Re: [libvirt] [PATCH v2 1/5] Add public API to register a callback to be invoked on connection close

From: "Daniel P. Berrange" <berrange(a)redhat.com&gt; Define new virConnect{Register,Unregister}CloseCallback() public APIs which allows registering/unregistering a callback to be invoked when the connection to a hypervisor is closed. The callback is provided with the reason for the close, which may be 'error', 'eof' or 'keepalive'.

diff --git a/include/libvirt/libvirt.h.in b/include/libvirt/libvirt.h.in index fcef461..d9f0397 100644 --- a/include/libvirt/libvirt.h.in +++ b/include/libvirt/libvirt.h.in

@@ -1148,6 +1166,27 @@ int virConnectSetKeepAlive(virConnectPtr conn, int interval, unsigned int count); +typedef enum { + VIR_CONNECT_CLOSE_REASON_ERROR = 0, /* Misc I/O error */ + VIR_CONNECT_CLOSE_REASON_EOF = 1, /* End-of-file from server */ + VIR_CONNECT_CLOSE_REASON_KEEPALIVE = 2, /* Keepalive timer triggered */ + VIR_CONNECT_CLOSE_REASON_CLIENT = 3, /* Client requested it */ + +# ifdef VIR_ENUM_SENTINELS + VIR_CONNECT_CLOSE_REASON_LAST +# endif +} virConnectCloseReason;

diff --git a/src/libvirt.c b/src/libvirt.c index 8315b4f..9cfabc5 100644 --- a/src/libvirt.c +++ b/src/libvirt.c @@ -18613,6 +18613,117 @@ error: /** + * virConnectRegisterCloseCallback: + * @conn: pointer to connection object + * @cb: callback to invoke upon close + * @opaque: user data to pass to @cb + * @freecb: callback to free @opaque + * + * Registers a callback to be invoked when the connection + * is closed. This callback is invoked when there is any + * condition that causes the socket connection to the + * hypervisor to be closed. + * + * This function is only applicable to hypervisor drivers + * which maintain a persistent open connection. Drivers + * which open a new connection for every operation will + * not invoke this. + * + * The @freecb must not invoke any other libvirt public + * APIs, since it is not called from a re-entrant safe + * context. + * + * Returns 0 on success, -1 on error + */ +int virConnectRegisterCloseCallback(virConnectPtr conn, + virConnectCloseFunc cb, + void *opaque, + virFreeCallback freecb) +{ + VIR_DEBUG("conn=%p", conn); + + virResetLastError(); + + if (!VIR_IS_CONNECT(conn)) { + virLibConnError(VIR_ERR_INVALID_CONN, __FUNCTION__); + virDispatchError(NULL); + return -1; + } + + virMutexLock(&conn->lock); + + virCheckNonNullArgGoto(cb, error); + + if (conn->closeCallback) { + virLibConnError(VIR_ERR_OPERATION_INVALID, "%s", + _("A close callback is already registered")); + goto error; + } + + conn->closeCallback = cb; + conn->closeOpaque = opaque; + conn->closeFreeCallback = freecb; + + virMutexUnlock(&conn->lock); + + return 0; + +error: + virMutexUnlock(&conn->lock); + virDispatchError(NULL); + return -1; +} + +/** + * virConnectUnregisterCloseCallback: + * @conn: pointer to connection object + * @cb: pointer to the current registered callback + * + * Unregisters the callback previously set with the + * virConnectRegisterCloseCallback method. The callback + * will no longer received notifications when the connection

+ * closes.

+ * + * Returns 0 on success, -1 on error + */ +int virConnectUnregisterCloseCallback(virConnectPtr conn, + virConnectCloseFunc cb) +{ + VIR_DEBUG("conn=%p", conn); + + virResetLastError(); + + if (!VIR_IS_CONNECT(conn)) { + virLibConnError(VIR_ERR_INVALID_CONN, __FUNCTION__); + virDispatchError(NULL); + return -1; + } + + virMutexLock(&conn->lock); + + virCheckNonNullArgGoto(cb, error); + + if (conn->closeCallback != cb) { + virLibConnError(VIR_ERR_OPERATION_INVALID, "%s", + _("A different callback was requested")); + goto error; + } + + conn->closeCallback = NULL; + if (conn->closeFreeCallback) + conn->closeFreeCallback(conn->closeOpaque);

+ + virMutexUnlock(&conn->lock); + + return 0; + +error: + virMutexUnlock(&conn->lock); + virDispatchError(NULL); + return -1; +} + +/** * virDomainSetBlockIoTune: * @dom: pointer to domain object * @disk: path to the block device, or device shorthand