Check pending conf change before campaign

[BusyJay]

Fix #221.

This is a fix for 0.4.x, I will do the fix for master later.

[CLAassistant]

All committers have signed the CLA.

[siddontang]

@nolouch

I think we should contribute to etcd later.

[siddontang]

PTAL @xiang90

[siddontang]

if we don't call self.hub(true), the test can fail?

[BusyJay]

Yes. The case was written before the fix, and it failed.

[BusyJay]

Seems criterion's API is broken. @Hoverbear Would you like to take a look?

[siddontang]

@BusyJay

seem some failed tests were not caused by criterion API changes.

[BusyJay]

@siddontang can you name some? I can't find them.

[siddontang]

thread 'raft_log::test::test_commit_to' panicked at ' to_commit 4 is out of range [last_index 3]', src/raft_log.rs:248:13
test raft_log::test::test_append ... ok
thread 'raft_log::test::test_compaction' panicked at 'compact 1001 is out of bound lastindex(1000)', src/storage.rs:174:13
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
stack backtrace:
   0: std::sys::unix::backtrace::tracing::imp::unwind_backtrace
             at src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:39
   1: std::sys_common::backtrace::_print
             at src/libstd/sys_common/backtrace.rs:70
   2: std::panicking::default_hook::{{closure}}
             at src/libstd/sys_common/backtrace.rs:58
             at src/libstd/panicking.rs:200
   3: std::panicking::default_hook
             at src/libstd/panicking.rs:215
   4: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:478
   5: std::panicking::continue_panic_fmt
             at src/libstd/panicking.rs:385
   6: std::panicking::begin_panic_fmt
             at src/libstd/panicking.rs:340
   7: <raft::raft_log::RaftLog<T>>::commit_to
             at src/raft_log.rs:248
   8: raft::raft_log::test::test_commit_to::{{closure}}
             at src/raft_log.rs:1285
   9: core::ops::function::FnOnce::call_once
             at /rustc/fc50f328b0353b285421b8ff5d4100966387a997/src/libcore/ops/function.rs:231
  10: <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once
             at /rustc/fc50f328b0353b285421b8ff5d4100966387a997/src/libstd/panic.rs:309
  11: std::panicking::try::do_call
             at /rustc/fc50f328b0353b285421b8ff5d4100966387a997/src/libstd/panicking.rs:297
  12: __rust_maybe_catch_panic
             at src/libpanic_unwind/lib.rs:87
  13: std::panicking::try
             at /rustc/fc50f328b0353b285421b8ff5d4100966387a997/src/libstd/panicking.rs:276
  14: std::panic::catch_unwind
             at /rustc/fc50f328b0353b285421b8ff5d4100966387a997/src/libstd/panic.rs:388
  15: raft::raft_log::test::test_commit_to
             at src/raft_log.rs:1285
  16: raft::raft_log::test::test_commit_to::{{closure}}
             at src/raft_log.rs:1270
  17: core::ops::function::FnOnce::call_once
             at /rustc/fc50f328b0353b285421b8ff5d4100966387a997/src/libcore/ops/function.rs:231
  18: <F as alloc::boxed::FnBox<A>>::call_box
             at src/libtest/lib.rs:1497
             at /rustc/fc50f328b0353b285421b8ff5d4100966387a997/src/libcore/ops/function.rs:231
             at /rustc/fc50f328b0353b285421b8ff5d4100966387a997/src/liballoc/boxed.rs:749
  19: __rust_maybe_catch_panic
             at src/libpanic_unwind/lib.rs:87
  20: test::run_test::run_test_inner::{{closure}}
             at /rustc/fc50f328b0353b285421b8ff5d4100966387a997/src/libstd/panicking.rs:276
             at /rustc/fc50f328b0353b285421b8ff5d4100966387a997/src/libstd/panic.rs:388
             at src/libtest/lib.rs:1452

[BusyJay]

Those tests are expected to panic. They are wrapped with UnwindSafe.

[hicqu]

If there is a pending snapshot, what will raft_log.applied be?

[hicqu]

In this case I think raft_log.applied must be less than snapshot.index, so I think only n != 0 is ok here.

[BusyJay]

raft_log.applied can be any value less than the snapshot index.

[hicqu]

LGTM.