On 01/15/2014 10:52 PM, Alvaro Herrera wrote:
> I gave this patch a look. There was a bug that the final bounds check
> for int32 range was not done when there was no suffix, so in effect you
> could pass numbers larger than UINT_MAX and pg_basebackup would not
> complain until the number reached the server via BASE_BACKUP. Maybe
> that's fine, given that numbers above 1G will cause a failure on the
> server side anyway, but it looked like a bug to me. I tweaked the parse
> routine slightly; other than fix the bug, I made it accept fractional
> numbers, so you can say 0.5M for instance.
Thanks.
> Perhaps we should make sure pg_basebackup rejects numbers larger than 1G
> as well.
Is there a good place to define the constant, so that both backend and
client can use it? I'd say 'include/common' but no existing file seems
to be appropriate. I'm not sure if it's worth to add a new file there.
> Another thing I found a bit strange was the use of the latch. What this
> patch does is create a separate latch which is used for the throttling.
> This means that if the walsender process receives a signal, it will not
> wake up if it's sleeping in throttling. Perhaps this is okay: as Andres
> was quoted upthread as saying, maybe this is not a problem because the
> sleep times are typically short anyway. But we're pretty much used to
> the idea that whenever a signal is sent, processes act on it
> *immediately*. Maybe some admin will not feel comfortable about waiting
> some extra 20ms when they cancel their base backups. In any case,
> having a secondary latch to sleep on in a process seems weird. Maybe
> this should be using MyWalSnd->latch somehow.
o.k., MyWalSnd->latch is used now.
> You have this interesting THROTTLING_MAX_FREQUENCY constant defined to
> 128, with the comment "check this many times per second".
> Let's see: if the user requests 1MB/s, this value results in
> throttling_sample = 1MB / 128 = 8192. So for every 8kB transferred, we
> would stop, check the wall clock time, and if less time has lapsed than
> we were supposed to spend transferring those 8kB then we sleep. Isn't a
> check every 8kB a bit too frequent? This doesn't seem sensible to me.
> I think we should be checking perhaps every tenth of the requested
> maximum rate, or something like that, not every 1/128th.
>
> Now, what the code actually does is not necessarily that, because the
> sampling value is clamped to a minimum of 32 kB. But then if we're
> going to do that, why use such a large divisor value in the first place?
> I propose we set that constant to a smaller value such as 8.
I tried to use THROTTLING_SAMPLE_MIN and THROTTLING_MAX_FREQUENCY to
control both the minimum and maximum chunk size. It was probably too
generic, THROTTLING_SAMPLE_MIN is no longer there.
New patch version is attached.
// Antonin Houska (Tony)
diff --git a/doc/src/sgml/protocol.sgml b/doc/src/sgml/protocol.sgml
index 7d99976..799d214 100644
--- a/doc/src/sgml/protocol.sgml
+++ b/doc/src/sgml/protocol.sgml
@@ -1720,7 +1720,7 @@ The commands accepted in walsender mode are:
</varlistentry>
<varlistentry>
- <term>BASE_BACKUP [<literal>LABEL</literal> <replaceable>'label'</replaceable>] [<literal>PROGRESS</literal>] [<literal>FAST</literal>] [<literal>WAL</literal>] [<literal>NOWAIT</literal>]</term>
+ <term>BASE_BACKUP [<literal>LABEL</literal> <replaceable>'label'</replaceable>] [<literal>PROGRESS</literal>] [<literal>FAST</literal>] [<literal>WAL</literal>] [<literal>NOWAIT</literal>] [<literal>MAX_RATE</literal>]</term>
<listitem>
<para>
Instructs the server to start streaming a base backup.
@@ -1788,7 +1788,23 @@ The commands accepted in walsender mode are:
the waiting and the warning, leaving the client responsible for
ensuring the required log is available.
</para>
- </listitem>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><literal>MAX_RATE</literal> <replaceable>rate</></term>
+ <listitem>
+ <para>
+ Limit (throttle) the maximum amount of data transferred from server
+ to client per unit of time. The expected unit is bytes per second.
+ If this option is specified, the value must either be equal to zero
+ or it must fall within the range from 32 kB through 1 GB (inclusive).
+ If zero is passed or the option is not specified, no restriction is
+ imposed on the transfer.
+ </para>
+ <para>
+ <literal>MAX_RATE</literal> does not affect WAL streaming.
