10 files changed, 321 insertions, 176 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index f11487fe33..8e59e094d8 100755
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -152,7 +152,7 @@ set(NETDATA_SOURCE_FILES
         src/web_client.h
         src/web_server.c
         src/web_server.h
-        src/locks.h src/statsd.c src/statsd.h src/statistical.c src/statistical.h)
+        src/locks.h src/statsd.c src/statsd.h src/statistical.c src/statistical.h src/backend_prometheus.c src/backend_prometheus.h)
 
 set(APPS_PLUGIN_SOURCE_FILES
         src/appconfig.c
diff --git a/src/Makefile.am b/src/Makefile.am
index 4891908a94..601d3204ff 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -44,6 +44,8 @@ netdata_SOURCES = \
 	appconfig.h \
 	avl.c \
 	avl.h \
+	backend_prometheus.c \
+	backend_prometheus.h \
 	backends.c \
 	backends.h \
 	clocks.c \
diff --git a/src/backend_prometheus.c b/src/backend_prometheus.c
new file mode 100644
index 0000000000..1739b11666
--- /dev/null
+++ b/src/backend_prometheus.c
@@ -0,0 +1,234 @@
+#include "common.h"
+
+// ----------------------------------------------------------------------------
+// PROMETHEUS
+// /api/v1/allmetrics?format=prometheus
+
+static struct prometheus_server {
+    const char *server;
+    uint32_t hash;
+    time_t last_access;
+    struct prometheus_server *next;
+} *prometheus_server_root = NULL;
+
+static inline time_t prometheus_server_last_access(const char *server, time_t now) {
+    uint32_t hash = simple_hash(server);
+
+    struct prometheus_server *ps;
+    for(ps = prometheus_server_root; ps ;ps = ps->next) {
+        if (hash == ps->hash && !strcmp(server, ps->server)) {
+            time_t last = ps->last_access;
+            ps->last_access = now;
+            return last;
+        }
+    }
+
+    ps = callocz(1, sizeof(struct prometheus_server));
+    ps->server = strdupz(server);
+    ps->hash = hash;
+    ps->last_access = now;
+    ps->next = prometheus_server_root;
+    prometheus_server_root = ps;
+
+    return 0;
+}
+
+static inline size_t prometheus_name_copy(char *d, const char *s, size_t usable) {
+    size_t n;
+
+    for(n = 0; *s && n < usable ; d++, s++, n++) {
+        register char c = *s;
+
+        if(!isalnum(c)) *d = '_';
+        else *d = c;
+    }
+    *d = '\0';
+
+    return n;
+}
+
+static inline size_t prometheus_label_copy(char *d, const char *s, size_t usable) {
+    size_t n;
+
+    // make sure we can escape one character without overflowing the buffer
+    usable--;
+
+    for(n = 0; *s && n < usable ; d++, s++, n++) {
+        register char c = *s;
+
+        if(unlikely(c == '"' || c == '\\' || c == '\n')) {
+            *d++ = '\\';
+            n++;
+        }
+        *d = c;
+    }
+    *d = '\0';
+
+    return n;
+}
+
+#define PROMETHEUS_ELEMENT_MAX 256
+#define PROMETHEUS_LABELS_MAX 1024
+
+void rrd_stats_api_v1_charts_allmetrics_prometheus(RRDHOST *host, BUFFER *wb, uint32_t options, time_t after, time_t before, int allhosts, int help, int types, int names) {
+    rrdhost_rdlock(host);
+
+    char hostname[PROMETHEUS_ELEMENT_MAX + 1];
+    prometheus_label_copy(hostname, host->hostname, PROMETHEUS_ELEMENT_MAX);
+
+    char labels[PROMETHEUS_LABELS_MAX + 1] = "";
+    if(allhosts) {
+        if(host->tags && *(host->tags))
+            buffer_sprintf(wb, "netdata_host_tags{instance=\"%s\",%s} 1 %llu\n", hostname, host->tags, now_realtime_usec() / USEC_PER_MS);
+
+        snprintfz(labels, PROMETHEUS_LABELS_MAX, ",instance=\"%s\"", hostname);
+    }
+    else {
+        if(host->tags && *(host->tags))
+            buffer_sprintf(wb, "netdata_host_tags{%s} 1 %llu\n", host->tags, now_realtime_usec() / USEC_PER_MS);
+    }
+
+    // for each chart
+    RRDSET *st;
+    rrdset_foreach_read(st, host) {
+        char chart[PROMETHEUS_ELEMENT_MAX + 1];
+        char context[PROMETHEUS_ELEMENT_MAX + 1];
+        char family[PROMETHEUS_ELEMENT_MAX + 1];
+
+        prometheus_label_copy(chart, (names && st->name)?st->name:st->id, PROMETHEUS_ELEMENT_MAX);
+        prometheus_label_copy(family, st->family, PROMETHEUS_ELEMENT_MAX);
+        prometheus_name_copy(context, st->context, PROMETHEUS_ELEMENT_MAX);
+
+        if(unlikely(help || types))
+            buffer_strcat(wb, "\n");
+
+        if(rrdset_is_available_for_backends(st)) {
+            rrdset_rdlock(st);
+
+            // for each dimension
+            RRDDIM *rd;
+            rrddim_foreach_read(rd, st) {
+                if(rd->collections_counter) {
+                    char dimension[PROMETHEUS_ELEMENT_MAX + 1];
+
+                    if ((options & BACKEND_SOURCE_BITS) == BACKEND_SOURCE_DATA_AS_COLLECTED) {
+                        // we need as-collected / raw data
+
+                        prometheus_name_copy(dimension, (names && rd->name) ? rd->name : rd->id, PROMETHEUS_ELEMENT_MAX);
+
+                        const char *t = "gauge", *h = "gives";
+                        if (rd->algorithm == RRD_ALGORITHM_INCREMENTAL ||
+                            rd->algorithm == RRD_ALGORITHM_PCENT_OVER_DIFF_TOTAL) {
+                            t = "counter";
+                            h = "delta gives";
+                        }
+
+                        if (unlikely(help))
+                            buffer_sprintf(wb, "# HELP %s_%s netdata chart \"%s\", context \"%s\", family \"%s\", dimension \"%s\", value * " COLLECTED_NUMBER_FORMAT " / " COLLECTED_NUMBER_FORMAT " %s %s (%s)\n",
