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author | Javier Peletier <jpeletier@users.noreply.github.com> | 2018-09-28 18:07:17 +0800 |
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committer | Martin Holst Swende <martin@swende.se> | 2018-09-28 18:07:17 +0800 |
commit | 2c110c81ee92290d3e5ce6134a065c8d2abfbb60 (patch) | |
tree | db263ba1b6f051da8d3e5d0faaafec1c868e453d /swarm/storage/mru/lookup/lookup.go | |
parent | 0da3b17a112a75b54c8b3e5a2bf65a27a1c8c999 (diff) | |
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Swarm MRUs: Adaptive frequency / Predictable lookups / API simplification (#17559)
* swarm/storage/mru: Adaptive Frequency
swarm/storage/mru/lookup: fixed getBaseTime
Added NewEpoch constructor
swarm/api/client: better error handling in GetResource()
swarm/storage/mru: Renamed structures.
Renamed ResourceMetadata to ResourceID.
Renamed ResourceID.Name to ResourceID.Topic
swarm/storage/mru: Added binarySerializer interface and test tools
swarm/storage/mru/lookup: Changed base time to time and + marshallers
swarm/storage/mru: Added ResourceID (former resourceMetadata)
swarm/storage/mru: Added ResourceViewId and serialization tests
swarm/storage/mru/lookup: fixed epoch unmarshaller. Added Epoch Equals
swarm/storage/mru: Fixes as per review comments
cmd/swarm: reworded resource create/update help text regarding topic
swarm/storage/mru: Added UpdateLookup and serializer tests
swarm/storage/mru: Added UpdateHeader, serializers and tests
swarm/storage/mru: changed UpdateAddr / epoch to Base()
swarm/storage/mru: Added resourceUpdate serializer and tests
swarm/storage/mru: Added SignedResourceUpdate tests and serializers
swarm/storage/mru/lookup: fixed GetFirstEpoch bug
swarm/storage/mru: refactor, comments, cleanup
Also added tests for Topic
swarm/storage/mru: handler tests pass
swarm/storage/mru: all resource package tests pass
swarm/storage/mru: resource test pass after adding
timestamp checking support
swarm/storage/mru: Added JSON serializers to ResourceIDView structures
swarm/storage/mru: Sever, client, API test pass
swarm/storage/mru: server test pass
swarm/storage/mru: Added topic length check
swarm/storage/mru: removed some literals,
improved "previous lookup" test case
swarm/storage/mru: some fixes and comments as per review
swarm/storage/mru: first working version without metadata chunk
swarm/storage/mru: Various fixes as per review
swarm/storage/mru: client test pass
swarm/storage/mru: resource query strings and manifest-less queries
swarm/storage/mru: simplify naming
swarm/storage/mru: first autofreq working version
swarm/storage/mru: renamed ToValues to AppendValues
swarm/resource/mru: Added ToValues / FromValues for URL query strings
swarm/storage/mru: Changed POST resource to work with query strings.
No more JSON.
swarm/storage/mru: removed resourceid
swarm/storage/mru: Opened up structures
swarm/storage/mru: Merged Request and SignedResourceUpdate
swarm/storage/mru: removed initial data from CLI resource create
swarm/storage/mru: Refactor Topic as a direct fixed-length array
swarm/storage/mru/lookup: Comprehensive GetNextLevel tests
swarm/storage/mru: Added comments
Added length checks in Topic
swarm/storage/mru: fixes in tests and some code comments
swarm/storage/mru/lookup: new optimized lookup algorithm
swarm/api: moved getResourceView to api out of server
swarm/storage/mru: Lookup algorithm working
swarm/storage/mru: comments and renamed NewLookupParams
Deleted commented code
swarm/storage/mru/lookup: renamed Epoch.LaterThan to After
swarm/storage/mru/lookup: Comments and tidying naming
swarm/storage/mru: fix lookup algorithm
swarm/storage/mru: exposed lookup hint
removed updateheader
swarm/storage/mru/lookup: changed GetNextEpoch for initial values
swarm/storage/mru: resource tests pass
swarm/storage/mru: valueSerializer interface and tests
swarm/storage/mru/lookup: Comments, improvements, fixes, more tests
swarm/storage/mru: renamed UpdateLookup to ID, LookupParams to Query
swarm/storage/mru: renamed query receiver var
swarm/cmd: MRU CLI tests
* cmd/swarm: remove rogue fmt
* swarm/storage/mru: Add version / header for future use
* swarm/storage/mru: Fixes/comments as per review
cmd/swarm: remove rogue fmt
swarm/storage/mru: Add version / header for future use-
* swarm/storage/mru: fix linter errors
* cmd/swarm: Speeded up TestCLIResourceUpdate
Diffstat (limited to 'swarm/storage/mru/lookup/lookup.go')
-rw-r--r-- | swarm/storage/mru/lookup/lookup.go | 180 |
1 files changed, 180 insertions, 0 deletions
diff --git a/swarm/storage/mru/lookup/lookup.go b/swarm/storage/mru/lookup/lookup.go new file mode 100644 index 000000000..c98248d70 --- /dev/null +++ b/swarm/storage/mru/lookup/lookup.go @@ -0,0 +1,180 @@ +// Copyright 2018 The go-ethereum Authors +// This file is part of the go-ethereum library. +// +// The go-ethereum library is free software: you can redistribute it and/or modify +// it under the terms of the GNU Lesser General Public License as published by +// the Free Software Foundation, either version 3 of the License, or +// (at your option) any later version. +// +// The go-ethereum library is distributed in the hope that it will be useful, +// but WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +// GNU Lesser General Public License for more details. +// +// You should have received a copy of the GNU Lesser General Public License +// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>. + +/* +Package