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Add more comments and clean up code

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The binlog event processing code is now better commented and is slightly
easier to read.
This commit is contained in:
Markus Makela
2016-12-05 15:35:29 +02:00
parent 2f082cb7fb
commit f5eb4e21dc
2 changed files with 84 additions and 44 deletions
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126
server/modules/routing/binlogrouter/blr_master.c
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@ -996,6 +996,38 @@ static bool verify_checksum(ROUTER_INSTANCE *router, size_t len, uint8_t *ptr)
return rval;
}
/**
* @brief Reset router errors
*
* @param router Router instance
* @param hdr Replication header
*/
static void reset_errors(ROUTER_INSTANCE *router, REP_HEADER *hdr)
{
spinlock_acquire(&router->lock);
/* set mysql errno to 0 */
router->m_errno = 0;
/* Remove error message */
if (router->m_errmsg)
{
MXS_FREE(router->m_errmsg);
}
router->m_errmsg = NULL;
spinlock_release(&router->lock);
#ifdef SHOW_EVENTS
printf("blr: len %lu, event type 0x%02x, flags 0x%04x, "
"event size %d, event timestamp %lu\n",
(unsigned long)len - 4,
hdr->event_type,
hdr->flags,
hdr->event_size,
(unsigned long)hdr->timestamp);
#endif
}
/**
* blr_handle_binlog_record - we have received binlog records from
* the master and we must now work out what to do with them.
@ -1052,6 +1084,7 @@ blr_handle_binlog_record(ROUTER_INSTANCE *router, GWBUF *pkt)
{
if (router->master_event_state == BLR_EVENT_DONE)
{
/** This is the start of a new event */
spinlock_acquire(&router->lock);
router->stats.n_binlogs++;
router->stats.n_binlogs_ses++;
@ -1113,9 +1146,12 @@ blr_handle_binlog_record(ROUTER_INSTANCE *router, GWBUF *pkt)
break;
}
/** Store the header for later use */
memcpy(&router->stored_header, &hdr, sizeof(hdr));
/** This is the first (and possibly last) packet of a replication
* event. We store the header in case the event is large and
* it is transmitted over multiple network packets. */
router->master_event_state = BLR_EVENT_STARTED;
memcpy(&router->stored_header, &hdr, sizeof(hdr));
reset_errors(router, &hdr);
}
else
{
@ -1127,32 +1163,11 @@ blr_handle_binlog_record(ROUTER_INSTANCE *router, GWBUF *pkt)
break;
}
if (hdr.ok == 0)
{
spinlock_acquire(&router->lock);
/* set mysql errno to 0 */
router->m_errno = 0;
/* Remove error message */
if (router->m_errmsg)
{
MXS_FREE(router->m_errmsg);
}
router->m_errmsg = NULL;
spinlock_release(&router->lock);
#ifdef SHOW_EVENTS
printf("blr: len %lu, event type 0x%02x, flags 0x%04x, "
"event size %d, event timestamp %lu\n",
(unsigned long)len - 4,
hdr.event_type,
hdr.flags,
hdr.event_size,
(unsigned long)hdr.timestamp);
#endif
}
}
else
{
/** We're processing a multi-packet replication event */
ss_dassert(router->master_event_state == BLR_EVENT_ONGOING);
}
/** Gather the event into one big buffer */
@ -1169,7 +1184,11 @@ blr_handle_binlog_record(ROUTER_INSTANCE *router, GWBUF *pkt)
if (router->master_event_state == BLR_EVENT_ONGOING)
{
/** Only consume the network header */
/**
* Consume the network header so that we can append the raw
* event data to the original buffer. This allows both checksum
* calculations and encryption to process it as a contiguous event
*/
part = gwbuf_consume(part, MYSQL_HEADER_LEN);
}
@ -1177,24 +1196,43 @@ blr_handle_binlog_record(ROUTER_INSTANCE *router, GWBUF *pkt)
if (len < MYSQL_PACKET_LENGTH_MAX)
{
/** This is the last packet, we can now write it to disk */
/**
* This is either the only packet for the event or the last
* packet in a series for this event. The buffer now contains
* the network header of the first packet (4 bytes) and one OK byte.