+                                context, dimension, (names && st->name) ? st->name : st->id, st->context,
+                                st->family, (names && rd->name) ? rd->name : rd->id, rd->multiplier,
+                                rd->divisor, h, st->units, t
+                        );
+
+                        if (unlikely(types))
+                            buffer_sprintf(wb, "# TYPE %s_%s %s\n", context, dimension, t);
+
+                        buffer_sprintf(wb, "%s_%s{chart=\"%s\",family=\"%s\"%s} " COLLECTED_NUMBER_FORMAT " %llu\n",
+                                context, dimension, chart, family, labels, rd->last_collected_value,
+                                timeval_msec(&rd->last_collected_time)
+                        );
+                    }
+                    else {
+                        // we need average or sum of the data
+
+                        calculated_number value = backend_calculate_value_from_stored_data(st, rd, after, before, options);
+
+                        if(!isnan(value) && !isinf(value)) {
+                            prometheus_label_copy(dimension, (names && rd->name) ? rd->name : rd->id, PROMETHEUS_ELEMENT_MAX);
+
+                            if (unlikely(help))
+                                buffer_sprintf(wb, "# HELP %s netdata chart \"%s\", context \"%s\", family \"%s\", dimension \"%s\", value gives %s (gauge)\n",
+                                               context, (names && st->name) ? st->name : st->id, st->context,
+                                               st->family, (names && rd->name) ? rd->name : rd->id,
+                                               st->units
+                                );
+
+                            if (unlikely(types))
+                                buffer_sprintf(wb, "# TYPE %s gauge\n", context);
+
+                            buffer_sprintf(wb, "%s{chart=\"%s\",family=\"%s\",dimension=\"%s\"%s} " CALCULATED_NUMBER_FORMAT " %llu\n",
+                                    context, chart, family, dimension, labels, value,
+                                    timeval_msec(&rd->last_collected_time)
+                            );
+                        }
+                    }
+                }
+            }
+
+            rrdset_unlock(st);
+        }
+    }
+
+    rrdhost_unlock(host);
+}
+
+static inline time_t prometheus_preparation(RRDHOST *host, BUFFER *wb, uint32_t options, const char *server, time_t now, int help) {
+    if(!server || !*server) server = "default";
+
+    time_t after  = prometheus_server_last_access(server, now);
+
+    int first_seen = 0;
+    if(!after) {
+        after = now - backend_update_every;
+        first_seen = 1;
+    }
+
+    if(help) {
+        int show_range = 1;
+        char *mode;
+        if((options & BACKEND_SOURCE_BITS) == BACKEND_SOURCE_DATA_AS_COLLECTED) {
+            mode = "as collected";
+            show_range = 0;
+        }
+        else if((options & BACKEND_SOURCE_BITS) == BACKEND_SOURCE_DATA_AVERAGE)
+            mode = "average";
+        else if((options & BACKEND_SOURCE_BITS) == BACKEND_SOURCE_DATA_SUM)
+            mode = "sum";
+        else
+            mode = "unknown";
+
+        buffer_sprintf(wb, "# HELP netdata \"%s\" to %sprometheus \"%s\", source \"%s\", last seen %lu %s\n"
+                , host->hostname
+                , (first_seen)?"FIRST SEEN ":""
+                , server
+                , mode
+                , (unsigned long)((first_seen)?0:(now - after))
+                , (first_seen)?"never":"seconds ago"
+        );
+
+        if(show_range)
+            buffer_sprintf(wb, "# HELP netdata values for time range %lu to %lu\n", (unsigned long)after, (unsigned long)now);
+
+        buffer_strcat(wb, "\n");
+    }
+
+    return after;
+}
+
+void rrd_stats_api_v1_charts_allmetrics_prometheus_single_host(RRDHOST *host, BUFFER *wb, const char *server, uint32_t options, int help, int types, int names) {
+    time_t before = now_realtime_sec();
+    time_t after = prometheus_preparation(host, wb, options, server, before, help);
+
+    rrd_stats_api_v1_charts_allmetrics_prometheus(host, wb, options, after, before, 0, help, types, names);
+}
+
+void rrd_stats_api_v1_charts_allmetrics_prometheus_all_hosts(RRDHOST *host, BUFFER *wb, const char *server, uint32_t options, int help, int types, int names) {
+    time_t before = now_realtime_sec();
+    time_t after = prometheus_preparation(host, wb, options, server, before, help);
+
+    rrd_rdlock();
+    rrdhost_foreach_read(host) {
+        rrd_stats_api_v1_charts_allmetrics_prometheus(host, wb, options, after, before, 1, help, types, names);
+    }
+    rrd_unlock();
+}
diff --git a/src/backend_prometheus.h b/src/backend_prometheus.h
new file mode 100644
index 0000000000..b17252900b
--- /dev/null
+++ b/src/backend_prometheus.h
@@ -0,0 +1,11 @@
+//
+// Created by costa on 09/07/17.
+//
+
+#ifndef NETDATA_BACKEND_PROMETHEUS_H
+#define NETDATA_BACKEND_PROMETHEUS_H
+
+extern void rrd_stats_api_v1_charts_allmetrics_prometheus_single_host(RRDHOST *host, BUFFER *wb, const char *server, uint32_t options, int help, int types, int names);
+extern void rrd_stats_api_v1_charts_allmetrics_prometheus_all_hosts(RRDHOST *host, BUFFER *wb, const char *server, uint32_t options, int help, int types, int names);
+
+#endif //NETDATA_BACKEND_PROMETHEUS_H
diff --git a/src/backends.c b/src/backends.c
index 4c817f16a9..ef617ce372 100644
--- a/src/backends.c
+++ b/src/backends.c
@@ -22,11 +22,9 @@
 // 5. repeats the above forever.
 //
 
