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Fix potential deadlock in the table manager #5472

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merged 5 commits into from
Feb 28, 2022
Merged

Fix potential deadlock in the table manager #5472

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1b7c0f9
Fix potential deadlock in the table manager
MasslessParticle Feb 24, 2022
ea2e94d
Ensure second lock is released on return
MasslessParticle Feb 25, 2022
8069e39
Merge remote-tracking branch 'upstream/main' into 'MasslessParticle/t…
sandeepsukhani Feb 28, 2022
72778af
use t.TempDir instead of os.TempDir
sandeepsukhani Feb 28, 2022
13eea15
fix broken test
sandeepsukhani Feb 28, 2022
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34 changes: 15 additions & 19 deletions pkg/storage/stores/shipper/downloads/table_manager.go
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Original file line number Diff line number Diff line change
Expand Up @@ -153,31 +153,27 @@ func (tm *TableManager) query(ctx context.Context, tableName string, queries []c
}

func (tm *TableManager) getOrCreateTable(tableName string) (*Table, error) {
// if table is already there, use it.
tm.tablesMtx.RLock()
defer tm.tablesMtx.RUnlock()
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@owen-d owen-d Feb 25, 2022 •
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I think we're fixing a deadlock and introducing a new one. We use RLock first as a lower-cost way to check if the table exists, but must RUnlock it after (the previous PR did this). We cannot defer it here because we need to Lock it later if the table wasn't found. I think we can introduce a 1 line fix:defer tm.tablesMtx.Unlock() immediately after the write lock is acquired, which will ensure we release the write lock correctly in all cases it's acquired.

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Yeah, I missed the Rlock vs. Lock

The latest commit just defers tm.tablesMtx.Unlock() after it's created.


// if table is already there, use it.
table, ok := tm.tables[tableName]
tm.tablesMtx.RUnlock()
if ok {
return table, nil
}

if !ok {
tm.tablesMtx.Lock()
// check if some other competing goroutine got the lock before us and created the table, use it if so.
table, ok = tm.tables[tableName]
if !ok {
// table not found, creating one.
level.Info(util_log.Logger).Log("msg", fmt.Sprintf("downloading all files for table %s", tableName))

tablePath := filepath.Join(tm.cfg.CacheDir, tableName)
err := chunk_util.EnsureDirectory(tablePath)
if err != nil {
return nil, err
}
// table not found, creating one.
level.Info(util_log.Logger).Log("msg", fmt.Sprintf("downloading all files for table %s", tableName))

table = NewTable(tableName, filepath.Join(tm.cfg.CacheDir, tableName), tm.indexStorageClient, tm.boltIndexClient, tm.metrics)
tm.tables[tableName] = table
}
tm.tablesMtx.Unlock()
tablePath := filepath.Join(tm.cfg.CacheDir, tableName)
err := chunk_util.EnsureDirectory(tablePath)
if err != nil {
return nil, err
}

table = NewTable(tableName, filepath.Join(tm.cfg.CacheDir, tableName), tm.indexStorageClient, tm.boltIndexClient, tm.metrics)
tm.tables[tableName] = table
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don't you need to write lock here for this ?

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@MasslessParticle MasslessParticle Feb 25, 2022 •
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I missed that we're using RLock at the top. I've changed it to Lock


return table, nil
}

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60 changes: 41 additions & 19 deletions pkg/storage/stores/shipper/downloads/table_manager_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@ import (
"context"
"fmt"
"math"
"os"
"path/filepath"
"testing"
"time"
Expand Down Expand Up @@ -35,29 +36,50 @@ func buildTestTableManager(t *testing.T, path string) (*TableManager, stopFunc)
}

func TestTableManager_QueryPages(t *testing.T) {
tempDir := t.TempDir()

objectStoragePath := filepath.Join(tempDir, objectsStorageDirName)
t.Run("QueryPages", func(t *testing.T) {
tempDir := t.TempDir()
objectStoragePath := filepath.Join(tempDir, objectsStorageDirName)

var queries []chunk.IndexQuery
for i, name := range []string{"table1", "table2"} {
testutil.SetupTable(t, filepath.Join(objectStoragePath, name), testutil.DBsConfig{
NumUnCompactedDBs: 5,
DBRecordsStart: i * 1000,
}, testutil.PerUserDBsConfig{
DBsConfig: testutil.DBsConfig{
var queries []chunk.IndexQuery
for i, name := range []string{"table1", "table2"} {
testutil.SetupTable(t, filepath.Join(objectStoragePath, name), testutil.DBsConfig{
NumUnCompactedDBs: 5,
DBRecordsStart: i*1000 + 500,
},
NumUsers: 1,
})
queries = append(queries, chunk.IndexQuery{TableName: name})
}
DBRecordsStart: i * 1000,
}, testutil.PerUserDBsConfig{
DBsConfig: testutil.DBsConfig{
NumUnCompactedDBs: 5,
DBRecordsStart: i*1000 + 500,
},
NumUsers: 1,
})
queries = append(queries, chunk.IndexQuery{TableName: name})
}

tableManager, stopFunc := buildTestTableManager(t, tempDir)
defer stopFunc()
tableManager, stopFunc := buildTestTableManager(t, tempDir)
defer stopFunc()

testutil.TestMultiTableQuery(t, testutil.BuildUserID(0), queries, tableManager, 0, 2000)
testutil.TestMultiTableQuery(t, testutil.BuildUserID(0), queries, tableManager, 0, 2000)
})

t.Run("it doesn't deadlock when table create fails", func(t *testing.T) {
tempDir := os.TempDir()
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Just a nit, lets use t.TempDir like other places.

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Sorry, I pushed this change and resolved the merge conflict because I wanted to cut a new release with this fix.


// This file forces chunk_util.EnsureDirectory to fail. Any write error would cause this
// deadlock
f, err := os.CreateTemp(filepath.Join(tempDir, "cache"), "not-a-directory")
require.NoError(t, err)
badTable := filepath.Base(f.Name())

tableManager, stopFunc := buildTestTableManager(t, tempDir)
defer stopFunc()

err = tableManager.query(context.Background(), badTable, nil, nil)
require.Error(t, err)

// This one deadlocks without the fix
err = tableManager.query(context.Background(), badTable, nil, nil)
require.Error(t, err)
})
}

func TestTableManager_cleanupCache(t *testing.T) {
Expand Down