nixos: overhaul datadog module

This overhauls the Datadog module a bit to be much more useful. In
particular, it adds support for nginx and postgresql monitoring
integrations to dd-agent. These have to exist in separate files under
/etc/dd-agent, so the module just exposes then as separate options. In
the future, more integrations could be added this way.

In the process of doing this, I also had to rename the dd-agent user to
datadog. Note the UIDs did not change, so this is strictly backwards
compatible. The reason for this is to make it easier to create a
'datadog' postgres user with access to pg_stats, as 'dd-agent' typically
isn't a valid username. This allows the out of the box configurations to
be used.

Signed-off-by: Austin Seipp <aseipp@pobox.com>

2 files changed, 85 insertions, 24 deletions

diff --git a/nixos/modules/misc/ids.nix b/nixos/modules/misc/ids.nix
index 3f6aaa15bb4f..207da2a39bfe 100644
--- a/nixos/modules/misc/ids.nix
+++ b/nixos/modules/misc/ids.nix
@@ -84,7 +84,7 @@
       postgres = 71;
       smbguest = 74;
       varnish = 75;
-      dd-agent = 76;
+      datadog = 76;
       lighttpd = 77;
       lightdm = 78;
       freenet = 79;
@@ -201,7 +201,7 @@
       vboxsf = 73;
       smbguest = 74;
       varnish = 75;
-      dd-agent = 76;
+      datadog = 76;
       lighttpd = 77;
       lightdm = 78;
       freenet = 79;
diff --git a/nixos/modules/services/monitoring/dd-agent.nix b/nixos/modules/services/monitoring/dd-agent.nix
index bddf102ee517..5794ee7fe534 100644
--- a/nixos/modules/services/monitoring/dd-agent.nix
+++ b/nixos/modules/services/monitoring/dd-agent.nix
@@ -5,54 +5,113 @@ with lib;
 let
   cfg = config.services.dd-agent;
 
-  datadog_conf = pkgs.runCommand "datadog.conf" {} ''
-    sed -e 's|^api_key:|api_key: ${cfg.api_key}|' ${optionalString (cfg.hostname != null)
-      "-e 's|^#hostname: mymachine.mydomain|hostname: ${cfg.hostname}|'"
-    } ${pkgs.dd-agent}/etc/dd-agent/datadog.conf.example > $out
+  ddConf = pkgs.writeText "datadog.conf" ''
+    [Main]
+    dd_url: https://app.datadoghq.com
+    skip_ssl_validation: no
+    api_key: ${cfg.api_key}
+    ${optionalString (cfg.hostname != null) "hostname: ${cfg.hostname}"}
+
+    collector_log_file: /var/log/datadog/collector.log
+    forwarder_log_file: /var/log/datadog/forwarder.log
+    dogstatsd_log_file: /var/log/datadog/dogstatsd.log
+    pup_log_file:       /var/log/datadog/pup.log
+
+    # proxy_host: my-proxy.com
+    # proxy_port: 3128
+    # proxy_user: user
+    # proxy_password: password
+
+    # tags: mytag0, mytag1
+
+    # collect_ec2_tags: no
+    # recent_point_threshold: 30
+    # use_mount: no
+    # listen_port: 17123
+    # graphite_listen_port: 17124
+    # non_local_traffic: no
+    # use_curl_http_client: False
+    # bind_host: localhost
+
+    # use_pup: no
+    # pup_port: 17125
+    # pup_interface: localhost
+    # pup_url: http://localhost:17125
+
+    # dogstatsd_port : 8125
+    # dogstatsd_interval : 10
+    # dogstatsd_normalize : yes
+    # statsd_forward_host: address_of_own_statsd_server
+    # statsd_forward_port: 8125
+
+    # device_blacklist_re: .*\/dev\/mapper\/lxc-box.*
+
+    # ganglia_host: localhost
+    # ganglia_port: 8651
   '';
+
+  postgresqlConfig = pkgs.writeText "postgres.yaml" cfg.postgresqlConfig;
+  nginxConfig = pkgs.writeText "nginx.yaml" cfg.nginxConfig;
+
+  etcfiles =
+    [ { source = ddConf;
+        target = "dd-agent/datadog.conf";
+      } ] ++
+    (optional (cfg.postgresqlConfig != null)
+      { source = postgresqlConfig;
+        target = "dd-agent/conf.d/postgres.yaml";
+      }) ++
+    (optional (cfg.nginxConfig != null)
+      { source = nginxConfig;
+        target = "dd-agent/conf.d/nginx.yaml";
+      });
+
 in {
   options.services.dd-agent = {
     enable = mkOption {
       description = "Whether to enable the dd-agent montioring service";
-
       default = false;
-
       type = types.bool;
     };
 