-#define BACKEND_SOURCE_DATA_AS_COLLECTED 0x00000001
-#define BACKEND_SOURCE_DATA_AVERAGE      0x00000002
-#define BACKEND_SOURCE_DATA_SUM          0x00000004
-
 int backend_send_names = 1;
+int backend_update_every = 10;
+uint32_t backend_options = BACKEND_SOURCE_DATA_AVERAGE;
 
 // ----------------------------------------------------------------------------
 // helper functions for backends
@@ -48,7 +46,7 @@ static inline size_t backend_name_copy(char *d, const char *s, size_t usable) {
 // calculate the SUM or AVERAGE of a dimension, for any timeframe
 // may return NAN if the database does not have any value in the give timeframe
 
-static inline calculated_number backend_calculate_value_from_stored_data(
+inline calculated_number backend_calculate_value_from_stored_data(
           RRDSET *st                // the chart
         , RRDDIM *rd                // the dimension
         , time_t after              // the start timestamp
@@ -124,7 +122,7 @@ static inline calculated_number backend_calculate_value_from_stored_data(
         return NAN;
     }
 
-    if(unlikely(options & BACKEND_SOURCE_DATA_SUM))
+    if(unlikely((options & BACKEND_SOURCE_BITS) == BACKEND_SOURCE_DATA_SUM))
         return sum;
 
     return sum / (calculated_number)counter;
@@ -457,7 +455,7 @@ static inline int backends_can_send_rrdset(uint32_t options, RRDSET *st) {
         return 0;
     }
 
-    if(unlikely(st->rrd_memory_mode == RRD_MEMORY_MODE_NONE && !(options & BACKEND_SOURCE_DATA_AS_COLLECTED))) {
+    if(unlikely(st->rrd_memory_mode == RRD_MEMORY_MODE_NONE && !((options & BACKEND_SOURCE_BITS) == BACKEND_SOURCE_DATA_AS_COLLECTED))) {
         debug(D_BACKEND, "BACKEND: not sending chart '%s' of host '%s' because its memory mode is '%s' and the backend requires database access.", st->id, st->rrdhost->hostname, rrd_memory_mode_name(st->rrdhost->rrd_memory_mode));
         return 0;
     }
@@ -465,6 +463,26 @@ static inline int backends_can_send_rrdset(uint32_t options, RRDSET *st) {
     return 1;
 }
 
