support multi-command statements

[pav-kv]

The amount of boilerplate to run a sequence of commands in a datadriven test is excessive. For example, here is a typical script. This is visually unsatisfying (the amount of signal per screen is low, and one has to scroll to read it), and slow to type.

It would be good to be able to batch multiple commands in a single statement, i.e. instead of:

command1
----
output1

command2
----
output2

command3
----
output3

have something like:

command1
command2
command3
----
output1
output2
output3

Variations are possible. For example, multiple ok outputs could be squashed into a single ok:

command1
command2
command3
----
ok

This format is in conflict with the current syntax which treats a multi-line statement as a single command with additional input.

We may need some way to mark the multi-command statements. For example:

+ command1  # assumming there are no existing tests with "+" command
+ command2  # we could restrict command names to be "identifiers" starting with a letter
+ command3
----
output1
output2
output3

or:

---- # or other special preamble
command1
command2
command3
----
output1
output2
output3

The first option works better with multiple multi-line commands:

+ command1
<input> # must not have a line starting with "+"
+ command2
<input>
+ command3
<input>
----
output1
output2
output3

Although the given syntax could be restricted to single-line commands, for simplicity. This would give most of the value anyway.

For extra niceness, it would be good to support inline comments next to the commands. With all the modifications, the scripts can look more satisfactory:

Details

# Start with 3 nodes, with a limited in-flight capacity.
add-nodes 3 voters=(1,2,3) index=10 inflight=3
----
ok

+ campaign 1  # elect node 1 to be the leader
+ stabilize
----
ok

+ propose 1 prop_1_12  # propose a few entries
+ propose 1 prop_1_13
+ propose 1 prop_1_14
+ process-ready 1  # store entries and send proposals to followers
----
ok

# Expect that in-flight tracking to nodes 2 and 3 is saturated.
+ log-level debug
+ status 1
+ log-level none
----
1: StateReplicate match=14 next=15
2: StateReplicate match=11 next=15 paused inflight=3[full]
3: StateReplicate match=11 next=15 paused inflight=3[full]

# etc

[petermattis]

This doesn't feel like a bug in the ycsb load generator, but our usage of haproxy. Might be worthwhile moving the bug to cockroachdb/cockroach so that it doesn't get lost here in this separate repo.

[bdarnell]

I'd place the blame in the client driver instead of haproxy. The client library should occasionally close connections and recreate them so it can react to things like changing DNS aliases.