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Only write monitor journal when it changes

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The state of the monitored servers is only persisted if the states of the
servers have changed. This removes the unnecessary disk IO caused by the
writing on the monitor journal.
This commit is contained in:
Markus Mäkelä
2017-11-15 18:08:24 +02:00
parent db61ec0d7e
commit 703230a930
2 changed files with 29 additions and 14 deletions
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41
server/core/monitor.cc
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@ -137,6 +137,7 @@ MXS_MONITOR* monitor_alloc(const char *name, const char *module)
mon->script_timeout = DEFAULT_SCRIPT_TIMEOUT;
mon->parameters = NULL;
mon->server_pending_changes = false;
memset(mon->journal_hash, 0, sizeof(mon->journal_hash));
spinlock_init(&mon->lock);
spinlock_acquire(&monLock);
mon->next = allMonitors;
@ -2262,27 +2263,39 @@ void store_server_journal(MXS_MONITOR *monitor, MXS_MONITORED_SERVER *master)
if (data)
{
/** Store the data in memory first */
/** Store the data in memory first and compare the current hash to
* the hash of the last stored journal. This isn't a fool-proof
* method of detecting changes but any failures are mainly of
* theoretical nature. */
store_data(monitor, master, data, size);
uint8_t hash[SHA_DIGEST_LENGTH];
SHA1(data, size, hash);
FILE *file = open_tmp_file(monitor, path);
if (file)
if (memcmp(monitor->journal_hash, hash, sizeof(hash)) != 0)
{
/** Write the data to a temp file and rename it to the final name */
if (fwrite(data, 1, buffer_size, file) == buffer_size && fflush(file) == 0)
FILE *file = open_tmp_file(monitor, path);
if (file)
{
if (!rename_tmp_file(monitor, path))
/** Write the data to a temp file and rename it to the final name */
if (fwrite(data, 1, buffer_size, file) == buffer_size && fflush(file) == 0)
{
unlink(path);
if (!rename_tmp_file(monitor, path))
{
unlink(path);
}
else
{
memcpy(monitor->journal_hash, hash, sizeof(hash));
}
}
else
{
MXS_ERROR("Failed to write journal data to disk: %d, %s",
errno, mxs_strerror(errno));
}
fclose(file);
}
else
{
MXS_ERROR("Failed to write journal data to disk: %d, %s",
errno, mxs_strerror(errno));
}
fclose(file);
}
}
MXS_FREE(data);