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Add document describes how a get/commit is done in FDB

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Xiaoge Su 2021-03-16 05:05:03 -07:00
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# How a commit is done in FDB
## Overall description
Legend:
* `alt` means alternative paths
* The texts in `[]` are conditions
* The texts above the arrow are messages.
The diagrams are generated using https://sequencediagram.org. The source code of the diagrams are the `*.sequence` files.
![CommitOverall](CommitOverall.svg)
## Description of each sections
Before all RPCs mentioned below, the client would first verify if the commit proxies and GRV proxies are changed, by comparing the client information ID it holds to the ID the cluster coordinator holds. If they are different, the proxies are changed and the client will refresh the proxies list.
### GetReadVersion Section
* The GRV Proxy sends a request to master to retrieve the current commit version. This version is the read version of the request.
### Preresolution Section
* The commit proxy sends a request for commit version, with a request number.
* - The request number is a monotonically increasing number per commit proxy.
- This ensures for each proxy, the master will process the requests in order.
* The master server waits until the request number is current.
When the current request number is larger than the incoming request number
* If a commit version is already assigned to the incoming request number, return the commit version and the version that is immediately before the commit version (prevVersion).
* Otherwise return `Never`
* Increase current commit version, return it back to the commit proxy.
* Only one process serves as master. Thus the commit version is unique for each cluster.
* The monotonically increasing commit version will ensure each transaction processed in strict ordering.
### Resolution section
* The commit proxy sends the transaction to the resolver.
* Resolver waits until its version reaches `prevVersion`
* Ensures all transactions having version smaller than this transaction are resolved.
* Detects conflicts for the given transaction:
* If there is no conflict, return `TransactionCommitted` as the status
* Any conflict, return `TransactionConflict` status
* If the read snapshot is not in MVCC, return `TransactionTooOld` status
### Post Resolution section
* The proxy waits until the local batch number is current
* The proxy will update the metadata keys and calculate which storage servers are affected
* The proxy then waits until the commit version is current, i.e. only those commits in the MVCC window should be processed.
* The proxy pushs the commit data to TLog
* TLog waits the commit version to current, then persist the commit.
### TLog section
* Wait until *all* TLogs returns the transaction result.
### Reply section
* The proxy will update the master its commit version
* Reply the result to the client, base on the result from the resolver.
## Tracking the process using `g_traceBatch`
`g_traceBatch` can be used for querying the transactions and commits. A typical query string:
```
index=iffdb LogGroup=loggroup Type=location Location=location
```
The format of `location` is, in general, `<source_file_name>.<function/actor name>.<log information>`, e.g.
```
NativeAPI.getConsistentReadVersion.Before
```
means the `location` is at `NativeAPI.actor.cpp`, `ACTOR` `getConsistentReadVersion`, `Before` requesting the read version from GRV Proxy.
In the following sections, <span style="color:green">green</span> tag indicates an attach; <span style="color:blue">blue</span> tag indicates an event that the location follows the format mentioned above, where only the `<log information>` is included; <span style="color:lightblue">light-blue</span> tag indicates an event that the location is not following the format, where the full location is included. All the `g_traceBatch` events are tabularized after the diagram.
`contrib/commit_debug.py` can be used to visualize the commit process.