+ </para>
+ </listitem>
</varlistentry>
</variablelist>
</para>
diff --git a/doc/src/sgml/ref/pg_basebackup.sgml b/doc/src/sgml/ref/pg_basebackup.sgml
index c379df5..2ec81b7 100644
--- a/doc/src/sgml/ref/pg_basebackup.sgml
+++ b/doc/src/sgml/ref/pg_basebackup.sgml
@@ -189,6 +189,27 @@ PostgreSQL documentation
</varlistentry>
<varlistentry>
+ <term><option>-r <replaceable class="parameter">rate</replaceable></option></term>
+ <term><option>--max-rate=<replaceable class="parameter">rate</replaceable></option></term>
+ <listitem>
+ <para>
+ The maximum amount of data transferred from server per second.
+ The purpose is to limit the impact of <application>pg_basebackup</application>
+ on the running server.
+ </para>
+ <para>
+ This option always affects transfer of the data directory. Transfer of
+ WAL files is only affected if the collection method is <literal>fetch</literal>.
+ </para>
+ <para>
+ Valid values are between <literal>32 kB</literal> and <literal>1024 MB</literal>
+ is expected. Suffixes <literal>k</literal> (kilobytes) and
+ <literal>M</literal> (megabytes) are accepted.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
<term><option>-R</option></term>
<term><option>--write-recovery-conf</option></term>
<listitem>
diff --git a/src/backend/replication/basebackup.c b/src/backend/replication/basebackup.c
index fc35f5b..a0216c1 100644
--- a/src/backend/replication/basebackup.c
+++ b/src/backend/replication/basebackup.c
@@ -33,6 +33,7 @@
#include "utils/builtins.h"
#include "utils/elog.h"
#include "utils/ps_status.h"
+#include "utils/timestamp.h"
#include "pgtar.h"
typedef struct
@@ -42,6 +43,7 @@ typedef struct
bool fastcheckpoint;
bool nowait;
bool includewal;
+ uint32 maxrate;
} basebackup_options;
@@ -59,6 +61,7 @@ static void perform_base_backup(basebackup_options *opt, DIR *tblspcdir);
static void parse_basebackup_options(List *options, basebackup_options *opt);
static void SendXlogRecPtrResult(XLogRecPtr ptr, TimeLineID tli);
static int compareWalFileNames(const void *a, const void *b);
+static void throttle(size_t increment);
/* Was the backup currently in-progress initiated in recovery mode? */
static bool backup_started_in_recovery = false;
@@ -68,6 +71,35 @@ static bool backup_started_in_recovery = false;
*/
#define TAR_SEND_SIZE 32768
+
+/*
+ * The maximum amount of data per second - bounds of the user input.
+ *
+ * If the maximum should be increased to more than 4 GB, uint64 must
+ * be introduced for the related variables. However such high values have
+ * little to do with throttling.
+ */
+#define MAX_RATE_LOWER 32768
+#define MAX_RATE_UPPER (1024 << 20)
+
+
+/*
+ * How frequently to throttle, as a fraction of the specified rate-second.
+ */
+#define THROTTLING_FREQUENCY 8
+
+/* The actual value, transfer of which may cause sleep. */
+static uint32 throttling_sample;
+
+/* Amount of data already transfered but not yet throttled. */
+static int32 throttling_counter;
+
+/* The minimum time required to transfer throttling_sample bytes. */
+static int64 elapsed_min_unit;
+
+/* The last check of the transfer rate. */
+static int64 throttled_last;
+
typedef struct
{
char *oid;
@@ -187,6 +219,30 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
/* Send tablespace header */
SendBackupHeader(tablespaces);
+ /* Setup and activate network throttling, if client requested it */
+ if (opt->maxrate > 0)
+ {
+ throttling_sample = opt->maxrate / THROTTLING_FREQUENCY;
+
+ /*
+ * opt->maxrate is bytes per second. Thus the expression in
+ * brackets is microseconds per byte.
