Adding upstream version 1.29.0.upstream/1.29.0

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

1 files changed, 916 insertions, 0 deletions

diff --git a/exporting/prometheus/prometheus.c b/exporting/prometheus/prometheus.c
new file mode 100644
index 00000000..371f5a52
--- /dev/null
+++ b/exporting/prometheus/prometheus.c
@@ -0,0 +1,916 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#define EXPORTINGS_INTERNALS
+#include "prometheus.h"
+
+// ----------------------------------------------------------------------------
+// PROMETHEUS
+// /api/v1/allmetrics?format=prometheus and /api/v1/allmetrics?format=prometheus_all_hosts
+
+/**
+ * Check if a chart can be sent to Prometheus
+ *
+ * @param instance an instance data structure.
+ * @param st a chart.
+ * @return Returns 1 if the chart can be sent, 0 otherwise.
+ */
+inline int can_send_rrdset(struct instance *instance, RRDSET *st)
+{
+    RRDHOST *host = st->rrdhost;
+
+    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(instance->config.charts_pattern, st->id) ||
+            simple_pattern_matches(instance->config.charts_pattern, st->name))
+            rrdset_flag_set(st, RRDSET_FLAG_BACKEND_SEND);
+        else {
+            rrdset_flag_set(st, RRDSET_FLAG_BACKEND_IGNORE);
+            debug(
+                D_BACKEND,
+                "EXPORTING: not sending chart '%s' of host '%s', because it is disabled for exporting.",
+                st->id,
+                host->hostname);
+            return 0;
+        }
+    }
+
+    if (unlikely(!rrdset_is_available_for_backends(st))) {
+        debug(
+            D_BACKEND,
+            "EXPORTING: not sending chart '%s' of host '%s', because it is not available for exporting.",
+            st->id,
+            host->hostname);
+        return 0;
+    }
+
+    if (unlikely(
+            st->rrd_memory_mode == RRD_MEMORY_MODE_NONE &&
+            !(EXPORTING_OPTIONS_DATA_SOURCE(instance->config.options) == EXPORTING_SOURCE_DATA_AS_COLLECTED))) {
+        debug(
+            D_BACKEND,
+            "EXPORTING: not sending chart '%s' of host '%s' because its memory mode is '%s' and the exporting connector requires database access.",
+            st->id,
+            host->hostname,
+            rrd_memory_mode_name(host->rrd_memory_mode));
+        return 0;
+    }
+
+    return 1;
+}
+
+static struct prometheus_server {
+    const char *server;
+    uint32_t hash;
+    RRDHOST *host;
+    time_t last_access;
+    struct prometheus_server *next;
+} *prometheus_server_root = NULL;
+
+static netdata_mutex_t prometheus_server_root_mutex = NETDATA_MUTEX_INITIALIZER;
+
+/**
+ * Clean server root local structure
+ */
+void prometheus_clean_server_root()
+{
+    if (prometheus_server_root) {
+        netdata_mutex_lock(&prometheus_server_root_mutex);
+
+        struct prometheus_server *ps;
+        for (ps = prometheus_server_root; ps; ) {
+            struct prometheus_server *current = ps;
+            ps = ps->next;
+            if(current->server)
+                freez((void *)current->server);
+
+            freez(current);
+        }
+        prometheus_server_root = NULL;
+        netdata_mutex_unlock(&prometheus_server_root_mutex);
+    }
+}
+
+/**
+ * Get the last time when a Prometheus server scraped the Netdata Prometheus exporter.
+ *
+ * @param server the name of the Prometheus server.
+ * @param host a data collecting host.
+ * @param now actual time.
+ * @return Returns the last time when the server accessed Netdata, or 0 if it is the first occurrence.
