extend server-log for journal/container/pods

Default to reading last 30000 lines.

If reading from file estimate that average line
length is 80 characters and read based that
far back from the end of file.

mysqltuner.pl

@@ -238,6 +238,9 @@ package main;
 my $cmd  = ( $opt{nocolor} == 0 ) ? "\e[1;32m[CMD]($me)" : "[CMD]($me)";
 my $end  = ( $opt{nocolor} == 0 ) ? "\e[0m"              : "";
 
+# Maximum lines of log output to read from end
+my $maxlines = 30000;
+
 # Checks for supported or EOL'ed MySQL versions
 my ( $mysqlvermajor, $mysqlverminor, $mysqlvermicro );
 
@@ -1244,6 +1247,7 @@ sub get_log_file_real_path {
 }
 
 sub log_file_recommendations {
+    my $fh;
     $myvar{'log_error'} = $opt{'server-log'} ||
       get_log_file_real_path( $myvar{'log_error'}, $myvar{'hostname'},
         $myvar{'datadir'} );
@@ -1253,41 +1257,54 @@ sub log_file_recommendations {
         badprint "log_error is set to $myvar{'log_error'} MT can't read stderr";
         return
     }
-    if ( -f "$myvar{'log_error'}" ) {
-        goodprint "Log file $myvar{'log_error'} exists";
+    elsif ( $myvar{'log_error'} =~ /^(docker|podman|kubectl):(.*)/ ) {
+        open( $fh, '-|', "$1 logs --tail=$maxlines '$2'" )
+            // die "Can't start $1 $!";
+        goodprint "Log from cloud` $myvar{'log_error'} exists";
     }
-    else {
-        badprint "Log file $myvar{'log_error'} doesn't exist";
-        return;
-    }
-    infoprint "Log file: "
-      . $myvar{'log_error'} . "("
-      . hr_bytes_rnd( ( stat $myvar{'log_error'} )[7] ) . ")";
-
-    if ( -r "$myvar{'log_error'}" ) {
-        goodprint "Log file $myvar{'log_error'} is readable.";
+    elsif ($myvar{'log_error'} =~ /^systemd:(.*)/ ) {
+        open( $fh, '-|', "journalctl -n $maxlines -b  -u '$1'" )
+            // die "Can't start journalctl $!";
+        goodprint "Log journal` $myvar{'log_error'} exists";
     }
-    else {
-        badprint "Log file $myvar{'log_error'} isn't readable.";
-        return;
-    }
-    if ( ( stat $myvar{'log_error'} )[7] > 0 ) {
-        goodprint "Log file $myvar{'log_error'} is not empty";
-    }
-    else {
-        infoprint
+    elsif ( -f "$myvar{'log_error'}" ) {
+        goodprint "Log file $myvar{'log_error'} exists";
+        my $size = ( stat $myvar{'log_error'} )[7];
+        infoprint "Log file: "
+          . $myvar{'log_error'} . "("
+          . hr_bytes_rnd( $size ) . ")";
+
+        if ( $size > 0 ) {
+            goodprint "Log file $myvar{'log_error'} is not empty";
+            if ( $size < 32 * 1024 * 1024 ) {
+                goodprint "Log file $myvar{'log_error'} is smaller than 32 Mb";
+            }
+            else {
+                badprint "Log file $myvar{'log_error'} is bigger than 32 Mb";
+                push @generalrec,
+                  $myvar{'log_error'}
+                  . " is > 32Mb, you should analyze why or implement a rotation log strategy such as logrotate!";
+            }
+        }
+        else {
+            infoprint
 "Log file $myvar{'log_error'} is empty. Assuming log-rotation. Use --server-log={file} for explicit file";
-        return;
-    }
+            return;
+	}
+        if ( ! open( $fh, '<', $myvar{'log_error'} ) ) {
+            badprint "Log file $myvar{'log_error'} isn't readable.";
+            return;
+        }
+        goodprint "Log file $myvar{'log_error'} is readable.";
 
-    if ( ( stat $myvar{'log_error'} )[7] < 32 * 1024 * 1024 ) {
-        goodprint "Log file $myvar{'log_error'} is smaller than 32 Mb";
+	if ( $maxlines * 80 < $size ) {
+          seek( $fh, -$maxlines * 80, 2);
+	  <$fh> ; # discard line fragment
+	}
     }
     else {
-        badprint "Log file $myvar{'log_error'} is bigger than 32 Mb";
-        push @generalrec,
-          $myvar{'log_error'}
-          . " is > 32Mb, you should analyze why or implement a rotation log strategy such as logrotate!";
+        badprint "Log file $myvar{'log_error'} doesn't exist";
+        return;
     }
 
     my $numLi     = 0;
@@ -1296,9 +1313,6 @@ sub log_file_recommendations {
     my @lastShutdowns;
     my @lastStarts;
 
-    open( my $fh, '<', $myvar{'log_error'} )
-      or die "Can't open $myvar{'log_error'} for read: $!";
-
     while ( my $logLi = <$fh> ) {
         chomp $logLi;
         $numLi++;