+inline uint32_t backend_parse_data_source(const char *source, uint32_t mode) {
+    if(!strcmp(source, "raw") || !strcmp(source, "as collected") || !strcmp(source, "as-collected") || !strcmp(source, "as_collected") || !strcmp(source, "ascollected")) {
+        mode |= BACKEND_SOURCE_DATA_AS_COLLECTED;
+        mode &= ~(BACKEND_SOURCE_BITS ^ BACKEND_SOURCE_DATA_AS_COLLECTED);
+    }
+    else if(!strcmp(source, "average")) {
+        mode |= BACKEND_SOURCE_DATA_AVERAGE;
+        mode &= ~(BACKEND_SOURCE_BITS ^ BACKEND_SOURCE_DATA_AVERAGE);
+    }
+    else if(!strcmp(source, "sum") || !strcmp(source, "volume")) {
+        mode |= BACKEND_SOURCE_DATA_SUM;
+        mode &= ~(BACKEND_SOURCE_BITS ^ BACKEND_SOURCE_DATA_SUM);
+    }
+    else {
+        error("BACKEND: invalid data source method '%s'.", source);
+    }
+
+    return mode;
+}
+
 void *backends_main(void *ptr) {
     int default_port = 0;
     int sock = -1;
@@ -489,16 +507,15 @@ void *backends_main(void *ptr) {
             .tv_sec = 0,
             .tv_usec = 0
     };
-    uint32_t options = 0x00000000;
     int enabled             = config_get_boolean(CONFIG_SECTION_BACKEND, "enabled", 0);
     const char *source      = config_get(CONFIG_SECTION_BACKEND, "data source", "average");
     const char *type        = config_get(CONFIG_SECTION_BACKEND, "type", "graphite");
     const char *destination = config_get(CONFIG_SECTION_BACKEND, "destination", "localhost");
     const char *prefix      = config_get(CONFIG_SECTION_BACKEND, "prefix", "netdata");
     const char *hostname    = config_get(CONFIG_SECTION_BACKEND, "hostname", localhost->hostname);
-    int frequency           = (int)config_get_number(CONFIG_SECTION_BACKEND, "update every", 10);
+    backend_update_every    = (int)config_get_number(CONFIG_SECTION_BACKEND, "update every", backend_update_every);
     int buffer_on_failures  = (int)config_get_number(CONFIG_SECTION_BACKEND, "buffer on failures", 10);
-    long timeoutms          = config_get_number(CONFIG_SECTION_BACKEND, "timeout ms", frequency * 2 * 1000);
+    long timeoutms          = config_get_number(CONFIG_SECTION_BACKEND, "timeout ms", backend_update_every * 2 * 1000);
     backend_send_names      = config_get_boolean(CONFIG_SECTION_BACKEND, "send names instead of ids", backend_send_names);
 
     charts_pattern = simple_pattern_create(config_get(CONFIG_SECTION_BACKEND, "send charts matching", "*"), SIMPLE_PATTERN_EXACT);
@@ -508,30 +525,17 @@ void *backends_main(void *ptr) {
     // validate configuration options
     // and prepare for sending data to our backend
 
-    if(!enabled || frequency < 1)
-        goto cleanup;
-
-    if(!strcmp(source, "as collected")) {
-        options |= BACKEND_SOURCE_DATA_AS_COLLECTED;
-    }
-    else if(!strcmp(source, "average")) {
-        options |= BACKEND_SOURCE_DATA_AVERAGE;
-    }
-    else if(!strcmp(source, "sum") || !strcmp(source, "volume")) {
-        options |= BACKEND_SOURCE_DATA_SUM;
-    }
-    else {
-        error("BACKEND: invalid data source method '%s' for backend given. Disabling backed.", source);
-        goto cleanup;
-    }
+    backend_options = backend_parse_data_source(source, backend_options);
 
     if(timeoutms < 1) {
-        error("BACKEND: invalid timeout %ld ms given. Assuming %d ms.", timeoutms, frequency * 2 * 1000);
-        timeoutms = frequency * 2 * 1000;
+        error("BACKEND: invalid timeout %ld ms given. Assuming %d ms.", timeoutms, backend_update_every * 2 * 1000);
+        timeoutms = backend_update_every * 2 * 1000;
     }
     timeout.tv_sec  = (timeoutms * 1000) / 1000000;
     timeout.tv_usec = (timeoutms * 1000) % 1000000;
 
+    if(!enabled || backend_update_every < 1)
+        goto cleanup;
 
