Measure cross-AZ traffic in safekeepers (#3806)

Create `safekeeper_pg_io_bytes_total` metric to track total amount of
bytes written/read in a postgres connections to safekeepers. This metric
has the following labels:
- `client_az` – availability zone of the connection initiator, or
`"unknown"`
- `sk_az` – availability zone of the safekeeper, or `"unknown"`
- `app_name` – `application_name` of the postgres client
- `dir` – data direction, either `"read"` or `"write"`
- `same_az` – `"true"`, `"false"` or `"unknown"`. Can be derived from
`client_az` and `sk_az`, exists purely for convenience.

This is implemented by passing availability zone in the connection
string, like this: `-c tenant_id=AAA timeline_id=BBB
availability-zone=AZ-1`.

Update ansible deployment scripts to add availability_zone argument
to safekeeper and pageserver in systemd service files.

.github/ansible/deploy.yaml

@@ -91,6 +91,15 @@
       tags:
       - pageserver
 
+    # used in `pageserver.service` template
+    - name: learn current availability_zone
+      shell:
+        cmd: "curl -s http://169.254.169.254/latest/meta-data/placement/availability-zone"
+      register: ec2_availability_zone
+
+    - set_fact: 
+        ec2_availability_zone={{ ec2_availability_zone.stdout }}
+
     - name: upload systemd service definition
       ansible.builtin.template:
         src: systemd/pageserver.service
@@ -153,6 +162,15 @@
       tags:
       - safekeeper
 
+    # used in `safekeeper.service` template
+    - name: learn current availability_zone
+      shell:
+        cmd: "curl -s http://169.254.169.254/latest/meta-data/placement/availability-zone"
+      register: ec2_availability_zone
+
+    - set_fact: 
+        ec2_availability_zone={{ ec2_availability_zone.stdout }}
+
     # in the future safekeepers should discover pageservers byself
     # but currently use first pageserver that was discovered
     - name: set first pageserver var for safekeepers

.github/ansible/systemd/pageserver.service

@@ -6,7 +6,7 @@ After=network.target auditd.service
 Type=simple
 User=pageserver
 Environment=RUST_BACKTRACE=1 NEON_REPO_DIR=/storage/pageserver LD_LIBRARY_PATH=/usr/local/v14/lib SENTRY_DSN={{ SENTRY_URL_PAGESERVER }} SENTRY_ENVIRONMENT={{ sentry_environment }}
-ExecStart=/usr/local/bin/pageserver -c "pg_distrib_dir='/usr/local'" -c "listen_pg_addr='0.0.0.0:6400'" -c "listen_http_addr='0.0.0.0:9898'" -c "broker_endpoint='{{ broker_endpoint }}'" -D /storage/pageserver/data
+ExecStart=/usr/local/bin/pageserver -c "pg_distrib_dir='/usr/local'" -c "listen_pg_addr='0.0.0.0:6400'" -c "listen_http_addr='0.0.0.0:9898'" -c "broker_endpoint='{{ broker_endpoint }}'" -c "availability_zone='{{ ec2_availability_zone }}'" -D /storage/pageserver/data
 ExecReload=/bin/kill -HUP $MAINPID
 KillMode=mixed
 KillSignal=SIGINT

.github/ansible/systemd/safekeeper.service

@@ -6,7 +6,7 @@ After=network.target auditd.service
 Type=simple
 User=safekeeper
 Environment=RUST_BACKTRACE=1 NEON_REPO_DIR=/storage/safekeeper/data LD_LIBRARY_PATH=/usr/local/v14/lib SENTRY_DSN={{ SENTRY_URL_SAFEKEEPER }} SENTRY_ENVIRONMENT={{ sentry_environment }}
-ExecStart=/usr/local/bin/safekeeper -l {{ inventory_hostname }}{{ hostname_suffix }}:6500 --listen-http {{ inventory_hostname }}{{ hostname_suffix }}:7676 -D /storage/safekeeper/data --broker-endpoint={{ broker_endpoint }} --remote-storage='{bucket_name="{{bucket_name}}", bucket_region="{{bucket_region}}", prefix_in_bucket="{{ safekeeper_s3_prefix }}"}'
+ExecStart=/usr/local/bin/safekeeper -l {{ inventory_hostname }}{{ hostname_suffix }}:6500 --listen-http {{ inventory_hostname }}{{ hostname_suffix }}:7676 -D /storage/safekeeper/data --broker-endpoint={{ broker_endpoint }} --remote-storage='{bucket_name="{{bucket_name}}", bucket_region="{{bucket_region}}", prefix_in_bucket="{{ safekeeper_s3_prefix }}"}' --availability-zone={{ ec2_availability_zone }}
 ExecReload=/bin/kill -HUP $MAINPID
 KillMode=mixed
 KillSignal=SIGINT