github.com/letsencrypt/trillian@v1.1.2-0.20180615153820-ae375a99d36a/quota/doc.go (about) 1 // Copyright 2017 Google Inc. All Rights Reserved. 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 // http://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 // Package quota defines Trillian's Quota Management service. 16 // 17 // The objective of the quota service is to protect Trillian from traffic peaks, rejecting requests 18 // that may put servers out of capacity or indirectly cause MMDs (maximum merge delays) to be 19 // missed. 20 // 21 // Each Trillian request, be it either a read or write request, requires certain tokens to be 22 // allowed to continue. Tokens exist at multiple layers: per-user, per-tree and global tokens. 23 // For example, a TrillianLog.QueueLeaves request consumes a Write token from User, Tree and Global 24 // quotas. If any of those quotas is out of tokens, the request is denied with a ResourceExhausted 25 // error code. 26 // 27 // Tokens are replenished according to each implementation. For example, User tokens may replenish 28 // over time, whereas {Write, Tree} tokens may replenish as sequencing happens. Implementations are 29 // free to ignore (effectively whitelisting) certain specs of tokens (e.g., only support Global and 30 // ignore User and Tree tokens). 31 // 32 // Quota users are defined according to each implementation. Note that quota users don't need to 33 // match authentication/authorization users; implementations are allowed their own representation of 34 // users. 35 package quota