+ */
+static inline time_t prometheus_server_last_access(const char *server, RRDHOST *host, time_t now)
+{
+#ifdef UNIT_TESTING
+    return 0;
+#endif
+    uint32_t hash = simple_hash(server);
+
+    netdata_mutex_lock(&prometheus_server_root_mutex);
+
+    struct prometheus_server *ps;
+    for (ps = prometheus_server_root; ps; ps = ps->next) {
+        if (host == ps->host && hash == ps->hash && !strcmp(server, ps->server)) {
+            time_t last = ps->last_access;
+            ps->last_access = now;
+            netdata_mutex_unlock(&prometheus_server_root_mutex);
+            return last;
+        }
+    }
+
+    ps = callocz(1, sizeof(struct prometheus_server));
+    ps->server = strdupz(server);
+    ps->hash = hash;
+    ps->host = host;
+    ps->last_access = now;
+    ps->next = prometheus_server_root;
+    prometheus_server_root = ps;
+
+    netdata_mutex_unlock(&prometheus_server_root_mutex);
+    return 0;
+}
+
+/**
+ * Copy and sanitize name.
+ *
+ * @param d a destination string.
+ * @param s a source sting.
+ * @param usable the number of characters to copy.
+ * @return Returns the length of the copied string.
+ */
+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;
+}
+
+/**
+ * Copy and sanitize label.
+ *
+ * @param d a destination string.
+ * @param s a source sting.
+ * @param usable the number of characters to copy.
+ * @return Returns the length of the copied string.
+ */
+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;
+}
+
+/**
+ * Copy and sanitize units.
+ *
+ * @param d a destination string.
+ * @param s a source sting.
+ * @param usable the number of characters to copy.
+ * @param showoldunits set this flag to 1 to show old (before v1.12) units.
+ * @return Returns the destination string.
+ */
+inline char *prometheus_units_copy(char *d, const char *s, size_t usable, int showoldunits)
+{
+    const char *sorig = s;
+    char *ret = d;
+    size_t n;
+
+    // Fix for issue 5227
+    if (unlikely(showoldunits)) {
+        static struct {
+            const char *newunit;
+            uint32_t hash;
+            const char *oldunit;
+        } units[] = { { "KiB/s", 0, "kilobytes/s" },
+                      { "MiB/s", 0, "MB/s" },
+                      { "GiB/s", 0, "GB/s" },
+                      { "KiB", 0, "KB" },
+                      { "MiB", 0, "MB" },
+                      { "GiB", 0, "GB" },
+                      { "inodes", 0, "Inodes" },
+                      { "percentage", 0, "percent" },
+                      { "faults/s", 0, "page faults/s" },
+                      { "KiB/operation", 0, "kilobytes per operation" },
+                      { "milliseconds/operation", 0, "ms per operation" },
+                      { NULL, 0, NULL } };
+        static int initialized = 0;
+        int i;
+
+        if (unlikely(!initialized)) {
+            for (i = 0; units[i].newunit; i++)
+                units[i].hash = simple_hash(units[i].newunit);
+            initialized = 1;
+        }
+
+        uint32_t hash = simple_hash(s);
+        for (i = 0; units[i].newunit; i++) {
+            if (unlikely(hash == units[i].hash && !strcmp(s, units[i].newunit))) {
+                // info("matched extension for filename '%s': '%s'", filename, last_dot);
+                s = units[i].oldunit;
+                sorig = s;
+                break;
+            }
+        }
+    }
+    *d++ = '_';
+    for (n = 1; *s && n < usable; d++, s++, n++) {
+        register char c = *s;
+
+        if (!isalnum(c))
+            *d = '_';
+        else
+            *d = c;
+    }
+
+    if (n == 2 && sorig[0] == '%') {
+        n = 0;
+        d = ret;
+        s = "_percent";
+        for (; *s && n < usable; n++)
+            *d++ = *s++;
+    } else if (n > 3 && sorig[n - 3] == '/' && sorig[n - 2] == 's') {
+        n = n - 2;
+        d -= 2;
+        s = "_persec";
+        for (; *s && n < usable; n++)
+            *d++ = *s++;
+    }
+
+    *d = '\0';
+
+    return ret;
+}
+
+/**
+ * Format host labels for the Prometheus exporter
+ *
+ * @param instance an instance data structure.
+ * @param host a data collecting host.
