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When performing a base backup, check for read errors.

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The old code didn't differentiate between a read error and a
concurrent truncation. fread reports both of these by returning 0;
you have to use feof() or ferror() to distinguish between them,
which this code did not do.

It might be a better idea to use read() rather than fread() here,
so that we can display a less-generic error message, but I'm not
sure that would qualify as a back-patchable bug fix, so just do
this much for now.

Jeevan Chalke, reviewed by Jeevan Ladhe and by me.

Discussion: http://postgr.es/m/CA+TgmobG4ywMzL5oQq2a8YKp8x2p3p1LOMMcGqpS7aekT9+ETA@mail.gmail.com
This commit is contained in:
Robert Haas
2019-09-06 08:22:32 -04:00
parent 4950f09e7a
commit 62fb12d7e1
1 changed files with 16 additions and 0 deletions
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16
src/backend/replication/basebackup.c
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@@ -85,6 +85,18 @@ static char *statrelpath = NULL;
*/ */
#define THROTTLING_FREQUENCY 8 #define THROTTLING_FREQUENCY 8
/*
* Checks whether we encountered any error in fread(). fread() doesn't give
* any clue what has happened, so we check with ferror(). Also, neither
* fread() nor ferror() set errno, so we just throw a generic error.
*/
#define CHECK_FREAD_ERROR(fp, filename) \
do { \
if (ferror(fp)) \
ereport(ERROR, \
(errmsg("could not read from file \"%s\"", filename))); \
} while (0)
/* The actual number of bytes, transfer of which may cause sleep. */ /* The actual number of bytes, transfer of which may cause sleep. */
static uint64 throttling_sample; static uint64 throttling_sample;
@@ -509,6 +521,8 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
break; break;
} }
CHECK_FREAD_ERROR(fp, pathbuf);
if (len != XLogSegSize) if (len != XLogSegSize)
{ {
CheckXLogRemoved(segno, tli); CheckXLogRemoved(segno, tli);
@@ -1245,6 +1259,8 @@ sendFile(char *readfilename, char *tarfilename, struct stat *statbuf,
} }
} }
CHECK_FREAD_ERROR(fp, readfilename);
/* If the file was truncated while we were sending it, pad it with zeros */ /* If the file was truncated while we were sending it, pad it with zeros */
if (len < statbuf->st_size) if (len < statbuf->st_size)
{ {