resolves #34: watch for configuration changes

Reload the configuration if a change is detected
without requiring a server restart

src/conf.cpp

@@ -25,7 +25,7 @@ int StringMap::convert(std::string e) { return atoi(e.c_str()); }
 
 StringMap parseConfFile(const char* path) {
     StringMap result;
-    std::fstream f(path);
+    std::ifstream f(path);
     std::string line;
     while(std::getline(f, line)) {
         if(line[0] == '#')

src/interface.h

@@ -131,6 +131,9 @@ struct LaminarInterface {
 
     // Callback for laminar to reap child processes.
     virtual void reapChildren() = 0;
+
+    // Callback to handle a configuration modification notification
+    virtual void notifyConfigChanged() = 0;
 };
 
 #endif // LAMINAR_INTERFACE_H_

src/laminar.cpp

@@ -364,6 +364,8 @@ void Laminar::run() {
     const char* listen_http = getenv("LAMINAR_BIND_HTTP") ?: INTADDR_HTTP_DEFAULT;
 
     srv = new Server(*this, listen_rpc, listen_http);
+    srv->addWatchPath(fs::path(fs::path(homeDir)/"cfg"/"nodes").string().c_str());
+    srv->addWatchPath(fs::path(fs::path(homeDir)/"cfg"/"jobs").string().c_str());
     srv->start();
 }
 
@@ -530,6 +532,13 @@ void Laminar::reapChildren() {
     assignNewJobs();
 }
 
+void Laminar::notifyConfigChanged()
+{
+    loadConfiguration();
+    // config change may allow stuck jobs to dequeue
+    assignNewJobs();
+}
+
 void Laminar::abortAll() {
     for(std::shared_ptr<Run> run : activeJobs) {
         run->abort();

src/laminar.h

@@ -57,8 +57,9 @@ public:
     bool setParam(std::string job, uint buildNum, std::string param, std::string value) override;
     bool getArtefact(std::string path, std::string& result) override;
     std::string getCustomCss() override;
-    void reapChildren() override;
     void abortAll() override;
+    void reapChildren() override;
+    void notifyConfigChanged() override;
 
 private:
     bool loadConfiguration();

src/server.cpp

@@ -32,6 +32,7 @@
 #include <websocketpp/server.hpp>
 
 #include <sys/eventfd.h>
+#include <sys/inotify.h>
 #include <sys/signal.h>
 #include <sys/signalfd.h>
 
@@ -401,6 +402,7 @@ Server::Server(LaminarInterface& li, kj::StringPtr rpcBindAddress,
     }));
 
     // handle SIGCHLD
+    {
         sigset_t mask;
         sigemptyset(&mask);
         sigaddset(&mask, SIGCHLD);
@@ -413,6 +415,17 @@ Server::Server(LaminarInterface& li, kj::StringPtr rpcBindAddress,
             KJ_ASSERT(siginfo->ssi_signo == SIGCHLD);
             laminarInterface.reapChildren();
         }).attach(std::move(event)).attach(std::move(buffer));
+    }
+
+    // handle watched paths
+    {
+        inotify_fd = inotify_init1(IN_NONBLOCK | IN_CLOEXEC);
+        auto event = ioContext.lowLevelProvider->wrapInputFd(inotify_fd, kj::LowLevelAsyncIoProvider::TAKE_OWNERSHIP);
+        auto buffer = kj::heapArrayBuilder<char>(PROC_IO_BUFSIZE);
+        pathWatch = handleFdRead(event, buffer.asPtr().begin(), [this](const char*, size_t){
+            laminarInterface.notifyConfigChanged();
+        }).attach(std::move(event)).attach(std::move(buffer));
+    }
 }
 
 Server::~Server() {
@@ -455,6 +468,10 @@ void Server::addDescriptor(int fd, std::function<void(const char*,size_t)> cb) {
     childTasks.add(handleFdRead(event, buffer.asPtr().begin(), cb).attach(std::move(event)).attach(std::move(buffer)));
 }
 
+void Server::addWatchPath(const char* dpath) {
+    inotify_add_watch(inotify_fd, dpath, IN_ONLYDIR | IN_CLOSE_WRITE | IN_CREATE | IN_DELETE);
+}
+
 kj::Promise<void> Server::acceptHttpClient(kj::Own<kj::ConnectionReceiver>&& listener) {
     kj::ConnectionReceiver& cr = *listener.get();
     return cr.accept().then(kj::mvCapture(kj::mv(listener),

src/server.h

@@ -43,6 +43,9 @@ public:
     // invoked with the read data
     void addDescriptor(int fd, std::function<void(const char*,size_t)> cb);
 
+    // add a path to be watched for changes
+    void addWatchPath(const char* dpath);
+
 private:
     kj::Promise<void> acceptHttpClient(kj::Own<kj::ConnectionReceiver>&& listener);
     kj::Promise<void> acceptRpcClient(kj::Own<kj::ConnectionReceiver>&& listener);
@@ -63,6 +66,8 @@ private:
     kj::TaskSet childTasks;
     kj::TaskSet httpConnections;
     kj::Maybe<kj::Promise<void>> reapWatch;
+    int inotify_fd;
+    kj::Maybe<kj::Promise<void>> pathWatch;
 
     // TODO: restructure so this isn't necessary
     friend class ServerTest;

test/test-server.cpp

@@ -64,6 +64,7 @@ public:
     MOCK_METHOD0(getCustomCss, std::string());
     MOCK_METHOD0(abortAll, void());
     MOCK_METHOD0(reapChildren, void());
+    MOCK_METHOD0(notifyConfigChanged, void());
 };
 
 class ServerTest : public ::testing::Test {