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Merge pull request #68 from cockroachdb/spencerkimball/address-bens-c…
…omments Created new block ID allocator & put it into use.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,109 @@ | ||
| // Copyright 2014 The Cockroach Authors. | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License"); | ||
| // you may not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, | ||
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or | ||
| // implied. See the License for the specific language governing | ||
| // permissions and limitations under the License. See the AUTHORS file | ||
| // for names of contributors. | ||
| // | ||
| // Author: Spencer Kimball ([email protected]) | ||
|
|
||
| package storage | ||
|
|
||
| import ( | ||
| "github.com/cockroachdb/cockroach/proto" | ||
| "github.com/cockroachdb/cockroach/storage/engine" | ||
| "github.com/cockroachdb/cockroach/util/log" | ||
| ) | ||
|
|
||
| const ( | ||
| // allocationTrigger is a special ID which if encountered, | ||
| // causes allocation of the next block of IDs. | ||
| allocationTrigger = 0 | ||
| ) | ||
|
|
||
| type IDAllocator struct { | ||
| idKey engine.Key | ||
| db DB | ||
| minID int64 // Minimum ID to return | ||
| blockSize int64 // Block allocation size | ||
| ids chan int64 // Channel of available IDs | ||
| } | ||
|
|
||
| // NewIDAllocator creates a new ID allocator which increments the | ||
| // specified key in allocation blocks of size blockSize, with | ||
| // allocated IDs starting at minID. Allocated IDs are positive | ||
| // integers. | ||
| func NewIDAllocator(idKey engine.Key, db DB, minID int64, blockSize int64) *IDAllocator { | ||
| if minID <= allocationTrigger { | ||
| log.Fatalf("minID must be > %d", allocationTrigger) | ||
| } | ||
| if blockSize < 1 { | ||
| log.Fatalf("blockSize must be a positive integer: %d", blockSize) | ||
| } | ||
| ia := &IDAllocator{ | ||
| idKey: idKey, | ||
| db: db, | ||
| minID: minID, | ||
| blockSize: blockSize, | ||
| ids: make(chan int64, blockSize+blockSize/2+1), | ||
| } | ||
| ia.ids <- allocationTrigger | ||
| return ia | ||
| } | ||
|
|
||
| // Allocate allocates a new ID from the global KV DB. If multiple | ||
| func (ia *IDAllocator) Allocate() int64 { | ||
| for { | ||
| id := <-ia.ids | ||
| if id == allocationTrigger { | ||
| go ia.allocateBlock(ia.blockSize) | ||
| } else { | ||
| return id | ||
| } | ||
| } | ||
| } | ||
|
|
||
| // allocateBlock allocates a block of IDs using db.Increment and | ||
| // sends all IDs on the ids channel. Midway through the block, a | ||
| // special allocationTrigger ID is inserted which causes allocation | ||
| // to occur before IDs run out to hide Increment latency. | ||
| func (ia *IDAllocator) allocateBlock(incr int64) { | ||
| ir := <-ia.db.Increment(&proto.IncrementRequest{ | ||
| RequestHeader: proto.RequestHeader{ | ||
| Key: ia.idKey, | ||
| User: UserRoot, | ||
| }, | ||
| Increment: ia.blockSize, | ||
| }) | ||
| if ir.Error != nil { | ||
| log.Errorf("unable to allocate %d %q IDs: %v", ia.blockSize, ia.idKey, ir.Error) | ||
| } | ||
| if ir.NewValue <= ia.minID { | ||
| log.Warningf("allocator key is currently set at %d; minID is %d; allocating again to skip %d IDs", | ||
| ir.NewValue, ia.minID, ia.minID-ir.NewValue) | ||
| ia.allocateBlock(ia.minID - ir.NewValue + ia.blockSize) | ||
| return | ||
| } | ||
|
|
||
| // Add all new ids to the channel for consumption. | ||
| start := ir.NewValue - ia.blockSize + 1 | ||
| end := ir.NewValue + 1 | ||
| if start < ia.minID { | ||
| start = ia.minID | ||
| } | ||
|
|
||
| for i := start; i < end; i++ { | ||
| ia.ids <- i | ||
| if i == (start+end)/2 { | ||
| ia.ids <- allocationTrigger | ||
| } | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,86 @@ | ||
| // Copyright 2014 The Cockroach Authors. | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License"); | ||
| // you may not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, | ||
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or | ||
| // implied. See the License for the specific language governing | ||
| // permissions and limitations under the License. See the AUTHORS file | ||
| // for names of contributors. | ||
| // | ||
| // Author: Spencer Kimball ([email protected]) | ||
|
|
||
| package storage | ||
|
|
||
| import ( | ||
| "sort" | ||
| "testing" | ||
|
|
||
| "github.com/cockroachdb/cockroach/storage/engine" | ||
| ) | ||
|
|
||
| // TestIDAllocator creates an ID allocator which allocates from | ||
| // the Raft ID generator system key in blocks of 10 with a minimum | ||
| // ID value of 2 and then starts up 10 goroutines each allocating | ||
| // 10 IDs. All goroutines deposit the allocated IDs into a final | ||
| // channel, which is queried at the end to ensure that all IDs | ||
| // from 2 to 101 are present. | ||
| func TestIDAllocator(t *testing.T) { | ||
| store, _ := createTestStore(false, t) | ||
| allocd := make(chan int, 100) | ||
| idAlloc := NewIDAllocator(engine.KeyRaftIDGenerator, store.db, 2, 10) | ||
|
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||
| for i := 0; i < 10; i++ { | ||
| go func() { | ||
| for j := 0; j < 10; j++ { | ||
| allocd <- int(idAlloc.Allocate()) | ||
| } | ||
| }() | ||
| } | ||
|
|
||
| // Verify all IDs accounted for. | ||
| ids := make([]int, 100) | ||
| for i := 0; i < 100; i++ { | ||
| ids[i] = <-allocd | ||
| } | ||
| sort.Ints(ids) | ||
| for i := 0; i < 100; i++ { | ||
| if ids[i] != i+2 { | ||
| t.Error("expected \"%d\"th ID to be %d; got %d", i, i+2, ids[i]) | ||
| } | ||
| } | ||
|
|
||
| // Verify no leftover IDs. | ||
| select { | ||
| case id := <-allocd: | ||
| t.Error("there appear to be leftover IDs, starting with %d", id) | ||
| default: | ||
| // Expected; noop. | ||
| } | ||
| } | ||
|
|
||
| // TestIDAllocatorNegativeValue creates an ID allocator against an | ||
| // increment key which is preset to a negative value. We verify that | ||
| // the id allocator makes a double-alloc to make up the difference | ||
| // and push the id allocation into positive integers. | ||
| func TestIDAllocatorNegativeValue(t *testing.T) { | ||
| store, _ := createTestStore(false, t) | ||
| // Increment our key to a negative value. | ||
| newValue, err := engine.Increment(store.engine, engine.KeyRaftIDGenerator, -1024) | ||
| if err != nil { | ||
| t.Fatal(err) | ||
| } | ||
| if newValue != -1024 { | ||
| t.Errorf("expected new value to be -1024; got %d", newValue) | ||
| } | ||
| idAlloc := NewIDAllocator(engine.KeyRaftIDGenerator, store.db, 2, 10) | ||
| value := idAlloc.Allocate() | ||
| if value != 2 { | ||
| t.Errorf("expected id allocation to have value 2; got %d", value) | ||
| } | ||
| } |
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