+ */
+void format_host_labels_prometheus(struct instance *instance, RRDHOST *host)
+{
+    if (unlikely(!sending_labels_configured(instance)))
+        return;
+
+    if (!instance->labels)
+        instance->labels = buffer_create(1024);
+
+    int count = 0;
+    rrdhost_check_rdlock(host);
+    netdata_rwlock_rdlock(&host->labels.labels_rwlock);
+    for (struct label *label = host->labels.head; label; label = label->next) {
+        if (!should_send_label(instance, label))
+            continue;
+
+        char key[PROMETHEUS_ELEMENT_MAX + 1];
+        char value[PROMETHEUS_ELEMENT_MAX + 1];
+
+        prometheus_name_copy(key, label->key, PROMETHEUS_ELEMENT_MAX);
+        prometheus_label_copy(value, label->value, PROMETHEUS_ELEMENT_MAX);
+
+        if (*key && *value) {
+            if (count > 0)
+                buffer_strcat(instance->labels, ",");
+            buffer_sprintf(instance->labels, "%s=\"%s\"", key, value);
+            count++;
+        }
+    }
+    netdata_rwlock_unlock(&host->labels.labels_rwlock);
+}
+
+struct host_variables_callback_options {
+    RRDHOST *host;
+    BUFFER *wb;
+    EXPORTING_OPTIONS exporting_options;
+    PROMETHEUS_OUTPUT_OPTIONS output_options;
+    const char *prefix;
+    const char *labels;
+    time_t now;
+    int host_header_printed;
+    char name[PROMETHEUS_VARIABLE_MAX + 1];
+};
+
+/**
+ * Print host variables.
+ *
+ * @param rv a variable.
+ * @param data callback options.
+ * @return Returns 1 if the chart can be sent, 0 otherwise.
+ */
+static int print_host_variables(RRDVAR *rv, void *data)
+{
+    struct host_variables_callback_options *opts = data;
+
+    if (rv->options & (RRDVAR_OPTION_CUSTOM_HOST_VAR | RRDVAR_OPTION_CUSTOM_CHART_VAR)) {
+        if (!opts->host_header_printed) {
+            opts->host_header_printed = 1;
+
+            if (opts->output_options & PROMETHEUS_OUTPUT_HELP) {
+                buffer_sprintf(opts->wb, "\n# COMMENT global host and chart variables\n");
+            }
+        }
+
+        calculated_number value = rrdvar2number(rv);
+        if (isnan(value) || isinf(value)) {
+            if (opts->output_options & PROMETHEUS_OUTPUT_HELP)
+                buffer_sprintf(
+                    opts->wb, "# COMMENT variable \"%s\" is %s. Skipped.\n", rv->name, (isnan(value)) ? "NAN" : "INF");
+
+            return 0;
+        }
+
+        char *label_pre = "";
+        char *label_post = "";
+        if (opts->labels && *opts->labels) {
+            label_pre = "{";
+            label_post = "}";
+        }
+
+        prometheus_name_copy(opts->name, rv->name, sizeof(opts->name));
+
+        if (opts->output_options & PROMETHEUS_OUTPUT_TIMESTAMPS)
+            buffer_sprintf(
+                opts->wb,
+                "%s_%s%s%s%s " CALCULATED_NUMBER_FORMAT " %llu\n",
+                opts->prefix,
+                opts->name,
+                label_pre,
+                opts->labels,
+                label_post,
+                value,
+                opts->now * 1000ULL);
+        else
+            buffer_sprintf(
+                opts->wb,
+                "%s_%s%s%s%s " CALCULATED_NUMBER_FORMAT "\n",
+                opts->prefix,
+                opts->name,
+                label_pre,
+                opts->labels,
+                label_post,
+                value);
+
+        return 1;
+    }
+
+    return 0;
+}
+
+struct gen_parameters {
+    const char *prefix;
+    char *context;
+    char *suffix;
+
+    char *chart;
+    char *dimension;
+    char *family;
+    char *labels;
+
+    PROMETHEUS_OUTPUT_OPTIONS output_options;
+    RRDSET *st;
+    RRDDIM *rd;
+
+    const char *relation;
+    const char *type;
+};
+
+/**
+ * Write an as-collected help comment to a buffer.
+ *
+ * @param wb the buffer to write the comment to.
+ * @param p parameters for generating the comment string.
+ * @param homogeneous a flag for homogeneous charts.
+ * @param prometheus_collector a flag for metrics from prometheus collector.
