Summary:
This should allow us to more easily decouple the code which should be
open sourced. Unfortunately, the downside of this approach is that we
cannot rely on virtual calls to dispatch the serialization to correct
type. Another downside is that members need to be publicly accessible
for serialization.
Reviewers: mtomic, msantl
Reviewed By: mtomic
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D1596
Summary:
This diff changes the RPC layer to directly return `TResponse` to the user when
issuing a `Call<...>` RPC call. The call throws an exception on failure
(instead of the previous return `nullopt`).
All servers (network, RPC and distributed) are set to have explicit `Shutdown`
methods so that a controlled shutdown can always be performed. The object
destructors now have `CHECK`s to enforce that the `AwaitShutdown` methods were
called.
The distributed memgraph is changed that none of the binaries (master/workers)
crash when there is a communication failure. Instead, the whole cluster starts
a graceful shutdown when a persistent communication error is detected.
Transient errors are allowed during execution. The transaction that errored out
will be aborted on the whole cluster. The cluster state is managed using a new
Heartbeat RPC call.
Reviewers: buda, teon.banek, msantl
Reviewed By: teon.banek
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D1604
Summary:
This change introduces a pure virtual initial implementation of the transaction
engine which is then implemented in two versions: single node and distributed.
The interface classes now have the following hierarchy:
```
Engine (pure interface)
|
+----+---------- EngineDistributed (common logic)
| |
EngineSingleNode +-------+--------+
| |
EngineMaster EngineWorker
```
In addition to this layout the `EngineMaster` uses `EngineSingleNode` as its
underlying storage engine and only changes the necessary functions to make
them work with the `EngineWorker`.
After this change I recommend that you delete the following leftover files:
```
rm src/distributed/transactional_cache_cleaner_rpc_messages.*
rm src/transactions/common.*
rm src/transactions/engine_rpc_messages.*
```
Reviewers: teon.banek, msantl, buda
Reviewed By: teon.banek
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D1589
Summary:
Wal on workers didn't contain committed transactions ids, this is needed for
distributed recovery so that the master may decide which transactions are
present on all the workers.
Reviewers: buda, msantl
Reviewed By: buda
Subscribers: pullbot, msantl, buda
Differential Revision: https://phabricator.memgraph.io/D1440
Summary:
Converts the RPC stack to use Cap'n Proto for serialization instead of
boost. There are still some traces of boost in other places in the code,
but most of it is removed. A future diff should cleanup boost for good.
The RPC API is now changed to be more flexible with regards to how
serialize data. This makes the simplest cases a bit more verbose, but
allows complex serialization code to be correctly written instead of
relying on hacks. (For reference, look for the old serialization of
`PullRpc` which had a nasty pointer hacks to inject accessors in
`TypedValue`.)
Since RPC messages were uselessly modeled via inheritance of Message
base class, that class is now removed. Furthermore, that approach
doesn't really work with Cap'n Proto. Instead, each message type is
required to have some type information. This can be automated, so
`define-rpc` has been added to LCP, which hopefully simplifies defining
new RPC request and response messages.
Specify Cap'n Proto schema ID in cmake
This preserves Cap'n Proto generated typeIds across multiple generations
of capnp schemas through LCP. It is imperative that typeId stays the
same to ensure that different compilations of Memgraph may communicate
via RPC in a distributed cluster.
Use CLOS for meta information on C++ types in LCP
Since some structure slots and functions have started to repeat
themselves, it makes sense to model C++ meta information via Common Lisp
Object System.
Depends on D1391
Reviewers: buda, dgleich, mferencevic, mtomic, mculinovic, msantl
Reviewed By: msantl
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D1407
Summary:
Command id is necessary in remote produce to identify an ongoing pull
because a transaction can have multiple commands that all belong under
the same plan and tx id.
Reviewers: teon.banek, mtomic, buda
Reviewed By: teon.banek
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D1386
Summary: Adds a commit log garbage collector, which clears old transactions from the commit log
Reviewers: florijan
Reviewed By: florijan
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D1310
Summary:
When commiting/aborting a transaction in tx master engine, make a two
phase commit to all workers so they can stop all futures and clear
transactional cache.
