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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 /.

    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.

    Restart Synapse.

  3. Add a Prometheus target for Synapse.

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

    - job_name: "synapse"
  metrics_path: "/_synapse/metrics"
  static_configs:
    - targets: ["my.server.here:9092"]

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

    Restart Prometheus.

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