|
| 1 | +// Copyright 2025 Google LLC |
| 2 | +// |
| 3 | +// Licensed under the Apache License, Version 2.0 (the "License"): |
| 4 | +// you may not use this file except in compliance with the License. |
| 5 | +// You may obtain a copy of the License at |
| 6 | +// |
| 7 | +// https://www.apache.org/licenses/LICENSE-2.0 |
| 8 | +// |
| 9 | +// Unless required by applicable law or agreed to in writing, software |
| 10 | +// distributed under the License is distributed on an "AS IS" BASIS, |
| 11 | +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 12 | +// See the License for the specific language governing permissions and |
| 13 | +// limitations under the License. |
| 14 | + |
| 15 | +using Google.Api.Gax; |
| 16 | +using Google.Api.Gax.Grpc; |
| 17 | +using Google.Cloud.Spanner.Common.V1; |
| 18 | +using Google.Cloud.Spanner.V1.Internal; |
| 19 | +using Google.Cloud.Spanner.V1.Internal.Logging; |
| 20 | +using System; |
| 21 | +using System.Threading; |
| 22 | +using System.Threading.Tasks; |
| 23 | + |
| 24 | +namespace Google.Cloud.Spanner.V1; |
| 25 | + |
| 26 | +/// <summary> |
| 27 | +/// TODO: Add summary for mux sessions |
| 28 | +/// </summary> |
| 29 | +public class MultiplexSession |
| 30 | +{ |
| 31 | + private readonly SemaphoreSlim _sessionCreateSemaphore; |
| 32 | + private readonly Logger _logger; |
| 33 | + private readonly CreateSessionRequest _createSessionRequestTemplate; |
| 34 | + |
| 35 | + internal Session _session; |
| 36 | + internal int _markedForRefresh; |
| 37 | + |
| 38 | + private const double ForceRefreshIntervalInDays = 28.0; |
| 39 | + private const double SoftRefreshIntervalInDays = 7.0; |
| 40 | + |
| 41 | + private readonly IClock _clock; |
| 42 | + |
| 43 | + /// <summary> |
| 44 | + /// The client used for all operations in this multiplex session. |
| 45 | + /// </summary> |
| 46 | + internal SpannerClient Client { get; } |
| 47 | + |
| 48 | + internal Task<Session> CreateSessionTask { get; } |
| 49 | + |
| 50 | + /// <summary> |
| 51 | + /// The name of the session. This is never null. |
| 52 | + /// </summary> |
| 53 | + public SessionName SessionName => Session.SessionName; |
| 54 | + |
| 55 | + /// <summary> |
| 56 | + /// The Spanner session resource associated to this pooled session. |
| 57 | + /// Won't be null. |
| 58 | + /// </summary> |
| 59 | + internal Session Session |
| 60 | + { |
| 61 | + get { return _session; } |
| 62 | + private set { _session = value; } |
| 63 | + } |
| 64 | + |
| 65 | + private bool MarkedForRefresh => Interlocked.CompareExchange(ref _markedForRefresh, 0, 0) == 1; |
| 66 | + |
| 67 | + /// <summary> |
| 68 | + /// The options governing this multiplex session. |
| 69 | + /// </summary> |
| 70 | + public MultiplexSessionOptions Options { get; } |
| 71 | + |
| 72 | + /// <summary> |
| 73 | + /// The database for this multiplex session |
| 74 | + /// </summary> |
| 75 | + public DatabaseName DatabaseName { get; } |
| 76 | + |
| 77 | + /// <summary> |
| 78 | + /// The database role of the multiplex session |
| 79 | + /// </summary> |
| 80 | + public string DatabaseRole { get; } |
| 81 | + |
| 82 | + /// <summary> |
| 83 | + /// |
| 84 | + /// </summary> |
| 85 | + /// <param name="client"></param> |
| 86 | + /// <param name="dbName"></param> |
| 87 | + /// <param name="dbRole"></param> |
| 88 | + /// <param name="options"></param> |
| 89 | + public MultiplexSession(SpannerClient client, DatabaseName dbName, string dbRole, MultiplexSessionOptions options) |
| 90 | + { |
| 91 | + Client = GaxPreconditions.CheckNotNull(client, nameof(client)); |
| 92 | + Options = options ?? new MultiplexSessionOptions(); |
| 93 | + _logger = client.Settings.Logger; // Just to avoid fetching it all the time |
| 94 | + _sessionCreateSemaphore = new SemaphoreSlim(1); |
| 95 | + |
| 96 | + DatabaseName = dbName; |
