New upstream version 1.11.0+dfsgupstream/1.11.0+dfsg

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 662 insertions, 0 deletions

diff --git a/backends/backends.c b/backends/backends.c
new file mode 100644
index 000000000..53a9a2395
--- /dev/null
+++ b/backends/backends.c
@@ -0,0 +1,662 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#define BACKENDS_INTERNALS
+#include "backends.h"
+
+// ----------------------------------------------------------------------------
+// How backends work in netdata:
+//
+// 1. There is an independent thread that runs at the required interval
+//    (for example, once every 10 seconds)
+//
+// 2. Every time it wakes, it calls the backend formatting functions to build
+//    a buffer of data. This is a very fast, memory only operation.
+//
+// 3. If the buffer already includes data, the new data are appended.
+//    If the buffer becomes too big, because the data cannot be sent, a
+//    log is written and the buffer is discarded.
+//
+// 4. Then it tries to send all the data. It blocks until all the data are sent
+//    or the socket returns an error.
+//    If the time required for this is above the interval, it starts skipping
+//    intervals, but the calculated values include the entire database, without
+//    gaps (it remembers the timestamps and continues from where it stopped).
+//
+// 5. repeats the above forever.
+//
+
+const char *global_backend_prefix = "netdata";
+int global_backend_update_every = 10;
+BACKEND_OPTIONS global_backend_options = BACKEND_SOURCE_DATA_AVERAGE | BACKEND_OPTION_SEND_NAMES;
+
+// ----------------------------------------------------------------------------
+// helper functions for backends
+
+size_t backend_name_copy(char *d, const char *s, size_t usable) {
+    size_t n;
+
+    for(n = 0; *s && n < usable ; d++, s++, n++) {
+        char c = *s;
+
+        if(c != '.' && !isalnum(c)) *d = '_';
+        else *d = c;
+    }
+    *d = '\0';
+
+    return n;
+}
+
+// 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
+
+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
+        , BACKEND_OPTIONS backend_options // BACKEND_SOURCE_* bitmap
+        , time_t *first_timestamp   // the first point of the database used in this response
+        , time_t *last_timestamp    // the timestamp that should be reported to backend
+) {
+    RRDHOST *host = st->rrdhost;
+    (void)host;
+
+    // find the edges of the rrd database for this chart
+    time_t first_t = rrdset_first_entry_t(st);
+    time_t last_t  = rrdset_last_entry_t(st);
+    time_t update_every = st->update_every;
+
+    // step back a little, to make sure we have complete data collection
+    // for all metrics
+    after  -= update_every * 2;
+    before -= update_every * 2;
+
+    // align the time-frame
+    after  = after  - (after  % update_every);
+    before = before - (before % update_every);
+
+    // for before, loose another iteration
+    // the latest point will be reported the next time
+    before -= update_every;
+
+    if(unlikely(after > before))
+        // this can happen when update_every > before - after
+        after = before;
+
+    if(unlikely(after < first_t))
+        after = first_t;
+
+    if(unlikely(before > last_t))
+        before = last_t;
+
+    if(unlikely(before < first_t || after > last_t)) {
+        // the chart has not been updated in the wanted timeframe
+        debug(D_BACKEND, "BACKEND: %s.%s.%s: aligned timeframe %lu to %lu is outside the chart's database range %lu to %lu",
+              host->hostname, st->id, rd->id,
+              (unsigned long)after, (unsigned long)before,
+              (unsigned long)first_t, (unsigned long)last_t
+        );
+        return NAN;
+    }
+
+    *first_timestamp = after;
+    *last_timestamp = before;
+
+    size_t counter = 0;
+    calculated_number sum = 0;
+
+    long    start_at_slot = rrdset_time2slot(st, before),
+            stop_at_slot  = rrdset_time2slot(st, after),
+            slot, stop_now = 0;
+
+    for(slot = start_at_slot; !stop_now ; slot--) {
+
+        if(unlikely(slot < 0)) slot = st->entries - 1;
+        if(unlikely(slot == stop_at_slot)) stop_now = 1;
+
+        storage_number n = rd->values[slot];
+
