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sql: add in-memory sessions FIFO cache for closed sessions.
This the first phase of cockroachdb#67888 which simply adds a FIFO cache for closed sessions. The cache's eviction policy is both row-based and time-based. Both the capacity and the time to live can be set using the `settings` package. Further PRs will focus on exposing these closed sessions to the frontend via the `ListSessions` endpoint, optimizing the capacity and timeToLive variables, and making appropriate UI changes. Release note: None
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Gerardo Torres
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Mar 23, 2022
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,146 @@ | ||
| // Copyright 2022 The Cockroach Authors. | ||
| // | ||
| // Use of this software is governed by the Business Source License | ||
| // included in the file licenses/BSL.txt. | ||
| // | ||
| // As of the Change Date specified in that file, in accordance with | ||
| // the Business Source License, use of this software will be governed | ||
| // by the Apache License, Version 2.0, included in the file | ||
| // licenses/APL.txt. | ||
|
|
||
| package sql | ||
|
|
||
| import ( | ||
| "time" | ||
|
|
||
| "github.com/cockroachdb/cockroach/pkg/server/serverpb" | ||
| "github.com/cockroachdb/cockroach/pkg/settings" | ||
| "github.com/cockroachdb/cockroach/pkg/settings/cluster" | ||
| "github.com/cockroachdb/cockroach/pkg/util/cache" | ||
| "github.com/cockroachdb/cockroach/pkg/util/syncutil" | ||
| "github.com/cockroachdb/cockroach/pkg/util/timeutil" | ||
| ) | ||
|
|
||
| // ClosedSessionCacheCapacity is the cluster setting that controls the maximum number | ||
| // of sessions in the cache. | ||
| var ClosedSessionCacheCapacity = settings.RegisterIntSetting( | ||
| settings.TenantWritable, | ||
| "sql.closed_session_cache.capacity", | ||
| "the maximum number of sessions in the cache", | ||
| 100, // TODO(gtr): Totally arbitrary for now, adjust later. | ||
| ).WithPublic() | ||
|
|
||
| // ClosedSessionCacheTimeToLive is the cluster setting that controls the maximum time | ||
| // to live for a session's information in the cache, in seconds. | ||
| var ClosedSessionCacheTimeToLive = settings.RegisterIntSetting( | ||
| settings.TenantWritable, | ||
| "sql.closed_session_cache.time_to_live", | ||
| "the maximum time to live, in seconds", | ||
| 3600, // One hour | ||
| ).WithPublic() | ||
|
|
||
| // ClosedSessionCache is an in-memory FIFO cache for closed sessions. | ||
| type ClosedSessionCache struct { | ||
| st *cluster.Settings | ||
|
|
||
| mu struct { | ||
| syncutil.RWMutex | ||
| data *cache.UnorderedCache | ||
| } | ||
| } | ||
|
|
||
| // NewClosedSessionCache returns a new ClosedSessionCache. | ||
| func NewClosedSessionCache(st *cluster.Settings) *ClosedSessionCache { | ||
| c := &ClosedSessionCache{st: st} | ||
|
|
||
| c.mu.data = cache.NewUnorderedCache(cache.Config{ | ||
| Policy: cache.CacheFIFO, | ||
| ShouldEvict: func(size int, _, _ interface{}) bool { | ||
| capacity := ClosedSessionCacheCapacity.Get(&st.SV) | ||
| return int64(size) > capacity | ||
| }, | ||
| }) | ||
|
|
||
| return c | ||
| } | ||
|
|
||
| // Add adds a closed session to the ClosedSessionCache. | ||
| func (c *ClosedSessionCache) Add(id ClusterWideID, session serverpb.Session) { | ||
| c.mu.Lock() | ||
| defer c.mu.Unlock() | ||
|
|
||
| node := &SessionNode{id: id, data: session, timestamp: timeutil.Now()} | ||
| c.mu.data.Add(id, node) | ||
| } | ||
|
|
||
| func (c *ClosedSessionCache) size() int { | ||
| c.mu.Lock() | ||
| defer c.mu.Unlock() | ||
|
|
||
| return c.mu.data.Len() | ||
| } | ||
|
|
||
| // GetSerializedSessions returns a list of []serverpb.Session, ordered from | ||
| // newest to oldest in the cache. | ||
| func (c *ClosedSessionCache) GetSerializedSessions() []serverpb.Session { | ||
