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Improved multi-statement detection in readwritesplit

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Now comment blocks and identifiers quoted with backticks are taken into
consideration when multi-statements are processed.
This commit is contained in:
Markus Makela 2016-03-02 09:55:24 +02:00
parent 9b2748f50c
commit 9bfef5c7c1
3 changed files with 146 additions and 24 deletions
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109
server/core/modutil.c
View File

@ -801,6 +801,115 @@ void* strnchr_esc(char* ptr, char c, int len)
return NULL;
}
/**
* Find the first occurrence of a character in a string. This function ignores
* escaped characters and all characters that are enclosed in single or double quotes.
* Also MySQL style comment blocks are ignored.
* @param ptr Pointer to area of memory to inspect
* @param c Character to search for
* @param len Size of the memory area
* @return Pointer to the first non-escaped, non-quoted occurrence of the character.
* If the character is not found, NULL is returned.
*/
void* strnchr_esc_mysql(char* ptr, char c, int len)
{
char* p = (char*) ptr;
char* start = p;
bool quoted = false, escaped = false, backtick = false;
char qc;
while (p < start + len)
{
if (escaped)
{
escaped = false;
}
else
{
switch (*p)
{
case '\\':
escaped = true;
break;
case'\'':
case '"':
if (!quoted)
{
quoted = true;
qc = *p;
}
else if (*p == qc)
{
quoted = false;
}
break;
case '`':
backtick = !backtick;
break;
case '#':
if (!backtick)
{
return NULL;
}
break;
case '-':
if (!backtick && p + 1 < start + len && *(p + 1) == '-')
{
return NULL;
}
break;
}
if (*p == c && !escaped && !quoted)
{
return p;
}
p++;
}
}
return NULL;
}
/**
* Check if the start of the token is the start of a MySQL style comment block
* @param ptr String with at least two non-null characters in it
* @return True if the token starts a comment block
*/
bool is_mysql_comment_start(const char* start, int len)
{
const char *ptr = start;
while (ptr - start < len && isspace(*ptr))
{
ptr++;
}
switch (*ptr)
{
case '-':
if (*(ptr + 1) == '-')
{
return true;
}
break;
case '#':
return true;
case '/':
if (*(ptr + 1) == '*')
{
return true;
}
break;
}
return false;
}
/**
* Create a COM_QUERY packet from a string.
* @param query Query to create.

4
server/include/modutil.h
View File

@ -67,6 +67,10 @@ GWBUF* modutil_create_mysql_err_msg(int packet_number,
const char *msg);
int modutil_count_signal_packets(GWBUF*,int,int,int*);
mxs_pcre2_result_t modutil_mysql_wildcard_match(const char* pattern, const char* string);
/** Character and token searching functions */
void* strnchr_esc(char* ptr, char c, int len);
void* strnchr_esc_mysql(char* ptr, char c, int len);
bool is_mysql_comment_start(const char* start, int len);
#endif

57
server/modules/routing/readwritesplit/readwritesplit.c
View File

@ -308,6 +308,8 @@ static ROUTER_INSTANCE* instances;
static int hashkeyfun(void* key);
static int hashcmpfun (void *, void *);
static void check_for_multi_stmt(ROUTER_CLIENT_SES* rses, GWBUF *buf,
mysql_server_cmd_t packet_type);
static int hashkeyfun(
void* key)
@ -2156,23 +2158,7 @@ static bool route_single_stmt(
/** Check for multi-statement queries. We assume here that the client
* protocol is MySQLClient.
* TODO: add warnings when incompatible protocols are used */
MySQLProtocol *proto = (MySQLProtocol*)rses->client_dcb->protocol;
if (proto->client_capabilities & GW_MYSQL_CAPABILITIES_MULTI_STATEMENTS &&
packet_type == MYSQL_COM_QUERY && rses->forced_node != rses->rses_master_ref)
{
for (GWBUF *buf = querybuf; buf != NULL; buf = buf->next)
{
if (strnchr_esc(GWBUF_DATA(buf), ';', GWBUF_LENGTH(buf)))
{
/** It is possible that the session state is modified inside
* the multi-statement query which would leave any slave sessions
* in an inconsistent state. Due to this, for the duration of
* this session, all queries will be sent to the master. */
rses->forced_node = rses->rses_master_ref;
MXS_INFO("Multi-statement query, routing all future queries to master.");
}
}
}
check_for_multi_stmt(rses, querybuf, packet_type);
/**
* Check if the query has anything to do with temporary tables.
@ -5357,12 +5343,35 @@ static backend_ref_t* get_root_master_bref(
return candidate_bref;
}
/**
* @brief Detect multi-statement queries
*
* It is possible that the session state is modified inside a multi-statement
* query which would leave any slave sessions in an inconsistent state. Due to
* this, for the duration of this session, all queries will be sent to the master
* if the current query contains a multi-statement query.
* @param rses Router client session
* @param buf Buffer containing the full query
*/
static void check_for_multi_stmt(ROUTER_CLIENT_SES* rses, GWBUF *buf,
mysql_server_cmd_t packet_type)
{
MySQLProtocol *proto = (MySQLProtocol*) rses->client_dcb->protocol;
if (proto->client_capabilities & GW_MYSQL_CAPABILITIES_MULTI_STATEMENTS &&
packet_type == MYSQL_COM_QUERY && rses->forced_node != rses->rses_master_ref)
{
char *ptr, *data = GWBUF_DATA(buf) + 5;
int buflen = GWBUF_LENGTH(buf) - 5;
if ((ptr = strnchr_esc_mysql(data, ';', buflen)))
{
ptr++;
if (ptr - data < buflen && !is_mysql_comment_start(ptr, ptr - data))
{
rses->forced_node = rses->rses_master_ref;
MXS_INFO("Multi-statement query, routing all future queries to master.");
}
}
}
}