| 97 | + DatabaseRole = dbRole; |
| 98 | + |
| 99 | + _clock = client.Settings.Clock ?? SystemClock.Instance; |
| 100 | + |
| 101 | + _createSessionRequestTemplate = new CreateSessionRequest |
| 102 | + { |
| 103 | + DatabaseAsDatabaseName = DatabaseName, |
| 104 | + Session = new Session |
| 105 | + { |
| 106 | + CreatorRole = DatabaseRole ?? "", |
| 107 | + Multiplexed = true |
| 108 | + } |
| 109 | + }; |
| 110 | + } |
| 111 | + |
| 112 | + private async Task<Boolean> UpdateMuxSession(bool needsRefresh, double intervalInDays) |
| 113 | + { |
| 114 | + Session oldSession = _session; |
| 115 | + await CreateOrRefreshSessionsAsync(default).ConfigureAwait(false); |
| 116 | + |
| 117 | + return _session != oldSession; |
| 118 | + } |
| 119 | + |
| 120 | + internal void MaybeRefreshWithTimePeriodCheck() |
| 121 | + { |
| 122 | + if (SessionHasExpired(ForceRefreshIntervalInDays)) |
| 123 | + { |
| 124 | + // If the session has expired on a client RPC request call, or has exceeded the 28 day Mux session refresh guidance |
| 125 | + // No request can proceed without us having a new Session to work with |
| 126 | + // Block on refreshing and getting a new session |
| 127 | + bool sessionIsRefreshed = UpdateMuxSession(true, ForceRefreshIntervalInDays).Result; |
| 128 | + |
| 129 | + if (!sessionIsRefreshed) |
| 130 | + { |
| 131 | + throw new Exception("Unable to refresh multiplex session, and the old session has expired or is 28 days past refresh"); |
| 132 | + } |
| 133 | + |
| 134 | + _logger.Info($"Refreshed session since it was expired or past 28 days refresh period. New session {SessionName}"); |
| 135 | + } |
| 136 | + |
| 137 | + if (SessionHasExpired(SoftRefreshIntervalInDays)) |
| 138 | + { |
| 139 | + // The Mux sessions have a lifespan of 28 days. We check if we need a session refresh in every request needing the session |
| 140 | + // If the timespan of a request needing a session and the session creation time is greater than 7 days, we proactively refresh the mux session |
| 141 | + // The request can safely use the older session since it is still valid while we do this refresh to fetch the new session. |
| 142 | + // Hence fire and forget the session refresh. |
| 143 | + _ = Task.Run(() => UpdateMuxSession(true, SoftRefreshIntervalInDays)); |
| 144 | + } |
| 145 | + } |
| 146 | + |
| 147 | + // internal for testing |
| 148 | + internal bool SessionHasExpired(double intervalInDays = SoftRefreshIntervalInDays) |
| 149 | + { |
| 150 | + DateTime currentTime = _clock.GetCurrentDateTimeUtc(); |
| 151 | + DateTime? sessionCreateTime = _session?.CreateTime.ToDateTime(); // Inherent conversion into UTC DateTime |
| 152 | + |
| 153 | + if (_session == null || _session.Expired || currentTime - sessionCreateTime >= TimeSpan.FromDays(intervalInDays)) |
| 154 | + { |
| 155 | + return true; |
| 156 | + } |
| 157 | + |
| 158 | + return false; |
| 159 | + } |
| 160 | + |
| 161 | + private async Task CreateOrRefreshSessionsAsync(CancellationToken cancellationToken, bool needsRefresh = false) |
| 162 | + { |
| 163 | + try |
| 164 | + { |
| 165 | + var callSettings = Client.Settings.CreateSessionSettings |
| 166 | + .WithExpiration(Expiration.FromTimeout(Options.Timeout)) |
| 167 | + .WithCancellationToken(cancellationToken); |
| 168 | + |
| 169 | + Session multiplexSession; |
| 170 | + |
| 171 | + bool acquiredSemaphore = false; |
| 172 | + try |
| 173 | + { |
| 174 | + if (needsRefresh && MarkedForRefresh && !SessionHasExpired(ForceRefreshIntervalInDays)) |
| 175 | + { |
| 176 | + // If the refresh was triggered for the soft refresh timeline (7 days) |
| 177 | + // Some other thread has already marked this session to be refreshed |
| 178 | + // Any subsequent request threads can continue using the 'stale' session so let's not block |