* The semi-sync bytes are always consumed at an earlier stage.
*/
ss_dassert(router->master_event_state != BLR_EVENT_DONE);
if (router->master_event_state != BLR_EVENT_STARTED)
{
/** This is not the first packet of the event, copy the
* stored header */
/**
* This is not the first packet for this event. We must use
* the stored header.
*/
memcpy(&hdr, &router->stored_header, sizeof(hdr));
}
/** The event is now complete */
router->master_event_state = BLR_EVENT_DONE;
}
else
{
/**
* This packet is a part of a series of packets that contain an
* event larger than MYSQL_PACKET_LENGTH_MAX bytes.
*
* For each partial event chunk, we remove the network header and
* append it to router->stored_event. The first event is an
* exception to this and it is appended as-is with the network
* header and the extra OK byte.
*/
ss_dassert(len == MYSQL_PACKET_LENGTH_MAX);
router->master_event_state = BLR_EVENT_ONGOING;
continue;
}
/** We have the complete event in one contiguous buffer */
/** We now have the complete event in one contiguous buffer */
router->stored_event = gwbuf_make_contiguous(router->stored_event);
ptr = GWBUF_DATA(router->stored_event);
@ -1202,9 +1240,9 @@ blr_handle_binlog_record(ROUTER_INSTANCE *router, GWBUF *pkt)
* header and one OK byte. Semi-sync bytes are never stored. */
len = gwbuf_length(router->stored_event);
/*
* First check that the checksum we calculate matches the
* checksum in the packet we received.
/**
* If checksums are enabled, verify that the stored checksum
* matches the one we calculated
*/
if (router->master_chksum && !verify_checksum(router, len, ptr))
{
@ -1406,9 +1444,6 @@ blr_handle_binlog_record(ROUTER_INSTANCE *router, GWBUF *pkt)
}
else if (hdr.flags != LOG_EVENT_ARTIFICIAL_F)
{
ptr = ptr + MYSQL_HEADER_LEN + 1; // Skip header and OK byte
uint32_t offset = MYSQL_HEADER_LEN + 1;
if (hdr.event_type == ROTATE_EVENT)
{
spinlock_acquire(&router->binlog_lock);
@ -1416,8 +1451,13 @@ blr_handle_binlog_record(ROUTER_INSTANCE *router, GWBUF *pkt)
spinlock_release(&router->binlog_lock);
}
/* Write event to disk */
if (blr_write_binlog_record(router, &hdr, len - offset, ptr) == 0)
uint32_t offset = MYSQL_HEADER_LEN + 1; // Skip header and OK byte
/**
* Write the raw event data to disk without the network
* header or the OK byte
*/
if (blr_write_binlog_record(router, &hdr, len - offset, ptr + offset) == 0)
{
gwbuf_free(pkt);
blr_master_close(router);
@ -1425,7 +1465,7 @@ blr_handle_binlog_record(ROUTER_INSTANCE *router, GWBUF *pkt)
return;
}
/* Check for rotete event */
/* Check for rotate event */
if (hdr.event_type == ROTATE_EVENT)
{
if (!blr_rotate_event(router, ptr, &hdr))
@ -1437,7 +1477,7 @@ blr_handle_binlog_record(ROUTER_INSTANCE *router, GWBUF *pkt)
}
}
/* Handle semi-sync request fom master */
/* Handle semi-sync request from master */
if (router->master_semi_sync != MASTER_SEMISYNC_NOT_AVAILABLE &&
semi_sync_send_ack == BLR_MASTER_SEMI_SYNC_ACK_REQ &&
(router->master_event_state == BLR_EVENT_DONE))