| var serializedSessions []serverpb.Session | ||
|
|
||
| sessions := c.getSessions() | ||
| for _, s := range sessions { | ||
| serializedSessions = append(serializedSessions, s.data) | ||
| } | ||
|
|
||
| return serializedSessions | ||
| } | ||
|
|
||
| // getSessions iterates through each SessionNode, evicting those whose age | ||
| // exceeds the cache's maximum time to live, and returns a list of the | ||
| // remaining SessionNodes | ||
| func (c *ClosedSessionCache) getSessions() []*SessionNode { | ||
| c.mu.Lock() | ||
| defer c.mu.Unlock() | ||
|
|
||
| var result []*SessionNode | ||
| var sessionsToEvict []*SessionNode | ||
|
|
||
| c.mu.data.Do(func(entry *cache.Entry) { | ||
| node := entry.Value.(*SessionNode) | ||
| if int64(node.getAge().Seconds()) > ClosedSessionCacheTimeToLive.Get(&c.st.SV) { | ||
| sessionsToEvict = append(sessionsToEvict, node) | ||
| } else { | ||
| result = append(result, node) | ||
| } | ||
| }) | ||
|
|
||
| c.evictSessionsLocked(sessionsToEvict) | ||
| return result | ||
| } | ||
|
|
||
| func (c *ClosedSessionCache) evictSessionsLocked(toEvict []*SessionNode) { | ||
| for _, entry := range toEvict { | ||
| c.mu.data.Del(entry.id) | ||
| } | ||
| } | ||
|
|
||
| func (c *ClosedSessionCache) clear() { | ||
| c.mu.Lock() | ||
| defer c.mu.Unlock() | ||
|
|
||
| c.mu.data.Clear() | ||
| } | ||
|
|
||
| // SessionNode encapsulates the session information that will be inserted into | ||
| // the cache. | ||
| type SessionNode struct { | ||
| id ClusterWideID | ||
| data serverpb.Session | ||
| timestamp time.Time | ||
| } | ||
|
|
||
| func (n *SessionNode) getAge() time.Duration { | ||
| return timeutil.Since(n.timestamp) | ||
| } | ||
|
|
||
| func (n *SessionNode) getAgeString() string { | ||
| return n.getAge().Round(time.Second).String() | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,105 @@ | ||
| // Copyright 2022 The Cockroach Authors. | ||
| // | ||
| // Use of this software is governed by the Business Source License | ||
| // included in the file licenses/BSL.txt. | ||
| // | ||
| // As of the Change Date specified in that file, in accordance with | ||
| // the Business Source License, use of this software will be governed | ||
| // by the Apache License, Version 2.0, included in the file | ||
| // licenses/APL.txt. | ||
|
|
||
| package sql | ||
|
|
||
| import ( | ||
| "context" | ||
| "fmt" | ||
| "strings" | ||
| "testing" | ||
| "time" | ||
|
|
||
| "github.com/cockroachdb/cockroach/pkg/server/serverpb" | ||
| "github.com/cockroachdb/cockroach/pkg/settings/cluster" | ||
| "github.com/cockroachdb/cockroach/pkg/testutils" | ||
| "github.com/cockroachdb/cockroach/pkg/util/leaktest" | ||
| "github.com/cockroachdb/cockroach/pkg/util/uint128" | ||
| "github.com/cockroachdb/datadriven" | ||
| "github.com/stretchr/testify/require" | ||
| ) | ||
|
|
||
| func TestSessionCacheBasic(t *testing.T) { | ||
| defer leaktest.AfterTest(t)() | ||
| var cache *ClosedSessionCache | ||
|
|
||
| datadriven.Walk(t, testutils.TestDataPath(t, "closed_session_cache"), func(t *testing.T, path string) { | ||
| datadriven.RunTest(t, path, func(t *testing.T, d *datadriven.TestData) string { | ||
| switch d.Cmd { | ||
| case "init": | ||
| var capacity, timeToLive int | ||
| d.ScanArgs(t, "capacity", &capacity) | ||
| d.ScanArgs(t, "timeToLive", &timeToLive) | ||
|
|
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| ctx := context.Background() | ||
| st := &cluster.Settings{} | ||
| cache = NewClosedSessionCache(st) | ||
|
|
||
| ClosedSessionCacheCapacity.Override(ctx, &st.SV, int64(capacity)) | ||
| ClosedSessionCacheTimeToLive.Override(ctx, &st.SV, int64(timeToLive)) | ||
|
|
||
| return fmt.Sprintf("cache_size: %d", cache.size()) | ||
| case "addSession": | ||
| var idStr string | ||
| d.ScanArgs(t, "id", &idStr) | ||
| id, err := uint128.FromString(idStr) | ||
| require.NoError(t, err) | ||
|
|
