Process Threads list and minidump gcdump diagsession

Overview

To diagnose issues, one may need to get the list of running processes, their cpu and memory usages, or even take a minidump. Kudu service exposes processes and threads endpoint (/diagnostics/processes) enabling users to achieve exactly that. If you start at the root of the Kudu service, you'll see a Processes and mini-dumps link that lets you easily navigate the REST API (a browser extension like JSONView is recommended).

Using /diagnostics/processes

<kudu-service-url>/diagnostics/processes endpoint returns the list of running processes in json format. Each process info contains process name, id and a link /diagnostics/processes/{id} to its detail information (such as memory, cpu usages, etc.). Note: the id 0 is reserved for current w3wp.exe process allowing a shortcut to this via /diagnostics/processes/0. One can take the minidump of any given process by simply connect to /diagnostics/processes/{id}/dump. For Windows Azure, we include support for taking a gcdump and diagsession format (/diagnostics/processes/{id}/gcdump?format=raw and /diagnostics/processes/{id}/gcdump?format=diagsession respectively).

Using /diagnostics/processes/{id}/threads

<kudu-service-url>/diagnostics/processes/{id}/threads endpoint returns the list of threads for a given process. Each thread info contains id, state and a link /diagnostics/processes/{id}/threads/{tid} to its detail information (such as memory, cpu usages, etc.).

Summary

• HTTP GET /diagnostics/processes => list of processes.
• HTTP GET /diagnostics/processes/{id} => detail information of process with id.
• HTTP GET /diagnostics/processes/{id}/threads => list of threads for process with id.
• HTTP GET /diagnostics/processes/{id}/threads/{tid} => detail information of the thread.
• HTTP DELETE /diagnostics/processes/{id} => terminate process with id and its children.
• HTTP GET /diagnostics/processes/0 => detail process information of current w3wp.exe.
• HTTP DELETE /diagnostics/processes/0 => terminate w3wp.exe process and its children.
• HTTP GET /diagnostics/processes/{id}/dump => minidump of process with id. By default, this is minimum dump without memory (dumptType=0).
• HTTP GET /diagnostics/processes/{id}/dump?dumpType=2 => full memory minidump of process with id. The available dumpType value can be found at MINIDUMP_TYPE.
• HTTP GET /diagnostics/processes/{id}/dump?dumpType=2&format=zip => full memory minidump of process with id. This will include matching sos.dll and mscordackws.dll in the zip package.
• (Windows Azure only) HTTP GET /diagnostics/processes/{id}/gcdump => take managed gcdump. This returns a diagsession format file. VS 2013 Ultimate (or newer) is needed to open this type of file. You can also specify different format query string such as ?format=raw (returning in raw gcdump format readable by perfview or ?format=zip to compress the raw gcdump in zip file.

For web sites running on multiple instances the WEBSITE_INSTANCE_ID environment variable can indicate the current instance ID. An instance ID can be used to modify the cookie that directs a request to a specific instance of the web site - before dump requests above. Listing all instance IDs for a web site requires use of the Azure Web Sites REST API.

Limitations

It cannot get dumps for crashed processes

This feature is about getting dumps for running processes, and not for crashed processes.

w3wp needs to be healthy enough to process the dump request

Since the Kudu service runs in the same w3wp process as the site, w3wp needs to be able to process the dump request. In most cases, it will be, but it's possible for w3wp to be corrupted enough not to be able to handle the request.

Full dump could cause download quota to be reached

The resources used by the dump feature are counted toward the site limits. For the default small dump, it's not an issue, but if requesting a full dump for a Free Azure site, you could reach the quota which could cause some site downtime.