go.chromium.org/luci@v0.0.0-20240309015107-7cdc2e660f33/server/dsmapper/doc.go (about)

     1  // Copyright 2018 The LUCI Authors.
     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 dsmapper implements a simple Datastore mapper.
    16  //
    17  // It provides a way to apply some function to all datastore entities of some
    18  // particular kind, in parallel, but with bounded concurrency (to avoid burning
    19  // through all CPU/Datastore quota at once). This may be useful when examining
    20  // or mutating large amounts of datastore entities.
    21  //
    22  // It works by splitting the range of keys into N shards, and launching N worker
    23  // tasks that each sequentially processes a shard assigned to it, slice by
    24  // slice.
    25  package dsmapper