     // ------------------------------------------------------------------------
     // select the backend type
@@ -541,7 +545,7 @@ void *backends_main(void *ptr) {
         default_port = 2003;
         backend_response_checker = process_graphite_response;
 
-        if(options & BACKEND_SOURCE_DATA_AS_COLLECTED)
+        if((backend_options & BACKEND_SOURCE_BITS) == BACKEND_SOURCE_DATA_AS_COLLECTED)
             backend_request_formatter = format_dimension_collected_graphite_plaintext;
         else
             backend_request_formatter = format_dimension_stored_graphite_plaintext;
@@ -552,7 +556,7 @@ void *backends_main(void *ptr) {
         default_port = 4242;
         backend_response_checker = process_opentsdb_response;
 
-        if(options & BACKEND_SOURCE_DATA_AS_COLLECTED)
+        if((backend_options & BACKEND_SOURCE_BITS) == BACKEND_SOURCE_DATA_AS_COLLECTED)
             backend_request_formatter = format_dimension_collected_opentsdb_telnet;
         else
             backend_request_formatter = format_dimension_stored_opentsdb_telnet;
@@ -563,7 +567,7 @@ void *backends_main(void *ptr) {
         default_port = 5448;
         backend_response_checker = process_json_response;
 
-        if (options & BACKEND_SOURCE_DATA_AS_COLLECTED)
+        if ((backend_options & BACKEND_SOURCE_BITS) == BACKEND_SOURCE_DATA_AS_COLLECTED)
             backend_request_formatter = format_dimension_collected_json_plaintext;
         else
             backend_request_formatter = format_dimension_stored_json_plaintext;
@@ -600,18 +604,18 @@ void *backends_main(void *ptr) {
             chart_backend_reconnects = 0,
             chart_backend_latency = 0;
 
-    RRDSET *chart_metrics = rrdset_create_localhost("netdata", "backend_metrics", NULL, "backend", NULL, "Netdata Buffered Metrics", "metrics", 130600, frequency, RRDSET_TYPE_LINE);
+    RRDSET *chart_metrics = rrdset_create_localhost("netdata", "backend_metrics", NULL, "backend", NULL, "Netdata Buffered Metrics", "metrics", 130600, backend_update_every, RRDSET_TYPE_LINE);
     rrddim_add(chart_metrics, "buffered", NULL,  1, 1, RRD_ALGORITHM_ABSOLUTE);
     rrddim_add(chart_metrics, "lost",     NULL,  1, 1, RRD_ALGORITHM_ABSOLUTE);
     rrddim_add(chart_metrics, "sent",     NULL,  1, 1, RRD_ALGORITHM_ABSOLUTE);
 
-    RRDSET *chart_bytes = rrdset_create_localhost("netdata", "backend_bytes", NULL, "backend", NULL, "Netdata Backend Data Size", "KB", 130610, frequency, RRDSET_TYPE_AREA);
+    RRDSET *chart_bytes = rrdset_create_localhost("netdata", "backend_bytes", NULL, "backend", NULL, "Netdata Backend Data Size", "KB", 130610, backend_update_every, RRDSET_TYPE_AREA);
     rrddim_add(chart_bytes, "buffered", NULL, 1, 1024, RRD_ALGORITHM_ABSOLUTE);
     rrddim_add(chart_bytes, "lost",     NULL, 1, 1024, RRD_ALGORITHM_ABSOLUTE);
     rrddim_add(chart_bytes, "sent",     NULL, 1, 1024, RRD_ALGORITHM_ABSOLUTE);
     rrddim_add(chart_bytes, "received", NULL, 1, 1024, RRD_ALGORITHM_ABSOLUTE);
 
-    RRDSET *chart_ops = rrdset_create_localhost("netdata", "backend_ops", NULL, "backend", NULL, "Netdata Backend Operations", "operations", 130630, frequency, RRDSET_TYPE_LINE);
+    RRDSET *chart_ops = rrdset_create_localhost("netdata", "backend_ops", NULL, "backend", NULL, "Netdata Backend Operations", "operations", 130630, backend_update_every, RRDSET_TYPE_LINE);
     rrddim_add(chart_ops, "write",     NULL, 1, 1, RRD_ALGORITHM_ABSOLUTE);
     rrddim_add(chart_ops, "discard",   NULL, 1, 1, RRD_ALGORITHM_ABSOLUTE);
     rrddim_add(chart_ops, "reconnect", NULL, 1, 1, RRD_ALGORITHM_ABSOLUTE);
@@ -625,11 +629,11 @@ void *backends_main(void *ptr) {
      *
      * issue #1432 and https://www.softlab.ntua.gr/facilities/documentation/unix/unix-socket-faq/unix-socket-faq-2.html
      *
-    RRDSET *chart_latency = rrdset_create_localhost("netdata", "backend_latency", NULL, "backend", NULL, "Netdata Backend Latency", "ms", 130620, frequency, RRDSET_TYPE_AREA);
+    RRDSET *chart_latency = rrdset_create_localhost("netdata", "backend_latency", NULL, "backend", NULL, "Netdata Backend Latency", "ms", 130620, backend_update_every, RRDSET_TYPE_AREA);
     rrddim_add(chart_latency, "latency",   NULL,  1, 1000, RRD_ALGORITHM_ABSOLUTE);
     */
 