Reviewers: dgleich, florijan
Reviewed By: dgleich
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D1320
Summary:
Remove semicolon.
Semicolon shouldn't be used within macros and should
be explicitly provided by the user of the said macro.
Reviewers: teon.banek
Reviewed By: teon.banek
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D1321
Summary:
Add different priority VLOGs for distributed memgraph.
For level 3 you'll get logs for dispatching/consuming plans.
For level 4 you'll get logs for tx start/commit/abort, remote produce, remote
pull, remote result consume,
For level 5 there will be a log for each request/response made by the RPC
client.
Master log snippet P9
Worker log snippet P10
Reviewers: florijan, teon.banek
Reviewed By: florijan
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D1296
Summary:
When performing recovery, ensure that the transaction ID in engine is
bumped to one after the max tx id seen in recovery.
Reviewers: dgleich
Reviewed By: dgleich
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D1312
Summary:
Instead of passing `coordination`, pass `rpc_worker_clients` that
holds a map of worker_id->clientPool. By having only one instance of
`RpcWorkerClients` that is owned by `GraphDB` and passing it by refference
we'll share the same client pools for rpc clients.
Reviewers: teon.banek, florijan, dgleich, mferencevic
Reviewed By: florijan
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D1261
Summary: It was possible for transaction to be double freed because both the AllClear and SingleClear of transactions could delete the pointer
Reviewers: florijan, mferencevic
Reviewed By: mferencevic
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D1250
Summary:
Release of per-transaction data in distributed Memgraph refactored. The
master node no longer releases each time a transaction is done, thus
offloading some work from the engine.
Reviewers: dgleich
Reviewed By: dgleich
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D1235
Summary:
Remove a method in tx::Engine whose results can be obtained from commit
log info (also guaranteed to be globally correct in distributed).
Reviewers: dgleich
Reviewed By: dgleich
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D1240
Summary:
To see the thread names in htop press <F2> to enter setup and under
'Display options' choose 'Show custom thread names'.
Reviewers: buda, teon.banek, florijan
Reviewed By: teon.banek
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D1234
Summary:
Previously, the RPC stack used the network stack only to receive messages. The
messages were then added to a separate queue that was processed by different
thread pools. This design was inefficient because there was a lock when
inserting and getting messages from the common queue.
This diff removes the need for separate thread pools by utilising the new
network stack design. This is possible because the new network stack allows
full processing of the network request without blocking the whole queue.
Reviewers: buda, florijan, teon.banek, dgleich, mislav.bradac
Reviewed By: buda
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D1229
Summary:
On the master cleanups are hooked directly into the transaction engine.
This is beneficial because the master might have bigger caches and we
want to clear them as soon as possible.
On the workers there is a periodic RPC call to the master about living
transactions, which takes care of releasing local caches. This is
suboptimal because long transactions will prevent cache GC (like with
data GC). It is however fairly simple.
Note that all cleanup is not done automatically and `RemotePull` has
been reduced accordingly. @msantl, please verify correctness and
consider if the code can be additionally simplified.
Reviewers: teon.banek, msantl
Reviewed By: msantl
Subscribers: pullbot, msantl
Differential Revision: https://phabricator.memgraph.io/D1202
Summary:
Start removal of old logic
Remove more obsolete classes
Move Message class to RPC
Remove client logic from system
Remove messaging namespace
Move protocol from messaging to rpc
Move System from messaging to rpc
Remove unnecessary namespace
Remove System from RPC Client
Split Client and Server into separate files
Start implementing new client logic
First semi-working state
Changed network protocol layout
Rewrite client
Fix client receive bug
Cleanup code of debug lines
Migrate to accessors
Migrate back to binary boost archives
Remove debug logging from server
Disable timeout test
Reduce message_id from uint64_t to uint32_t
Add multiple workers to server
Fix compiler warnings
Apply clang-format
Reviewers: teon.banek, florijan, dgleich, buda, mtomic
Reviewed By: teon.banek
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D1129
Summary:
- End to end distributed GraphDb testing
- Refactors as necessary
- Basic RemoteCache for storing remote data
- RemoteDataRpc
As we are on a tight schedule, please let's focus on the essentials:
functionality and proper testing.