+        if(unlikely(!does_storage_number_exist(n))) {
+            // not collected
+            continue;
+        }
+
+        calculated_number value = unpack_storage_number(n);
+        sum += value;
+
+        counter++;
+    }
+
+    if(unlikely(!counter)) {
+        debug(D_BACKEND, "BACKEND: %s.%s.%s: no values stored in database for range %lu to %lu",
+              host->hostname, st->id, rd->id,
+              (unsigned long)after, (unsigned long)before
+        );
+        return NAN;
+    }
+
+    if(unlikely(BACKEND_OPTIONS_DATA_SOURCE(backend_options) == BACKEND_SOURCE_DATA_SUM))
+        return sum;
+
+    return sum / (calculated_number)counter;
+}
+
+
+// discard a response received by a backend
+// after logging a simple of it to error.log
+
+int discard_response(BUFFER *b, const char *backend) {
+    char sample[1024];
+    const char *s = buffer_tostring(b);
+    char *d = sample, *e = &sample[sizeof(sample) - 1];
+
+    for(; *s && d < e ;s++) {
+        char c = *s;
+        if(unlikely(!isprint(c))) c = ' ';
+        *d++ = c;
+    }
+    *d = '\0';
+
+    info("BACKEND: received %zu bytes from %s backend. Ignoring them. Sample: '%s'", buffer_strlen(b), backend, sample);
+    buffer_flush(b);
+    return 0;
+}
+
+
+// ----------------------------------------------------------------------------
+// the backend thread
+
+static SIMPLE_PATTERN *charts_pattern = NULL;
+static SIMPLE_PATTERN *hosts_pattern = NULL;
+
+inline int backends_can_send_rrdset(BACKEND_OPTIONS backend_options, RRDSET *st) {
+    RRDHOST *host = st->rrdhost;
+    (void)host;
+
+    if(unlikely(rrdset_flag_check(st, RRDSET_FLAG_BACKEND_IGNORE)))
+        return 0;
+
+    if(unlikely(!rrdset_flag_check(st, RRDSET_FLAG_BACKEND_SEND))) {
+        // we have not checked this chart
+        if(simple_pattern_matches(charts_pattern, st->id) || simple_pattern_matches(charts_pattern, st->name))
+            rrdset_flag_set(st, RRDSET_FLAG_BACKEND_SEND);
+        else {
+            rrdset_flag_set(st, RRDSET_FLAG_BACKEND_IGNORE);
+            debug(D_BACKEND, "BACKEND: not sending chart '%s' of host '%s', because it is disabled for backends.", st->id, host->hostname);
+            return 0;
+        }
+    }
+
+    if(unlikely(!rrdset_is_available_for_backends(st))) {
+        debug(D_BACKEND, "BACKEND: not sending chart '%s' of host '%s', because it is not available for backends.", st->id, host->hostname);
+        return 0;
+    }
+
+    if(unlikely(st->rrd_memory_mode == RRD_MEMORY_MODE_NONE && !(BACKEND_OPTIONS_DATA_SOURCE(backend_options) == 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, host->hostname, rrd_memory_mode_name(host->rrd_memory_mode));
+        return 0;
+    }
+
+    return 1;
+}
+
+inline BACKEND_OPTIONS backend_parse_data_source(const char *source, BACKEND_OPTIONS backend_options) {
+    if(!strcmp(source, "raw") || !strcmp(source, "as collected") || !strcmp(source, "as-collected") || !strcmp(source, "as_collected") || !strcmp(source, "ascollected")) {
+        backend_options |= BACKEND_SOURCE_DATA_AS_COLLECTED;
+        backend_options &= ~(BACKEND_OPTIONS_SOURCE_BITS ^ BACKEND_SOURCE_DATA_AS_COLLECTED);
+    }
+    else if(!strcmp(source, "average")) {
+        backend_options |= BACKEND_SOURCE_DATA_AVERAGE;
+        backend_options &= ~(BACKEND_OPTIONS_SOURCE_BITS ^ BACKEND_SOURCE_DATA_AVERAGE);
+    }
+    else if(!strcmp(source, "sum") || !strcmp(source, "volume")) {
+        backend_options |= BACKEND_SOURCE_DATA_SUM;
+        backend_options &= ~(BACKEND_OPTIONS_SOURCE_BITS ^ BACKEND_SOURCE_DATA_SUM);
+    }
+    else {
+        error("BACKEND: invalid data source method '%s'.", source);
+    }
+
+    return backend_options;
+}
+
+static void backends_main_cleanup(void *ptr) {
+    struct netdata_static_thread *static_thread = (struct netdata_static_thread *)ptr;
+    static_thread->enabled = NETDATA_MAIN_THREAD_EXITING;
+
+    info("cleaning up...");
+
+    static_thread->enabled = NETDATA_MAIN_THREAD_EXITED;
+}
+
+void *backends_main(void *ptr) {
+    netdata_thread_cleanup_push(backends_main_cleanup, ptr);
+
+    int default_port = 0;
+    int sock = -1;
+    BUFFER *b = buffer_create(1), *response = buffer_create(1);