+ */
+static void generate_as_collected_prom_help(BUFFER *wb, struct gen_parameters *p, int homogeneous, int prometheus_collector)
+{
+    buffer_sprintf(wb, "# COMMENT %s_%s", p->prefix, p->context);
+
+    if (!homogeneous)
+        buffer_sprintf(wb, "_%s", p->dimension);
+
+    buffer_sprintf(
+        wb,
+        "%s: chart \"%s\", context \"%s\", family \"%s\", dimension \"%s\", value * ",
+        p->suffix,
+        (p->output_options & PROMETHEUS_OUTPUT_NAMES && p->st->name) ? p->st->name : p->st->id,
+        p->st->context,
+        p->st->family,
+        (p->output_options & PROMETHEUS_OUTPUT_NAMES && p->rd->name) ? p->rd->name : p->rd->id);
+
+    if (prometheus_collector)
+        buffer_sprintf(wb, "1 / 1");
+    else
+        buffer_sprintf(wb, COLLECTED_NUMBER_FORMAT " / " COLLECTED_NUMBER_FORMAT, p->rd->multiplier, p->rd->divisor);
+
+    buffer_sprintf(wb, " %s %s (%s)\n", p->relation, p->st->units, p->type);
+}
+
+/**
+ * Write an as-collected metric to a buffer.
+ *
+ * @param wb the buffer to write the metric to.
+ * @param p parameters for generating the metric string.
+ * @param homogeneous a flag for homogeneous charts.
+ * @param prometheus_collector a flag for metrics from prometheus collector.
+ */
+static void generate_as_collected_prom_metric(BUFFER *wb, struct gen_parameters *p, int homogeneous, int prometheus_collector)
+{
+    buffer_sprintf(wb, "%s_%s", p->prefix, p->context);
+
+    if (!homogeneous)
+        buffer_sprintf(wb, "_%s", p->dimension);
+
+    buffer_sprintf(wb, "%s{chart=\"%s\",family=\"%s\"", p->suffix, p->chart, p->family);
+
+    if (homogeneous)
+        buffer_sprintf(wb, ",dimension=\"%s\"", p->dimension);
+
+    buffer_sprintf(wb, "%s} ", p->labels);
+
+    if (prometheus_collector)
+        buffer_sprintf(
+            wb,
+            CALCULATED_NUMBER_FORMAT,
+            (calculated_number)p->rd->last_collected_value * (calculated_number)p->rd->multiplier /
+                (calculated_number)p->rd->divisor);
+    else
+        buffer_sprintf(wb, COLLECTED_NUMBER_FORMAT, p->rd->last_collected_value);
+
+    if (p->output_options & PROMETHEUS_OUTPUT_TIMESTAMPS)
+        buffer_sprintf(wb, " %llu\n", timeval_msec(&p->rd->last_collected_time));
+    else
+        buffer_sprintf(wb, "\n");
+}
+
+/**
+ * Write metrics in Prometheus format to a buffer.
+ *
+ * @param instance an instance data structure.
+ * @param host a data collecting host.
+ * @param wb the buffer to fill with metrics.
+ * @param prefix a prefix for every metric.
+ * @param exporting_options options to configure what data is exported.
+ * @param allhosts set to 1 if host instance should be in the output for tags.
+ * @param output_options options to configure the format of the output.
