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Add metric for showing the errant GTIDs in VTOrc #13281

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merged 5 commits into from
Jun 15, 2023
Merged

Add metric for showing the errant GTIDs in VTOrc #13281

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2443ec1
feat: add metric for errant gtid
GuptaManan100 Jun 9, 2023
08b3ebe
feat: update the errant gtid map always, so that once errant gtids ar…
GuptaManan100 Jun 9, 2023
088f559
feat: fix the test to match the new expectations
GuptaManan100 Jun 9, 2023
84098ee
feat: add mutex to protect the access to the map storing errant gtids
GuptaManan100 Jun 14, 2023
0fe73a4
feat: update the errant gtid map in a goroutine
GuptaManan100 Jun 14, 2023
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20 changes: 20 additions & 0 deletions go/test/endtoend/vtorc/api/api_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -17,7 +17,9 @@ limitations under the License.
package api

import (
"encoding/json"
"fmt"
"reflect"
"testing"
"time"

Expand Down Expand Up @@ -197,5 +199,23 @@ func TestAPIEndpoints(t *testing.T) {
require.NoError(t, err)
assert.Equal(t, 400, status, resp)
assert.Equal(t, "Filtering by shard without keyspace isn't supported\n", resp)

// Also verify that the metric for errant GTIDs is reporting the correct information.
_, resp, err = utils.MakeAPICall(t, vtorc, "/debug/vars")
require.NoError(t, err)
resultMap := make(map[string]any)
err = json.Unmarshal([]byte(resp), &resultMap)
require.NoError(t, err)
errantGTIDMap := reflect.ValueOf(resultMap["ErrantGtidMap"])
errantGtidTablets := errantGTIDMap.MapKeys()
require.Len(t, errantGtidTablets, 3)

errantGTIDinReplica := ""
for _, tabletKey := range errantGtidTablets {
if tabletKey.String() == replica.Alias {
errantGTIDinReplica = errantGTIDMap.MapIndex(tabletKey).Interface().(string)
}
}
require.NotEmpty(t, errantGTIDinReplica)
})
}
18 changes: 18 additions & 0 deletions go/vt/vtorc/inst/instance_dao.go
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Expand Up @@ -31,6 +31,7 @@ import (
"github.com/rcrowley/go-metrics"
"github.com/sjmudd/stopwatch"

"vitess.io/vitess/go/stats"
"vitess.io/vitess/go/vt/external/golib/sqlutils"

vitessmysql "vitess.io/vitess/go/mysql"
Expand All @@ -56,6 +57,12 @@ const (
var instanceReadChan = make(chan bool, backendDBConcurrency)
var instanceWriteChan = make(chan bool, backendDBConcurrency)

var (
// Mutex to protect the access of the following variable
errantGtidMapMu = sync.Mutex{}
errantGtidMap = make(map[string]string)
)

// Constant strings for Group Replication information
// See https://dev.mysql.com/doc/refman/8.0/en/replication-group-members-table.html for additional information.
const (
Expand Down Expand Up @@ -88,6 +95,11 @@ func init() {
_ = metrics.Register("instance.write", writeInstanceCounter)
_ = writeBufferLatency.AddMany([]string{"wait", "write"})
writeBufferLatency.Start("wait")
stats.NewStringMapFuncWithMultiLabels("ErrantGtidMap", "Metric to track the errant GTIDs detected by VTOrc", []string{"TabletAlias"}, "ErrantGtid", func() map[string]string {
errantGtidMapMu.Lock()
defer errantGtidMapMu.Unlock()
return errantGtidMap
})

go initializeInstanceDao()
}
Expand Down Expand Up @@ -429,6 +441,12 @@ Cleanup:
instance.GtidErrant, err = vitessmysql.Subtract(redactedExecutedGtidSet.String(), redactedPrimaryExecutedGtidSet.String())
}
}
// update the errant gtid map
go func() {
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Curious why this is done in a goroutine rather than an inline sequential routine?

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We run this code path of refreshing tablet data parallelly for all the tablets sometimes. In that case, I didn't want this function to be blocked. I think it is okay for them to spawn go-routines that sequentially update the map asynchornously from the function. This map is used only for the metric, so as long as the updates flow, its all okay (even if slightly delayed)

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I considered an alternate where instead of updating the map on this read, I would just read the information from the database on a time-tick. This approach has a slight advantage wherein it is faster in its updation.

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That makes sense. Thank you!

errantGtidMapMu.Lock()
defer errantGtidMapMu.Unlock()
errantGtidMap[topoproto.TabletAliasString(tablet.Alias)] = instance.GtidErrant
}()
}

latency.Stop("instance")
Expand Down