To make this possible, two things are added:
 - The capability to lock all tables on a tablet, to momenterily stop updates
 - Once the database is locked, we can create multiple consistent snapshot
   transactions that all share the same view of the data
 - Adds the capability to have replication move forward to a specific point
   in the transaction log

Signed-off-by: Andres Taylor <antaylor@squareup.com>

Signed-off-by: Andres Taylor <antaylor@squareup.com>

Signed-off-by: Andres Taylor <antaylor@squareup.com>

Signed-off-by: Andres Taylor <antaylor@squareup.com>

Instead of the tabletserver keeping track of when it's safe
to close transactions to change serving type, the tx engine
now keeps track of it's current state and what is needed for
safe state changes.

Signed-off-by: Andres Taylor <antaylor@squareup.com>

Signed-off-by: Andres Taylor <antaylor@squareup.com>

Signed-off-by: Andres Taylor <antaylor@squareup.com>

 * Handle the case when ReadOnly is requested during transition.

 * Instead of allowing the outside deciding when to forcefully
   shut down transactions, hide this behaviour behind a method,
   so state can properly be updated.

Signed-off-by: Andres Taylor <antaylor@squareup.com>

 * Remove unused splitColumns argument
 * Remove unused error argument

Signed-off-by: Andres Taylor <antaylor@squareup.com>

…d of the TxEngine class

Signed-off-by: Andres Taylor <antaylor@squareup.com>

Signed-off-by: Andres Taylor <antaylor@squareup.com>

Signed-off-by: Andres Taylor <antaylor@squareup.com>

Signed-off-by: Andres Taylor <antaylor@squareup.com>

The particular race condition is:

 * Thread 1: tsv.Begin is called, which calls startRequest through execRequest.
 * Thread 1: tsv.mu is released once startRequest returns.
 * Thread 2: A call to setServingType is received.
 * Thread 2: goes in: there are no begin requests in the wait group. So, it closes the TxEngine, or changes its state.
 * Thread 1: TxEngine.Begin executes on a TxEngine. If the state has changed so that a transaction should not be allowed, an error will not be returned.

Signed-off-by: Andres Taylor <antaylor@squareup.com>

Signed-off-by: Andres Taylor <antaylor@squareup.com>

Signed-off-by: Andres Taylor <antaylor@squareup.com>

Signed-off-by: Andres Taylor <antaylor@squareup.com>

Signed-off-by: Andres Taylor <antaylor@squareup.com>

Signed-off-by: Andres Taylor <antaylor@squareup.com>

Signed-off-by: Andres Taylor <antaylor@squareup.com>

Signed-off-by: Andres Taylor <antaylor@squareup.com>

Signed-off-by: Andres Taylor <antaylor@squareup.com>

* upstream/master:
  Skip ACL checks for dual pseudotable
  Makes sure the schema engine has started up before getting debug information.
  Support tables that have columns named desc
  exec_cases: add passing messages OnDup test
  exec_cases: add failing tests for msgs on dupe
  planbuilder: support ‘on duplicate key’ for msgs

This reverts commit a57c799.

Signed-off-by: Andres Taylor <antaylor@squareup.com>

* upstream/master:
  helm: release 1.0.5
  vreplication: address review comments
  tlstest_test: Go 1.12 / TLS 1.3 fix
  vreplication: vstream final tweaks
  vreplication: tests are done
  vreplication: handle singleton and mariadb issues
  vreplication: moved tests into vstreamer dir
  vreplication: more vstreamer tests
  vreplication: MariaDB test tweaks and more tests
  vreplication: tests: statements and DDL add column
  vreplication: make a singleton srvtopo.Server
  vreplication: got some basic tests working
  vreplication: tabletserver inits and other tweaks
  vreplication: vstreamer, plan and filtering
  vreplication: streamer planbuilder
  vreplication: vstreamer Engine

Signed-off-by: Andres Taylor <antaylor@squareup.com>

Signed-off-by: Andres Taylor <antaylor@squareup.com>

Signed-off-by: Andres Taylor <antaylor@squareup.com>

Signed-off-by: Andres Taylor <antaylor@squareup.com>

* upstream/master:
  vtctl: run BackupShard on replica, rdonly or spare
  Expose `glog.MaxSize` as `-log_rotate_max_size` flag
  inline ok check; while-range instead of bare while
  test the signal handler
  reload db-credentials-file upon SIGHUP
  change ClusterAlias in _vt.local_metadata to be keyspace/shard instead of keyspace.shard

Signed-off-by: Andres Taylor <antaylor@squareup.com>

Signed-off-by: Andres Taylor <antaylor@squareup.com>

Signed-off-by: Sugu Sougoumarane <ssougou@gmail.com>

Signed-off-by: Andres Taylor <antaylor@squareup.com>

* upstream/master:
  Adds a test to check regressions in parser
  Adding in SQL commands to prepare an instance to join an existing shard
  Revert "Support tables that have columns named desc"
  Use a truly random Destination for DestinationAnyShard

Signed-off-by: Andres Taylor <antaylor@squareup.com>

Signed-off-by: Andres Taylor <antaylor@squareup.com>

Signed-off-by: Andres Taylor <antaylor@squareup.com>

Signed-off-by: Andres Taylor <antaylor@squareup.com>

Trying to make it clearer what we are testing.

Signed-off-by: Andres Taylor <antaylor@squareup.com>