+ */
+static void rrd_stats_api_v1_charts_allmetrics_prometheus(
+    struct instance *instance,
+    RRDHOST *host,
+    BUFFER *wb,
+    const char *prefix,
+    EXPORTING_OPTIONS exporting_options,
+    int allhosts,
+    PROMETHEUS_OUTPUT_OPTIONS output_options)
+{
+    rrdhost_rdlock(host);
+
+    char hostname[PROMETHEUS_ELEMENT_MAX + 1];
+    prometheus_label_copy(hostname, host->hostname, PROMETHEUS_ELEMENT_MAX);
+
+    format_host_labels_prometheus(instance, host);
+
+    if (output_options & PROMETHEUS_OUTPUT_TIMESTAMPS)
+        buffer_sprintf(
+            wb,
+            "netdata_info{instance=\"%s\",application=\"%s\",version=\"%s\"} 1 %llu\n",
+            hostname,
+            host->program_name,
+            host->program_version,
+            now_realtime_usec() / USEC_PER_MS);
+    else
+        buffer_sprintf(
+            wb,
+            "netdata_info{instance=\"%s\",application=\"%s\",version=\"%s\"} 1\n",
+            hostname,
+            host->program_name,
+            host->program_version);
+
+    char labels[PROMETHEUS_LABELS_MAX + 1] = "";
+    if (allhosts) {
+        if (instance->labels && buffer_tostring(instance->labels)) {
+            if (output_options & PROMETHEUS_OUTPUT_TIMESTAMPS) {
+                buffer_sprintf(
+                    wb,
+                    "netdata_host_tags_info{instance=\"%s\",%s} 1 %llu\n",
+                    hostname,
+                    buffer_tostring(instance->labels),
+                    now_realtime_usec() / USEC_PER_MS);
+
+                // deprecated, exists only for compatibility with older queries
+                buffer_sprintf(
+                    wb,
+                    "netdata_host_tags{instance=\"%s\",%s} 1 %llu\n",
+                    hostname,
+                    buffer_tostring(instance->labels),
+                    now_realtime_usec() / USEC_PER_MS);
+            } else {
+                buffer_sprintf(
+                    wb, "netdata_host_tags_info{instance=\"%s\",%s} 1\n", hostname, buffer_tostring(instance->labels));
+
+                // deprecated, exists only for compatibility with older queries
+                buffer_sprintf(
+                    wb, "netdata_host_tags{instance=\"%s\",%s} 1\n", hostname, buffer_tostring(instance->labels));
+            }
+        }
+
+        snprintfz(labels, PROMETHEUS_LABELS_MAX, ",instance=\"%s\"", hostname);
+    } else {
+        if (instance->labels && buffer_tostring(instance->labels)) {
+            if (output_options & PROMETHEUS_OUTPUT_TIMESTAMPS) {
+                buffer_sprintf(
+                    wb,
+                    "netdata_host_tags_info{%s} 1 %llu\n",
+                    buffer_tostring(instance->labels),
+                    now_realtime_usec() / USEC_PER_MS);
+
+                // deprecated, exists only for compatibility with older queries
+                buffer_sprintf(
+                    wb,
+                    "netdata_host_tags{%s} 1 %llu\n",
+                    buffer_tostring(instance->labels),
+                    now_realtime_usec() / USEC_PER_MS);
+            } else {
+                buffer_sprintf(wb, "netdata_host_tags_info{%s} 1\n", buffer_tostring(instance->labels));
+
+                // deprecated, exists only for compatibility with older queries
+                buffer_sprintf(wb, "netdata_host_tags{%s} 1\n", buffer_tostring(instance->labels));
+            }
+        }
+    }
+
+    if (instance->labels)
+        buffer_flush(instance->labels);
+
+    // send custom variables set for the host
+    if (output_options & PROMETHEUS_OUTPUT_VARIABLES) {
+        struct host_variables_callback_options opts = { .host = host,
+                                                        .wb = wb,
+                                                        .labels = (labels[0] == ',') ? &labels[1] : labels,
+                                                        .exporting_options = exporting_options,
+                                                        .output_options = output_options,
+                                                        .prefix = prefix,
+                                                        .now = now_realtime_sec(),
+                                                        .host_header_printed = 0 };
+        foreach_host_variable_callback(host, print_host_variables, &opts);
+    }
+
+    // for each chart
+    RRDSET *st;
+    rrdset_foreach_read(st, host)
+    {
+
+        if (likely(can_send_rrdset(instance, st))) {
+            rrdset_rdlock(st);
+
+            char chart[PROMETHEUS_ELEMENT_MAX + 1];
+            char context[PROMETHEUS_ELEMENT_MAX + 1];
+            char family[PROMETHEUS_ELEMENT_MAX + 1];
