow up to 4
pending wait operations to be queued currently to not block the
pipeline.
This change implements safe.Mutex and safe.RWMutex, which wrap the
sync.Mutex and sync.RWMutex types and are assigned a globally unique
integer ID. The safe.Lock and safe.RLock methods sort the mutexes
by this integer ID before locking to ensure that locks for a given
set of mutexes are always performed in the same order, avoiding
deadlocks.
This fixes various race conditions and leaks related to the user's sync
and API event stream. It was possible for a sync/stream to begin after a
user was already closed; this change prevents that by managing the
goroutines related to sync/stream within cancellable groups.
We need to unlock the user keyring anyway to unlock the address keyring,
so we should just return it instead of re-unlocking the user keyring
when sending a message.