### Get Read Version
![GetReadVersion](GRV.svg)
| **Role** | **File name** | **Function/Actor** | **Trace** | **Type** | **Location** |
| ------------ | -------------- | --------------------------- | --------------------------------- | ------------------------------------------------------------ | ------------------------------------------------------------ |
| **Client** | NativeAPI | Transaction::getReadVersion | | | |
| | | readVersionBatcher | | [*TransactionAttachID*](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbclient/NativeAPI.actor.cpp#L4639) | |
| | | getConsistentReadVersion | Before | TransactionDebug | [NativeAPI.getConsistentReadVersion.Before](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbclient/NativeAPI.actor.cpp#L4564) |
| **GRVProxy** | GrvProxyServer | queueGetReadVersionRequests | Before | TransactionDebug | [GrvProxyServer.queueTransactionStartRequests.Before](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/GrvProxyServer.actor.cpp#L373-L375) |
| | | transactionStarter | | [*TransactionAttachID*](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/GrvProxyServer.actor.cpp#L734-L735) | |
| | | | AskLiveCommittedVersionFromMaster | TransactionDebug | [GrvProxyServer.transactionStarter.AskLiveCommittedVersionFromMaster](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/GrvProxyServer.actor.cpp#L787-L789) |
| | | getLiveCommittedVersion | confirmEpochLive | TransactionDebug | [GrvProxyServer.getLiveCommittedVersion.confirmEpochLive](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/GrvProxyServer.actor.cpp#L479-L480) |
| **Master** | MasterServer | serveLiveCommittedVersion | GetRawCommittedVersion | TransactionDebug | [MasterServer.serveLiveCommittedVersion.GetRawCommittedVersion](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/masterserver.actor.cpp#L1187-L1189) |
| **GRVProxy** | GrvProxyServer | getLiveCommittedVersion | After | TransactionDebug | [GrvProxyServer.getLiveCommittedVersion.After](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/GrvProxyServer.actor.cpp#L500-L501) |
| **Client** | NativeAPI | getConsistentReadVersion | After | TransactionDebug | [NativeAPI.getConsistentReadVersion.After](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbclient/NativeAPI.actor.cpp#L4594-L4595) |
### Get
![Get](Get.svg)
| **Role** | **File name** | **Function/Actor** | **Trace** | **Name** | **Location** | **Notes** |
| ------------------ | ------------------- | ----------------------------------- | ------------ | ------------------------------------------------------------ | ------------------------------------------------------------ | ------------------------------------------------------------ |
| **Client** | NativeAPI | Transaction::get | | | | |
| | | Transaction::getReadVersion | | | *(Refer to GetReadVersion)* | |
| | | getKeyLocation | Before | TransactionDebug | [NativeAPI.getKeyLocation.Before](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbclient/NativeAPI.actor.cpp#L1975-L1976) | getKeyLocation is called by getValue, getKeyLocation actually calls getKeyLocation_internal |
| | | | After | TransactionDebug | [NativeAPI.getKeyLocation.After](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbclient/NativeAPI.actor.cpp#L1988-L1989) | |
| | | getValue | | [*GetValueAttachID*](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbclient/NativeAPI.actor.cpp#L2164) | | |
| | | | Before | GetValueDebug | [NativeAPI.getValue.Before](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbclient/NativeAPI.actor.cpp#L2165-L2167) | |
| **Storage Server** | StorageServer | serveGetValueRequests | received | GetValueDebug | [StorageServer.received](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/storageserver.actor.cpp#L4325-L4327) | |
| | | getValueQ | DoRead | GetValueDebug | [getValueQ.DoRead](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/storageserver.actor.cpp#L1115-L1117) | |
| | | | AfterVersion | GetValueDebug | [getValueQ.AfterVersion](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/storageserver.actor.cpp#L1122-L1124) | |
| | KeyValueStoreSQLite | KeyValueStoreSQLite::Reader::action | Before | GetValueDebug | [Reader.Before](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/KeyValueStoreSQLite.actor.cpp#L1654-L1656) | |