+            char units[PROMETHEUS_ELEMENT_MAX + 1] = "";
+
+            prometheus_label_copy(
+                chart, (output_options & PROMETHEUS_OUTPUT_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);
+
+            int as_collected = (EXPORTING_OPTIONS_DATA_SOURCE(exporting_options) == EXPORTING_SOURCE_DATA_AS_COLLECTED);
+            int homogeneous = 1;
+            int prometheus_collector = 0;
+            if (as_collected) {
+                if (rrdset_flag_check(st, RRDSET_FLAG_HOMOGENEOUS_CHECK))
+                    rrdset_update_heterogeneous_flag(st);
+
+                if (rrdset_flag_check(st, RRDSET_FLAG_HETEROGENEOUS))
+                    homogeneous = 0;
+
+                if (st->module_name && !strcmp(st->module_name, "prometheus"))
+                    prometheus_collector = 1;
+            } else {
+                if (EXPORTING_OPTIONS_DATA_SOURCE(exporting_options) == EXPORTING_SOURCE_DATA_AVERAGE &&
+                    !(output_options & PROMETHEUS_OUTPUT_HIDEUNITS))
+                    prometheus_units_copy(
+                        units, st->units, PROMETHEUS_ELEMENT_MAX, output_options & PROMETHEUS_OUTPUT_OLDUNITS);
+            }
+
+            if (unlikely(output_options & PROMETHEUS_OUTPUT_HELP))
+                buffer_sprintf(
+                    wb,
+                    "\n# COMMENT %s chart \"%s\", context \"%s\", family \"%s\", units \"%s\"\n",
+                    (homogeneous) ? "homogeneous" : "heterogeneous",
+                    (output_options & PROMETHEUS_OUTPUT_NAMES && st->name) ? st->name : st->id,
+                    st->context,
+                    st->family,
+                    st->units);
+
+            // for each dimension
+            RRDDIM *rd;
+            rrddim_foreach_read(rd, st)
+            {
+                if (rd->collections_counter && !rrddim_flag_check(rd, RRDDIM_FLAG_OBSOLETE)) {
+                    char dimension[PROMETHEUS_ELEMENT_MAX + 1];
+                    char *suffix = "";
+
+                    if (as_collected) {
+                        // we need as-collected / raw data
+
+                        struct gen_parameters p;
+                        p.prefix = prefix;
+                        p.context = context;
+                        p.suffix = suffix;
+                        p.chart = chart;
+                        p.dimension = dimension;
+                        p.family = family;
+                        p.labels = labels;
+                        p.output_options = output_options;
+                        p.st = st;
+                        p.rd = rd;
+
+                        if (unlikely(rd->last_collected_time.tv_sec < instance->after))
+                            continue;
+
+                        p.type = "gauge";
+                        p.relation = "gives";
+                        if (rd->algorithm == RRD_ALGORITHM_INCREMENTAL ||
+                            rd->algorithm == RRD_ALGORITHM_PCENT_OVER_DIFF_TOTAL) {
+                            p.type = "counter";
+                            p.relation = "delta gives";
+                            p.suffix = "_total";
+                        }
+
+                        if (homogeneous) {
+                            // all the dimensions of the chart, has the same algorithm, multiplier and divisor
+                            // we add all dimensions as labels
+
+                            prometheus_label_copy(
+                                dimension,
+                                (output_options & PROMETHEUS_OUTPUT_NAMES && rd->name) ? rd->name : rd->id,
+                                PROMETHEUS_ELEMENT_MAX);
+
+                            if (unlikely(output_options & PROMETHEUS_OUTPUT_HELP))
+                                generate_as_collected_prom_help(wb, &p, homogeneous, prometheus_collector);
+
+                            if (unlikely(output_options & PROMETHEUS_OUTPUT_TYPES))
+                                buffer_sprintf(wb, "# TYPE %s_%s%s %s\n", prefix, context, suffix, p.type);
+
+                            generate_as_collected_prom_metric(wb, &p, homogeneous, prometheus_collector);
+                        } else {
+                            // the dimensions of the chart, do not have the same algorithm, multiplier or divisor
+                            // we create a metric per dimension
+
+                            prometheus_name_copy(
+                                dimension,
+                                (output_options & PROMETHEUS_OUTPUT_NAMES && rd->name) ? rd->name : rd->id,
+                                PROMETHEUS_ELEMENT_MAX);
+
+                            if (unlikely(output_options & PROMETHEUS_OUTPUT_HELP))
