Add structure warning to `replication-analysis` when all masters are read_only #878

jfudally · 2019-05-08T15:15:45Z

Add structure warning to replication-analysis when all master nodes are read_only

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Related issue: #865

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Description

This PR adds NoWriteableMasterStructureWarning to replication-analysis during scenarios when every master node in the cluster is read_only, omitting intermediate masters.

# Cluster with cyclical replication between two masters, and an intermediate master
bash-4.4# ./orchestrator -c topology -i mysql_1
+ mysql_1:3306     [0s,ok,5.7.25-log,rw,ROW]
  + mysql_2:3306   [0s,ok,5.7.25-log,ro,ROW]
    + mysql_3:3306 [0s,ok,5.7.25-log,ro,ROW]
+ mysql_4:3306     [0s,ok,5.7.25-log,rw,ROW]
  + mysql_5:3306   [0s,ok,5.7.25-log,ro,ROW]

# No warnings for the intermediate master
bash-4.4# ./orchestrator -c replication-analysis -i mysql_1

# mysql_1 master is now R/O
bash-4.4# ./orchestrator -c topology -i mysql_1
+ mysql_1:3306     [0s,ok,5.7.25-log,ro,ROW]
  + mysql_2:3306   [0s,ok,5.7.25-log,ro,ROW]
    + mysql_3:3306 [0s,ok,5.7.25-log,ro,ROW]
+ mysql_4:3306     [0s,ok,5.7.25-log,rw,ROW]
  + mysql_5:3306   [0s,ok,5.7.25-log,ro,ROW]

# No warnings from 1 of 2 co-masters being R/O
bash-4.4# ./orchestrator -c replication-analysis -i mysql_1

# Both co-masters mysql_1 & mysql_3 are now R/O
bash-4.4# ./orchestrator -c topology -i mysql_1
+ mysql_1:3306     [0s,ok,5.7.25-log,ro,ROW]
  + mysql_2:3306   [0s,ok,5.7.25-log,ro,ROW]
    + mysql_3:3306 [0s,ok,5.7.25-log,ro,ROW]
+ mysql_4:3306     [0s,ok,5.7.25-log,ro,ROW]
  + mysql_5:3306   [0s,ok,5.7.25-log,ro,ROW]

🎉 
bash-4.4# ./orchestrator -c replication-analysis -i mysql_1
mysql_4:3306 (cluster mysql_1:3306): NoWriteableMasterStructureWarning

In case this PR introduced Go code changes:

contributed code is using same conventions as original code
code is formatted via gofmt (please avoid goimports)
code is built via ./build.sh
code is tested via go test ./go/...

… cluster are read_only

shlomi-noach · 2019-05-08T16:04:02Z

go/inst/analysis.go

@@ -64,6 +64,7 @@ const (
 	DifferentGTIDModesStructureWarning                                       = "DifferentGTIDModesStructureWarning"
 	ErrantGTIDStructureWarning                                               = "ErrantGTIDStructureWarning"
 	NoFailoverSupportStructureWarning                                        = "NoFailoverSupportStructureWarning"
+	NoWriteableNodesWarning                                                  = "NoWriteableNodesStructureWarning"


We should be concerned with non-writable master, for sure. The rest of the nodes are practically irrelevant (that is, we expect them to be read-only anyhow).

I'd name this: NonWritableMasterWarning

@shlomi-noach Make sense, I've updated to warn if the current master is read-only.

shlomi-noach · 2019-05-08T16:16:12Z

To elaborate, on a normal topology, we only expect the master to be writable. Right now we're interested in a scenario where the master is read-only. We normally expect (and hope) for replicas to be read-only, too, but I've seen cases out there where intermediate master could be taking writes. Since we're aiming at the global audience, my suggestion is to let go of looking into the replicas.

So we should only care if we have a read-only master.