-    RRDSET *chart_rusage = rrdset_create_localhost("netdata", "backend_thread_cpu", NULL, "backend", NULL, "NetData Backend Thread CPU usage", "milliseconds/s", 130630, frequency, RRDSET_TYPE_STACKED);
+    RRDSET *chart_rusage = rrdset_create_localhost("netdata", "backend_thread_cpu", NULL, "backend", NULL, "NetData Backend Thread CPU usage", "milliseconds/s", 130630, backend_update_every, RRDSET_TYPE_STACKED);
     rrddim_add(chart_rusage, "user",   NULL, 1, 1000, RRD_ALGORITHM_INCREMENTAL);
     rrddim_add(chart_rusage, "system", NULL, 1, 1000, RRD_ALGORITHM_INCREMENTAL);
 
@@ -637,9 +641,9 @@ void *backends_main(void *ptr) {
     // ------------------------------------------------------------------------
     // prepare the backend main loop
 
-    info("BACKEND: configured ('%s' on '%s' sending '%s' data, every %d seconds, as host '%s', with prefix '%s')", type, destination, source, frequency, hostname, prefix);
+    info("BACKEND: configured ('%s' on '%s' sending '%s' data, every %d seconds, as host '%s', with prefix '%s')", type, destination, source, backend_update_every, hostname, prefix);
 
-    usec_t step_ut = frequency * USEC_PER_SEC;
+    usec_t step_ut = backend_update_every * USEC_PER_SEC;
     time_t after = now_realtime_sec();
     int failures = 0;
     heartbeat_t hb;
@@ -680,7 +684,7 @@ void *backends_main(void *ptr) {
 
             RRDSET *st;
             rrdset_foreach_read(st, host) {
-                if(likely(backends_can_send_rrdset(options, st))) {
+                if(likely(backends_can_send_rrdset(backend_options, st))) {
                     rrdset_rdlock(st);
 
                     count_charts++;
@@ -688,7 +692,7 @@ void *backends_main(void *ptr) {
                     RRDDIM *rd;
                     rrddim_foreach_read(rd, st) {
                         if (likely(rd->last_collected_time.tv_sec >= after)) {
-                            chart_buffered_metrics += backend_request_formatter(b, prefix, host, __hostname, st, rd, after, before, options);
+                            chart_buffered_metrics += backend_request_formatter(b, prefix, host, __hostname, st, rd, after, before, backend_options);
                             count_dims++;
                         }
                         else {
diff --git a/src/backends.h b/src/backends.h
index afd246e6e4..aa1967ee9b 100644
--- a/src/backends.h
+++ b/src/backends.h
@@ -1,7 +1,25 @@
 #ifndef NETDATA_BACKENDS_H
 #define NETDATA_BACKENDS_H 1
 
+#define BACKEND_SOURCE_DATA_AS_COLLECTED 0x00000001
+#define BACKEND_SOURCE_DATA_AVERAGE      0x00000002
+#define BACKEND_SOURCE_DATA_SUM          0x00000004
+
+#define BACKEND_SOURCE_BITS (BACKEND_SOURCE_DATA_AS_COLLECTED|BACKEND_SOURCE_DATA_AVERAGE|BACKEND_SOURCE_DATA_SUM)
+
 extern int backend_send_names;
+extern int backend_update_every;
+extern uint32_t backend_options;
 extern void *backends_main(void *ptr);
 
+extern uint32_t backend_parse_data_source(const char *source, uint32_t mode);
+
+extern calculated_number backend_calculate_value_from_stored_data(
+        RRDSET *st                  // the chart
+        , RRDDIM *rd                // the dimension
+        , time_t after              // the start timestamp
+        , time_t before             // the end timestamp
+        , uint32_t options          // BACKEND_SOURCE_* bitmap
+);
+
 #endif /* NETDATA_BACKENDS_H */
diff --git a/src/common.h b/src/common.h
index 55155db070..efeebf16f0 100644
--- a/src/common.h
+++ b/src/common.h
@@ -220,6 +220,7 @@
 #include "unit_test.h"
 #include "ipc.h"
 #include "backends.h"
+#include "backend_prometheus.h"
 #include "inlined.h"
 #include "adaptive_resortable_list.h"
 #include "rrdpush.h"
diff --git a/src/rrd2json.c b/src/rrd2json.c
index 16806b03b0..98080139ca 100644
--- a/src/rrd2json.c
+++ b/src/rrd2json.c
@@ -167,137 +167,6 @@ void rrd_stats_api_v1_charts(RRDHOST *host, BUFFER *wb) {
 }
 