+ */
+ elapsed_min_unit = throttling_sample *
+ ((double) USECS_PER_SEC / opt->maxrate);
+
+ /* Enable throttling. */
+ throttling_counter = 0;
+
+ /* The 'real data' starts now (header was ignored). */
+ throttled_last = GetCurrentIntegerTimestamp();
+ }
+ else
+ {
+ /* Disable throttling. */
+ throttling_counter = -1;
+ }
+
/* Send off our tablespaces one by one */
foreach(lc, tablespaces)
{
@@ -414,6 +470,8 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
(errmsg("base backup could not send data, aborting backup")));
len += cnt;
+ throttle(cnt);
+
if (len == XLogSegSize)
break;
}
@@ -484,6 +542,7 @@ parse_basebackup_options(List *options, basebackup_options *opt)
bool o_fast = false;
bool o_nowait = false;
bool o_wal = false;
+ bool o_maxrate = false;
MemSet(opt, 0, sizeof(*opt));
foreach(lopt, options)
@@ -535,6 +594,29 @@ parse_basebackup_options(List *options, basebackup_options *opt)
opt->includewal = true;
o_wal = true;
}
+ else if (strcmp(defel->defname, "maxrate") == 0)
+ {
+ long maxrate;
+
+ if (o_maxrate)
+ ereport(ERROR,
+ (errcode(ERRCODE_SYNTAX_ERROR),
+ errmsg("duplicate option \"%s\"", defel->defname)));
+ maxrate = intVal(defel->arg);
+
+ opt->maxrate = (uint32) maxrate;
+ if (opt->maxrate > 0 &&
+ (opt->maxrate < MAX_RATE_LOWER || opt->maxrate > MAX_RATE_UPPER))
+ {
+ ereport(ERROR,
+ (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+ errmsg("transfer rate %u bytes per second is out of range",
+ opt->maxrate),
+ errhint("The accepted range is %u through %u kB per second",
+ MAX_RATE_LOWER >> 10, MAX_RATE_UPPER >> 10)));
+ }
+ o_maxrate = true;
+ }
else
elog(ERROR, "option \"%s\" not recognized",
defel->defname);
@@ -1071,6 +1153,7 @@ sendFile(char *readfilename, char *tarfilename, struct stat * statbuf,
(errmsg("base backup could not send data, aborting backup")));
len += cnt;
+ throttle(cnt);
if (len >= statbuf->st_size)
{
@@ -1092,10 +1175,14 @@ sendFile(char *readfilename, char *tarfilename, struct stat * statbuf,
cnt = Min(sizeof(buf), statbuf->st_size - len);
pq_putmessage('d', buf, cnt);
len += cnt;
+ throttle(cnt);
}
}
- /* Pad to 512 byte boundary, per tar format requirements */
+ /*
+ * Pad to 512 byte boundary, per tar format requirements. (This small
+ * piece of data is probably not worth throttling.)
+ */
pad = ((len + 511) & ~511) - len;
if (pad > 0)
{
@@ -1121,3 +1208,64 @@ _tarWriteHeader(const char *filename, const char *linktarget,
pq_putmessage('d', h, 512);
}
+
+/*
+ * Increment the network transfer counter by the given number of bytes,
+ * and sleep if necessary to comply with the requested network transfer
+ * rate.
+ */
+static void
+throttle(size_t increment)
+{
+ int64 elapsed,
+ elapsed_min,
+ sleep;
+ int wait_result = 0;
+
+ if (throttling_counter < 0)
+ return;
+
+ throttling_counter += increment;
+ if (throttling_counter < throttling_sample)
+ return;
+
+ /* Time elapsed since the last measuring (and possible wake up). */
+ elapsed = GetCurrentIntegerTimestamp() - throttled_last;
+ /* How much should have elapsed at minimum? */
+ elapsed_min = elapsed_min_unit * (throttling_counter / throttling_sample);
+ sleep = elapsed_min - elapsed;
+ /* Only sleep if the transfer is faster than it should be. */
+ if (sleep > 0)
+ {
+ Assert(MyWalSnd);
+ ResetLatch(&MyWalSnd->latch);
+
+ /*
+ * (TAR_SEND_SIZE / throttling_sample * elapsed_min_unit) should be
+ * the maximum time to sleep. Thus the cast to long is safe.
+ */
+ wait_result = WaitLatch(&MyWalSnd->latch, WL_LATCH_SET | WL_TIMEOUT
+ | WL_POSTMASTER_DEATH, (long) (sleep / 1000));
+ }
+ else
+ {
+ /*
+ * The actual transfer rate is below the limit. Negative value would
+ * distort the adjustment of throttled_last.
+ */
+ sleep = 0;
+ }
+
+ /*
+ * Only a whole multiple of throttling_sample was processed. The rest will
+ * be done during the next call of this function.