Another thing is that we want to check is the case where we have co-masters. In a co-master (circular master-master) setup, it's OK if one of the co-masters is read-only. It's also OK (though generally discouraged) if both co-masters are writable. It's not OK if both are read-only...

jfudally · 2019-05-08T16:30:51Z

I'l take a look at the co-master scenarios as well

jfudally · 2019-05-10T21:13:46Z

@shlomi-noach I've updated the PR body. I've tested new logic to omit warnings on intermediate masters being R/O, and if at least 1 co-master is still R/W.

shlomi-noach · 2019-05-13T12:30:15Z

go/inst/analysis_dao.go

@@ -90,15 +91,17 @@ func GetReplicationAnalysis(clusterName string, hints *ReplicationAnalysisHints)
 		    SELECT
 		        master_instance.hostname,
 		        master_instance.port,
-						MIN(master_instance.data_center) AS data_center,
-						MIN(master_instance.physical_environment) AS physical_environment,
+			master_instance.read_only AS read_only,


shlomi-noach · 2019-05-13T12:30:21Z

go/inst/analysis_dao.go

-						MIN(master_instance.data_center) AS data_center,
-						MIN(master_instance.physical_environment) AS physical_environment,
+			master_instance.read_only AS read_only,
+			SUM(master_instance.is_co_master) AS co_master_count,


this will be either 0 or 1, not what you'd expect. See later discussion.

shlomi-noach · 2019-05-13T12:33:39Z

go/inst/analysis_dao.go

@@ -296,6 +301,10 @@ func GetReplicationAnalysis(clusterName string, hints *ReplicationAnalysisHints)
 		a.CountDelayedReplicas = m.GetUint("count_delayed_replicas")
 		a.CountLaggingReplicas = m.GetUint("count_lagging_replicas")

+		if a.IsCoMaster && m.GetUint("read_only") == 1 {


Please read m.GetUint("read_only") into a variable first. In fact, it's really interesting information, make that a member in the ReplicationAnalysis struct

shlomi-noach · 2019-05-13T12:45:10Z

go/inst/analysis_dao.go

@@ -296,6 +301,10 @@ func GetReplicationAnalysis(clusterName string, hints *ReplicationAnalysisHints)
 		a.CountDelayedReplicas = m.GetUint("count_delayed_replicas")
 		a.CountLaggingReplicas = m.GetUint("count_lagging_replicas")

+		if a.IsCoMaster && m.GetUint("read_only") == 1 {
+			coMasterROCount++


This look can iterate over multiple clusters. You only want to count the number of co masters per cluster. So this trick of coMasterROCount++ won't work.

A cluster with two co-masters appears in orchestrator as a single cluster, not as two clusters. One of the two co-masters is deemed to be the "primary" master. If one is read-only and another is writable, it's the writable. If both are read-only or both are writable, I believe the choice is alphabetic.

So, as I'm writing this, I'm rethinking our earlier discussion. if the master is a co_master and is read_only, then the other co-master is also read_only (or else IT would have been the primary master!). This simplifies things and you can get rid of coMasterROCount.

shlomi-noach · 2019-05-13T12:47:05Z

go/inst/analysis_dao.go

@@ -477,6 +486,14 @@ func GetReplicationAnalysis(clusterName string, hints *ReplicationAnalysisHints)
 			if a.MaxReplicaGTIDErrant != "" {
 				a.StructureAnalysis = append(a.StructureAnalysis, ErrantGTIDStructureWarning)
 			}
+
+			if a.IsMaster && m.GetUint("read_only") == 1 && m.GetString("master_host") == "" {


"master_host" is already read in a.AnalyzedInstanceMasterKey. You can ask if a.AnalyzedInstanceMasterKey.IsValid() (== non empty)

Given earlier discussion, I think we can skip the check about master_host altogether.

shlomi-noach · 2019-05-13T12:48:58Z

go/inst/analysis_dao.go

+			if a.IsMaster && m.GetUint("read_only") == 1 && m.GetString("master_host") == "" {
+				a.StructureAnalysis = append(a.StructureAnalysis, NoWriteableMasterStructureWarning)
+			}
+			if a.IsCoMaster && coMasterROCount == m.GetInt("co_master_count") {


Given earlier discussion, I think we can skip this block altogether.

shlomi-noach

This looks good to me! Let's deploy to our staging environment and experiment

shlomi-noach · 2019-06-05T05:53:42Z

go/inst/analysis_dao.go

@@ -90,6 +91,7 @@ func GetReplicationAnalysis(clusterName string, hints *ReplicationAnalysisHints)
 		    SELECT
 		        master_instance.hostname,
 		        master_instance.port,
+            master_instance.read_only AS read_only,


inconsistent indentation here

jfudally · 2019-06-06T17:08:13Z

Sounds good...as soon as Travis decides to work I can deploy to our test environment.

shlomi-noach · 2019-06-07T07:15:35Z

Travis is used for our external facing builds; our internal builds are all that is needed (and at this time we will need to kick the build manually).

