<p class="p"><strong class="ph b">Logs</strong></p> <p class="p">A log is an ordered collection of operation records and results that are appended in chronological order.</p> <img class="image" id="Concepts__image_bzn_jjb_vmb" src="https://obs-cn-shanghai.yun.pingan.com/pcp-portal/20210106133705-1126ad749b7e.png"> <p class="p">A log contains the following fields:</p> <table class="table" id="Concepts__table_lw4_djb_vmb"><caption></caption><colgroup><col><col></colgroup><thead class="thead"> <tr class="row"> <th class="entry" id="Concepts__table_lw4_djb_vmb__entry__1">Field</th> <th class="entry" id="Concepts__table_lw4_djb_vmb__entry__2">Description</th> </tr> </thead><tbody class="tbody"> <tr class="row"> <td class="entry" headers="Concepts__table_lw4_djb_vmb__entry__1 "> <p class="p">appname</p> </td> <td class="entry" headers="Concepts__table_lw4_djb_vmb__entry__2 "> <p class="p">Project ID of the log.</p> </td> </tr> <tr class="row"> <td class="entry" headers="Concepts__table_lw4_djb_vmb__entry__1 "> <p class="p">message</p> </td> <td class="entry" headers="Concepts__table_lw4_djb_vmb__entry__2 "> <p class="p">Content of the log.</p> </td> </tr> <tr class="row"> <td class="entry" headers="Concepts__table_lw4_djb_vmb__entry__1 "> <p class="p">source</p> </td> <td class="entry" headers="Concepts__table_lw4_djb_vmb__entry__2 "> <p class="p">Name of the device that generates the log. </p> </td> </tr> <tr class="row"> <td class="entry" headers="Concepts__table_lw4_djb_vmb__entry__1 "> <p class="p">collector_node_id</p> </td> <td class="entry" headers="Concepts__table_lw4_djb_vmb__entry__2 "> <p class="p">IP address of the device that generates the log.</p> </td> </tr> <tr class="row"> <td class="entry" headers="Concepts__table_lw4_djb_vmb__entry__1 "> <p class="p">file</p> </td> <td class="entry" headers="Concepts__table_lw4_djb_vmb__entry__2 "> <p class="p">Name of the file to which the log belongs.</p> </td> </tr> <tr class="row"> <td class="entry" headers="Concepts__table_lw4_djb_vmb__entry__1 "> <p class="p">timestamp</p> </td> <td class="entry" headers="Concepts__table_lw4_djb_vmb__entry__2 "> <p class="p">Timestamp of the log.</p> </td> </tr> </tbody></table> <p class="p"><strong class="ph b">Indexes</strong></p> <p class="p">An index is a basic logical storage unit of Log Service. You can quickly access the collected log data by using an index.</p> <p class="p">The Index feature has the following benefits:</p> <ul class="ul" id="Concepts__ul_efj_k21_4nb"> <li class="li"><strong class="ph b">User Data isolation</strong>—The log data stored in one index is logically isolated from that in other indexes. Each user in the same region can create only one index. The log data of different users is stored in different indexes and does not affect each other.</li> <li class="li"><strong class="ph b">Security and high availability</strong>—Log Service distributes the copies of log data of an index on multiple servers. If one server goes down, the system can quickly restore the log data from one of these copies. </li> </ul> <p class="p"><strong class="ph b">Projects</strong></p> <p class="p">A project is a basic logical resource management unit of Log Service. It isolates the data of a user on a per-application basis. You can use a project to manage all the logs of an application. One index can have multiple projects in a region.</p> <p class="p"><strong class="ph b">Host Groups</strong></p> <p class="p">A host group is a set of cloud hosts. Each project contains one or multiple host groups. A cloud host can be added to different host groups.</p> <p class="p">Generally, an application is deployed on multiple cloud hosts to ensure high availability. These cloud hosts are typically configured with the same log collection policy. To reduce the workload of configuring and updating the log collection policy on these cloud hosts, add these cloud hosts to one host group.</p> <img class="image" id="Concepts__image_cxp_qjb_vmb" src="https://obs-cn-shanghai.yun.pingan.com/pcp-portal/20210106133705-1e75fc189986.png">