MultiplexV2 is a new connection multiplex header that supports multiplex both
RPC and streaming requests over the same Yamux connection.
MultiplexV2 was added in 0.8.0 as part of
https://github.com/hashicorp/nomad/pull/3892 . So Nomad 0.11 can expect it to
be supported. Though, some more rigorous testing is required before merging
this.
I want to call out some implementation details:
First, the current connection pool reuses the Yamux stream for multiple RPC calls,
and doesn't close them until an error is encountered. This commit doesn't
change it, and sets the `RpcNomad` byte only at stream creation.
Second, the StreamingRPC session gets closed by callers and cannot be reused.
Every StreamingRPC opens a new Yamux session.
Introduce limits to prevent unauthorized users from exhausting all
ephemeral ports on agents:
* `{https,rpc}_handshake_timeout`
* `{http,rpc}_max_conns_per_client`
The handshake timeout closes connections that have not completed the TLS
handshake by the deadline (5s by default). For RPC connections this
timeout also separately applies to first byte being read so RPC
connections with TLS enabled have `rpc_handshake_time * 2` as their
deadline.
The connection limit per client prevents a single remote TCP peer from
exhausting all ephemeral ports. The default is 100, but can be lowered
to a minimum of 26. Since streaming RPC connections create a new TCP
connection (until MultiplexV2 is used), 20 connections are reserved for
Raft and non-streaming RPCs to prevent connection exhaustion due to
streaming RPCs.
All limits are configurable and may be disabled by setting them to `0`.
This also includes a fix that closes connections that attempt to create
TLS RPC connections recursively. While only users with valid mTLS
certificates could perform such an operation, it was added as a
safeguard to prevent programming errors before they could cause resource
exhaustion.
Allows addressing servers with nomad monitor using the servers name or
ID.
Also unifies logic for addressing servers for client_agent_endpoint
commands and makes addressing logic region aware.
rpc getServer test
This ensures that server-to-server streaming RPC calls use the tls
wrapped connections.
Prior to this, `streamingRpcImpl` function uses tls for setting header
and invoking the rpc method, but returns unwrapped tls connection.
Thus, streaming writes fail with tls errors.
This tls streaming bug existed since 0.8.0[1], but PR #5654[2]
exacerbated it in 0.9.2. Prior to PR #5654, nomad client used to
shuffle servers at every heartbeat -- `servers.Manager.setServers`[3]
always shuffled servers and was called by heartbeat code[4]. Shuffling
servers meant that a nomad client would heartbeat and establish a
connection against all nomad servers eventually. When handling
streaming RPC calls, nomad servers used these local connection to
communicate directly to the client. The server-to-server forwarding
logic was left mostly unexercised.
PR #5654 means that a nomad client may connect to a single server only
and caused the server-to-server forward streaming RPC code to get
exercised more and unearthed the problem.
[1] https://github.com/hashicorp/nomad/blob/v0.8.0/nomad/rpc.go#L501-L515
[2] https://github.com/hashicorp/nomad/pull/5654
[3] https://github.com/hashicorp/nomad/blob/v0.9.1/client/servers/manager.go#L198-L216
[4] https://github.com/hashicorp/nomad/blob/v0.9.1/client/client.go#L1603
Here, we ensure that when leader only responds to RPC calls when state
store is up to date. At leadership transition or launch with restored
state, the server local store might not be caught up with latest raft
logs and may return a stale read.
The solution here is to have an RPC consistency read gate, enabled when
`establishLeadership` completes before we respond to RPC calls.
`establishLeadership` is gated by a `raft.Barrier` which ensures that
all prior raft logs have been applied.
Conversely, the gate is disabled when leadership is lost.
This is very much inspired by https://github.com/hashicorp/consul/pull/3154/files
Multiplexer continues to create rpc connections even when
the context which is passed to the underlying rpc connections
is cancelled by the server.
This was causing #4413 - when a SIGHUP causes everything to reload,
it uses context to cancel the underlying http/rpc connections
so that they may come up with the new configuration.
The multiplexer was not being cancelled properly so it would
continue to create rpc connections and constantly fail,
causing communication issues with other nomad agents.
Fixes#4413
This PR introduces an ack allowing the receiving end of the streaming
RPC to return any error that may have occured during the establishment
of the streaming RPC.
* Allow server TLS configuration to be reloaded via SIGHUP
* dynamic tls reloading for nomad agents
* code cleanup and refactoring
* ensure keyloader is initialized, add comments
* allow downgrading from TLS
* initalize keyloader if necessary
* integration test for tls reload
* fix up test to assert success on reloaded TLS configuration
* failure in loading a new TLS config should remain at current
Reload only the config if agent is already using TLS
* reload agent configuration before specific server/client
lock keyloader before loading/caching a new certificate
* introduce a get-or-set method for keyloader
* fixups from code review
* fix up linting errors
* fixups from code review
* add lock for config updates; improve copy of tls config
* GetCertificate only reloads certificates dynamically for the server
* config updates/copies should be on agent
* improve http integration test
* simplify agent reloading storing a local copy of config
* reuse the same keyloader when reloading
* Test that server and client get reloaded but keep keyloader
* Keyloader exposes GetClientCertificate as well for outgoing connections
* Fix spelling
* correct changelog style
Fixes#2525
We used to be checking a RequireTLS field that was never set. Instead we
can just check the TLSConfig.EnableRPC field and require TLS if it's
enabled.
Added a few unfortunately slow integration tests to assert the intended
behavior of misconfigured RPC TLS.
Also disable a lot of noisy test logging when -v isn't specified.
