.. cmake-manual-description: CMake Server cmake-server(7) *************** .. only:: html .. contents:: Introduction ============ :manual:`cmake(1)` is capable of providing semantic information about CMake code it executes to generate a buildsystem. If executed with the ``-E server`` command line options, it starts in a long running mode and allows a client to request the available information via a JSON protocol. The protocol is designed to be useful to IDEs, refactoring tools, and other tools which have a need to understand the buildsystem in entirety. A single :manual:`cmake-buildsystem(7)` may describe buildsystem contents and build properties which differ based on :manual:`generation-time context ` including: * The Platform (eg, Windows, APPLE, Linux). * The build configuration (eg, Debug, Release, Coverage). * The Compiler (eg, MSVC, GCC, Clang) and compiler version. * The language of the source files compiled. * Available compile features (eg CXX variadic templates). * CMake policies. The protocol aims to provide information to tooling to satisfy several needs: #. Provide a complete and easily parsed source of all information relevant to the tooling as it relates to the source code. There should be no need for tooling to parse generated buildsystems to access include directories or compile definitions for example. #. Semantic information about the CMake buildsystem itself. #. Provide a stable interface for reading the information in the CMake cache. #. Information for determining when cmake needs to be re-run as a result of file changes. Operation ========= Start :manual:`cmake(1)` in the server command mode, supplying the path to the build directory to process:: cmake -E server (--debug|--pipe ) The server will communicate using stdin/stdout (with the ``--debug`` parameter) or using a named pipe (with the ``--pipe `` parameter). When connecting to the server (via named pipe or by starting it in ``--debug`` mode), the server will reply with a hello message:: [== CMake Server ==[ {"supportedProtocolVersions":[{"major":1,"minor":0}],"type":"hello"} ]== CMake Server ==] Messages sent to and from the process are wrapped in magic strings:: [== CMake Server ==[ { ... some JSON message ... } ]== CMake Server ==] The server is now ready to accept further requests via the named pipe or stdin. Debugging ========= CMake server mode can be asked to provide statistics on execution times, etc. or to dump a copy of the response into a file. This is done passing a "debug" JSON object as a child of the request. The debug object supports the "showStats" key, which takes a boolean and makes the server mode return a "zzzDebug" object with stats as part of its response. "dumpToFile" takes a string value and will cause the cmake server to copy the response into the given filename. This is a response from the cmake server with "showStats" set to true:: [== CMake Server ==[ { "cookie":"", "errorMessage":"Waiting for type \"handshake\".", "inReplyTo":"unknown", "type":"error", "zzzDebug": { "dumpFile":"/tmp/error.txt", "jsonSerialization":0.011016, "size":111, "totalTime":0.025995 } } ]== CMake Server ==] The server has made a copy of this response into the file /tmp/error.txt and took 0.011 seconds to turn the JSON response into a string, and it took 0.025 seconds to process the request in total. The reply has a size of 111 bytes. Protocol API ============ General Message Layout ---------------------- All messages need to have a "type" value, which identifies the type of message that is passed back or forth. E.g. the initial message sent by the server is of type "hello". Messages without a type will generate an response of type "error". All requests sent to the server may contain a "cookie" value. This value will he handed back unchanged in all responses triggered by the request. All responses will contain a value "inReplyTo", which may be empty in case of parse errors, but will contain the type of the request message in all other cases. Type "reply" ^^^^^^^^^^^^ This type is used by the server to reply to requests. The message may -- depending on the type of the original request -- contain values. Example:: [== CMake Server ==[ {"cookie":"zimtstern","inReplyTo":"handshake","type":"reply"} ]== CMake Server ==] Type "error" ^^^^^^^^^^^^ This type is used to return an error condition to the client. It will contain an "errorMessage". Example:: [== CMake Server ==[ {"cookie":"","errorMessage":"Protocol version not supported.","inReplyTo":"handshake","type":"error"} ]== CMake Server ==] Type "progress" ^^^^^^^^^^^^^^^ When the server is busy for a long time, it is polite to send back replies of type "progress" to the client. These will contain a "progressMessage" with a string describing the action currently taking place as well as "progressMinimum", "progressMaximum" and "progressCurrent" with integer values describing the range of progess. Messages of type "progress" will be followed by more "progress" messages or with a message of type "reply" or "error" that complete the request. "progress" messages may not be emitted after the "reply" or "error" message for the request that triggered the responses was delivered. Type "message" ^^^^^^^^^^^^^^ A message is triggered when the server processes a request and produces some form of output that should be displayed to the user. A Message has a "message" with the actual text to display as well as a "title" with a suggested dialog box title. Example:: [== CMake Server ==[ {"cookie":"","message":"Something happened.","title":"Title Text","inReplyTo":"handshake","type":"message"} ]== CMake Server ==] Type "signal" ^^^^^^^^^^^^^ The server can send signals when it detects changes in the system state. Signals are of type "signal", have an empty "cookie" and "inReplyTo" field and always have a "name" set to show which signal was sent. Specific Message Types ---------------------- Type "hello" ^^^^^^^^^^^^ The initial message send by the cmake server on startup is of type "hello". This is the only message ever sent by the server that is not of type "reply", "progress" or "error". It will contain "supportedProtocolVersions" with an array of server protocol versions supported by the cmake server. These are JSON objects with "major" and "minor" keys containing non-negative integer values. Example:: [== CMake Server ==[ {"supportedProtocolVersions":[{"major":0,"minor":1}],"type":"hello"} ]== CMake Server ==] Type "handshake" ^^^^^^^^^^^^^^^^ The first request that the client may send to the server is of type "handshake". This request needs to pass one of the "supportedProtocolVersions" of the "hello" type response received earlier back to the server in the "protocolVersion" field. Each protocol version may request additional attributes to be present. Protocol version 1.0 requires the following attributes to be set: * "sourceDirectory" with a path to the sources * "buildDirectory" with a path to the build directory * "generator" with the generator name * "extraGenerator" (optional!) with the extra generator to be used. Example:: [== CMake Server ==[ {"cookie":"zimtstern","type":"handshake","protocolVersion":{"major":0}, "sourceDirectory":"/home/code/cmake", "buildDirectory":"/tmp/testbuild", "generator":"Ninja"} ]== CMake Server ==] which will result in a response type "reply":: [== CMake Server ==[ {"cookie":"zimtstern","inReplyTo":"handshake","type":"reply"} ]== CMake Server ==] indicating that the server is ready for action.