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| session := serverpb.Session{} | ||
| sessionID := ClusterWideID{id} | ||
| cache.Add(sessionID, session) | ||
|
|
||
| return fmt.Sprintf("cache_size: %d", cache.size()) | ||
| case "addSessionBatch": | ||
| var startIDStr string | ||
| var sessions int | ||
| var seconds int | ||
| d.ScanArgs(t, "startId", &startIDStr) | ||
| d.ScanArgs(t, "sessions", &sessions) | ||
| d.ScanArgs(t, "seconds", &seconds) | ||
| id, err := uint128.FromString(startIDStr) | ||
| require.NoError(t, err) | ||
|
|
||
| for i := 0; i < sessions; i++ { | ||
| time.Sleep(time.Duration(seconds) * time.Second) | ||
| session := serverpb.Session{} | ||
| sessionID := ClusterWideID{id} | ||
| cache.Add(sessionID, session) | ||
| id = id.Add(1) | ||
| } | ||
|
|
||
| return fmt.Sprintf("cache_size: %d", cache.size()) | ||
| case "wait": | ||
| var secondsStr int | ||
| d.ScanArgs(t, "seconds", &secondsStr) | ||
| time.Sleep(time.Duration(secondsStr) * time.Second) | ||
|
|
||
| return "ok" | ||
| case "clear": | ||
| cache.clear() | ||
|
|
||
| return fmt.Sprintf("cache_size: %d", cache.size()) | ||
| case "show": | ||
| var result []string | ||
|
|
||
| sessions := cache.getSessions() | ||
| for _, s := range sessions { | ||
| result = append(result, fmt.Sprintf("id: %s age: %s session: {}", s.id, s.getAgeString())) | ||
| } | ||
| if len(result) == 0 { | ||
| return "empty" | ||
| } | ||
| return strings.Join(result, "\n") | ||
| } | ||
| return "" | ||
| }) | ||
| }) | ||
|
|
||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,71 @@ | ||
| # Initialize a cache with a capacity of 4 members and a timeToLive of 10 | ||
| # seconds. | ||
| init capacity=4 timeToLive=10 | ||
| ---- | ||
| cache_size: 0 | ||
|
|
||
| # Add 6 (empty) sessions with ids ranging from 00 to 05, inclusive. | ||
| addSession id=00 | ||
| ---- | ||
| cache_size: 1 | ||
|
|
||
| addSession id=01 | ||
| ---- | ||
| cache_size: 2 | ||
|
|
||
| addSession id=02 | ||
| ---- | ||
| cache_size: 3 | ||
|
|
||
| addSession id=03 | ||
| ---- | ||
| cache_size: 4 | ||
|
|
||
| addSession id=04 | ||
| ---- | ||
| cache_size: 4 | ||
|
|
||
| addSession id=05 | ||
| ---- | ||
| cache_size: 4 | ||
|
|
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| # There have been 6 sessions added but the capacity is 4. The sessions with | ||
| # id=00 an id=01 should have been evicted. | ||
| show | ||
| ---- | ||
| id: 00000000000000000000000000000005 age: 0s session: {} | ||
| id: 00000000000000000000000000000004 age: 0s session: {} | ||
| id: 00000000000000000000000000000003 age: 0s session: {} | ||
| id: 00000000000000000000000000000002 age: 0s session: {} | ||
|
|
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| # Wait for 15 seconds, enough time for all sessions in the cache to be evicted. | ||
| wait seconds=15 | ||
| ---- | ||
| ok | ||
|
|
||
| # The cache should be empty now. | ||
| show | ||
| ---- | ||
| empty | ||
|
|
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| # Once the cache is empty, add a session every 3 seconds for a total of 4 | ||
| # sessions and 12 seconds. The cache should be full. | ||
| addSessionBatch startId=06 sessions=4 seconds=3 | ||
| ---- | ||
| cache_size: 4 | ||
|
|
||
| # Wait 5 seconds so that that the oldest session is 17 seconds old and the | ||
| # newest is 5 seconds old. | ||
| wait seconds=5 | ||
| ---- | ||
| ok | ||
|
|
||
| # After 15 seconds, only sessions added in the last 10 seconds should be in the | ||
| # cache, those with id=08 (8 seconds old) and id=09 (5 seconds old). Note that | ||
| # the session with id=07 would be 11 seconds old, which is greater than the | ||
| # allowed timeToLive so that session and all sessions added before that one | ||
| # should have been evicted. | ||
| show | ||
| ---- | ||
| id: 00000000000000000000000000000009 age: 5s session: {} | ||
| id: 00000000000000000000000000000008 age: 8s session: {} |