internal/functions/Test-DbaLsnChain.ps1
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function Test-DbaLsnChain { <# .SYNOPSIS Checks that a filtered array from Get-FilteredRestore contains a restorabel chain of LSNs .DESCRIPTION Finds the anchoring Full backup (or multiple if it's a striped set). Then filters to ensure that all the backups are from that anchor point (LastLSN) and that they're all on the same RecoveryForkID Then checks that we have either enough Diffs and T-log backups to get to where we want to go. And checks that there is no break between LastLSN and FirstLSN in sequential files .PARAMETER FilteredRestoreFiles This is just an object consisting of the output from Read-DbaBackupHeader. Normally this will have been filtered down to a restorable chain before arriving here. (ie; only 1 anchoring Full backup) .NOTES Author: Stuart Moore (@napalmgram), stuart-moore.com Tags: dbatools PowerShell module (https://dbatools.io) Copyright: (c) 2018 by dbatools, licensed under MIT License: MIT https://opensource.org/licenses/MIT .EXAMPLE Test-DbaLsnChain -FilteredRestoreFiles $FilteredFiles Checks that the Restore chain in $FilteredFiles is complete and can be fully restored #> [CmdletBinding()] param ( [parameter(Mandatory, ValueFromPipeline)] [object[]]$FilteredRestoreFiles, [switch]$Continue, [switch]$EnableException ) begin { #Need to anchor with full backup: $TestHistory = @() } process { foreach ($bh in $FilteredRestoreFiles) { $TestHistory += $bh } } end { if ($continue) { return $true } Write-Message -Level Verbose -Message "Testing LSN Chain" if ($null -eq $TestHistory[0].BackupTypeDescription) { $TypeName = 'Type' } else { $TypeName = "BackupTypeDescription" } Write-Message -Level VeryVerbose -Message "Testing LSN Chain - Type $typename" $FullDBAnchor = $TestHistory | Where-Object { $_.$TypeName -in ('Database', 'Full') } if (($FullDBAnchor | Group-Object -Property FirstLSN | Measure-Object).Count -ne 1) { $cnt = ($FullDBAnchor | Group-Object -Property FirstLSN | Measure-Object).Count foreach ($tFile in $FullDBAnchor) { Write-Message -Level Debug -Message "$($tfile.FirstLsn) - $($tfile.TypeName)" } Write-Message -Level Verbose -Message "db count = $cnt" Write-Message -Level Warning -Message "More than 1 full backup from a different LSN, or less than 1, neither supported" return $false break; } #Via LSN chain: [BigInt]$CheckPointLSN = ($FullDBAnchor | Select-Object -First 1).CheckPointLSN.ToString() [BigInt]$FullDBLastLSN = ($FullDBAnchor | Select-Object -First 1).LastLSN.ToString() $BackupWrongLSN = $FilteredRestoreFiles | Where-Object { $_.DatabaseBackupLSN -ne $CheckPointLSN } #Should be 0 in there, if not, lets check that they're from during the full backup if ($BackupWrongLSN.count -gt 0 ) { if (($BackupWrongLSN | Where-Object { [BigInt]$_.LastLSN.ToString() -lt $FullDBLastLSN }).count -gt 0) { Write-Message -Level Warning -Message "We have non matching LSNs - not supported" return $false break; } } $DiffAnchor = $TestHistory | Where-Object { $_.$TypeName -in ('Database Differential', 'Differential') } #Check for no more than a single Differential backup if (($DiffAnchor.FirstLSN | Select-Object -unique | Measure-Object).count -gt 1) { Write-Message -Level Warning -Message "More than 1 differential backup, not supported" return $false break; } elseif (($DiffAnchor | Measure-Object).Count -eq 1) { Write-Message -Level VeryVerbose -Message "Found a diff file, setting Log Anchor" $TlogAnchor = $DiffAnchor } else { $TlogAnchor = $FullDBAnchor } #Check T-log LSNs form a chain. $TranLogBackups = $TestHistory | Where-Object { $_.$TypeName -in ('Transaction Log', 'Log') -and $_.DatabaseBackupLSN -eq $FullDBAnchor.CheckPointLSN } | Sort-Object -Property LastLSN, FirstLsn for ($i = 0; $i -lt ($TranLogBackups.count)) { Write-Message -Level Debug -Message "looping t logs" if ($i -eq 0) { if ($TranLogBackups[$i].FirstLSN -gt $TlogAnchor.LastLSN) { Write-Message -Level Warning -Message "Break in LSN Chain between $($TlogAnchor.FullName) and $($TranLogBackups[($i)].FullName) " Write-Message -Level Verbose -Message "Anchor $($TlogAnchor.LastLSN) - FirstLSN $($TranLogBackups[$i].FirstLSN)" return $false break } } else { if ($TranLogBackups[($i - 1)].LastLsn -ne $TranLogBackups[($i)].FirstLSN -and ($TranLogBackups[($i)] -ne $TranLogBackups[($i - 1)])) { Write-Message -Level Warning -Message "Break in transaction log between $($TranLogBackups[($i-1)].FullName) and $($TranLogBackups[($i)].FullName) " return $false break } } $i++ } Write-Message -Level VeryVerbose -Message "Passed LSN Chain checks" return $true } } |