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Allow BASE_BACKUP to be throttled

A new MAX_RATE option allows imposing a limit to the network transfer
rate from the server side.  This is useful to limit the stress that
taking a base backup has on the server.

pg_basebackup is now able to specify a value to the server, too.

Author: Antonin Houska

Patch reviewed by Stefan Radomski, Andres Freund, Zoltán Böszörményi,
Fujii Masao, and Álvaro Herrera.
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alvherre committed Feb 27, 2014
1 parent 1161d89 commit ef5856fd9b77ef9d0d0c31fb314bb61bbfb1d704
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@@ -1772,7 +1772,7 @@ 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> <replaceable>rate</replaceable>]</term>
<listitem>
<para>
Instructs the server to start streaming a base backup.
@@ -1840,7 +1840,21 @@ 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 kilobytes 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>
+ </listitem>
</varlistentry>
</variablelist>
</para>
@@ -188,6 +188,27 @@ PostgreSQL documentation
</listitem>
</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 transfer rate of data transferred from the server. Values are
+ in kilobytes per second. Use a suffix of <literal>M</> to indicate megabytes
+ per second. A suffix of <literal>k</> is also accepted, and has no effect.
+ Valid values are between 32 kilobytes per second and 1024 megabytes per second.
+ </para>
+ <para>
+ 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>
+ </listitem>
+ </varlistentry>
+
<varlistentry>
<term><option>-R</option></term>
<term><option>--write-recovery-conf</option></term>
@@ -25,6 +25,7 @@
#include "libpq/pqformat.h"
#include "miscadmin.h"
#include "nodes/pg_list.h"
+#include "pgtar.h"
#include "pgstat.h"
#include "replication/basebackup.h"
#include "replication/walsender.h"
@@ -34,7 +35,8 @@
#include "utils/builtins.h"
#include "utils/elog.h"
#include "utils/ps_status.h"
-#include "pgtar.h"
+#include "utils/timestamp.h"
+
typedef struct
{
@@ -43,6 +45,7 @@ typedef struct
bool fastcheckpoint;
bool nowait;
bool includewal;
+ uint32 maxrate;
} basebackup_options;
@@ -60,6 +63,7 @@ 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;
@@ -72,6 +76,23 @@ static char *statrelpath = NULL;
*/
#define TAR_SEND_SIZE 32768
+/*
+ * How frequently to throttle, as a fraction of the specified rate-second.
+ */
+#define THROTTLING_FREQUENCY 8
+
+/* The actual number of bytes, transfer of which may cause sleep. */
+static uint64 throttling_sample;
+
+/* Amount of data already transfered but not yet throttled. */
+static int64 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;
@@ -203,6 +224,29 @@ 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 * 1024 / THROTTLING_FREQUENCY;
+
+ /*
+ * The minimum amount of time for throttling_sample
+ * bytes to be transfered.
+ */
+ elapsed_min_unit = USECS_PER_SEC / THROTTLING_FREQUENCY;
+
+ /* 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)
{
@@ -430,6 +474,8 @@ 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;
}
@@ -500,6 +546,7 @@ 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)
@@ -551,6 +598,25 @@ parse_basebackup_options(List *options, basebackup_options *opt)
opt->includewal = true;
o_wal = true;
}
+ else if (strcmp(defel->defname, "max_rate") == 0)
+ {
+ long maxrate;
+
+ if (o_maxrate)
+ ereport(ERROR,
+ (errcode(ERRCODE_SYNTAX_ERROR),
+ errmsg("duplicate option \"%s\"", defel->defname)));
+
+ maxrate = intVal(defel->arg);
+ if (maxrate < MAX_RATE_LOWER || maxrate > MAX_RATE_UPPER)
+ ereport(ERROR,
+ (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+ errmsg("%d is outside the valid range for parameter \"%s\" (%d .. %d)",
+ (int) maxrate, "MAX_RATE", MAX_RATE_LOWER, MAX_RATE_UPPER)));
+
+ opt->maxrate = (uint32) maxrate;
+ o_maxrate = true;
+ }
else
elog(ERROR, "option \"%s\" not recognized",
defel->defname);
@@ -1112,6 +1178,7 @@ 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)
{
@@ -1133,10 +1200,14 @@ 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)
{
@@ -1162,3 +1233,65 @@ _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;
+
+ if (throttling_counter < 0)
+ return;
+
+ throttling_counter += increment;
+ if (throttling_counter < throttling_sample)
+ return;
+
+ /* Time elapsed since the last measurement (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)
+ {
+ 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. A negative value would
+ * distort the adjustment of throttled_last.
+ */
+ wait_result = 0;
+ 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();
+}
@@ -69,6 +69,7 @@ Node *replication_parse_result;
%token K_PROGRESS
%token K_FAST
%token K_NOWAIT
+%token K_MAX_RATE
%token K_WAL
%token K_TIMELINE
%token K_PHYSICAL
@@ -113,7 +114,7 @@ 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
@@ -157,6 +158,11 @@ base_backup_opt:
$$ = makeDefElem("nowait",
(Node *)makeInteger(TRUE));
}
+ | K_MAX_RATE UCONST
+ {
+ $$ = makeDefElem("max_rate",
+ (Node *)makeInteger($2));
+ }
;
/* CREATE_REPLICATION_SLOT SLOT slot PHYSICAL */
@@ -86,6 +86,7 @@ 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; }
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