| 179 | + // On the other hand if the refresh is for the forced refresh timeline (28 days) |
| 180 | + // Any subsequent request threads need to be blocked on the Session refresh |
| 181 | + return; |
| 182 | + } |
| 183 | + |
| 184 | + await _sessionCreateSemaphore.WaitAsync(cancellationToken).ConfigureAwait(false); |
| 185 | + acquiredSemaphore = true; |
| 186 | + |
| 187 | + if (_session == null || (needsRefresh && SessionHasExpired())) |
| 188 | + { |
| 189 | + Interlocked.Exchange(ref _markedForRefresh, 1); |
| 190 | + multiplexSession = await Client.CreateSessionAsync(_createSessionRequestTemplate, callSettings).ConfigureAwait(false); |
| 191 | + |
| 192 | + Interlocked.Exchange(ref _session, multiplexSession); |
| 193 | + Interlocked.Exchange(ref _markedForRefresh, 0); |
| 194 | + } |
| 195 | + } |
| 196 | + catch (OperationCanceledException) |
| 197 | + { |
| 198 | + _logger.Warn(() => $"Creation request cancelled before we could procure a Multiplex Session for DatabaseName: {DatabaseName}, DatabaseRole: {DatabaseRole}"); |
| 199 | + throw; |
| 200 | + } |
| 201 | + finally |
| 202 | + { |
| 203 | + if (acquiredSemaphore) |
| 204 | + { |
| 205 | + _sessionCreateSemaphore.Release(); |
| 206 | + } |
| 207 | + } |
| 208 | + } |
| 209 | + catch (Exception e) |
| 210 | + { |
| 211 | + _logger.Warn(() => $"Failed to create multiplex session for DatabaseName: {DatabaseName}, DatabaseRole: {DatabaseRole}", e); |
| 212 | + throw; |
| 213 | + } |
| 214 | + finally |
| 215 | + { |
| 216 | + // Nothing to do here since for legacy SessionPool we had to have some logging for when the pool went from healthy to unhealthy. |
| 217 | + // This could mean n number of things went wrong in the pool |
| 218 | + // But with the MUX session, we essentially only have 1 session we need to manage per client. |
| 219 | + // So there is no case of the mux session going back and forth in terms of its healthiness. |
| 220 | + } |
| 221 | + |
| 222 | + } |
| 223 | + |
| 224 | + /// <summary> |
| 225 | + /// |
| 226 | + /// </summary> |
| 227 | + public sealed partial class MultiplexSessionBuilder |
| 228 | + { |
| 229 | + /// <summary> |
| 230 | + /// |
| 231 | + /// </summary> |
| 232 | + public MultiplexSessionBuilder(DatabaseName databaseName, SpannerClient client) |
| 233 | + { |
| 234 | + DatabaseName = GaxPreconditions.CheckNotNull(databaseName, nameof(databaseName)); |
| 235 | + Client = GaxPreconditions.CheckNotNull(client, nameof(client)); |
| 236 | + } |
| 237 | + |
| 238 | + /// <summary> |
| 239 | + /// The options governing this multiplex session. |
| 240 | + /// </summary> |
| 241 | + public MultiplexSessionOptions Options { get; set; } |
| 242 | + |
| 243 | + /// <summary> |
| 244 | + /// The database for this multiplex session |
| 245 | + /// </summary> |
| 246 | + public DatabaseName DatabaseName { get; set; } |
| 247 | + |
| 248 | + /// <summary> |
| 249 | + /// The database role of the multiplex session |
| 250 | + /// </summary> |
| 251 | + public string DatabaseRole { get; set; } |
| 252 | + |
| 253 | + /// <summary> |
| 254 | + /// The client used for all operations in this multiplex session. |
| 255 | + /// </summary> |
| 256 | + public SpannerClient Client { get; set; } |
| 257 | + |
| 258 | + /// <summary> |
| 259 | + /// |
| 260 | + /// </summary> |
| 261 | + /// <param name="cancellationToken"></param> |
| 262 | + /// <returns></returns> |
| 263 | + public async Task<MultiplexSession> BuildAsync(CancellationToken cancellationToken = default) |
| 264 | + { |
| 265 | + MultiplexSession multiplexSession = new MultiplexSession(Client, DatabaseName, DatabaseRole, Options); |
| 266 | + |
| 267 | + await multiplexSession.CreateOrRefreshSessionsAsync(cancellationToken).ConfigureAwait(false); |
| 268 | + |
| 269 | + return multiplexSession; |
| 270 | + } |
| 271 | + } |
| 272 | +} |
0 commit comments