+    int (*backend_request_formatter)(BUFFER *, const char *, RRDHOST *, const char *, RRDSET *, RRDDIM *, time_t, time_t, BACKEND_OPTIONS) = NULL;
+    int (*backend_response_checker)(BUFFER *) = NULL;
+
+    // ------------------------------------------------------------------------
+    // collect configuration options
+
+    struct timeval timeout = {
+            .tv_sec = 0,
+            .tv_usec = 0
+    };
+    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");
+    global_backend_prefix       = config_get(CONFIG_SECTION_BACKEND, "prefix", "netdata");
+    const char *hostname        = config_get(CONFIG_SECTION_BACKEND, "hostname", localhost->hostname);
+    global_backend_update_every = (int)config_get_number(CONFIG_SECTION_BACKEND, "update every", global_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", global_backend_update_every * 2 * 1000);
+
+    if(config_get_boolean(CONFIG_SECTION_BACKEND, "send names instead of ids", (global_backend_options & BACKEND_OPTION_SEND_NAMES)))
+        global_backend_options |= BACKEND_OPTION_SEND_NAMES;
+    else
+        global_backend_options &= ~BACKEND_OPTION_SEND_NAMES;
+
+    charts_pattern = simple_pattern_create(config_get(CONFIG_SECTION_BACKEND, "send charts matching", "*"), NULL, SIMPLE_PATTERN_EXACT);
+    hosts_pattern  = simple_pattern_create(config_get(CONFIG_SECTION_BACKEND, "send hosts matching", "localhost *"), NULL, SIMPLE_PATTERN_EXACT);
+
+
+    // ------------------------------------------------------------------------
+    // validate configuration options
+    // and prepare for sending data to our backend
+
+    global_backend_options = backend_parse_data_source(source, global_backend_options);
+
+    if(timeoutms < 1) {
+        error("BACKEND: invalid timeout %ld ms given. Assuming %d ms.", timeoutms, global_backend_update_every * 2 * 1000);
+        timeoutms = global_backend_update_every * 2 * 1000;
+    }
+    timeout.tv_sec  = (timeoutms * 1000) / 1000000;
+    timeout.tv_usec = (timeoutms * 1000) % 1000000;
+
+    if(!enabled || global_backend_update_every < 1)
+        goto cleanup;
+
+    // ------------------------------------------------------------------------
+    // select the backend type
+
+    if(!strcmp(type, "graphite") || !strcmp(type, "graphite:plaintext")) {
+
+        default_port = 2003;
+        backend_response_checker = process_graphite_response;
+
+        if(BACKEND_OPTIONS_DATA_SOURCE(global_backend_options) == BACKEND_SOURCE_DATA_AS_COLLECTED)
+            backend_request_formatter = format_dimension_collected_graphite_plaintext;
+        else
+            backend_request_formatter = format_dimension_stored_graphite_plaintext;
+
+    }
+    else if(!strcmp(type, "opentsdb") || !strcmp(type, "opentsdb:telnet")) {
+
+        default_port = 4242;
+        backend_response_checker = process_opentsdb_response;
+
+        if(BACKEND_OPTIONS_DATA_SOURCE(global_backend_options) == BACKEND_SOURCE_DATA_AS_COLLECTED)
+            backend_request_formatter = format_dimension_collected_opentsdb_telnet;
+        else
+            backend_request_formatter = format_dimension_stored_opentsdb_telnet;
+
+    }
+    else if (!strcmp(type, "json") || !strcmp(type, "json:plaintext")) {
+
+        default_port = 5448;
+        backend_response_checker = process_json_response;
+
+        if (BACKEND_OPTIONS_DATA_SOURCE(global_backend_options) == BACKEND_SOURCE_DATA_AS_COLLECTED)
+            backend_request_formatter = format_dimension_collected_json_plaintext;
+        else
+            backend_request_formatter = format_dimension_stored_json_plaintext;
+
+    }
+    else {
+        error("BACKEND: Unknown backend type '%s'", type);
+        goto cleanup;
+    }
+
+    if(backend_request_formatter == NULL || backend_response_checker == NULL) {
+        error("BACKEND: backend is misconfigured - disabling it.");
+        goto cleanup;
+    }
+
+
+    // ------------------------------------------------------------------------
+    // prepare the charts for monitoring the backend operation
+
+    struct rusage thread;
+
+    collected_number
+            chart_buffered_metrics = 0,
+            chart_lost_metrics = 0,
+            chart_sent_metrics = 0,
+            chart_buffered_bytes = 0,
+            chart_received_bytes = 0,