-    # !!! This gets stored in the store (world-readable), wish we had https://github.com/NixOS/nix/issues/8
     api_key = mkOption {
       description = "The Datadog API key to associate the agent with your account";
-
       example = "ae0aa6a8f08efa988ba0a17578f009ab";
-
       type = types.str;
     };
 
     hostname = mkOption {
       description = "The hostname to show in the Datadog dashboard (optional)";
-
       default = null;
-
       example = "mymachine.mydomain";
+      type = types.uniq (types.nullOr types.string);
+    };
+
+    postgresqlConfig = mkOption {
+      description = "Datadog PostgreSQL integration configuration";
+      default = null;
+      type = types.uniq (types.nullOr types.string);
+    };
 
+    nginxConfig = mkOption {
+      description = "Datadog nginx integration configuration";
+      default = null;
       type = types.uniq (types.nullOr types.string);
     };
   };
 
   config = mkIf cfg.enable {
-    environment.etc = [ { source = datadog_conf; target = "dd-agent/datadog.conf"; } ];
     environment.systemPackages = [ pkgs."dd-agent" pkgs.sysstat pkgs.procps ];
 
-    users.extraUsers."dd-agent" = {
+    users.extraUsers.datadog = {
       description = "Datadog Agent User";
-      uid = config.ids.uids.dd-agent;
-      group = "dd-agent";
+      uid = config.ids.uids.datadog;
+      group = "datadog";
       home = "/var/log/datadog/";
       createHome = true;
     };
 
-    users.extraGroups.dd-agent.gid = config.ids.gids.dd-agent;
+    users.extraGroups.datadog.gid = config.ids.gids.datadog;
 
     systemd.services.dd-agent = {
       description = "Datadog agent monitor";
@@ -60,12 +119,12 @@ in {
       wantedBy = [ "multi-user.target" ];
       serviceConfig = {
         ExecStart = "${pkgs.dd-agent}/bin/dd-agent foreground";
-        User = "dd-agent";
-        Group = "dd-agent";
+        User = "datadog";
+        Group = "datadog";
         Restart = "always";
         RestartSec = 2;
       };
-      restartTriggers = [ pkgs.dd-agent datadog_conf ];
+      restartTriggers = [ pkgs.dd-agent ddConf postgresqlConfig nginxConfig ];
     };
 
     systemd.services.dogstatsd = {
@@ -74,14 +133,16 @@ in {
       wantedBy = [ "multi-user.target" ];
       serviceConfig = {
         ExecStart = "${pkgs.dd-agent}/bin/dogstatsd start";
-        User = "dd-agent";
-        Group = "dd-agent";
+        User = "datadog";
+        Group = "datadog";
         Type = "forking";
         PIDFile = "/tmp/dogstatsd.pid";
         Restart = "always";
         RestartSec = 2;
       };
-      restartTriggers = [ pkgs.dd-agent datadog_conf ];
+      restartTriggers = [ pkgs.dd-agent ddConf postgresqlConfig nginxConfig ];
     };
+
+    environment.etc = etcfiles;
   };
 }