Docker Compose override files for environment-specific configuration

<p>I want to use a base docker-compose.yml for common configuration and override files for environment-specific settings (development with hot reload, production with resource limits, CI with test setup).</p>

<p>Docker Compose override pattern:</p> <div class="highlight"><pre><span></span><code><span class="c1"># docker-compose.yml -- base config (committed)</span> <span class="nt">services</span><span class="p">:</span> <span class="w"> </span><span class="nt">api</span><span class="p">:</span> <span class="w"> </span><span class="nt">build</span><span class="p">:</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">./api</span> <span class="w"> </span><span class="nt">environment</span><span class="p">:</span> <span class="w"> </span><span class="nt">DATABASE_URL</span><span class="p">:</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">${DATABASE_URL}</span> <span class="w"> </span><span class="nt">depends_on</span><span class="p">:</span> <span class="w"> </span><span class="nt">postgres</span><span class="p">:</span> <span class="w"> </span><span class="nt">condition</span><span class="p">:</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">service_healthy</span> <span class="c1"># docker-compose.dev.yml -- development overrides</span> <span class="nt">services</span><span class="p">:</span> <span class="w"> </span><span class="nt">api</span><span class="p">:</span> <span class="w"> </span><span class="nt">volumes</span><span class="p">:</span> <span class="w"> </span><span class="p p-Indicator">-</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">./api:/app</span><span class="w"> </span><span class="c1"># Hot reload with bind mount</span> <span class="w"> </span><span class="nt">command</span><span class="p">:</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">uvicorn app.main:app --host 0.0.0.0 --port 8000 --reload</span> <span class="w"> </span><span class="nt">environment</span><span class="p">:</span> <span class="w"> </span><span class="nt">DEBUG</span><span class="p">:</span><span class="w"> </span><span class="s">'true'</span> <span class="c1"># docker-compose.prod.yml -- production overrides</span> <span class="nt">services</span><span class="p">:</span> <span class="w"> </span><span class="nt">api</span><span class="p">:</span> <span class="w"> </span><span class="nt">deploy</span><span class="p">:</span> <span class="w"> </span><span class="nt">resources</span><span class="p">:</span> <span class="w"> </span><span class="nt">limits</span><span class="p">:</span> <span class="w"> </span><span class="nt">memory</span><span class="p">:</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">512m</span> <span class="w"> </span><span class="nt">cpus</span><span class="p">:</span><span class="w"> </span><span class="s">'1.0'</span> <span class="w"> </span><span class="nt">restart</span><span class="p">:</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">unless-stopped</span> <span class="w"> </span><span class="nt">command</span><span class="p">:</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">uvicorn app.main:app --host 0.0.0.0 --port 8000 --workers 4</span> <span class="c1"># docker-compose.ci.yml -- CI overrides</span> <span class="nt">services</span><span class="p">:</span> <span class="w"> </span><span class="nt">api</span><span class="p">:</span> <span class="w"> </span><span class="nt">environment</span><span class="p">:</span> <span class="w"> </span><span class="nt">DATABASE_URL</span><span class="p">:</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">postgresql+asyncpg://test:test@postgres:5432/test</span> </code></pre></div> <div class="highlight"><pre><span></span><code><span class="c1"># Usage:</span> docker<span class="w"> </span>compose<span class="w"> </span>-f<span class="w"> </span>docker-compose.yml<span class="w"> </span>-f<span class="w"> </span>docker-compose.dev.yml<span class="w"> </span>up docker<span class="w"> </span>compose<span class="w"> </span>-f<span class="w"> </span>docker-compose.yml<span class="w"> </span>-f<span class="w"> </span>docker-compose.prod.yml<span class="w"> </span>up<span class="w"> </span>-d <span class="c1"># Or set COMPOSE_FILE env var:</span> <span class="nb">export</span><span class="w"> </span><span class="nv">COMPOSE_FILE</span><span class="o">=</span>docker-compose.yml:docker-compose.dev.yml docker<span class="w"> </span>compose<span class="w"> </span>up </code></pre></div> <p>Key points: - Override files merge with base -- array values are replaced, not extended - Bind mount in dev enables hot reload without rebuilding image - In production: set restart policy, resource limits, multiple workers - COMPOSE_FILE env var avoids specifying -f on every command - Keep secrets out of both files -- use .env or secrets management</p>