| | | | After | GetValueDebug | [Reader.After](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/KeyValueStoreSQLite.actor.cpp#L1662-L1664) | |
| | StorageServer | | AfterRead | GetValueDebug | [getValueQ.AfterRead](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/storageserver.actor.cpp#L1185-L1187) | |
| **Client** | NativeAPI | getValue | After | GetValueDebug | [NativeAPI.getValue.After](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbclient/NativeAPI.actor.cpp#L2216-L2218) | (When successful) |
| | | | Error | GetValueDebug | [NativeAPI.getValue.Error](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbclient/NativeAPI.actor.cpp#L2232-L2234) | (Wehn failure) |
### Get Range
![GetRange](GetRange.svg)
| **Role** | **File name** | **Function/Actor** | **Trace** | **Name** | **Location** | **Notes** |
| ------------------ | ------------- | --------------------------- | -------------- | ---------------- | ------------------------------------------------------------ | ------------------------------------ |
| **Client** | NativeAPI | Transaction::getRange | | | | |
| | | Transaction::getReadVersion | | | *(Refer to GetReadVersion)* | |
| | | getKeyLocation | Before | TransactionDebug | [NativeAPI.getKeyLocation.Before](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbclient/NativeAPI.actor.cpp#L1975) | getKeyLocation is called by getRange |
| | | | After | TransactionDebug | [NativeAPI.getKeyLocation.After](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbclient/NativeAPI.actor.cpp#L1988-L1989) | |
| | | getRange | Before | TransactionDebug | [NativeAPI.getRange.Before](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbclient/NativeAPI.actor.cpp#L3004) | |
| **Storage Server** | storageserver | getKeyValuesQ | Before | TransactionDebug | [storageserver.getKeyValues.Before](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/storageserver.actor.cpp#L1812) | |
| | | | AfterVersion | TransactionDebug | [storageserver.getKeyValues.AfterVersion](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/storageserver.actor.cpp#L1821) | |
| | | | AfterKeys | TransactionDebug | [storageserver.getKeyValues.AfterKeys](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/storageserver.actor.cpp#L1846) | |
| | | | Send | TransactionDebug | [storageserver.getKeyValues.Send](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/storageserver.actor.cpp#L1866) | (When no keys found) |
| | | | AfterReadRange | TransactionDebug | [storageserver.getKeyValues.AfterReadRange](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/storageserver.actor.cpp#L1886) | (When found keys in this SS) |
| **Client** | NativeAPI | getRange | After | TransactionDebug | [NativeAPI.getRange.After](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbclient/NativeAPI.actor.cpp#L3044-L3046) | (When successful) |
| | | | Error | TransactionDebug | [NativeAPI.getRange.Error](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbclient/NativeAPI.actor.cpp#L3155-L3156) | (Wehn failure) |
### GetRange Fallback
![GetRangeFallback](GetRangeFallback.svg)
| **Role** | **File name** | **Function/Actor** | **Trace** | **Type** | **Location** | **Notes** |
| ---------- | ------------- | -------------------- | ------------ | ---------------- | ------------------------------------------------------------ | ----------------------------------------------- |
| **Client** | NativeAPI | getRangeFallback | | | | |
| | | getKey | | | *GetKeyAttachID* | |
| | | | AfterVersion | GetKeyDebug | [NativeAPI.getKey.AfterVersion](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbclient/NativeAPI.actor.cpp#L2263-L2266) | |
| | | | Before | GetKeyDebug | [NativeAPI.getKey.Before](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbclient/NativeAPI.actor.cpp#L2285-L2288) | |
| | | | After | GetKeyDebug | [NativeAPI.getKey.After](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbclient/NativeAPI.actor.cpp#L2316-L2318) | Success |
| | | | Error | GetKeyDebug | [NativeAPI.getKey.Error](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbclient/NativeAPI.actor.cpp#L2326) | Error |
| | | getReadVersion | | | | *(Refer to GetReadVersion)* |
