Exometer InfluxDB reporter

This reporter pushes data to InfluxDB.

Usage

1. Add exometer_influxdb to your list of dependencies in rebar.config:

   {deps, [
       {exometer_influxdb, ".*", {git, "https://github.com/travelping/exometer_influxdb.git", "master"}}
   ]}.

2. Ensure exometer_influxdb is started before your application:

   {applications, [exometer_influxdb]}.

3. Configure it:

   {exometer, 
       {reporters, [
           {exometer_report_influxdb, [{protocol, http}, 
                                       {host, <<"localhost">>},
                                       {port, 8086},
                                       {db, <<"exometer">>},
                                       {tags, [{region, ru}]}]}
       ]}
   }.

Available options:

• host - InfluxDB host. 127.0.0.1 by default.
• protocol - http or udp for operating with InfluxDB. http by default.
• port - InfluxDB port. 8086 by default.
• db - Database on InfluxDB for writing data. exometer by default.
• username - Username for authorization on InfluxDB.
• password - Password for authorization on InfluxDB.
• timestamping - Enable timestamping, false by default. To enable timestamping with the reporter you can use true or {true, Precision} where Precision is a unit taken from [n,u,ms,s,m,h]. The default unit is u.
• batch_window_size - set window size in ms for batch sending. This means the reporter will collect measurements within this interval and send all measurements in one packet. 0 by default.

The following options can be set globally in the reporter config or locally in a specific subscription. The latter case overwrites the first.

• tags - List of tags for each time series. The host is automatically included here.
• series_name - The name of a time series visible within the FROM field. By default this is set to the concatenated elements of the exometer id. Caution: If set in the global reporter config then every time series will have this name.
• formatting - Formatting options to alter the appearance of a series name or tags.

Subscription examples:

{exometer, 
    {subscriptions, [
         {exometer_report_influxdb, [erlang, memory], total, 5000, [{tags, {tag, value}}]},
    ]}
}.

By default the in InfluxDB visible name of the metric is derived from the exometer id: Here [erlang, memory] is translated to erlang_memory. It is possible to remove an item from this list by naming itself or its position with the from_name keyword. A removed element is then used as tag value:

exometer_report:subscribe(exometer_report_influxdb, [erlang, memory], total, 5000, [{tags, [{tag, {from_name, 2}}]}]).

This will result in a name erlang with the tag pair {tag, memory} (plus the default pair {host, Host}). To disable the removal of elements in the series name you can set:

{formatting, [{purge, [{all_from_name, false}]}]}

Further it might be handy to remove e.g. undefined tag keys or values. This can be done via:

{formatting, [{purge, [{tag_keys, undefined}, {tag_values, undefined}]}]}

Auto subscriptions:

There is capability for making a subscription automatically for each new entry. By default it is off. If you need to enable it in the reporter options and also provide a callback module which handles newly created entries.

{exometer, 
    {reporters, [
        {exometer_report_influxdb, [{autosubscribe, true}, 
                                    {subscriptions_module, exometer_influxdb_subscribe_mod}, 
                                    {protocol, http}, 
                                    {host, <<"localhost">>},
                                    {port, 8086},
                                    {db, <<"exometer">>},
                                    {tags, [{region, ru}]}]}
    ]}
}.

The callback module may look like:

-module(exometer_influxdb_subscribe_mod).
-export([subscribe/2]).

subscribe([metric, test], histogram) ->
    Tags = [{tags, [{type, {from_name, 2}}]}],
    [{[metric, test], min, 1000, Tags},
     {[metric, test], max, 1000, Tags},
     {[metric, test], median, 1000, Tags}];
subscribe([metric, test1], histogram) ->
    Tags = [{tags, [{type, {from_name, 2}}]}],
    [{[metric, test1], max, 1000, Tags},
     {[metric, test1], median, 1000, Tags}];
subscribe(_, _) -> [].

subscribe/2 calls for each new entry and it should return a list or just one subscription. Here a single subscription has the following layout:

{exometer_report:metric(), exometer_report:datapoint(), exometer_report:interval(), exometer_report:extra()}

TODO

• Reconfiguration on runtime
• Enhance the formatting options (e.g. concatenation chars, format strings, etc.)