Schema queries with configurable server-side timeouts

[sylwiaszunejko]

Adds USING TIMEOUT clause to schema queries when applicable.
Uses the timeout defined by MetadataSchemaRequestTimeout option in ClusterConfig.

Fixes: #172
Fixes: #157

[sylwiaszunejko]

I am not sure how to check if USING TIMEOUT should be applied. Every query to schema tables is executed through control connection, so it made same to me to put usingTimeoutClause in controlConn. An easy way to check if scylla is used is to use isScyllaConn https://github.com/scylladb/gocql/blob/master/scylla.go#L285, but it takes Conn not controlConn. I am not sure how to solve this.

[dkropachev]

Looks great.

[dkropachev]

Let's cover queryes from awaitSchemaAgreement, querySystemPeers and querySystemLocal

[sylwiaszunejko]

@dkropachev do you have any suggestions regarding differentiating between scylla and cassandra from the position of Session or controlConn? scylladb/java-driver#312 (comment)

[dkropachev]

Idea on testing it:

1. Set timeout to something that will break queries, 1ns
2. Establish session and make sure that schema is there and routing works properly.
3. Double check that you regular queries are failing by timeout

[dkropachev]

@dkropachev do you have any suggestions regarding differentiating between scylla and cassandra from the position of Session or controlConn? scylladb/java-driver#312 (comment)

1. Have a flag to disable this feature in ClusterConfig
2. Have separate flag to disable it on session level.
3. Test it out on Session.Init() and set the flag to disable feature if syntax error is received.

Perfect place for it is:

gocql/session.go

Lines 236 to 238 in c26ee43

	s.control.getConn().conn.mu.Lock()
	s.tabletsRoutingV1 = s.control.getConn().conn.isTabletSupported()
	s.control.getConn().conn.mu.Unlock()

[sylwiaszunejko]

Let's cover queryes from awaitSchemaAgreement, querySystemPeers and querySystemLocal

I was following scylladb/java-driver#312 and there such queries were not covered. @Bouncheck am I right?

[dkropachev]

Let's cover queryes from awaitSchemaAgreement, querySystemPeers and querySystemLocal

I was following scylladb/java-driver#312 and there such queries were not covered. @Bouncheck am I right?

It was not.

Why I think it makes sense to cover them too:
Bigger idea of this feature is to keep driver sane when cluster is under high preassure and/or when certain queries are taking a long time.
So, any query that is ran by the driver for it's internal needs to be covered.
Also, we don't loose much doing that, at worst driver will slow down instead of failing.

[mykaul]

Let's cover queryes from awaitSchemaAgreement, querySystemPeers and querySystemLocal

I was following scylladb/java-driver#312 and there such queries were not covered. @Bouncheck am I right?

It was not.

Why I think it makes sense to cover them too: Bigger idea of this feature is to keep driver sane when cluster is under high preassure and/or when certain queries are taking a long time. So, any query that is ran by the driver for it's internal needs to be covered. Also, we don't loose much doing that, at worst driver will slow down instead of failing.

Those are not large queries, IMHO:

private static final String SELECT_SCHEMA_PEERS =
      "SELECT peer, rpc_address, schema_version, host_id FROM system.peers";
  private static final String SELECT_SCHEMA_LOCAL =
      "SELECT schema_version, host_id FROM system.local WHERE key='local'";

[dkropachev]

Let's cover queryes from awaitSchemaAgreement, querySystemPeers and querySystemLocal

I was following scylladb/java-driver#312 and there such queries were not covered. @Bouncheck am I right?

It was not.
Why I think it makes sense to cover them too: Bigger idea of this feature is to keep driver sane when cluster is under high preassure and/or when certain queries are taking a long time. So, any query that is ran by the driver for it's internal needs to be covered. Also, we don't loose much doing that, at worst driver will slow down instead of failing.

Those are not large queries, IMHO:

private static final String SELECT_SCHEMA_PEERS =
      "SELECT peer, rpc_address, schema_version, host_id FROM system.peers";
  private static final String SELECT_SCHEMA_LOCAL =
      "SELECT schema_version, host_id FROM system.local WHERE key='local'";

True, but since code is already there it won't take much effort to cover them too.

[sylwiaszunejko]

Let's cover queryes from awaitSchemaAgreement, querySystemPeers and querySystemLocal

Done, and some simple tests added

[sylwiaszunejko]

@dkropachev could you take a look?

[roydahan]

Overall LGTM, but I would wait to @dkropachev and @Lorak-mmk to have their review.

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