+            chart_sent_bytes = 0,
+            chart_receptions = 0,
+            chart_transmission_successes = 0,
+            chart_transmission_failures = 0,
+            chart_data_lost_events = 0,
+            chart_lost_bytes = 0,
+            chart_backend_reconnects = 0;
+            // chart_backend_latency = 0;
+
+    RRDSET *chart_metrics = rrdset_create_localhost("netdata", "backend_metrics", NULL, "backend", NULL, "Netdata Buffered Metrics", "metrics", "backends", NULL, 130600, global_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", "backends", NULL, 130610, global_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", "backends", NULL, 130630, global_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);
+    rrddim_add(chart_ops, "failure",   NULL, 1, 1, RRD_ALGORITHM_ABSOLUTE);
+    rrddim_add(chart_ops, "read",      NULL, 1, 1, RRD_ALGORITHM_ABSOLUTE);
+
+    /*
+     * this is misleading - we can only measure the time we need to send data
+     * this time is not related to the time required for the data to travel to
+     * the backend database and the time that server needed to process them
+     *
+     * 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", "backends", NULL, 130620, global_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", "backends", NULL, 130630, global_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);
+
+
+    // ------------------------------------------------------------------------
+    // 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, global_backend_update_every, hostname, global_backend_prefix);
+
+    usec_t step_ut = global_backend_update_every * USEC_PER_SEC;
+    time_t after = now_realtime_sec();
+    int failures = 0;
+    heartbeat_t hb;
+    heartbeat_init(&hb);
+
+    while(!netdata_exit) {
+
+        // ------------------------------------------------------------------------
+        // Wait for the next iteration point.
+
+        heartbeat_next(&hb, step_ut);
+        time_t before = now_realtime_sec();
+        debug(D_BACKEND, "BACKEND: preparing buffer for timeframe %lu to %lu", (unsigned long)after, (unsigned long)before);
+
+        // ------------------------------------------------------------------------
+        // add to the buffer the data we need to send to the backend
+
+        netdata_thread_disable_cancelability();
+
+        size_t count_hosts = 0;
+        size_t count_charts_total = 0;
+        size_t count_dims_total = 0;
+
+        rrd_rdlock();
+        RRDHOST *host;
+        rrdhost_foreach_read(host) {
+            if(unlikely(!rrdhost_flag_check(host, RRDHOST_FLAG_BACKEND_SEND|RRDHOST_FLAG_BACKEND_DONT_SEND))) {
+                char *name = (host == localhost)?"localhost":host->hostname;
+                if (!hosts_pattern || simple_pattern_matches(hosts_pattern, name)) {
+                    rrdhost_flag_set(host, RRDHOST_FLAG_BACKEND_SEND);
+                    info("enabled backend for host '%s'", name);
+                }
+                else {
+                    rrdhost_flag_set(host, RRDHOST_FLAG_BACKEND_DONT_SEND);
+                    info("disabled backend for host '%s'", name);
+                }
+            }
+
+            if(unlikely(!rrdhost_flag_check(host, RRDHOST_FLAG_BACKEND_SEND)))
+                continue;
+
+            rrdhost_rdlock(host);
+
+            count_hosts++;
+            size_t count_charts = 0;
+            size_t count_dims = 0;
+            size_t count_dims_skipped = 0;
+
+            const char *__hostname = (host == localhost)?hostname:host->hostname;
+
+            RRDSET *st;
+            rrdset_foreach_read(st, host) {
+                if(likely(backends_can_send_rrdset(global_backend_options, st))) {
+                    rrdset_rdlock(st);
+
+                    count_charts++;
+
+                    RRDDIM *rd;
+                    rrddim_foreach_read(rd, st) {
+                        if (likely(rd->last_collected_time.tv_sec >= after)) {
+                            chart_buffered_metrics += backend_request_formatter(b, global_backend_prefix, host, __hostname, st, rd, after, before, global_backend_options);
+                            count_dims++;
+                        }
+                        else {