+                                generate_as_collected_prom_help(wb, &p, homogeneous, prometheus_collector);
+
+                            if (unlikely(output_options & PROMETHEUS_OUTPUT_TYPES))
+                                buffer_sprintf(
+                                    wb, "# TYPE %s_%s_%s%s %s\n", prefix, context, dimension, suffix, p.type);
+
+                            generate_as_collected_prom_metric(wb, &p, homogeneous, prometheus_collector);
+                        }
+                    } else {
+                        // we need average or sum of the data
+
+                        time_t first_time = instance->after;
+                        time_t last_time = instance->before;
+                        calculated_number value = exporting_calculate_value_from_stored_data(instance, rd, &last_time);
+
+                        if (!isnan(value) && !isinf(value)) {
+                            if (EXPORTING_OPTIONS_DATA_SOURCE(exporting_options) == EXPORTING_SOURCE_DATA_AVERAGE)
+                                suffix = "_average";
+                            else if (EXPORTING_OPTIONS_DATA_SOURCE(exporting_options) == EXPORTING_SOURCE_DATA_SUM)
+                                suffix = "_sum";
+
+                            prometheus_label_copy(
+                                dimension,
+                                (output_options & PROMETHEUS_OUTPUT_NAMES && rd->name) ? rd->name : rd->id,
+                                PROMETHEUS_ELEMENT_MAX);
+
+                            if (unlikely(output_options & PROMETHEUS_OUTPUT_HELP))
+                                buffer_sprintf(
+                                    wb,
+                                    "# COMMENT %s_%s%s%s: dimension \"%s\", value is %s, gauge, dt %llu to %llu inclusive\n",
+                                    prefix,
+                                    context,
+                                    units,
+                                    suffix,
+                                    (output_options & PROMETHEUS_OUTPUT_NAMES && rd->name) ? rd->name : rd->id,
+                                    st->units,
+                                    (unsigned long long)first_time,
+                                    (unsigned long long)last_time);
+
+                            if (unlikely(output_options & PROMETHEUS_OUTPUT_TYPES))
+                                buffer_sprintf(wb, "# TYPE %s_%s%s%s gauge\n", prefix, context, units, suffix);
+
+                            if (output_options & PROMETHEUS_OUTPUT_TIMESTAMPS)
+                                buffer_sprintf(
+                                    wb,
+                                    "%s_%s%s%s{chart=\"%s\",family=\"%s\",dimension=\"%s\"%s} " CALCULATED_NUMBER_FORMAT
+                                    " %llu\n",
+                                    prefix,
+                                    context,
+                                    units,
+                                    suffix,
+                                    chart,
+                                    family,
+                                    dimension,
+                                    labels,
+                                    value,
+                                    last_time * MSEC_PER_SEC);
+                            else
+                                buffer_sprintf(
+                                    wb,
+                                    "%s_%s%s%s{chart=\"%s\",family=\"%s\",dimension=\"%s\"%s} " CALCULATED_NUMBER_FORMAT
+                                    "\n",
+                                    prefix,
+                                    context,
+                                    units,
+                                    suffix,
+                                    chart,
+                                    family,
+                                    dimension,
+                                    labels,
+                                    value);
+                        }
+                    }
+                }
+            }
+
+            rrdset_unlock(st);
+        }
+    }
+
+    rrdhost_unlock(host);
+}
+
+/**
+ * Get the last time time when a server accessed Netdata. Write information about an API request to a buffer.
+ *
+ * @param instance an instance data structure.
+ * @param host a data collecting host.
+ * @param wb the buffer to write to.
+ * @param exporting_options options to configure what data is exported.
+ * @param server the name of a Prometheus server..
+ * @param now actual time.
+ * @param output_options options to configure the format of the output.
+ * @return Returns the last time when the server accessed Netdata.