| | | getKeyRangeLocations | Before | TransactionDebug | [NativeAPI.getKeyLocations.Before](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbclient/NativeAPI.actor.cpp#L2029) | |
| | | | After | TransactionDebug | [NativeAPI.getKeyLocations.After](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbclient/NativeAPI.actor.cpp#L2044) | |
| | | getExactRange | Before | TransactionDebug | [NativeAPI.getExactRange.Before](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbclient/NativeAPI.actor.cpp#L2674) | getKeyRangeLocations is called by getExactRange |
| | | | After | TransactionDebug | [NativeAPI.getExactRange.After](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbclient/NativeAPI.actor.cpp#L2707) | |
### Commit
![Commit](Commit.svg)
| **Role** | **File name** | **Function/Actor** | **Trace** | **Type** | **Location** | **Notes** |
| ---------------- | ----------------- | ------------------------------------------- | -------------------- | ------------------------------------------------------------ | ------------------------------------------------------------ | --------- |
| **Client** | NativeAPI | Transaction::commit | | | | |
| | | commitAndWatch | | | | |
| | | tryCommit | | *[commitAttachID](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbclient/NativeAPI.actor.cpp#L4100)* | | |
| | | | Before | CommitDebug | [NativeAPI.commit.Before](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbclient/NativeAPI.actor.cpp#L4101-L4102) | |
| **Commit Proxy** | CommitProxyServer | commitBatcher | batcher | CommitDebug | [CommitProxyServer.batcher](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/CommitProxyServer.actor.cpp#L244-L245) | |
| | | commitBatch | | | | |
| | | CommitBatchContext::setupTraceBatch | | *[CommitAttachID](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/CommitProxyServer.actor.cpp#L526)* | | |
| | | | Before | CommitDebug | [CommitProxyServer.commitBatch.Before](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/CommitProxyServer.actor.cpp#L532) | |
| | | CommitBatchContext::preresolutionProcessing | GettingCommitVersion | CommitDebug | [CommitProxyServer.commitBatch.GettingCommitVersion](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/CommitProxyServer.actor.cpp#L616-L617) | |
| | | | GotCommitVersion | CommitDebug | [CommitProxyServer.commitBatch.GotCommitVersion](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/CommitProxyServer.actor.cpp#L643) | |
| **Resolver** | Resolver | resolveBatch | | *[CommitAttachID](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/Resolver.actor.cpp#L116)* | | |
| | | | Before | CommitDebug | [Resolver.resolveBatch.Before](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/Resolver.actor.cpp#L117) | |
| | | | AfterQueueSizeCheck | CommitDebug | [Resolver.resolveBatch.AfterQueueSizeCheck](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/Resolver.actor.cpp#L137) | |
| | | | AfterOrderer | CommitDebug | [Resolver.resolveBatch.AfterOrderer](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/Resolver.actor.cpp#L172) | |
| | | | After | CommitDebug | [Resolver.resolveBatch.After](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/Resolver.actor.cpp#L296) | |
| **Commit Proxy** | CommitProxyServer | CommitBatchContext::postResolution | ProcessingMutations | CommitDebug | [CommitProxyServer.CommitBatch.ProcessingMutations](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/CommitProxyServer.actor.cpp#L1074) | |
| | | | AfterStoreCommits | CommitDebug | [CommitProxyServer.CommitBatch.AfterStoreCommits](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/CommitProxyServer.actor.cpp#L1154) | |
| **TLog** | TLogServer | tLogCommit | | *[commitAttachID](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/TLogServer.actor.cpp#L2047)* | | |
| | | | BeforeWaitForVersion | CommitDebug | [TLogServer.tLogCommit.BeforeWaitForVersion](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/TLogServer.actor.cpp#L2048) | |
| | | | Before | CommitDebug | [TLog.tLogCommit.Before](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/TLogServer.actor.cpp#L2083) | |
| | | | AfterTLogCommit | CommitDebug | [TLog.tLogCommit.AfterTLogCommit](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/TLogServer.actor.cpp#L2107) | |