+                            debug(D_BACKEND, "BACKEND: not sending dimension '%s' of chart '%s' from host '%s', its last data collection (%lu) is not within our timeframe (%lu to %lu)", rd->id, st->id, __hostname, (unsigned long)rd->last_collected_time.tv_sec, (unsigned long)after, (unsigned long)before);
+                            count_dims_skipped++;
+                        }
+                    }
+
+                    rrdset_unlock(st);
+                }
+            }
+
+            debug(D_BACKEND, "BACKEND: sending host '%s', metrics of %zu dimensions, of %zu charts. Skipped %zu dimensions.", __hostname, count_dims, count_charts, count_dims_skipped);
+            count_charts_total += count_charts;
+            count_dims_total += count_dims;
+
+            rrdhost_unlock(host);
+        }
+        rrd_unlock();
+
+        netdata_thread_enable_cancelability();
+
+        debug(D_BACKEND, "BACKEND: buffer has %zu bytes, added metrics for %zu dimensions, of %zu charts, from %zu hosts", buffer_strlen(b), count_dims_total, count_charts_total, count_hosts);
+
+        // ------------------------------------------------------------------------
+
+        chart_buffered_bytes = (collected_number)buffer_strlen(b);
+
+        // reset the monitoring chart counters
+        chart_received_bytes =
+        chart_sent_bytes =
+        chart_sent_metrics =
+        chart_lost_metrics =
+        chart_transmission_successes =
+        chart_transmission_failures =
+        chart_data_lost_events =
+        chart_lost_bytes =
+        chart_backend_reconnects = 0;
+        // chart_backend_latency = 0;
+
+        if(unlikely(netdata_exit)) break;
+
+        //fprintf(stderr, "\nBACKEND BEGIN:\n%s\nBACKEND END\n", buffer_tostring(b));
+        //fprintf(stderr, "after = %lu, before = %lu\n", after, before);
+
+        // prepare for the next iteration
+        // to add incrementally data to buffer
+        after = before;
+
+        // ------------------------------------------------------------------------
+        // if we are connected, receive a response, without blocking
+
+        if(likely(sock != -1)) {
+            errno = 0;
+
+            // loop through to collect all data
+            while(sock != -1 && errno != EWOULDBLOCK) {
+                buffer_need_bytes(response, 4096);
+
+                ssize_t r = recv(sock, &response->buffer[response->len], response->size - response->len, MSG_DONTWAIT);
+                if(likely(r > 0)) {
+                    // we received some data
+                    response->len += r;
+                    chart_received_bytes += r;
+                    chart_receptions++;
+                }
+                else if(r == 0) {
+                    error("BACKEND: '%s' closed the socket", destination);
+                    close(sock);
+                    sock = -1;
+                }
+                else {
+                    // failed to receive data
+                    if(errno != EAGAIN && errno != EWOULDBLOCK) {
+                        error("BACKEND: cannot receive data from backend '%s'.", destination);
+                    }
+                }
+            }
+
+            // if we received data, process them
+            if(buffer_strlen(response))
+                backend_response_checker(response);
+        }
+
+        // ------------------------------------------------------------------------
+        // if we are not connected, connect to a backend server
+
+        if(unlikely(sock == -1)) {
+            // usec_t start_ut = now_monotonic_usec();
+            size_t reconnects = 0;
+
+            sock = connect_to_one_of(destination, default_port, &timeout, &reconnects, NULL, 0);
+
+            chart_backend_reconnects += reconnects;
+            // chart_backend_latency += now_monotonic_usec() - start_ut;
+        }
+
+        if(unlikely(netdata_exit)) break;
+
+        // ------------------------------------------------------------------------
+        // if we are connected, send our buffer to the backend server
+
+        if(likely(sock != -1)) {
+            size_t len = buffer_strlen(b);
+            // usec_t start_ut = now_monotonic_usec();
+            int flags = 0;
+#ifdef MSG_NOSIGNAL
