This has the next wave of RTT integration with the router and also
factors some common RTT-related helpers out to lib. While we were
in here we also got rid of the coordinate disable config so we don't
need to deal with the complexity in the router (there was never a
user-visible way to disable coordinates).
* Updates Raft library to get new snapshot/restore API.
* Basic backup and restore working, but need some cleanup.
* Breaks out a snapshot module and adds a SHA256 integrity check.
* Adds snapshot ACL and fills in some missing comments.
* Require a consistent read for snapshots.
* Make sure snapshot works if ACLs aren't enabled.
* Adds a bit of package documentation.
* Returns an empty response from restore to avoid EOF errors.
* Adds API client support for snapshots.
* Makes internal file names match on-disk file snapshots.
* Adds DC and token coverage for snapshot API test.
* Adds missing documentation.
* Adds a unit test for the snapshot client endpoint.
* Moves the connection pool out of the client for easier testing.
* Fixes an incidental issue in the prepared query unit test.
I realized I had two servers in bootstrap mode so this wasn't a good setup.
* Adds a half close to the TCP stream and fixes panic on error.
* Adds client and endpoint tests for snapshots.
* Moves the pool back into the snapshot RPC client.
* Adds a TLS test and fixes half-closes for TLS connections.
* Tweaks some comments.
* Adds a low-level snapshot test.
This is independent of Consul so we can pull this out into a library
later if we want to.
* Cleans up snapshot and archive and completes archive tests.
* Sends a clear error for snapshot operations in dev mode.
Snapshots require the Raft snapshots to be readable, which isn't supported
in dev mode. Send a clear error instead of a deep-down Raft one.
* Adds docs for the snapshot endpoint.
* Adds a stale mode and index feedback for snapshot saves.
This gives folks a way to extract data even if the cluster has no
leader.
* Changes the internal format of a snapshot from zip to tgz.
* Pulls in Raft fix to cancel inflight before a restore.
* Pulls in new Raft restore interface.
* Adds metadata to snapshot saves and a verify function.
* Adds basic save and restore snapshot CLI commands.
* Gets rid of tarball extensions and adds restore message.
* Fixes an incidental bad link in the KV docs.
* Adds documentation for the snapshot CLI commands.
* Scuttle any request body when a snapshot is saved.
* Fixes archive unit test error message check.
* Allows for nil output writers in snapshot RPC handlers.
* Renames hash list Decode to DecodeAndVerify.
* Closes the client connection for snapshot ops.
* Lowers timeout for restore ops.
* Updates Raft vendor to get new Restore signature and integrates with Consul.
* Bounces the leader's internal state when we do a restore.
Reduce cognative load and perform an overdue rename. No functional change.
Rename the `server_manager` package to `servers`. Rename the `ServerManager` package to `Manager`. In `client`, rename `serverMgr` to `servers`.
Now that there is no longer an event loop driven directly by Serf, start the ServerManager task after Serf has been setup. When testing and adjusting timers and timeouts to unreasonably low values, it's possible to tickle a race condition where Serf's NumNodes() would fail because Serf had not been initialized.
In FindServer this is a useful warning hinting why its call failed. RPC returns error and leaves it to the higher level caller to do whatever it wants. As an operator, I'd have the detail necessary to know why the RPC call(s) failed.
Rely on Serf for liveliness. In the event of a failure, simply cycle the server to the end of the list. If the server is unhealthy, Serf will reap the dead server.
Additional simplifications:
*) Only rebalance servers based on timers, not when a new server is readded to the cluster.
*) Back out the failure count in server_details.ServerDetails
Instead of blocking the RPC call path and performing a potentially expensive calculation (including a call to `c.LANMembers()`), introduce a channel to request a rebalance. Some events don't force a reshuffle, instead the extend the duration of the current rebalance window because the environment thrashed enough to redistribute a client's load.
Relocated to its own package, server_manager. This now greatly simplifies the RPC() call path and appropriately hides the locking behind the package boundary. More work is needed to be done here
This may be short-lived, but it also seems like this is going to lead us down a path where ServerDetails is going to evolve into a more powerful package that will encapsulate more behavior behind a coherent API.
Move the management of c.consulServers (fka c.consuls) into consul/server_manager.go.
This commit brings in a background task that proactively manages the server list and:
*) reshuffles the list
*) manages the timer out of the RPC() path
*) uses atomics to detect a server has failed
This is a WIP, more work in testing needs to be completed.
Expanding the domain of lastServer beyond RPC() changes the meaning of this variable. Rename accordingly to match the intent coming in a subsequent commit: a background thread will be in charge of rotating preferredServer.
It is theoretically possible that the number of queued serf events can back up. If this happens, emit a warning message if there are more than 200 events in queue.
Most notably, this can happen if `c.consulServerLock` is held for an "extended period of time". The probability of anyone ever seeing this log message is hopefully low to nonexistent, but if it happens, the warning message indicating a large number of serf events fired while a lock was held is likely to be helpful (vs serf mysteriously blocking when attempting to add an event to a channel).
Introduce a low-level background connection expiration mechanism wherein connections will be recycled periodically based on the size and health of the cluster.
For the vast majority of consul users, this will mean an average connection age of 150s. For 10K node clusters it will take ~3min for clusters to rebalance their connections. In the pathological case for a 100K cluster where 99K clients are in the minority talking to 1x server it will take ~26min to rebalance all connections.
It's possibe for clients recovering from a parititon to become fixated on a single server until the server or agent is restarted. This is of particular interest to long-running environments with stable agents, where `allow_stale` is true, and partitions occur periodically.
Increase the max idle time for agents talking to servers from 30s to 127s in order to allow for the reuse of connections that are being initiated by cron.
127s was chosen as the first prime above 120s (arbitrarily chose to use a prime) with the intent of reusing connections who are used by once-a-minute cron(8) jobs *and* who use a 60s jitter window (e.g. in vixie cron job execution can drift by up to 59s per job, or 119s for a once-a-minute cron job).