| | | | After | CommitDebug | [TLog.tLogCommit.After](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/TLogServer.actor.cpp#L2125) | |
| **Commit Proxy** | CommitProxyServer | CommitBatchContext::reply | AfterLogPush | CommitDebug | [CommitProxyServer.CommitBatch.AfterLogPush](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbserver/CommitProxyServer.actor.cpp#L1263) | |
| **Client** | NativeAPI | tryCommit | After | CommitDebug | [NativeAPI.commit.After](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbclient/NativeAPI.actor.cpp#L4152) | |
| | | commitAndWatch | | | | |
| | | watchValue | | *[WatchValueAttachID](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbclient/NativeAPI.actor.cpp#L2408)* | | |
| | | | Before | WatchValueDebug | [NativeAPI.watchValue.Before]() | |
| | | | After | WatchValueDebug | [NativeAPI.watchValue.After](https://github.com/apple/foundationdb/blob/ffb8e27f4325db3dc8465e145bc308f6854500eb/fdbclient/NativeAPI.actor.cpp#L2431-L2433) | |

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title Commit
participantgroup **Client** (NativeAPI.actor.cpp)
participant "Transaction::commit" as tC
participant "commitAndWatch" as cAW
participant "tryCommit" as Commit
participant "watchValue" as wV
end
participantgroup **CommitProxy** (CommitProxyServer.actor.cpp)
participant "commitBatcher" as cB
participant "commitBatch" as Batch
participant "TagPartitionedLogSystem" as TPLS
end
participantgroup **Master**
participant "getVersion" as gV
participant "serveLiveCommittedVersion" as sLCV
end
participantgroup **Resolver** (Resolver.actor.cpp)
participant "resolveBatch" as rB
end
participantgroup **TLog** (TLogServer.actor.cpp)
participant "tLogCommit" as tLC
end
participantgroup **Storage Server** (storageserver.actor.cpp)
participant "serveWatchValueRequests" as sWVR
end
autoactivation off
tC -> cAW:
cAW -> Commit: CommitTransactionRequest
note right of Commit: <color:#green>//CommitAttachID//</color>
note right of Commit: <color:#lightblue>NativeAPI.commit.Before</color>
Commit -> cB: CommitTransactionRequest
loop Batch requests
box over cB: Batch commit requests
end
cB -> Batch: Batched CommitTransactionRequests
note right of Batch: <color:#lightblue>--CommitProxyServer.batcher--</color>
box over Batch: Preresolution
note right of Batch: <color:#blue>GettingCommitVersion</color>
Batch -> gV: GetCommitVersionRequest
gV -> Batch: GetCommitVersionReply
note right of Batch: <color:#blue>GotCommitVersion</color>
box over Batch: Resolve
Batch -> rB: ResolveTransactionBatchRequest
note right of rB: <color:#blue>Before</color>
box over rB: Wait for memory/needed version
note right of rB: <color:#blue>AfterQueueSizeCheck</color>
box over rB: Wait for resolver version
note right of rB: <color:#blue>AfterOrderer</color>
box over rB: Resolve the conflicts
note right of rB: <color:#blue>After</color>
rB --> Batch: ResolveTransactionBatchReply
note right of Batch: <color:#blue>ProcessingMutations</color>
box over Batch: Calculate the metadata
box over Batch: Determine which transactions should be committed
box over Batch: Assign storage server tags to mutations
loop Wait txn commit version enter the MVCC window
Batch -> sLCV: GetRawCommittedVersionRequest
sLCV --> Batch: GetRawCommittedVersionReply
end
note right of Batch: <color:#blue>AfterStoreCommits</color>
Batch -> TPLS: Version, LogPushData
TPLS -> tLC: TLogCommitRequest
note right of tLC: <color:#green>//CommitAttachID//</color>
note right of tLC: <color:#blue>BeforeWaitForVersion</color>
box over tLC: Wait for the version
note right of tLC: <color:#blue>Before</color>
box over tLC: Store the commit
box over tLC: Put commit into persistent queue
note right of tLC: <color:#blue>AfterTLogCommit</color>
box over tLC: Wait all prior message being committed
note right of tLC: <color:#blue>After</color>
tLC --> TPLS: TLogCommitReply
TPLS -> Batch: Version (min)
note right of Batch: AfterLogPush
Batch --> Commit: CommitID
note right of Commit: <color:#lightblue>--NativeAPI.commit.After--</color>
Commit --> cAW:
cAW -> wV: Version
note right of wV: <color:#green>//WatchValueAttachID//</color>
note right of wV: <color:#blue>Before</color>
wV -> sWVR: WatchValueRequest
note right of sWVR: <color:#lightblue>--watchValueQ.Before--</color>
box over sWVR: Ensure version is not too old