Reviewers: dgleich, teon.banek, buda
Reviewed By: dgleich
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D1121
Summary:
No logic changes, just split `tx::MasterEngine` into
`tx::SingleNodeEngine` and `tx::MasterEngine`. This gives better
responsibility separation and is more appropriate now there is no
Start/Shutdown.
Reviewers: dgleich, teon.banek, buda
Reviewed By: dgleich, teon.banek
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D1099
Summary:
This is a proposal on how the WAL recovery process can be implemented so
that Deltas aren't accumulated, but instead applied in the same order
they are written to the WAL.
I *believe* that the only additional requirement on the system are
atomic transaction Begin/Commit/Abort. By atomic I mean that they are
present in the WAL in exactly the same ordering like in the transaciton
engine, to ensure the same commitability of original and recovery
transactions.
This could be a requirement for HA recovery. It is desirable that WAL
and HA log become the same thing, and the recovery process too.
Reviewers: mtomic, dgleich, mislav.bradac
Reviewed By: mislav.bradac
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D1068
Summary: Remove two tx::Transaction methods that are not defined and never used.
Reviewers: dgleich
Reviewed By: dgleich
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D1072
Summary:
Rpc client wasn't thread safe and required a lock before each rpc call.
The locking functionality is now incorporated in Rpc client.
Reviewers: mislav.bradac
Reviewed By: mislav.bradac
Differential Revision: https://phabricator.memgraph.io/D1056
Summary:
The current idea is that the same MG binary can be used for single-node,
distributed master and distributed worker. The transactional engine in
the single-node and distributed master is the same: it determines the
transactional time and exposes all the "global" functionalities. In the
distributed worker the "global" functions must contact the master.
Reviewers: dgleich, mislav.bradac, buda
Reviewed By: dgleich
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D1013
Summary: Code simplification made possible by making `locks_` `mutable` in `tx::Transaction`.
Reviewers: dgleich, buda
Reviewed By: buda
Differential Revision: https://phabricator.memgraph.io/D1015
Summary:
This diff contains step 1:
- Remove clog exposure from tx::engine
- Reduce and cleanup tx::Engine API
All current functionality is kept, but the API is reduced. This is very
desirable because every function in tx::Engine will need to be
considered and implemented in both Master and Worker situations. The
less we have, the better.
Next step is exactly that: seeing how each of these functions behaves in
a distributed system and implementing accordingly.
Reviewers: dgleich, mislav.bradac, buda
Reviewed By: mislav.bradac
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D1008
Summary:
My dear fellow Memgraphians. It's friday afternoon, and I am as ready to pop as WAL is to get reviewed...
What's done:
- Vertices and Edges have global IDs, stored in `VersionList`. Main storage is now a concurrent map ID->vlist_ptr.
- WriteAheadLog class added. It's based around buffering WAL::Op objects (elementraly DB changes) and periodically serializing and flusing them to disk.
- Snapshot recovery refactored, WAL recovery added. Snapshot format changed again to include necessary info.
- Durability testing completely reworked.
What's not done (and should be when we decide how):
- Old WAL file purging.
- Config refactor (naming and organization). Will do when we discuss what we want.
- Changelog and new feature documentation (both depending on the point above).
- Better error handling and recovery feedback. Currently it's all returning bools, which is not fine-grained enough (neither for errors nor partial successes, also EOF is reported as a failure at the moment).
- Moving the implementation of WAL stuff to .cpp where possible.
- Not sure if there are transactions being created outside of `GraphDbAccessor` and it's `BuildIndex`. Need to look into.
- True write-ahead logic (flag controlled): not committing a DB transaction if the WAL has not flushed it's data. We can discuss the gain/effort ratio for this feature.
Reviewers: buda, mislav.bradac, teon.banek, dgleich
Reviewed By: dgleich
Subscribers: mtomic, pullbot
Differential Revision: https://phabricator.memgraph.io/D958
