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Tool to determine mapping from vindex and value to shard #17290

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merged 10 commits into from
Nov 29, 2024

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rohit-nayak-ps
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@rohit-nayak-ps rohit-nayak-ps commented Nov 27, 2024

Description

This is a separate tool in the vitess tools directory which can be used as a separate binary without needing to setup a cluster. It can be used to map a list of values from the stdin and outputs a csv format giving you the related keyspace id and the shard in which it will reside. The inputs are the vindex type and the sharding scheme.

I tested this by comparing about 2K results of vexplain by specifying a test vschema file like vtexplain --shards 128 --vschema-file test-vschema.json --sql "select * from users where id = $1" --schema-file "test-schema.sql" --output-mode json | jq -r '.[].TabletActions | keys[] | split("/") | .[1]' | awk -v id="$id" '{print id "," $0}' .

Features

  • Allows specifying the vindex type (e.g., hash, xxhash).
  • Allows specifying the full shard list, as a CSV, OR (for uniformly distributed shard ranges) the total number of shards to generate.
  • Designed as a filter: Reads input values from stdin and outputs the corresponding shard information, so it can be
    used to map values from a file or another program.

Usage

make build
echo "1\n-1\n99" | ./map-shard-for-value --total_shards=4 --vindex=xxhash
value,ksid,shard
1,d46405367612b4b7,c0-
-1,d8e2a6a7c8c7623d,c0-
99,200533312244abca,-40

echo "1\n-1\n99" | ./map-shard-for-value --vindex=hash --shards="-80,80-"
value,ksid,shard
1,166b40b44aba4bd6,-80
-1,355550b2150e2451,-80
99,2c40ad56f4593c47,-80

Flags

  • --vindex: Specifies the name of the vindex to use (e.g., hash, xxhash) (default xxhash)

One (and only one) of these is required:

  • --shards: Comma-separated list of shard ranges
  • --total_shards: Total number of shards, only if shards are uniformly distributed

Related Issue(s)

#17292

Checklist

  • "Backport to:" labels have been added if this change should be back-ported to release branches
  • If this change is to be back-ported to previous releases, a justification is included in the PR description
  • Tests were added or are not required
  • Did the new or modified tests pass consistently locally and on CI?
  • Documentation was added or is not required

Deployment Notes

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vitess-bot bot commented Nov 27, 2024

Review Checklist

Hello reviewers! 👋 Please follow this checklist when reviewing this Pull Request.

General

  • Ensure that the Pull Request has a descriptive title.
  • Ensure there is a link to an issue (except for internal cleanup and flaky test fixes), new features should have an RFC that documents use cases and test cases.

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  • Apply the release notes (needs details) label if users need to know about this change.
  • New features should be documented.
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  • Protobuf changes should be wire-compatible.
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  • RPC changes should be compatible with vitess-operator
  • If a flag is removed, then it should also be removed from vitess-operator and arewefastyet, if used there.
  • vtctl command output order should be stable and awk-able.

@vitess-bot vitess-bot bot added NeedsBackportReason If backport labels have been applied to a PR, a justification is required NeedsDescriptionUpdate The description is not clear or comprehensive enough, and needs work NeedsIssue A linked issue is missing for this Pull Request NeedsWebsiteDocsUpdate What it says labels Nov 27, 2024
@github-actions github-actions bot added this to the v22.0.0 milestone Nov 27, 2024
@rohit-nayak-ps rohit-nayak-ps added Type: Feature Component: Cluster management and removed NeedsDescriptionUpdate The description is not clear or comprehensive enough, and needs work NeedsBackportReason If backport labels have been applied to a PR, a justification is required labels Nov 27, 2024
… reported for a keyspace id

Signed-off-by: Rohit Nayak <[email protected]>
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codecov bot commented Nov 27, 2024

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 67.39%. Comparing base (8648264) to head (98ee23c).
Report is 6 commits behind head on main.

Additional details and impacted files
@@            Coverage Diff             @@
##             main   #17290      +/-   ##
==========================================
- Coverage   67.40%   67.39%   -0.02%     
==========================================
  Files        1574     1574              
  Lines      253205   253251      +46     
==========================================
- Hits       170676   170673       -3     
- Misses      82529    82578      +49     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

Signed-off-by: Rohit Nayak <[email protected]>
Signed-off-by: Rohit Nayak <[email protected]>
@rohit-nayak-ps rohit-nayak-ps removed NeedsWebsiteDocsUpdate What it says NeedsIssue A linked issue is missing for this Pull Request labels Nov 28, 2024
@rohit-nayak-ps rohit-nayak-ps marked this pull request as ready for review November 28, 2024 09:52
@harshit-gangal
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Do we have to print the ksid?
It does not seem user friendly.

Comment on lines 100 to 114
func getValue(valueStr string) (sqltypes.Value, int64, error) {
var value sqltypes.Value
valueInt, err := strconv.ParseInt(valueStr, 10, 64)
if err == nil {
value = sqltypes.NewInt64(int64(valueInt))
} else {
valueUint, err := strconv.ParseUint(valueStr, 10, 64)
if err == nil {
value = sqltypes.NewUint64(valueUint)
} else {
value = sqltypes.NewVarChar(valueStr)
}
}
return value, valueInt, err
}
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we should take value type as input using cli

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Done

Comment on lines 59 to 65
allShards := make([]*topodata.ShardReference, 0, len(shards))
for shard, keyRange := range shards {
allShards = append(allShards, &topodata.ShardReference{
Name: shard,
KeyRange: keyRange,
})
}
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This can be done as part of a struct init and passed along to methods

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Done

Comment on lines 93 to 96
foundShard, err := mapShard(shards, ksid)
if err != nil {
return "", nil, fmt.Errorf("failed to map shard: %w", err)
}
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we should add the original value as well to the error message

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Done

Comment on lines 121 to 133
var start, end []byte
if len(parts) > 0 && parts[0] != "" {
start, err = hex.DecodeString(parts[0])
if err != nil {
log.Fatalf("failed to decode shard start: %v", err)
}
}
if len(parts) > 1 && parts[1] != "" {
end, err = hex.DecodeString(parts[1])
if err != nil {
log.Fatalf("failed to decode shard end: %v", err)
}
}
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can use method key.ParseKeyRangeParts to create *topodatapb.KeyRange

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You can also look at topo.ValidateShardName method.

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Used topo.ValidateShardName

@mcrauwel
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Do we have to print the ksid? It does not seem user friendly.

certainly not needed, but it doesn't hurt, easy enough to work around like this:

echo "1
2
3
4
5
6
7
8
9
10" | ./map-shard-for-value --vindex xxhash --total_shards 4 | awk -F',' '{ print $3, $1}'

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I think it would make sense to move this to vt. We should also add some unit tests, seems like they would be easy to add.

@rohit-nayak-ps
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I think it would make sense to move this to vt. We should also add some unit tests, seems like they would be easy to add.

Refactored code and added a unit test.

I would prefer to keep this in vitess for now until we have had a larger discussion about where this fits. Doesn't seem to fit in the current goals ofvt.

Signed-off-by: Rohit Nayak <[email protected]>
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this file can be removed

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oops, not sure how that got committed. Good catch, removed!

@rohit-nayak-ps rohit-nayak-ps merged commit 9422e32 into vitessio:main Nov 29, 2024
100 checks passed
@rohit-nayak-ps rohit-nayak-ps deleted the rohit/shard-from-ids branch November 29, 2024 10:25
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4 participants