 // ----------------------------------------------------------------------------
-// PROMETHEUS
-// /api/v1/allmetrics?format=prometheus
-
-static inline size_t prometheus_name_copy(char *d, const char *s, size_t usable) {
-    size_t n;
-
-    for(n = 0; *s && n < usable ; d++, s++, n++) {
-        register char c = *s;
-
-        if(!isalnum(c)) *d = '_';
-        else *d = c;
-    }
-    *d = '\0';
-
-    return n;
-}
-
-static inline size_t prometheus_label_copy(char *d, const char *s, size_t usable) {
-    size_t n;
-
-    // make sure we can escape one character without overflowing the buffer
-    usable--;
-
-    for(n = 0; *s && n < usable ; d++, s++, n++) {
-        register char c = *s;
-
-        if(unlikely(c == '"' || c == '\\' || c == '\n')) {
-            *d++ = '\\';
-            n++;
-        }
-        *d = c;
-    }
-    *d = '\0';
-
-    return n;
-}
-
-#define PROMETHEUS_ELEMENT_MAX 256
-#define PROMETHEUS_LABELS_MAX 1024
-
-void rrd_stats_api_v1_charts_allmetrics_prometheus(RRDHOST *host, BUFFER *wb, int allhosts, int help, int types, int names) {
-    rrdhost_rdlock(host);
-
-    char hostname[PROMETHEUS_ELEMENT_MAX + 1];
-    prometheus_label_copy(hostname, host->hostname, PROMETHEUS_ELEMENT_MAX);
-
-    char labels[PROMETHEUS_LABELS_MAX + 1] = "";
-    if(allhosts) {
-        if(host->tags && *(host->tags))
-            buffer_sprintf(wb, "netdata_host_tags{instance=\"%s\",%s} 1 %llu\n", hostname, host->tags, now_realtime_usec() / USEC_PER_MS);
-
-        snprintfz(labels, PROMETHEUS_LABELS_MAX, ",instance=\"%s\"", hostname);
-    }
-    else {
-        if(host->tags && *(host->tags))
-            buffer_sprintf(wb, "netdata_host_tags{%s} 1 %llu\n", host->tags, now_realtime_usec() / USEC_PER_MS);
-    }
-
-    // for each chart
-    RRDSET *st;
-    rrdset_foreach_read(st, host) {
-        char chart[PROMETHEUS_ELEMENT_MAX + 1];
-        char context[PROMETHEUS_ELEMENT_MAX + 1];
-        char family[PROMETHEUS_ELEMENT_MAX + 1];
-
-        prometheus_label_copy(chart, (names && st->name)?st->name:st->id, PROMETHEUS_ELEMENT_MAX);
-        prometheus_name_copy(context, st->context, PROMETHEUS_ELEMENT_MAX);
-        prometheus_name_copy(family, st->family, PROMETHEUS_ELEMENT_MAX);
-
-        if(unlikely(help || types))
-            buffer_strcat(wb, "\n");
-
-        if(rrdset_is_available_for_backends(st)) {
-            rrdset_rdlock(st);
-
-            // for each dimension
-            RRDDIM *rd;
-            rrddim_foreach_read(rd, st) {
-                if(rd->collections_counter) {
-                    char dimension[PROMETHEUS_ELEMENT_MAX + 1];
-                    prometheus_name_copy(dimension, (names && rd->name)?rd->name:rd->id, PROMETHEUS_ELEMENT_MAX);
-
-                    const char *t = "gauge", *h = "gives";
-                    if(rd->algorithm == RRD_ALGORITHM_INCREMENTAL || rd->algorithm == RRD_ALGORITHM_PCENT_OVER_DIFF_TOTAL) {
-                        t = "counter";
-                        h = "delta gives";
-                    }
-
-                    if(unlikely(help))
-                        buffer_sprintf(wb, "# HELP %s_%s_%s netdata chart \"%s\", context \"%s\", family \"%s\", dimension \"%s\", value * " COLLECTED_NUMBER_FORMAT " / " COLLECTED_NUMBER_FORMAT " %s %s (%s)\n"
-                                       , context, family, dimension
-                                       , (names && st->name)?st->name:st->id
-                                       , st->context
-                                       , st->family
-                                       , (names && rd->name)?rd->name:rd->id
-                                       , rd->multiplier
-                                       , rd->divisor
-                                       , h
-                                       , st->units
-                                       , t
-                        );
-
-                    if(unlikely(types))
-                        buffer_sprintf(wb, "# TYPE %s_%s_%s %s\n", context, family, dimension, t);
-
-                    // calculated_number n = (calculated_number)rd->last_collected_value * (calculated_number)(abs(rd->multiplier)) / (calculated_number)(abs(rd->divisor));
-                    // buffer_sprintf(wb, "%s.%s " CALCULATED_NUMBER_FORMAT " %llu\n", st->id, rd->id, n, timeval_msec(&rd->last_collected_time));
-
-                    buffer_sprintf(wb, "%s_%s_%s{chart=\"%s\"%s} " COLLECTED_NUMBER_FORMAT " %llu\n",
-                            context, family, dimension, chart, labels, rd->last_collected_value, timeval_msec(&rd->last_collected_time)
-                    );
-                }
-            }
-
-            rrdset_unlock(st);
-        }
-    }
-
-    rrdhost_unlock(host);
-}
-
-void rrd_stats_api_v1_charts_allmetrics_prometheus_all_hosts(BUFFER *wb, int help, int types, int names) {
-    RRDHOST *host;
-    rrd_rdlock();
-    rrdhost_foreach_read(host) {
-        rrd_stats_api_v1_charts_allmetrics_prometheus(host, wb, 1, help, types, names);
-    }
-    rrd_unlock();
-}
-
-// ----------------------------------------------------------------------------
 // BASH
 // /api/v1/allmetrics?format=bash
 