…thub/orchestrator into jfudally-ro-structure-warning

shlomi-noach · 2019-06-20T13:37:37Z

Good to go! Identifies a read-only master on a single-master topology. Future PR to handle co-masters.

Justin Fudally added 2 commits May 8, 2019 09:50

Add structure warning to replication-analysis when all nodes in the…

f2f7402

… cluster are read_only

format

0848d25

jfudally requested a review from shlomi-noach May 8, 2019 15:15

Update analysis_dao.go

bd7d8e8

shlomi-noach reviewed May 8, 2019

View reviewed changes

Justin Fudally added 3 commits May 8, 2019 11:17

Only warn on RO master

2739486

merge

48ed4eb

fix indentation

eed30fc

jfudally requested a review from shlomi-noach May 8, 2019 16:27

Justin Fudally added 10 commits May 10, 2019 14:08

Ensure intermediate master is not flagged for R/O

895a011

Only warn if all co-masters are R/O

b3ccd73

merge conflict

4a5b67f

Delete init_docker.sh

1977891

Fix indentations

65d83f9

Fix small issue with counts

ff13e0b

go fmt

fa8c923

Remove extra script

a1b3080

merge conflict

f0078eb

formatting again

eb75598

shlomi-noach suggested changes May 13, 2019

View reviewed changes

Justin Fudally added 2 commits June 3, 2019 16:39

Simplify logic

e45511a

Merge branch 'master' into jfudally-ro-structure-warning

a2bbdce

jfudally changed the title ~~Add structure warning to replication-analysis when all nodes are read_only~~ Add structure warning to replication-analysis when all masters are read_only Jun 3, 2019

shlomi-noach approved these changes Jun 5, 2019

View reviewed changes

Fix indentation

7943eac

jfudally temporarily deployed to production/mysql_cluster=mysql6 June 6, 2019 21:11 Inactive

jfudally temporarily deployed to production/mysql_cluster=mysql6 June 7, 2019 07:15 Inactive

jfudally temporarily deployed to production/mysql_cluster=concertmaster June 10, 2019 13:33 Inactive

Justin Fudally added 2 commits June 10, 2019 09:17

UI fix

42f0747

Merge branch 'jfudally-ro-structure-warning' of https://github.com/gi…

940cc59

…thub/orchestrator into jfudally-ro-structure-warning

jfudally temporarily deployed to production/mysql_cluster=mysql6 June 10, 2019 14:24 Inactive

jfudally had a problem deploying to production/mysql_cluster=concertmaster June 10, 2019 14:24 Failure

jfudally temporarily deployed to production/mysql_cluster=mysql6 June 10, 2019 14:26 Inactive

jfudally temporarily deployed to production/mysql_cluster=concertmaster June 10, 2019 14:26 Inactive

Auto-merged master into jfudally-ro-structure-warning on deployment

b7e0df8

jfudally temporarily deployed to production/mysql_cluster=mysql6 June 20, 2019 08:51 Inactive

shlomi-noach had a problem deploying to production/mysql_cluster=concertmaster June 20, 2019 08:51 Failure

shlomi-noach merged commit b0cab8d into master Jun 20, 2019

shlomi-noach deleted the jfudally-ro-structure-warning branch June 20, 2019 13:37

jfudally mentioned this pull request Jun 20, 2019

No FailureDetection read_only=on on all servers in a topology #865

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Add structure warning to `replication-analysis` when all masters are read_only #878

Add structure warning to `replication-analysis` when all masters are read_only #878

jfudally commented May 8, 2019 •

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Add structure warning to replication-analysis when all masters are read_only #878

Add structure warning to replication-analysis when all masters are read_only #878

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jfudally commented Jun 6, 2019

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shlomi-noach commented Jun 20, 2019

Add structure warning to `replication-analysis` when all masters are read_only #878

Add structure warning to `replication-analysis` when all masters are read_only #878

jfudally commented May 8, 2019 •

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