note right of sWVR: <color:#lightblue>--watchValueQ.AfterVersion--</color>
loop Value not change
box over sWVR: Check storageserver::getValueQ
note right of sWVR: <color:#lightblue>--watchValueQ.AfterRead--</color>
end
sWVR --> wV: Version
note right of wV: <color:#blue>After</color>
cAW --> tC:

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title Commit in FoundationDB
participant "Client" as C
participant "GetReadVersionProxy" as GRV
participant "CommitProxy" as P
participant "Master" as M
participant "Resolver" as R
participant "TLog" as T
C ->> GRV: Request read version
GRV ->> M: Request committed version
M ->> GRV: Respond committed version
GRV ->> C: Respond read version
C ->> P: Commit a mutation with read version
box right of P: Pre-resolution
P ->> M: Request a commit version
alt New request
M ->> P: Commit version
else Replied before with a commit version
M ->> P: Commit version
else Replied before without commit version
M --x P: Never
end
box right of P: Resolution
P ->> R: Send the transaction to the resolver
alt No conflict
R ->> P: TransactionCommitted
else Conflict
R ->> P: TransactionConflict
else Read snapshot older than oldest version
R ->> P: TransactionTooOld
end
box right of P: Post-resolution
P ->> T: Push the transaction data to TLog
alt TLog not stopped
T ->> P: The version of the transactions that are already durable
else TLog stopped
T ->> P: tlog_stopped
end
box right of P: Reply
P ->> M: Report raw commit version
M -->> P: Void
alt Commit successful
P ->> C: Commit version
else Conflict
P ->> C: Not committed: conflict
else Transaction too old
P ->> C: Not committed: too old
end

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title Get
participantgroup **Client** (NativeAPI.actor.cpp)
participant "Transaction::get" as get
participant "Transaction::getReadVersion" as gRV
participant "getValue" as gV
participant "getKeyLocation" as gKL
end
participantgroup **CommitProxy** (CommitProxyServer.actor.cpp)
participant "doKeyServerLocationRequest" as dKSLR
end
participantgroup **Storage Server** (storageserver.actor.cpp)
participant "serveGetValueRequests" as sGVR
participant "getValueQ" as gVQ
end
participantgroup **KeyValueStoreSQLite** (KeyValueStoreSQLite.actor.cpp)
participant "KeyValueStoreSQLite::Reader::action" as axn
end
autoactivation off
get -> gRV:
box over gRV: //Consult Get Read Version section//
gRV --> get: Version
get -> gV: Version, Key
gV -> gKL: Key
note right of gKL: <color:#blue>Before</color>
gKL -> dKSLR: GetKeyServerLocationsRequest
dKSLR --> gKL: GetKeyServerLocationsReply
note right of gKL: <color:#blue>After</color>
gKL --> gV: LocationInfo
note right of gV: <color:#green>//GetValueAttachID//</color>
note right of gV: <color:#blue>Before</color>
gV -> sGVR: GetValueRequest
note right of sGVR: <color:#lightblue>--storageServer.received--</color>
sGVR -> gVQ: GetValueRequest
note right of gVQ: <color:#lightblue>--getValueQ.DoRead--</color>
note right of gVQ: <color:#lightblue>--getValueQ.AfterVersion--</color>
gVQ -> axn: Key
note right of axn: <color:#lightblue>--Reader.Before--</color>
note right of axn: <color:#lightblue>--Reader.After--</color>
axn --> gVQ: Value
note right of gVQ: <color:#lightblue>--getValueQ.AfterRead--</color>
gVQ --> gV: GetValueReply
alt Error
note right of gV: <color:#blue>Error</color>
gV --> get: Error
else Success
note right of gV: <color:#blue>After</color>
gV --> get: Value
end

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title GetRange
participantgroup **Client** (NativeAPI.actor.cpp)
participant "Transaction::getRange" as tGR
participant "Transaction::getReadVersion" as gRV
participant "getRange" as gR
participant "getKeyLocation" as gKL
end
participantgroup **Storage Server** (storageserver.actor.cpp)
participant "getKeyValuesQ" as gKVQ
end
autoactivation off
tGR -> gRV:
tGR -> gR: KeyRange
gRV -->(2) gR: Version
loop Keys in the range
gR -> gKL: Key
box over gKL: //Consult Get section//
gKL --> gR: LocationInfo
note right of gR: <color:#blue>Before</color>
gR -> gKVQ: GetKeyValuesRequest
note right of gKVQ: <color:#lightblue>--storageserver.getKeyValues.Before--</color>
box over gKVQ: Wait the SS version
note right of gKVQ: <color:#lightblue>--storageserver.getKeyValues.AfterVersion--</color>
