# How to monitor Synapse metrics using Prometheus

1. Install Prometheus:

   Follow instructions at http://prometheus.io/docs/introduction/install/

2. Enable Synapse metrics:

   There are two methods of enabling metrics in Synapse.

   The first serves the metrics as a part of the usual web server and can be enabled by adding the "metrics" resource to the existing listener as such:

         resources:
           - names:
             - client
             - metrics

   This provides a simple way of adding metrics to your Synapse installation, and serves under `/_synapse/metrics`. If you do not wish your metrics be publicly exposed, you will need to either filter it out at your load balancer, or use the second method.

   The second method runs the metrics server on a different port, in a different thread to Synapse. This can make it more resilient to heavy load meaning metrics cannot be retrieved, and can be exposed to just internal networks easier. The served metrics are available over HTTP only, and will be available at `/_synapse/metrics`.

   Add a new listener to homeserver.yaml:

         listeners:
           - type: metrics
             port: 9000
             bind_addresses:
               - '0.0.0.0'

   For both options, you will need to ensure that `enable_metrics` is set to `True`.

3. Restart Synapse.

4. Add a Prometheus target for Synapse.

   It needs to set the `metrics_path` to a non-default value (under `scrape_configs`):

         - job_name: "synapse"
           scrape_interval: 15s
           metrics_path: "/_synapse/metrics"
           static_configs:
             - targets: ["my.server.here:port"]

   where `my.server.here` is the IP address of Synapse, and `port` is the listener port configured with the `metrics` resource.

   If your prometheus is older than 1.5.2, you will need to replace `static_configs` in the above with `target_groups`.

5. Restart Prometheus.

6. Consider using the grafana dashboard and required recording rules

## Monitoring workers

To monitor a Synapse installation using workers, every worker needs to be monitored independently, in addition to the main homeserver process. This is because workers don't send their metrics to the main homeserver process, but expose them directly (if they are configured to do so).

To allow collecting metrics from a worker, you need to add a `metrics` listener to its configuration, by adding the following under `worker_listeners`:

      - type: metrics
        bind_address: ''
        port: 9101

The `bind_address` and `port` parameters should be set so that the resulting listener can be reached by prometheus, and they don't clash with an existing worker. With this example, the worker's metrics would then be available on `http://127.0.0.1:9101`.

Example Prometheus target for Synapse with workers:

      - job_name: "synapse"
        scrape_interval: 15s
        metrics_path: "/_synapse/metrics"
        static_configs:
          - targets: ["my.server.here:port"]
            labels:
              instance: "my.server"
              job: "master"
              index: 1
          - targets: ["my.workerserver.here:port"]
            labels:
              instance: "my.server"
              job: "generic_worker"
              index: 1
          - targets: ["my.workerserver.here:port"]
            labels:
              instance: "my.server"
              job: "generic_worker"
              index: 2
          - targets: ["my.workerserver.here:port"]
            labels:
              instance: "my.server"
              job: "media_repository"
              index: 1

Labels (`instance`, `job`, `index`) can be defined as anything. The labels are used to group graphs in grafana.

## Renaming of metrics & deprecation of old names in 1.2

Synapse 1.2 updates the Prometheus metrics to match the naming convention of the upstream `prometheus_client`. The old names are considered deprecated and will be removed in a future version of Synapse.

New Name | Old Name
--- | ---
python_gc_objects_collected_total | python_gc_objects_collected
python_gc_objects_uncollectable_total | python_gc_objects_uncollectable
python_gc_collections_total | python_gc_collections
process_cpu_seconds_total | process_cpu_seconds
synapse_federation_client_sent_transactions_total | synapse_federation_client_sent_transactions
synapse_federation_client_events_processed_total | synapse_federation_client_events_processed
synapse_event_processing_loop_count_total | synapse_event_processing_loop_count
synapse_event_processing_loop_room_count_total | synapse_event_processing_loop_room_count
synapse_util_metrics_block_count_total | synapse_util_metrics_block_count
synapse_util_metrics_block_time_seconds_total | synapse_util_metrics_block_time_seconds
synapse_util_metrics_block_ru_utime_seconds_total | synapse_util_metrics_block_ru_utime_seconds
synapse_util_metrics_block_ru_stime_seconds_total | synapse_util_metrics_block_ru_stime_seconds
synapse_util_metrics_block_db_txn_count_total | synapse_util_metrics_block_db_txn_count
synapse_util_metrics_block_db_txn_duration_seconds_total | synapse_util_metrics_block_db_txn_duration_seconds
synapse_util_metrics_block_db_sched_duration_seconds_total | synapse_util_metrics_block_db_sched_duration_seconds
synapse_background_process_start_count_total | synapse_background_process_start_count
synapse_background_process_ru_utime_seconds_total | synapse_background_process_ru_utime_seconds
synapse_background_process_ru_stime_seconds_total | synapse_background_process_ru_stime_seconds
synapse_background_process_db_txn_count_total | synapse_background_process_db_txn_count
synapse_background_process_db_txn_duration_seconds_total | synapse_background_process_db_txn_duration_seconds
synapse_background_process_db_sched_duration_seconds_total | synapse_background_process_db_sched_duration_seconds
synapse_storage_events_persisted_events_total | synapse_storage_events_persisted_events
synapse_storage_events_persisted_events_sep_total | synapse_storage_events_persisted_events_sep
synapse_storage_events_state_delta_total | synapse_storage_events_state_delta
synapse_storage_events_state_delta_single_event_total | synapse_storage_events_state_delta_single_event
synapse_storage_events_state_delta_reuse_delta_total | synapse_storage_events_state_delta_reuse_delta
synapse_federation_server_received_pdus_total | synapse_federation_server_received_pdus
synapse_federation_server_received_edus_total | synapse_federation_server_received_edus
synapse_handler_presence_notified_presence_total | synapse_handler_presence_notified_presence
synapse_handler_presence_federation_presence_out_total | synapse_handler_presence_federation_presence_out
synapse_handler_presence_presence_updates_total | synapse_handler_presence_presence_updates
synapse_handler_presence_timers_fired_total | synapse_handler_presence_timers_fired
synapse_handler_presence_federation_presence_total | synapse_handler_presence_federation_presence
synapse_handler_presence_bump_active_time_total | synapse_handler_presence_bump_active_time
synapse_federation_client_sent_edus_total | synapse_federation_client_sent_edus
synapse_federation_client_sent_pdu_destinations_count_total | synapse_federation_client_sent_pdu_destinations:count
synapse_federation_client_sent_pdu_destinations_total | synapse_federation_client_sent_pdu_destinations:total
synapse_handlers_appservice_events_processed_total | synapse_handlers_appservice_events_processed
synapse_notifier_notified_events_total | synapse_notifier_notified_events
synapse_push_bulk_push_rule_evaluator_push_rules_invalidation_counter_total | synapse_push_bulk_push_rule_evaluator_push_rules_invalidation_counter
synapse_push_bulk_push_rule_evaluator_push_rules_state_size_counter_total | synapse_push_bulk_push_rule_evaluator_push_rules_state_size_counter
synapse_http_httppusher_http_pushes_processed_total | synapse_http_httppusher_http_pushes_processed
synapse_http_httppusher_http_pushes_failed_total | synapse_http_httppusher_http_pushes_failed
synapse_http_httppusher_badge_updates_processed_total | synapse_http_httppusher_badge_updates_processed
synapse_http_httppusher_badge_updates_failed_total | synapse_http_httppusher_badge_updates_failed