+ */
+ throttling_counter %= throttling_sample;
+
+ /* Once the (possible) sleep has ended, new period starts. */
+ if (wait_result | WL_TIMEOUT)
+ throttled_last += elapsed + sleep;
+ else if (sleep > 0)
+ /* Sleep was necessary but might have been interrupted. */
+ throttled_last = GetCurrentIntegerTimestamp();
+}
diff --git a/src/backend/replication/repl_gram.y b/src/backend/replication/repl_gram.y
index 015aa44..5f1f091 100644
--- a/src/backend/replication/repl_gram.y
+++ b/src/backend/replication/repl_gram.y
@@ -78,6 +78,7 @@ Node *replication_parse_result;
%token K_PROGRESS
%token K_FAST
%token K_NOWAIT
+%token K_MAX_RATE
%token K_WAL
%token K_TIMELINE
@@ -116,7 +117,7 @@ identify_system:
;
/*
- * BASE_BACKUP [LABEL '<label>'] [PROGRESS] [FAST] [WAL] [NOWAIT]
+ * BASE_BACKUP [LABEL '<label>'] [PROGRESS] [FAST] [WAL] [NOWAIT] [MAX_RATE %d]
*/
base_backup:
K_BASE_BACKUP base_backup_opt_list
@@ -156,6 +157,11 @@ base_backup_opt:
$$ = makeDefElem("nowait",
(Node *)makeInteger(TRUE));
}
+ | K_MAX_RATE UCONST
+ {
+ $$ = makeDefElem("maxrate",
+ (Node *)makeInteger($2));
+ }
;
/*
diff --git a/src/backend/replication/repl_scanner.l b/src/backend/replication/repl_scanner.l
index 01e5ac6..74f7a34 100644
--- a/src/backend/replication/repl_scanner.l
+++ b/src/backend/replication/repl_scanner.l
@@ -71,6 +71,7 @@ IDENTIFY_SYSTEM { return K_IDENTIFY_SYSTEM; }
LABEL { return K_LABEL; }
NOWAIT { return K_NOWAIT; }
PROGRESS { return K_PROGRESS; }
+MAX_RATE { return K_MAX_RATE; }
WAL { return K_WAL; }
TIMELINE { return K_TIMELINE; }
START_REPLICATION { return K_START_REPLICATION; }
diff --git a/src/bin/pg_basebackup/pg_basebackup.c b/src/bin/pg_basebackup/pg_basebackup.c
index 9d13d57..1d198ad 100644
--- a/src/bin/pg_basebackup/pg_basebackup.c
+++ b/src/bin/pg_basebackup/pg_basebackup.c
@@ -46,6 +46,7 @@ static bool streamwal = false;
static bool fastcheckpoint = false;
static bool writerecoveryconf = false;
static int standby_message_timeout = 10 * 1000; /* 10 sec = default */
+static uint32 maxrate = 0; /* no limit by default */
/* Progress counters */
static uint64 totalsize;
@@ -76,6 +77,7 @@ static PQExpBuffer recoveryconfcontents = NULL;
static void usage(void);
static void verify_dir_is_empty_or_create(char *dirname);
static void progress_report(int tablespacenum, const char *filename);
+static uint32 parse_max_rate(char *src);
static void ReceiveTarFile(PGconn *conn, PGresult *res, int rownum);
static void ReceiveAndUnpackTarFile(PGconn *conn, PGresult *res, int rownum);
@@ -111,6 +113,7 @@ usage(void)
printf(_("\nOptions controlling the output:\n"));
printf(_(" -D, --pgdata=DIRECTORY receive base backup into directory\n"));
printf(_(" -F, --format=p|t output format (plain (default), tar)\n"));
+ printf(_(" -r, --max-rate=RATE maximum transfer rate to transfer data directory\n"));
printf(_(" -R, --write-recovery-conf\n"
" write recovery.conf after backup\n"));
printf(_(" -x, --xlog include required WAL files in backup (fetch mode)\n"));
@@ -475,6 +478,86 @@ progress_report(int tablespacenum, const char *filename)
fprintf(stderr, "\r");
}
+static uint32
+parse_max_rate(char *src)
+{
+ double factor;
+ double result;
+ char *after_num;
+
+ errno = 0;
+ result = strtod(src, &after_num);
+ if (src == after_num)
+ {
+ fprintf(stderr,
+ _("%s: transfer rate \"%s\" is not a valid value\n"),
+ progname, src);
+ exit(1);
+ }
+ if (errno != 0)
+ {
+ fprintf(stderr,
+ _("%s: invalid transfer rate \"%s\": %s\n"),
+ progname, src, strerror(errno));
+ exit(1);
+ }
+
+ if (result <= 0)
+ {
+ /*
+ * Reject obviously wrong values here. Exact check of the range to be
+ * done on server.