+            flags += MSG_NOSIGNAL;
+#endif
+
+            ssize_t written = send(sock, buffer_tostring(b), len, flags);
+            // chart_backend_latency += now_monotonic_usec() - start_ut;
+            if(written != -1 && (size_t)written == len) {
+                // we sent the data successfully
+                chart_transmission_successes++;
+                chart_sent_bytes += written;
+                chart_sent_metrics = chart_buffered_metrics;
+
+                // reset the failures count
+                failures = 0;
+
+                // empty the buffer
+                buffer_flush(b);
+            }
+            else {
+                // oops! we couldn't send (all or some of the) data
+                error("BACKEND: failed to write data to database backend '%s'. Willing to write %zu bytes, wrote %zd bytes. Will re-connect.", destination, len, written);
+                chart_transmission_failures++;
+
+                if(written != -1)
+                    chart_sent_bytes += written;
+
+                // increment the counter we check for data loss
+                failures++;
+
+                // close the socket - we will re-open it next time
+                close(sock);
+                sock = -1;
+            }
+        }
+        else {
+            error("BACKEND: failed to update database backend '%s'", destination);
+            chart_transmission_failures++;
+
+            // increment the counter we check for data loss
+            failures++;
+        }
+
+        if(failures > buffer_on_failures) {
+            // too bad! we are going to lose data
+            chart_lost_bytes += buffer_strlen(b);
+            error("BACKEND: reached %d backend failures. Flushing buffers to protect this host - this results in data loss on back-end server '%s'", failures, destination);
+            buffer_flush(b);
+            failures = 0;
+            chart_data_lost_events++;
+            chart_lost_metrics = chart_buffered_metrics;
+        }
+
+        if(unlikely(netdata_exit)) break;
+
+        // ------------------------------------------------------------------------
+        // update the monitoring charts
+
+        if(likely(chart_ops->counter_done)) rrdset_next(chart_ops);
+        rrddim_set(chart_ops, "read",         chart_receptions);
+        rrddim_set(chart_ops, "write",        chart_transmission_successes);
+        rrddim_set(chart_ops, "discard",      chart_data_lost_events);
+        rrddim_set(chart_ops, "failure",      chart_transmission_failures);
+        rrddim_set(chart_ops, "reconnect",    chart_backend_reconnects);
+        rrdset_done(chart_ops);
+
+        if(likely(chart_metrics->counter_done)) rrdset_next(chart_metrics);
+        rrddim_set(chart_metrics, "buffered", chart_buffered_metrics);
+        rrddim_set(chart_metrics, "lost",     chart_lost_metrics);
+        rrddim_set(chart_metrics, "sent",     chart_sent_metrics);
+        rrdset_done(chart_metrics);
+
+        if(likely(chart_bytes->counter_done)) rrdset_next(chart_bytes);
+        rrddim_set(chart_bytes, "buffered",   chart_buffered_bytes);
+        rrddim_set(chart_bytes, "lost",       chart_lost_bytes);
+        rrddim_set(chart_bytes, "sent",       chart_sent_bytes);
+        rrddim_set(chart_bytes, "received",   chart_received_bytes);
+        rrdset_done(chart_bytes);
+
+        /*
+        if(likely(chart_latency->counter_done)) rrdset_next(chart_latency);
+        rrddim_set(chart_latency, "latency",  chart_backend_latency);
+        rrdset_done(chart_latency);
+        */
+
+        getrusage(RUSAGE_THREAD, &thread);
+        if(likely(chart_rusage->counter_done)) rrdset_next(chart_rusage);
+        rrddim_set(chart_rusage, "user",   thread.ru_utime.tv_sec * 1000000ULL + thread.ru_utime.tv_usec);
+        rrddim_set(chart_rusage, "system", thread.ru_stime.tv_sec * 1000000ULL + thread.ru_stime.tv_usec);
+        rrdset_done(chart_rusage);
+
+        if(likely(buffer_strlen(b) == 0))
+            chart_buffered_metrics = 0;
+
+        if(unlikely(netdata_exit)) break;
+    }
+
+cleanup:
+    if(sock != -1)
+        close(sock);
+
+    buffer_free(b);
+    buffer_free(response);
+
+    netdata_thread_cleanup_pop(1);
+    return NULL;
+}