## Removal of deprecated metrics & time based counters becoming histograms in 0.31.0

The duplicated metrics deprecated in Synapse 0.27.0 have been removed.

All time duration-based metrics have been changed to be seconds. This affects:

msec -> sec metrics
python_gc_time
python_twisted_reactor_tick_time
synapse_storage_query_time
synapse_storage_schedule_time
synapse_storage_transaction_time

Several metrics have been changed to be histograms, which sort entries into buckets and allow better analysis. The following metrics are now histograms:

Altered metrics
python_gc_time
python_twisted_reactor_pending_calls
python_twisted_reactor_tick_time
synapse_http_server_response_time_seconds
synapse_storage_query_time
synapse_storage_schedule_time
synapse_storage_transaction_time

## Block and response metrics renamed for 0.27.0

Synapse 0.27.0 begins the process of rationalising the duplicate `*:count` metrics reported for the resource tracking for code blocks and HTTP requests.

At the same time, the corresponding `*:total` metrics are being renamed, as the `:total` suffix no longer makes sense in the absence of a corresponding `:count` metric.

To enable a graceful migration path, this release just adds new names for the metrics being renamed. A future release will remove the old ones.

The following table shows the new metrics, and the old metrics which they are replacing.

New name | Old name
--- | ---
synapse_util_metrics_block_count | synapse_util_metrics_block_timer:count
synapse_util_metrics_block_count | synapse_util_metrics_block_ru_utime:count
synapse_util_metrics_block_count | synapse_util_metrics_block_ru_stime:count
synapse_util_metrics_block_count | synapse_util_metrics_block_db_txn_count:count
synapse_util_metrics_block_count | synapse_util_metrics_block_db_txn_duration:count
synapse_util_metrics_block_time_seconds | synapse_util_metrics_block_timer:total
synapse_util_metrics_block_ru_utime_seconds | synapse_util_metrics_block_ru_utime:total
synapse_util_metrics_block_ru_stime_seconds | synapse_util_metrics_block_ru_stime:total
synapse_util_metrics_block_db_txn_count | synapse_util_metrics_block_db_txn_count:total
synapse_util_metrics_block_db_txn_duration_seconds | synapse_util_metrics_block_db_txn_duration:total
synapse_http_server_response_count | synapse_http_server_requests
synapse_http_server_response_count | synapse_http_server_response_time:count
synapse_http_server_response_count | synapse_http_server_response_ru_utime:count
synapse_http_server_response_count | synapse_http_server_response_ru_stime:count
synapse_http_server_response_count | synapse_http_server_response_db_txn_count:count
synapse_http_server_response_count | synapse_http_server_response_db_txn_duration:count
synapse_http_server_response_time_seconds | synapse_http_server_response_time:total
synapse_http_server_response_ru_utime_seconds | synapse_http_server_response_ru_utime:total
synapse_http_server_response_ru_stime_seconds | synapse_http_server_response_ru_stime:total
synapse_http_server_response_db_txn_count | synapse_http_server_response_db_txn_count:total
synapse_http_server_response_db_txn_duration_seconds | synapse_http_server_response_db_txn_duration:total

## Standard Metric Names

As of synapse version 0.18.2, the format of the process-wide metrics has been changed to fit prometheus standard naming conventions. Additionally the units have been changed to seconds, from miliseconds.

New name | Old name
--- | ---
process_cpu_user_seconds_total | process_resource_utime / 1000
process_cpu_system_seconds_total | process_resource_stime / 1000
process_open_fds (no 'type' label) | process_fds

The python-specific counts of garbage collector performance have been renamed.

New name | Old name
--- | ---
python_gc_time | reactor_gc_time
python_gc_unreachable_total | reactor_gc_unreachable
python_gc_counts | reactor_gc_counts

The twisted-specific reactor metrics have been renamed.

New name | Old name
--- | ---
python_twisted_reactor_pending_calls | reactor_pending_calls
python_twisted_reactor_tick_time | reactor_tick_time