First commit of memcached_stat, a collectd plugin

.travis.yml

@@ -0,0 +1,9 @@
+language: python
+env:
+  - TOXENV=py26
+  - TOXENV=py27
+  - TOXENV=lint
+install:
+  - pip install tox
+script:
+  - tox

memcached_stat.py

@@ -0,0 +1,124 @@
+import collectd
+import socket
+import re
+
+# Verbose logging on/off. Override in config by specifying 'Verbose'.
+VERBOSE_LOGGING = False
+
+# Global settings, one entry per instance
+CONFIGS = []
+
+def get_memcached_stats(conf):
+    stats={}
+    # connect to memcached
+    try:
+        # TODO: use python-memcached to get these stats, available in centos7
+        # (centos6 doesn't have a recent version that supports more than basic stats)
+        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        s.connect((conf['host'], conf['port']))
+        log_verbose("connected to memcached port %d"%conf['port'])
+    except socket.error, e:
+        collectd.error('memcached_stat plugin: Error connecting to %d - %r'
+                       % (conf['port'], e))
+    fp=s.makefile()
+    for verb in ['', 'slabs', 'items']:
+        stats[verb]=[]
+        s.sendall("stats %s\n"%verb)
+        log_verbose("query stats %s"%verb)
+        while True:
+            line=fp.readline()
+            if line.startswith("END"):
+                break
+            # skip the 'STAT' word at the beginning of the line
+            stats[verb].append(line.split()[1:3])
+    log_verbose("done extracting stats")
+    return stats
+
+def configure_callback(conf):
+    """Receive configuration block"""
+    host = None
+    port = None
+    instance = None
+    filtered_stat_types={}
+    global CONFIGS
+    log_verbose("memcached_stats plugin: reading configuration (%d elements)"%(len(conf.children)))
+    for node in conf.children:
+        key = node.key.lower()
+        val = node.values[0]
+        statfilter = re.search(r'filter_(.*)$', key)
+
+        if key == 'verbose':
+            global VERBOSE_LOGGING
+            VERBOSE_LOGGING = bool(val) or VERBOSE_LOGGING
+        elif key == 'host':
+            host = val
+        elif key == 'port':
+            port = int(val)
+        elif key == 'instance':
+            instance = val
+        elif statfilter:
+            log_verbose('Matching expression found: key: %s - value: %s' % (statfilter.group(1), val))
+            filtered_stat_types[statfilter.group(1)] = val
+        else:
+            collectd.warning('memcached_stat plugin: Unknown config key: %s.' % key )
+            continue
+    CONFIGS.append( { 'host': host, 'port': port, 'instance': instance, 'filtered_stat_types':  filtered_stat_types } )
+    log_verbose("memcached_stats plugin: configured pluging instance %s"%instance)
+
+def make_synthetic_stats(stats):
+    # create the slab memory size (chunk_size*total_chunks for each slabs)
+    chunk_sizes={}
+    total_chunks={}
+    for s in stats['slabs']:
+        if ':' not in s[0]:
+            continue
+        slabid, key = s[0].split(':')
+        if key == 'chunk_size':
+            chunk_sizes[slabid] = s[1]
+        elif key == 'total_chunks':
+            total_chunks[slabid] = s[1]
+    # prepare the intersection of keys in both maps
+    slabids = set(chunk_sizes.keys()) & set(total_chunks.keys())
+    log_verbose("preparing synthetic metrics for %d slabs"%len(slabids))
+    for slabid in slabids:
+        stats['slabs'].append(["synth:%s:slab_size"%slabid, int(chunk_sizes[slabid])*int(total_chunks[slabid])])
+        log_verbose("memcached_stats plugin: craeted a synthetic slab_size metric for slabid %s"%slabid)
+
+def read_callback():
+    for conf in CONFIGS:
+        stats=get_memcached_stats(conf)
+        make_synthetic_stats(stats)
+        for verb,stat in stats.iteritems():
+            stat = filter(lambda s: s[0].split(':')[-1] in conf['filtered_stat_types'], stat)
+            # fix keys by prepending the verb if it doesn't exist
+            stat=map(lambda s: [verb+':'+s[0],s[1]] if not s[0].startswith(verb) else s, stat)
+            for s in stat:
+                log_verbose("Having a stat[%s]=%s"%(s[0], s[1]))
+                dispatch_value(s[0],conf['filtered_stat_types'][s[0].split(':')[-1]],s[1], conf['instance'])
+
+def dispatch_value(key, type, value, plugin_instance=None, type_instance=None):
+    """Read a key from info response data and dispatch a value"""
+    if plugin_instance is None:
+        plugin_instance = 'unknown memcached'
+        collectd.error('memcached_stats plugin: plugin_instance is not set, Info key: %s' % key)
+
+    if not type_instance:
+        type_instance = key
+
+    log_verbose('Sending value: %s=%s' % (type_instance, value))
+
+    val = collectd.Values(plugin='memcached')
+    val.type = type
+    val.type_instance = type_instance
+    val.plugin_instance = plugin_instance
+    val.values = [value]
+    val.dispatch()
+
+def log_verbose(msg):
+    if not VERBOSE_LOGGING:
+        return
+    collectd.info('memcached plugin [verbose]: %s' % msg)
+
+# register callbacks
+collectd.register_config(configure_callback)
+collectd.register_read(read_callback)