box over gKVQ: Realign the keys
note right of gKVQ: <color:#lightblue>--storageserver.getKeyValues.AfterKeys--</color>
alt No KV pair stored in this server
note right of gKVQ: <color:#lightblue>--storageserver.getKeyValues.Send--</color>
gKVQ --> gR: GetKeyValuesReply (empty)
else KV pair found
note right of gKVQ: <color:#lightblue>--storageserver.getKeyValues.AfterReadRange--</color>
gKVQ --> gR: GetKeyValuesReply
end
note right of gR: <color:#blue>After</color>
box over gR: Combines the results
end
alt Error
note right of gR: <color:#blue>Error</color>
box over gR: Fallback
gR -> tGR: RangeResultRef or Error
else Successful
gR -> tGR: RangeResultRef
end

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title GetRange Fallback
participantgroup **Client** (NativeAPI.actor.cpp)
participant "getRangeFallback" as gRF
participant "getKey" as gK
participant "getExactRange" as gER
participant "getKeyRangeLocations" as gKRL
end
participantgroup **Storage Server** (storageserver.actor.cpp)
participant "serveGetKeyValuesRequests" as sGKVR
participant "serveGetKeyRequests" as sGKR
end
autoactivation off
opt Key need resolve
gRF -> gK: KeySelector
box over gK: Wait for the version
note right of gK: <color:#green>//GetKeyAttachID//</color>
note right of gK: <color:#blue>AfterVersion</color>
box over gK: See getKeyLocation in Get
note right of gK: <color:#blue>Before</color>
gK -> sGKR: GetKeyRequest
sGKR --> gK: GetKeyReply
alt Success
note right of gK: <color:#blue>After</color>
gK --> gRF: Key
else Error
note right of gK: <color:#blue>Error</color>
end
end
box over gRF: Update read version if necessary
gRF -> gER: Version, KeyRangeRef
loop Loop over keys in the range
gER -> gKRL: KeyRange
note right of gKRL: <color:#blue>Before</color>
box over gKRL: Get the locations
note right of gKRL: <color:#blue>After</color>
gKRL --> gER: LocationInfo
loop Loop over shards
note right of gER: <color:#blue>Before</color>
gER -> sGKVR: GetKeyValuesRequest
note right of sGKVR: <color:#lightblue>--storageserver.getKeyValues.Before--</color>
box over sGKVR: Wait the SS version
note right of sGKVR: <color:#lightblue>--storageserver.getKeyValues.AfterVersion--</color>
box over sGKVR: Realign the keys
note right of sGKVR: <color:#lightblue>--storageserver.getKeyValues.AfterKeys--</color>
alt No KV pair stored in this server
note right of sGKVR: <color:#lightblue>--storageserver.getKeyValues.Send--</color>
sGKVR --> gER: GetKeyValuesReply (empty)
else KV pair found
note right of sGKVR: <color:#lightblue>--storageserver.getKeyValues.AfterReadRange--</color>
sGKVR --> gER: GetKeyValuesReply
end
note right of gER: <color:#blue>After</color>
end
end
gER --> gRF: RangeResultRef

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title Get Read Version
participantgroup **Client** (NativeAPI.actor.cpp)
participant "Transaction::getReadVersion" as gRV
participant "readVersionBatcher" as rVB
participant "getConsistentReadVersion" as gCRV
end
participantgroup **GRVProxy** (GrvProxyServer.actor.cpp)
participant "queueGetReadVersionRequests" as qGRVR
participant "transactionStarter" as tS
participant "getLiveCommittedVersion" as gLCV
end
participantgroup **Master** (masterserver.actor.cpp)
participant "serveLiveCommittedVersion" as sLCV
end
autoactivation off
gRV -> rVB: VersionRequest
loop Batch requests
box over rVB:Batch read version requests
end
note right of rVB: <color:#green>//TransactionAttachID//</color>
rVB -> gCRV:
note right of gCRV: <color:#blue>Before</color>
gCRV -> qGRVR: GetReadVersionRequest
loop Batch requests
box over qGRVR: Batch read version requests
end
note right of qGRVR: <color:#lightblue>--GrvProxyServer.queueTransactionStartRequests.Before--</color>
qGRVR -> tS:
note right of tS: <color:#green>//TransactionAttachID//</color>
note right of tS: <color:#blue>AskLiveCommittedVersionFromMaster</color>
tS -> gLCV:
note right of gLCV: <color:#blue>confirmEpochLive</color>
gLCV -> sLCV: GetRawCommittedVersionRequest
note right of sLCV: <color:#blue>GetRawCommittedVersion</color>
sLCV --> gLCV: GetRawCommittedVersionReply
note right of gLCV: <color:#blue>After</color>
gLCV --> gCRV: GetReadVersionReply
note right of gCRV: <color:#blue>After</color>
gCRV --> rVB: GetReadVersionReply
rVB --> gRV: GetReadVersionReply