diff --git a/src/rrd2json.h b/src/rrd2json.h
index dc163ce73b..a3b9c9509b 100644
--- a/src/rrd2json.h
+++ b/src/rrd2json.h
@@ -67,8 +67,6 @@ extern void rrd_stats_api_v1_charts(RRDHOST *host, BUFFER *wb);
 
 extern void rrd_stats_api_v1_charts_allmetrics_json(RRDHOST *host, BUFFER *wb);
 extern void rrd_stats_api_v1_charts_allmetrics_shell(RRDHOST *host, BUFFER *wb);
-extern void rrd_stats_api_v1_charts_allmetrics_prometheus(RRDHOST *host, BUFFER *wb, int allhosts, int help, int types, int names);
-extern void rrd_stats_api_v1_charts_allmetrics_prometheus_all_hosts(BUFFER *wb, int help, int types, int names);
 
 extern int rrdset2anything_api_v1(RRDSET *st, BUFFER *out, BUFFER *dimensions, uint32_t format, long points
                             , long long after, long long before, int group_method, uint32_t options
diff --git a/src/web_api_v1.c b/src/web_api_v1.c
index e4bd617def..eef4f78665 100644
--- a/src/web_api_v1.c
+++ b/src/web_api_v1.c
@@ -209,6 +209,8 @@ inline int web_client_api_request_v1_charts(RRDHOST *host, struct web_client *w,
 inline int web_client_api_request_v1_allmetrics(RRDHOST *host, struct web_client *w, char *url) {
     int format = ALLMETRICS_SHELL;
     int help = 0, types = 0, names = backend_send_names; // prometheus options
+    const char *prometheus_server = w->client_ip;
+    uint32_t prometheus_options = backend_options;
 
     while(url) {
         char *value = mystrsep(&url, "?&");
@@ -248,6 +250,12 @@ inline int web_client_api_request_v1_allmetrics(RRDHOST *host, struct web_client
             else
                 names = 0;
         }
+        else if(!strcmp(name, "server")) {
+            prometheus_server = value;
+        }
+        else if(!strcmp(name, "source")) {
+            prometheus_options = backend_parse_data_source(value, prometheus_options);
+        }
     }
 
     buffer_flush(w->response.data);
@@ -266,12 +274,12 @@ inline int web_client_api_request_v1_allmetrics(RRDHOST *host, struct web_client
 
         case ALLMETRICS_PROMETHEUS:
             w->response.data->contenttype = CT_PROMETHEUS;
-            rrd_stats_api_v1_charts_allmetrics_prometheus(host, w->response.data, 0, help, types, names);
+            rrd_stats_api_v1_charts_allmetrics_prometheus_single_host(host, w->response.data, prometheus_server, prometheus_options, help, types, names);
             return 200;
 
         case ALLMETRICS_PROMETHEUS_ALL_HOSTS:
             w->response.data->contenttype = CT_PROMETHEUS;
-            rrd_stats_api_v1_charts_allmetrics_prometheus_all_hosts(w->response.data, help, types, names);
+            rrd_stats_api_v1_charts_allmetrics_prometheus_all_hosts(host, w->response.data, prometheus_server, prometheus_options, help, types, names);
             return 200;
 
         default: