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Loki is the log aggregation backend in this stack. It receives log streams from Promtail and stores them on the local filesystem. This page explains each field in loki-config.yml and the matching Docker Compose service.

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Full configuration

auth_enabled: false

server:
  http_listen_port: 3100


common:
  path_prefix: /loki
  storage:
    filesystem:
      chunks_directory: /loki/chunks
      rules_directory: /loki/rules
  replication_factor: 1
  ring:
    instance_addr: 127.0.0.1
    kvstore:
      store: inmemory

schema_config:
  configs:
    - from: 2020-10-24
      store: tsdb
      object_store: filesystem
      schema: v13
      index:
        prefix: index_
        period: 24h

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Configuration fields

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auth_enabled
boolean
default:"false"
Controls whether Loki requires an X-Scope-OrgID header on every request to identify the tenant. When set to false, Loki operates in single-tenant mode and accepts requests without authentication headers.
auth_enabled: false is suitable for local development only. In a production or shared environment you should enable multi-tenancy and place an authenticating proxy in front of Loki.
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server.http_listen_port
number
default:"3100"
The port Loki’s HTTP server listens on. Promtail pushes logs to this port, and Grafana queries it for log data.
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common.path_prefix
string
default:"/loki"
The root directory under which Loki stores all data. The chunks_directory and rules_directory paths below are resolved relative to this prefix.
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common.storage.filesystem.chunks_directory
string
default:"/loki/chunks"
Where Loki writes compressed log chunks on the filesystem.
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common.storage.filesystem.rules_directory
string
default:"/loki/rules"
Where Loki stores alerting and recording rules.
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common.replication_factor
number
default:"1"
The number of replicas for each log chunk. A value of 1 means no replication, which is appropriate for a single-node local setup.
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common.ring.instance_addr
string
default:"127.0.0.1"
The address this Loki instance advertises to the ring. Set to the loopback address for single-node deployments.
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common.ring.kvstore.store
string
default:"inmemory"
The key-value store used by the ring for membership coordination. inmemory keeps all state in the process, which is only viable for a single Loki instance.

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Schema configuration

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schema_config.configs[].from
string
default:"2020-10-24"
The date from which this schema version applies. Loki uses the schema that was active when a chunk was written to read it back correctly.
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schema_config.configs[].store
string
default:"tsdb"
The index store type. tsdb is the recommended store for Loki v2.8 and later.
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schema_config.configs[].object_store
string
default:"filesystem"
Where Loki stores chunk data. filesystem writes directly to local disk, which is appropriate for local development.
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schema_config.configs[].schema
string
default:"v13"
The schema version used to encode index entries. v13 is the current recommended version.
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schema_config.configs[].index.prefix
string
default:"index_"
A string prepended to all index table names.
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schema_config.configs[].index.period
string
default:"24h"
How often Loki rotates index tables. A period of 24h creates one table per day.

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Docker Compose service

The loki service in docker-compose.yml is defined as follows: 
loki:
  image: grafana/loki:latest
  container_name: loki
  ports:
    - "3100:3100"
  volumes:
    - ./loki/loki-config.yml:/etc/loki/local-config.yaml
  • image — uses the official grafana/loki:latest image.
  • ports — maps host port 3100 to container port 3100, allowing Grafana (and your browser) to reach Loki at http://localhost:3100.
  • volumes — mounts your local loki/loki-config.yml into the container at /etc/loki/local-config.yaml, the path Loki reads by default on startup.