+ */
+ fprintf(stderr, _("%s: transfer rate must be greater than zero\n"),
+ progname);
+ exit(1);
+ }
+
+ /*
+ * Evaluate (optional) suffix after skipping over possible whitespace.
+ */
+ factor = 1.0;
+ while (*after_num != '\0' && isspace(*after_num))
+ after_num++;
+ switch (*after_num)
+ {
+ case 'M':
+ factor = 1048576.0;
+ after_num++;
+ break;
+ case 'k':
+ factor = 1024.0;
+ after_num++;
+ break;
+ }
+
+ /* The rest can only consist of white space. */
+ while (*after_num != '\0')
+ {
+ if (!isspace(*after_num))
+ {
+ fprintf(stderr,
+ _("%s: invalid --max-rate units: \"%s\"\n"),
+ progname, after_num);
+ exit(1);
+ }
+ after_num++;
+ }
+
+ if (factor > 1)
+ result *= factor;
+
+ /* Check the integer range */
+ if ((uint64) result != (uint64) ((uint32) result))
+ {
+ fprintf(stderr,
+ _("%s: transfer rate \"%s\" exceeds integer range\n"),
+ progname, src);
+ exit(1);
+ }
+
+ return (uint32) result;
+}
/*
* Write a piece of tar data
@@ -1308,8 +1391,9 @@ BaseBackup(void)
char *sysidentifier;
uint32 latesttli;
uint32 starttli;
- char current_path[MAXPGPATH];
+ char *basebkp;
char escaped_label[MAXPGPATH];
+ char *maxrate_clause = NULL;
int i;
char xlogstart[64];
char xlogend[64];
@@ -1382,15 +1466,20 @@ BaseBackup(void)
* Start the actual backup
*/
PQescapeStringConn(conn, escaped_label, label, sizeof(escaped_label), &i);
- snprintf(current_path, sizeof(current_path),
- "BASE_BACKUP LABEL '%s' %s %s %s %s",
- escaped_label,
- showprogress ? "PROGRESS" : "",
- includewal && !streamwal ? "WAL" : "",
- fastcheckpoint ? "FAST" : "",
- includewal ? "NOWAIT" : "");
-
- if (PQsendQuery(conn, current_path) == 0)
+
+ if (maxrate > 0)
+ maxrate_clause = psprintf("MAX_RATE %u", maxrate);
+
+ basebkp =
+ psprintf("BASE_BACKUP LABEL '%s' %s %s %s %s %s",
+ escaped_label,
+ showprogress ? "PROGRESS" : "",
+ includewal && !streamwal ? "WAL" : "",
+ fastcheckpoint ? "FAST" : "",
+ includewal ? "NOWAIT" : "",
+ maxrate_clause ? maxrate_clause : "");
+
+ if (PQsendQuery(conn, basebkp) == 0)
{
fprintf(stderr, _("%s: could not send replication command \"%s\": %s"),
progname, "BASE_BACKUP", PQerrorMessage(conn));
@@ -1657,6 +1746,7 @@ main(int argc, char **argv)
{"pgdata", required_argument, NULL, 'D'},
{"format", required_argument, NULL, 'F'},
{"checkpoint", required_argument, NULL, 'c'},
+ {"max-rate", required_argument, NULL, 'r'},
{"write-recovery-conf", no_argument, NULL, 'R'},
{"xlog", no_argument, NULL, 'x'},
{"xlog-method", required_argument, NULL, 'X'},
@@ -1697,7 +1787,7 @@ main(int argc, char **argv)
}
}
- while ((c = getopt_long(argc, argv, "D:F:RxX:l:zZ:d:c:h:p:U:s:wWvP",
+ while ((c = getopt_long(argc, argv, "D:F:r:RxX:l:zZ:d:c:h:p:U:s:wWvP",
long_options, &option_index)) != -1)
{
switch (c)
@@ -1718,6 +1808,9 @@ main(int argc, char **argv)
exit(1);
}
break;
+ case 'r':
+ maxrate = parse_max_rate(optarg);
+ break;
case 'R':
writerecoveryconf = true;
break;
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