lookup defines resource lookup algorithms and provides tools to place updates +so they can be found +*/ +package lookup + +const maxuint64 = ^uint64(0) + +// LowestLevel establishes the frequency resolution of the lookup algorithm as a power of 2. +const LowestLevel uint8 = 0 // default is 0 (1 second) + +// HighestLevel sets the lowest frequency the algorithm will operate at, as a power of 2. +// 25 -> 2^25 equals to roughly one year. +const HighestLevel = 25 // default is 25 (~1 year) + +// DefaultLevel sets what level will be chosen to search when there is no hint +const DefaultLevel = HighestLevel + +//Algorithm is the function signature of a lookup algorithm +type Algorithm func(now uint64, hint Epoch, read ReadFunc) (value interface{}, err error) + +// Lookup finds the update with the highest timestamp that is smaller or equal than 'now' +// It takes a hint which should be the epoch where the last known update was +// If you don't know in what epoch the last update happened, simply submit lookup.NoClue +// read() will be called on each lookup attempt +// Returns an error only if read() returns an error +// Returns nil if an update was not found +var Lookup Algorithm = FluzCapacitorAlgorithm + +// ReadFunc is a handler called by Lookup each time it attempts to find a value +// It should return <nil> if a value is not found +// It should return <nil> if a value is found, but its timestamp is higher than "now" +// It should only return an error in case the handler wants to stop the +// lookup process entirely. +type ReadFunc func(epoch Epoch, now uint64) (interface{}, error) + +// NoClue is a hint that can be provided when the Lookup caller does not have +// a clue about where the last update may be +var NoClue = Epoch{} + +// getBaseTime returns the epoch base time of the given +// time and level +func getBaseTime(t uint64, level uint8) uint64 { + return t & (maxuint64 << level) +} + +// Hint creates a hint based only on the last known update time +func Hint(last uint64) Epoch { + return Epoch{ + Time: last, + Level: DefaultLevel, + } +} + +// GetNextLevel returns the frequency level a next update should be placed at, provided where +// the last update was and what time it is now. +// This is the first nonzero bit of the XOR of 'last' and 'now', counting from the highest significant bit +// but limited to not return a level that is smaller than the last-1 +func GetNextLevel(last Epoch, now uint64) uint8 { + // First XOR the last epoch base time with the current clock. + // This will set all the common most significant bits to zero. + mix := (last.Base() ^ now) + + // Then, make sure we stop the below loop before one level below the current, by setting + // that level's bit to 1. + // If the next level is lower than the current one, it must be exactly level-1 and not lower. + mix |= (1 << (last.Level - 1)) + + // if the last update was more than 2^highestLevel seconds ago, choose the highest level + if mix > (maxuint64 >> (64 - HighestLevel - 1)) { + return HighestLevel + } + + // set up a mask to scan for nonzero bits, starting at the highest level + mask := uint64(1 << (HighestLevel)) + + for i := uint8(HighestLevel); i > LowestLevel; i-- { + if mix&mask != 0 { // if we find a nonzero bit, this is the level the next update should be at. + return i + } + mask = mask >> 1 // move our bit one position to the right + } + return 0 +} + +// GetNextEpoch returns the epoch where the next update should be located +// according to where the previous update was +// and what time it is now. +func GetNextEpoch(last Epoch, now uint64) Epoch { + if last == NoClue { + return GetFirstEpoch(now) + } + level := GetNextLevel(last, now) + return Epoch{ + Level: level, + Time: now, + } +} + +// GetFirstEpoch returns the epoch where the first update should be located +// based on what time it is now. +func GetFirstEpoch(now uint64) Epoch { + return Epoch{Level: HighestLevel, Time: now} +} + +var worstHint = Epoch{Time: 0, Level: 63} + +// FluzCapacitorAlgorithm works by narrowing the epoch search area if an update is found +// going back and forth in time +// First, it will attempt to find an update where it should be now if the hint was +// really the last update. If that lookup fails, then the last update must be either the hint itself +// or the epochs right below. If however, that lookup succeeds, then the update must be +// that one or within the epochs right below. +// see the guide for a more graphical representation +func FluzCapacitorAlgorithm(now uint64, hint Epoch, read ReadFunc) (value interface{}, err error) { + var lastFound interface{} + var epoch Epoch + if hint == NoClue { + hint = worstHint + } + + t := now + + for { + epoch = GetNextEpoch(hint, t) + value, err = read(epoch, now) + if err != nil { + return nil, err + } + if value != nil { + lastFound = value + if epoch.Level == LowestLevel || epoch.Equals(hint) { + return value, nil + } + hint = epoch + continue + } + if epoch.Base() == hint.Base() { + if lastFound != nil { + return lastFound, nil + } + // we have reached the hint itself + if hint == worstHint { + return nil, nil + } + // check it out + value, err = read(hint, now) + if err != nil { + return nil, err + } + if value != nil { + return value, nil + } + // bad hint. + epoch = hint + hint = worstHint + } + base := epoch.Base() + if base == 0 { + return nil, nil + } + t = base - 1 + } +} |