+ */
+static inline time_t prometheus_preparation(
+    struct instance *instance,
+    RRDHOST *host,
+    BUFFER *wb,
+    EXPORTING_OPTIONS exporting_options,
+    const char *server,
+    time_t now,
+    PROMETHEUS_OUTPUT_OPTIONS output_options)
+{
+    if (!server || !*server)
+        server = "default";
+
+    time_t after = prometheus_server_last_access(server, host, now);
+
+    int first_seen = 0;
+    if (!after) {
+        after = now - instance->config.update_every;
+        first_seen = 1;
+    }
+
+    if (after > now) {
+        // oops! this should never happen
+        after = now - instance->config.update_every;
+    }
+
+    if (output_options & PROMETHEUS_OUTPUT_HELP) {
+        char *mode;
+        if (EXPORTING_OPTIONS_DATA_SOURCE(exporting_options) == EXPORTING_SOURCE_DATA_AS_COLLECTED)
+            mode = "as collected";
+        else if (EXPORTING_OPTIONS_DATA_SOURCE(exporting_options) == EXPORTING_SOURCE_DATA_AVERAGE)
+            mode = "average";
+        else if (EXPORTING_OPTIONS_DATA_SOURCE(exporting_options) == EXPORTING_SOURCE_DATA_SUM)
+            mode = "sum";
+        else
+            mode = "unknown";
+
+        buffer_sprintf(
+            wb,
+            "# COMMENT netdata \"%s\" to %sprometheus \"%s\", source \"%s\", last seen %lu %s, time range %lu to %lu\n\n",
+            host->hostname,
+            (first_seen) ? "FIRST SEEN " : "",
+            server,
+            mode,
+            (unsigned long)((first_seen) ? 0 : (now - after)),
+            (first_seen) ? "never" : "seconds ago",
+            (unsigned long)after,
+            (unsigned long)now);
+    }
+
+    return after;
+}
+
+/**
+ * Write metrics and auxiliary information for one host to a buffer.
+ *
+ * @param host a data collecting host.
+ * @param wb the buffer to write to.
+ * @param server the name of a Prometheus server.
+ * @param prefix a prefix for every metric.
+ * @param exporting_options options to configure what data is exported.
+ * @param output_options options to configure the format of the output.
+ */
+void rrd_stats_api_v1_charts_allmetrics_prometheus_single_host(
+    RRDHOST *host,
+    BUFFER *wb,
+    const char *server,
+    const char *prefix,
+    EXPORTING_OPTIONS exporting_options,
+    PROMETHEUS_OUTPUT_OPTIONS output_options)
+{
+    if (unlikely(!prometheus_exporter_instance))
+        return;
+
+    prometheus_exporter_instance->before = now_realtime_sec();
+
+    // we start at the point we had stopped before
+    prometheus_exporter_instance->after = prometheus_preparation(
+        prometheus_exporter_instance,
+        host,
+        wb,
+        exporting_options,
+        server,
+        prometheus_exporter_instance->before,
+        output_options);
+
+    rrd_stats_api_v1_charts_allmetrics_prometheus(
+        prometheus_exporter_instance, host, wb, prefix, exporting_options, 0, output_options);
+}
+
+/**
+ * Write metrics and auxiliary information for all hosts to a buffer.
+ *
+ * @param host a data collecting host.
+ * @param wb the buffer to write to.
+ * @param server the name of a Prometheus server.
+ * @param prefix a prefix for every metric.
+ * @param exporting_options options to configure what data is exported.
+ * @param output_options options to configure the format of the output.
+ */
+void rrd_stats_api_v1_charts_allmetrics_prometheus_all_hosts(
+    RRDHOST *host,
+    BUFFER *wb,
+    const char *server,
+    const char *prefix,
+    EXPORTING_OPTIONS exporting_options,
+    PROMETHEUS_OUTPUT_OPTIONS output_options)
+{
+    if (unlikely(!prometheus_exporter_instance))
+        return;
+
+    prometheus_exporter_instance->before = now_realtime_sec();
+
+    // we start at the point we had stopped before
+    prometheus_exporter_instance->after = prometheus_preparation(
+        prometheus_exporter_instance,
+        host,
+        wb,
+        exporting_options,
+        server,
+        prometheus_exporter_instance->before,
+        output_options);
+
+    rrd_rdlock();
+    rrdhost_foreach_read(host)
+    {
+        rrd_stats_api_v1_charts_allmetrics_prometheus(
+            prometheus_exporter_instance, host, wb, prefix, exporting_options, 1, output_options);
+    }
+    rrd_unlock();
+}