implement fast-accept handler #182

pengsven · 2020-03-12T12:10:24Z

Description

implement fast-accept handler

Self-review: I have performed a self-review of my own code
Comment: I have commented my code, particularly in hard-to-understand areas
Doc: I have made corresponding changes to the documentation
No-warnings: My changes generate no new warnings
Add-test: I have added tests that prove my fix is effective or that my feature works
Pass: New and existing unit tests pass locally with my changes

liubaohai · 2020-03-12T13:33:06Z

components/epaxos/src/replica/replica.rs

+        let mut inst = match self.storage.get_instance(iid)? {
+            Some(_) => return Err(Error::Existed {}),
+            None => self._empty_instance(Some(iid)),
+        };


对于COMMITTED，ACCEPTED，EXECUTED的instance，是不需要走下面的流程的吧，recover的时候可能会遇到

COMMITTED，ACCEPTED，EXECUTED的instance,貌似就不应该发送fast-accept请求

两个replica先后恢复一个inst的时候呢，其中一个恢复成功了，两位一个恢复的时候就会遇到这样的情况

恢复的时候不会用到 fast_accept 吧..

恩...恢复不用fast.

liubaohai · 2020-03-12T13:34:41Z

components/epaxos/src/replica/replica.rs

+            None => self._empty_instance(Some(iid)),
+        };
+
+        inst.ballot = Some(ballot);


这里需要判断req.ballot < inst.ballot吧

req.ballot > inst.ballot吧

一样的啊，看你怎么处理了，我得意思是req.ballot < inst.ballot直接返回

不明白这块为啥要判断 ballot，求讲。我理解 fast_accept 是无论怎样都接收请求，直接把 req.ballot 填在 inst 就好啊...

如果在恢复中, ballot会大于0. 阻止leader继续运行. 否则recover进程和leader可能commit不同的值.

components/epaxos/src/qpaxos/mod.rs

drmingdrmer · 2020-03-12T16:21:57Z

components/epaxos/src/replica/replica.rs

+        let (ballot, iid) = self._check_req_common(&req.cmn)?;
+
+        let mut inst = match self.storage.get_instance(iid)? {
+            Some(_) => return Err(Error::Existed {}),


按照paxos的尿性, 如果遇到重发的消息应该处理下

可, 处理下重复消息

components/epaxos/src/replica/replica.rs

liubaohai · 2020-03-13T03:40:43Z

components/epaxos/src/replica/replica.rs

+            for x in self.storage.get_instance_iter(start_iid, true) {
+                if x.deps[la] < iid && (inst.conflict(&x) || x.committed) {
+                    if let Some(x_iid) = x.instance_id {
+                        let lx = x_iid.leader_of() as usize;
+
+                        if x_iid > inst.deps[lx] {
+                            inst.deps[lx] = x_iid;
+                            deps_committed[lx] = x.committed;
+                        } else if x_iid == inst.deps[lx] {
+                            deps_committed[lx] = deps_committed[lx] || x.committed;
+                        }
+                    }
+                }
+            }


.c ↙ | d d | ↓ ↓↘ ↙ a a→b c x y z x y z x y z ----- ----- ----- R0 R1 R2

这一种逻辑下，d,c依次发送到R1，由于d->a，间接c->a，a发送到R1的时候是不能依赖c的

逻辑是这样的, a只依赖z

a.deps=[x, b, z], 测试用例就是这个例子

liubaohai · 2020-03-13T07:29:48Z

components/epaxos/src/replica/replica.rs

+            let start_iid = (*rid, 0).into();
+
+            for x in self.storage.get_instance_iter(start_iid, true) {
+                if x.deps[la] < iid && (inst.conflict(&x) || x.committed) {


不能这样读取deps，deps是Vec，你得find，replicaid可能是不连续的，或者非常大

wenbobuaa

除了读 inst.deps 的问题，没看出别的..

wenbobuaa · 2020-03-13T08:43:42Z

components/epaxos/src/replica/replica.rs

+            None => self._empty_instance(Some(iid)),
+        };
+
+        inst.ballot = Some(ballot);


不明白这块为啥要判断 ballot，求讲。我理解 fast_accept 是无论怎样都接收请求，直接把 req.ballot 填在 inst 就好啊...

wenbobuaa · 2020-03-13T08:49:35Z

components/epaxos/src/replica/replica.rs

+        let mut inst = match self.storage.get_instance(iid)? {
+            Some(_) => return Err(Error::Existed {}),
+            None => self._empty_instance(Some(iid)),
+        };


恢复的时候不会用到 fast_accept 吧..

components/epaxos/src/replica/replica.rs

drmingdrmer · 2020-03-16T19:07:22Z

components/epaxos/src/replica/replica.rs

+        let mut inst = match self.storage.get_instance(iid)? {
+            Some(v) => {
+                if v.ballot.is_none() || v.ballot.unwrap().num != 0 {
+                    return Err(Error::Existed {});


如果是ballot大的话下面通过返回把last_ballot返回给调用者来处理,不作为错误了.

pengsven requested review from drmingdrmer, wenbobuaa, lishulong and liubaohai March 12, 2020 12:10

liubaohai reviewed Mar 12, 2020

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drmingdrmer mentioned this pull request Mar 13, 2020

这块应该是还需要一步把请求中指定的committed标记应用到本地replica上. 要不先留个todo不做这步优化也行... #183

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components/epaxos/src/replica/replica.rs Outdated Show resolved Hide resolved

pengsven force-pushed the shuwen.fast-accept branch from e19f7f1 to 4f4c5aa Compare March 16, 2020 10:14

drmingdrmer reviewed Mar 16, 2020

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liubaohai approved these changes Mar 18, 2020

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shuwen added 2 commits March 18, 2020 11:43

implement fast-accept handler

8434ebc

reverse iterative instance

5fdb8de

pengsven force-pushed the shuwen.fast-accept branch from 4f4c5aa to 5fdb8de Compare March 18, 2020 03:44

pr-triage bot added PR: unreviewed and removed PR: reviewed-approved labels Mar 18, 2020

pengsven merged commit 5fdb8de into master Mar 18, 2020

pengsven deleted the shuwen.fast-accept branch March 18, 2020 03:44

pr-triage bot added PR: merged and removed PR: unreviewed labels Mar 18, 2020

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implement fast-accept handler #182

implement fast-accept handler #182

pengsven commented Mar 12, 2020

liubaohai Mar 12, 2020

pengsven Mar 13, 2020

liubaohai Mar 13, 2020

wenbobuaa Mar 13, 2020

drmingdrmer Mar 13, 2020

liubaohai Mar 12, 2020

pengsven Mar 13, 2020

liubaohai Mar 13, 2020

wenbobuaa Mar 13, 2020

drmingdrmer Mar 13, 2020 •

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implement fast-accept handler #182

implement fast-accept handler #182

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pengsven commented Mar 12, 2020

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drmingdrmer Mar 13, 2020 • edited Loading

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drmingdrmer Mar 13, 2020 •

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