简单理解skywalking数据上报的span概念

简单理解

spanType总共有三种：

1. Entry：表示整个进程的span
2. Local：表示进程内部的处理，是EntrySpan的一部分
3. Exit：表示发起一个远程调用，如请求db、redis，如发起http请求、rpc调用

spanLayer总共有六种（和jaeger不一样，它以span.tags数组key=component的值来分类）：

1. Unknown：未知
2. Database：请求db
3. RPCFramework：rpc调用
4. Http：发起http请求（或者本身是http服务）
5. MQ：消息服务
6. Cache：缓存服务

场景一：一个http请求，处理上传和请求db，则创建三个span
spanId=0 parentSpanId=-1 spanType=entry spanLayer=http
spanId=1 parentSpanId= 0 spanType=local spanLayer=Unknown
spanId=2 parentSpanId= 0 spanType=exit spanLayer=database

场景二：一个http请求，有http请求，则创建两个个span
spanId=0 parentSpanId=-1 spanType=entry spanLayer=http
spanId=1 parentSpanId= 0 spanType=exit spanLayer=http

场景三：一个http请求，有访问redis。场景二的第2个span正是访问的它。创建两个span（其中traceId和场景二的traceId相等）
spanId=0 parentSpanId=-1 spanType=entry spanLayer=http refs=包含场景二中第2个span的信息
spanId=1 parentSpanId= 0 spanType=exit spanLayer=cache

原始日志

这里记录一下真实的trace日志，来证实上面说的场景二和场景三

场景二

{
    "traceId": "6763beaf2ad8a9e4c05114b978a97072.17.756430259",
    "traceSegmentId": "6763beaf2ad8a9e4c05114b978a97072.17.756430259",
    "spans": [
        {
            "spanId": 0,
            "parentSpanId": -1,
            "startTime": "1639096358706",
            "endTime": "1639096359252",
            "refs": [],
            "operationName": "/answer4/activityStyle",
            "peer": "192.168.2.119:72",
            "spanType": "Entry",
            "spanLayer": "Http",
            "componentId": 8001,
            "isError": false,
            "tags": [
                {
                    "key": "url",
                    "value": "/answer4/activityStyle"
                },
                {
                    "key": "status_code",
                    "value": "200"
                }
            ],
            "logs": [],
            "skipAnalysis": false
        },
        {
            "spanId": 1,
            "parentSpanId": 0,
            "startTime": "1639096358775",
            "endTime": "1639096359250",
            "refs": [],
            "operationName": "/op/answer4/activityStyle",
            "peer": "container-ng9272:62",
            "spanType": "Exit",
            "spanLayer": "Http",
            "componentId": 8002,
            "isError": false,
            "tags": [
                {
                    "key": "url",
                    "value": "http://container-ng9272:62/op/answer4/activityStyle"
                },
                {
                    "key": "status_code",
                    "value": "200"
                }
            ],
            "logs": [],
            "skipAnalysis": false
        }
    ],
    "service": "op",
    "serviceInstance": "ca6185b0-752c-9aab-d9f9-6796da2c0646@172.18.0.5",
    "isSizeLimited": false
}

场景三

{
    "traceId": "6763beaf2ad8a9e4c05114b978a97072.17.756430259",
    "traceSegmentId": "6763beaf2ad8a9e4c05114b978a97072.18.4224945771",
    "spans": [
        {
            "spanId": 0,
            "parentSpanId": -1,
            "startTime": "1639096358782",
            "endTime": "1639096359250",
            "refs": [
                {
                    "refType": "CrossProcess",
                    "traceId": "6763beaf2ad8a9e4c05114b978a97072.17.756430259",
                    "parentTraceSegmentId": "6763beaf2ad8a9e4c05114b978a97072.17.756430259",
                    "parentSpanId": 1,
                    "parentService": "op",
                    "parentServiceInstance": "ca6185b0-752c-9aab-d9f9-6796da2c0646@172.18.0.5",
                    "parentEndpoint": "/answer4/activityStyle",
                    "networkAddressUsedAtPeer": "container-ng9272:62"
                }
            ],
            "operationName": "/op/answer4/activityStyle",
            "peer": "container-ng9272:62",
            "spanType": "Entry",
            "spanLayer": "Http",
            "componentId": 8001,
            "isError": false,
            "tags": [
                {
                    "key": "url",
                    "value": "/op/answer4/activityStyle"
                },
                {
                    "key": "status_code",
                    "value": "200"
                }
            ],
            "logs": [],
            "skipAnalysis": false
        },
        {
            "spanId": 1,
            "parentSpanId": 0,
            "startTime": "1639096358942",
            "endTime": "1639096358966",
            "refs": [],
            "operationName": "Redis->get",
            "peer": "localhost:6379",
            "spanType": "Exit",
            "spanLayer": "Cache",
            "componentId": 7,
            "isError": false,
            "tags": [
                {
                    "key": "db.type",
                    "value": "redis"
                },
                {
                    "key": "redis.command",
                    "value": "GET answer4:opdb"
                }
            ],
            "logs": [],
            "skipAnalysis": false
        }
    ],
    "service": "op",
    "serviceInstance": "ca6185b0-752c-9aab-d9f9-6796da2c0646@172.18.0.5",
    "isSizeLimited": false
}

本作品采用《CC 协议》，转载必须注明作者和本文链接